Spent Nuclear Fuel
Options Exist to Further Enhance Security Gao ID: GAO-03-426 July 15, 2003Spent nuclear fuel, the used fuel periodically removed from nuclear power reactors, is one of the most hazardous materials made by man. Nuclear power companies currently store 50,000 tons of spent fuel at 72 sites in 33 states. That amount will increase through 2010, when the Department of Energy (DOE) expects to open a permanent repository for this fuel at Yucca Mountain, Nevada. Concerns have been raised since September 11, 2001, that terrorists might target spent fuel. GAO was asked to (1) review federally sponsored studies that assessed the potential health effects of a terrorist attack or a severe accident on spent fuel, either in transit or in storage, and (2) identify options for DOE to further enhance the security of spent fuel during shipping to Yucca Mountain.
The likelihood of widespread harm from a terrorist attack or a severe accident involving commercial spent nuclear fuel is low, according to studies conducted by DOE and NRC. Largely because spent fuel is hard to disperse and is stored in protective containers, these studies found that most terrorist or accident scenarios would cause little or no release of spent fuel, with little harm to human health. Some assessments found widespread harm is possible under certain severe but extremely unlikely conditions involving spent fuel stored in storage pools. As part of its ongoing research program and to respond to increased security concerns, NRC has ongoing and planned studies of the safety and security of spent fuel, including the potential effects of more extreme attack scenarios, including deliberate aircraft crashes. While NRC and DOE have found that spent fuel may be relatively safe and secure, DOE could potentially enhance the security of this fuel through options such as minimizing the number of shipments and picking up fuel in an order that would reduce risk, such as moving older less dangerous fuel first. These options could reduce the risk during transport and at some locations where the fuel is currently stored. However, contractual agreements between DOE and owners of spent fuel may limit DOE's ability to choose among these options. In addition, it is not clear that the benefits of these measures would justify the potential costs, including a possible renegotiation of the contracts between DOE and the spent fuel owners.
RecommendationsOur recommendations from this work are listed below with a Contact for more information. Status will change from "In process" to "Open," "Closed - implemented," or "Closed - not implemented" based on our follow up work.
Director: Team: Phone:GAO-03-426, Spent Nuclear Fuel: Options Exist to Further Enhance Security
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Report to the Chairman, Subcommittee on Energy and Air Quality,
Committee on Energy and Commerce, U.S. House of Representatives:
United States General Accounting Office:
GAO:
July 2003:
Spent Nuclear Fuel:
Options Exist to Further Enhance Security:
GAO-03-426:
GAO Highlights:
Highlights of GAO-03-426, a report to the Chairman, Subcommittee on
Energy and Air Quality, Committee on Energy and Commerce, U.S. House
of Representatives
Why GAO Did This Study:
Spent nuclear fuel, the used fuel periodically removed from nuclear
power reactors, is one of the most hazardous materials made by man.
Nuclear power companies currently store 50,000 tons of spent fuel at
72 sites in 33 states. That amount will increase through 2010, when
the Department of Energy (DOE) expects to open a permanent repository
for this fuel at Yucca Mountain, Nevada. Concerns have been raised
since September 11, 2001, that terrorists might target spent fuel. GAO
was asked to (1) review federally sponsored studies that assessed the
potential health effects of a terrorist attack or a severe accident on
spent fuel, either in transit or in storage, and (2) identify options
for DOE to further enhance the security of spent fuel during shipping
to Yucca Mountain.
What GAO Found:
The likelihood of widespread harm from a terrorist attack or a severe
accident involving commercial spent nuclear fuel is low, according to
studies conducted by DOE and NRC. Largely because spent fuel is hard
to disperse and is stored in protective containers, these studies
found that most terrorist or accident scenarios would cause little or
no release of spent fuel, with little harm to human health. Some
assessments found widespread harm is possible under certain severe but
extremely unlikely conditions involving spent fuel stored in storage
pools. As part of its ongoing research program and to respond to
increased security concerns, NRC has ongoing and planned studies of
the safety and security of spent fuel, including the potential effects
of more extreme attack scenarios, including deliberate aircraft
crashes.
While NRC and DOE have found that spent fuel may be relatively safe
and secure, DOE could potentially enhance the security of this fuel
through options such as minimizing the number of shipments and picking
up fuel in an order that would reduce risk, such as moving older less
dangerous fuel first. These options could reduce the risk during
transport and at some locations where the fuel is currently stored.
However, contractual agreements between DOE and owners of spent fuel
may limit DOE's ability to choose among these options. In addition, it
is not clear that the benefits of these measures would justify the
potential costs, including a possible renegotiation of the contracts
between DOE and the spent fuel owners.
What GAO Recommends:
GAO is recommending that, as DOE develops its plans for transporting
spent fuel to Yucca Mountain, it assess potential options to further
enhance the security and safety of this fuel.
In commenting on GAO‘s report, DOE and NRC generally concurred with
the facts of the report. DOE noted that the information on transit was
accurate and well-balanced, while the Nuclear Regulatory Commission
(NRC) noted that the information provides a reasonable
characterization of the current understanding of risks associated with
spent fuel storage.
www.gao.gov/cgi-bin/getrpt?GAO-03-426.
To view the full product, including the scope
and methodology, click on the link above.
For more information, contact Robin M. Nazarro at (202) 512-3841 or
nazarror@gao.gov.
[End of section]
Contents:
Letter:
Results in Brief:
Background:
Likelihood of Widespread Harm from Terrorist Attacks or Severe
Accidents Involving Spent Fuel Is Low:
Options May Exist to Further Enhance Security and Safety:
Conclusions:
Recommendations for Executive Action:
Agency Comments and Our Evaluation:
Scope and Methodology:
Appendix I: Nuclear Regulatory Commission Requirements for Safety and
Security of Spent Fuel:
Appendix II: Additional Information on Studies on the Safety and Security
of Spent Fuel in Transit:
Appendix III: Comments from the Department of Energy:
Appendix IV: Comments from the Nuclear Regulatory Commission:
Appendix V: GAO Contact and Staff Acknowledgments:
Table:
Table 1: Potential Health Effects of Fire in a Spent Fuel Pool:
Figures:
Figure 1: Locations for Wet and Dry Storage Sites for Commercial Spent
Nuclear Fuel and Yucca Mountain, as of April 2003:
Figure 2: Cutaway Graphic of a Spent Fuel Truck Transportation Cask:
Figure 3: Spent Fuel Rail Container:
Figure 4: Spent Fuel Truck Container on a Trailer:
Figure 5: A Wet Storage Pool:
Figure 6: A Spent Fuel Dry Storage Container:
Abbreviations:
DOE: Department of Energy:
NRC: Nuclear Regulatory Commission:
United States General Accounting Office:
Washington, DC 20548:
July 15, 2003:
The Honorable Joe Barton
Chairman,
Subcommittee on Energy and Air Quality
Committee on Energy and Commerce
House of Representatives:
Dear Mr. Chairman:
One of the most hazardous materials made by man is spent nuclear fuel-
-the used fuel periodically removed from reactors in nuclear power
plants. Without protective shielding, the fuel's intense radioactivity
can kill a person exposed directly to it within minutes or cause cancer
in those who receive smaller doses. As the fuel ages, it begins to cool
and becomes less radiologically dangerous--some of the radioactive
particles decay quickly, within days or weeks, while others exist for
many thousands of years. Currently, more than 50,000 tons of commercial
spent fuel are stored at 72 sites at or near nuclear power plants in
33 states. Most of this nuclear fuel is stored immersed in pools of
water designed to cool the fuel, but some sites also keep older, cooler
fuel in "dry storage" units that generally consist of steel containers
placed inside reinforced concrete vaults or bunkers. Concerns about the
security of these sites and their spent fuel inventories have been
raised following the terrorist attacks of September 11, 2001.
To provide secure, permanent disposal for spent fuel, the President
and the Congress have approved development of a deep underground
repository at Yucca Mountain, Nevada. The Department of Energy (DOE) is
to construct and operate the repository after receiving a license from
the Nuclear Regulatory Commission (NRC). Shipping this fuel from
current storage locations to Yucca Mountain will be managed by DOE,
which in 1983 entered into contracts with owners of spent fuel
(essentially owners and operators of nuclear power plants) requiring
DOE to take title to and dispose of this fuel. DOE estimates that
175 shipments per year over 24 years will be required to move the
accumulated inventory of spent nuclear fuel. These shipments have
increased public concern about nuclear security. Recent media reports
suggest that if terrorists could release spent fuel into the
environment during transit or from wet or dry storage sites,
particularly near large cities, the human health effects could be
severe.
We agreed with your office to (1) review federally sponsored studies
that examined the potential health effects of a terrorist attack or a
severe accident involving commercial spent nuclear fuel, either in
transit or in storage, and (2) identify options for DOE to enhance the
security of spent fuel as it develops its plans to ship the fuel to
Yucca Mountain. In conducting our review, we did not assess the
reliability of data or the methodologies used in the studies that
examined potential health effects. We also did not examine economic or
broader environmental effects of terrorist attacks or severe accidents,
nor did we examine the effectiveness of certain other safety and
security measures, such as the effectiveness of armed guards and
intrusion barriers.
Results in Brief:
NRC and DOE studies indicate a low likelihood of widespread harm to
human health from terrorist attacks or severe accidents involving spent
fuel--either in transit or dry or wet storage. Spent fuel is a heavy,
ceramic material that is neither explosive nor volatile and resists
easy dispersal. Tests to date on shipping containers and dry storage
containers have shown that, while they can be penetrated under
terrorist and severe accident scenarios, their construction allows
little release of spent fuel, with little harm to human health. While
release of a large quantity of radioactive material from a wet storage
pool is theoretically possible, such a release would require an
extremely unlikely chain of events. For example, coolant would have to
be drained from pools and the fuel left uncovered for a sustained
period. Studies reveal that such an event would be extremely unlikely
to occur by accident. To supplement the existing body of work on the
safety and security of spent fuel, NRC has commissioned additional
studies to address technical uncertainties and respond to heightened
security concerns.
While NRC and DOE have found that spent fuel may be relatively safe and
secure, DOE could potentially enhance the security of this fuel through
options such as minimizing the overall number of shipments and picking
up fuel in an order that would reduce risk, such as moving older, less
dangerous fuel first. DOE's ability to choose some of these options may
be limited by its contracts with the fuel owners. These contracts
generally require DOE to pick up increments of spent fuel based on the
dates that the owners removed these amounts of fuel from their nuclear
power reactors. Taken literally, the contracts would require DOE to
pick up small amounts of spent fuel at reactor sites scattered across
the country. For example, adhering to the shipping queue for the 12
largest nuclear power utilities would result in roughly 576 shipments.
In contrast, revising the contracts to allow DOE to pick up larger
quantities of fuel at each site could eliminate about 300 of
the shipments. The order in which spent fuel is shipped could also
affect safety and security because certain fuel poses more risks based
on its age and location. For example, shipping the oldest fuel first
could enhance security in transit because this fuel is relatively less
radiologically dangerous. However, DOE cannot unilaterally mandate this
approach because the contracts allow the fuel owners to decide, once
their turn in the shipping queue arrives, which increments of fuel from
which of their nuclear plants will actually be shipped. Under
contracts, owners could decide, based on operational needs, to ship
younger, more radioactive fuel out of wet storage pools first before
shipping fuel from dry storage--this choice could allow a fuel owner to
free up needed space in a storage pool. We are recommending that, as
DOE develops its plans for transporting spent fuel to Yucca Mountain,
it identify and assess potential options to enhance the safety and
security of this fuel. Exercising any of these options may require
renegotiating aspects of its shipping contracts with fuel owners if
necessary.
We provided a draft of this report to DOE and NRC for review and
comment. These agencies generally concurred with the facts of the
report. DOE noted that the information on transit was accurate and
balanced, and concurred with our recommendation with one exception. DOE
noted that the Department of Transportation is conducting a study of
the safety and security implications of transporting spent fuel by
railroad trains that haul only spent fuel. DOE explained that it would
prefer to wait for the outcome of this evaluation rather than duplicate
efforts. NRC noted that, overall, the report provides a reasonable
characterization of the current understanding of risks associated with
spent fuel storage. NRC raised concerns about our references to two NRC
studies in our report. NRC expressed concern that we needed to further
emphasize NRC's use of conservative assumptions in these two reports,
such as the assumption that a fire in a spent fuel pool would involve
100 percent of the spent fuel assemblies in a pool. We revised the
report to account for these concerns and added preliminary results from
NRC's ongoing work involving risks associated with spent fuel pools.
Background:
Fuel for nuclear power plants consists of fingernail-sized pellets of
uranium dioxide, a radioactive compound. The pellets are fitted into
hollow metal rods, typically constructed of zirconium alloy, and the
rods are then gas pressurized. The rods are generally 12 to 14 feet in
length and are bundled together into assemblies. A portion of the
assemblies must be replaced every 1 to 2 years as the fuel in the
reactor expends energy, becoming less efficient at producing heat. As
part of the process of expending energy during a nuclear reaction, the
fuel becomes highly radioactive and thermally hot. Spent fuel emits
radiation as a consequence of radioactive decay. Barriers such as thick
walls, sealed containers, and water are used to shield individuals from
exposure to this radiation.
NRC regulates not only the construction and operation of commercial
nuclear power plants but also the storage, transportation (together
with the Department of Transportation), and disposal of spent fuel. NRC
requires each operating nuclear power plant to have safety and security
programs. For example, NRC requires protective shielding and security
systems, including armed guards, at nuclear power plants. When spent
fuel assemblies are removed from a reactor, they are stored in large
pools of cooling water. These pools are constructed according to NRC's
requirements, typically with 4-to 6-foot thick steel-lined concrete
walls and floors. Pools are typically 30 to 60 feet long, 20 to 40 feet
wide, and 40 feet deep. The location of these pools is dependent on the
type of reactor. Essentially, all commercial power reactors in the
United States are one of two types, either a boiling water reactor or a
pressurized water reactor.[Footnote 1] For most boiling water reactors,
the pools are located close to the reactors, several stories above
ground. For pressurized water reactors, the pools are located in
structures outside the reactor building, on the ground or partially
embedded in the ground. Regardless of reactor type, these pools are
required by NRC to be constructed to protect public health against
radiation exposure, even after a natural disaster, such as an
earthquake. The water in the pool is constantly cooled and circulated,
and the fuel assemblies are generally 20 feet below the surface of the
water.
In 1982, through the Nuclear Waste Policy Act, the Congress directed
DOE to construct an underground repository for disposal of spent fuel
and other high-level radioactive waste.[Footnote 2] The Congress
amended the act in 1987 and required DOE to only consider Yucca
Mountain, Nevada, as a potential site for a repository.[Footnote 3] In
2002, the President recommended to the Congress, and the Congress
approved, Yucca Mountain as a suitable site for the development of a
permanent high-level waste repository. As we reported in 2001, for a
variety of reasons, DOE is unlikely to open the repository as planned
in 2010.[Footnote 4]
Lacking a long-term disposal option now, some nuclear utilities must
move a portion of their spent fuel into dry storage or face shutting
down their plants because their wet pools are reaching capacity.
Currently, 25 of the 72 storage sites use dry storage, and 11
other sites have plans to move some of their inventory of spent fuel
into dry storage. Dry storage facilities for spent fuel typically
consist of steel containers that are placed inside concrete vaults or
bunkers where the fuel is cooled by air rather than water. These
storage systems are required by NRC to be capable of protecting against
radiation exposure and of surviving natural disasters. Because the move
to dry storage is time-consuming and expensive, utilities are, wherever
possible, modifying wet pool storage capacity so they can store larger
quantities of spent fuel in these pools.
Figure 1: Locations for Wet and Dry Storage Sites for Commercial Spent
Nuclear Fuel and Yucca Mountain, as of April 2003:
[See PDF for image]
[End of figure]
To expose a large number of people to the harmful effects of radiation
from spent fuel, the fuel would have to be released from its protective
containers and dispersed over a wide or densely populated area.
However, unlike many other hazardous materials, spent fuel is a hard,
heavy ceramic material that is neither explosive nor volatile.[Footnote
5] To achieve a wide dispersal, some portion of the spent fuel
assemblies would have to be pulverized into small particles by an
external force--such as a high-speed impact or a violent explosion--or
some portion of the spent fuel assemblies would have to burn in a
sustained, high-temperature fire. According to NRC, the redundancy and
robustness of the designs of the fuel containers make wide dispersal
highly unlikely. In the event of a dispersal, the most significant
health effects would involve persons who inhaled very small
(respirable) particles--10 microns or less in diameter.[Footnote 6]
Such particles would be absorbed into the body and possibly remain
there for many years. In addition, these particles could be deposited
on buildings and the ground where, in the absence of a costly cleanup
effort, they could expose people to elevated levels of radiation.
The transportation of spent fuel to Yucca Mountain--most likely by both
truck and rail, but with a preference for using mostly rail--will be a
major undertaking, spanning 20 to 30 years.[Footnote 7] According to
DOE, more than 50,000 tons of the spent fuel have accumulated at
72 sites in 33 states, many located near urban areas in the Midwest and
the East. DOE has estimated that the accumulated inventory will have
grown to 69,000 tons by 2010 and that moving this volume could require
approximately 175 shipments per year over 24 years, relying on a
combination of truck and rail shipments.
For the transportation of spent fuel, NRC has certification and
inspection requirements for shipping containers to ensure that the
containers protect against radioactive releases under accident
scenarios. NRC has certified a number of shipping container designs for
use on trucks and rail. The Nuclear Waste Policy Act of 1982, as
amended, requires DOE to ship spent nuclear fuel and high-level
radioactive waste to Yucca Mountain in containers that have been
certified by NRC. The act also requires DOE to notify NRC in advance of
spent fuel and high-level radioactive waste shipments.
In addition to NRC, the Department of Transportation plays a role in
regulating the transportation of spent fuel and other high-level waste.
The department's Research and Special Programs Administration sets
certain safety standards for the transportation of hazardous materials,
including spent fuel. These standards include, among other things,
documentation and labeling of containers, including placards
identifying the shipment, and requirements for separating certain
radioactive materials while in transit. The Federal Motor Carrier
Safety Administration oversees the safety of shipments by highway, and
the Federal Railroad Administration oversees the safety of shipments by
rail. The U.S. Coast Guard oversees the safety of shipments that may be
made by barge.
Likelihood of Widespread Harm from Terrorist Attacks or Severe
Accidents Involving Spent Fuel Is Low:
Studies conducted by NRC and DOE have consistently found that the
likelihood of widespread harm to human health from a terrorist attack
or a severe accident involving spent fuel is very low. None of the
studies involving the transportation of spent fuel or dry storage of
spent fuel identified a scenario resulting in widespread harm--largely
because of the protective containers required by NRC. For example,
these studies repeatedly found that transportation containers would be
very difficult to penetrate, and in the worst-case scenarios where they
may be penetrated, only a small fraction of the material would be
released. Some studies involving spent fuel stored in pools of water
found that widespread harm is possible under severe but unlikely
accident conditions. Such conditions may include a catastrophic
earthquake or a severe but unlikely accident that could uncover the
fuel for several hours, possibly allowing it to spontaneously ignite
and scatter radioactive material over a wide area. To respond to
increased security concerns stemming from the September 11, 2001,
terrorist attacks, NRC is further studying the safety and security of
spent fuel in transit and in wet or dry storage, including
the potential effects of more extreme attack scenarios such as
deliberate aircraft crashes.
Shipping Containers Protect against Widespread Release of Fuel
in Transit:
Since the late 1970s, federal studies have examined the effects of both
terrorist acts of sabotage and severe accidents involving shipping
containers for spent fuel. Sabotage studies have sought to determine
whether radioactive material could be released from shipping containers
in specific sabotage scenarios, while accident studies have assessed
whether radioactive material could be released in a variety of
accidents, and the overall probability of their occurrence. Some of
these studies were commissioned by NRC, and others by DOE, and many of
them were conducted through DOE's Sandia National Laboratory and other
DOE laboratories. These studies collectively indicate that the
construction of the shipping containers helps to limit
releases.[Footnote 8] Although NRC is confident in these results, it is
sponsoring assessments to further validate computer models and address
heightened security concerns.
Sabotage Studies:
The most recent sabotage study--conducted by DOE's Sandia National
Laboratory for DOE in 1999--estimated the amounts and characteristics
of releases of radioactive materials from truck and rail spent fuel
containers subjected to two different types of weapons.[Footnote 9] The
results of this study confirmed the findings of earlier studies that
armor-piercing weapons could penetrate shipping containers and release
small quantities of radioactive material. The study found that, under a
worst-case scenario, the weapon could penetrate a shipping container
and release a small amount of material--equal to about 0.016 of
1 percent of the spent fuel in the container--as small, respirable
particles. These small, respirable particles could become airborne and
spread beyond the immediate vicinity of the attack.[Footnote 10]
A subsequent DOE-sponsored report used the results of the 1999 Sandia
National Laboratory study to estimate the human health impact of the
most severe release.[Footnote 11] Using a computer-based analytic model
and conservative assumptions, DOE's contractor found that the predicted
release from a truck container would cause about 48 cancer deaths over
the long term and that a predicted release from a rail container would
cause about 9 cancer deaths over the long term.[Footnote 12] DOE's
contractor's analysis explained that these cancer deaths should be
considered against a backdrop of an expected 1.1 million cancer deaths
among the same population expected from other causes. This analysis
assumed that the release would occur in an urban area with a population
projected to the year 2035 under stable weather conditions. The
analysis also assumed that the spent fuel release would contain twice
the radioactive content of a typical spent fuel shipment and that there
would be no evacuation or cleanup of the affected area for 1 year after
the incident.[Footnote 13]
These studies are the most recent in a series of studies dating back to
the 1970s. According to NRC and DOE officials, confidence in the
results of these studies has increased significantly as better data and
more sophisticated analytic techniques have been used. Appendix II
contains a fuller description of the methodology of these recent
studies and the results of previous studies.
Accident Studies:
Since the 1970s NRC has also sponsored a series of studies examining
the risk that spent fuel could be released during transportation
accidents. NRC's most recent assessment of spent fuel transportation
accident risks was conducted for NRC by Sandia National Laboratory and
was published in 2000.[Footnote 14] The 2000 Sandia National Laboratory
study, like preceding accident studies, found that an accidental
release of spent fuel in transit is very unlikely and that significant
human health impacts are even less likely. The study estimated that in
over 99.9 percent of all truck and rail accidents, the shipping
container would experience no significant damage, and no radioactive
material would be released. In fact, the analysis found that only 7 in
100,000 (0.007 of 1 percent) truck accidents and 4 in 100,000 (0.004 of
1 percent) rail accidents would involve spent fuel casks in impacts or
fires that might cause a release of radioactive material. While this
study did not project the human health impacts of particular accident
scenarios, it concluded that the overall risk of human exposure to
accidental releases of spent fuel was far less than that estimated in
the 1977 study, which confirmed that NRC's safety and security
regulations then in place were adequate.
A subsequent DOE-sponsored study used the results of the 2000 Sandia
National Laboratory study to determine the potential health effects of
the estimated quantity of material released.[Footnote 15] DOE's
contractor used the estimated amount of material released in what DOE
determined as the most severe reasonably foreseeable accident to
estimate the number of latent cancer fatalities that could result from
severe accidents while shipping spent fuel to the Yucca Mountain
repository.[Footnote 16] From this study, DOE concluded that this type
of accident--having a probability of occurring about 2.8 times in 10
million accidents per year--could cause about 5 long-term latent cancer
fatalities--far less than its estimate of 48 latent cancer deaths in
the event of a successful sabotage attack with armor-piercing weaponry.
Apart from this type accident, DOE found that the probability of any
deaths due to an accidental release of radiation was quite small. DOE's
final environmental impact statement for Yucca Mountain projected that
accidents over 24 years of shipping would cause fewer than 0.001 latent
cancer fatalities. In contrast, DOE projected that these same shipments
had a much greater probability of resulting in deaths due to normal
traffic accidents--between 2.3 and 4.9 traffic fatalities over the same
24-year period.
As with the sabotage studies, these studies of accident scenarios are
the most recent in a series of studies dating back to the 1970s.
According to NRC and DOE officials, confidence in the results of these
studies has increased significantly as better data and more
sophisticated analytic techniques have been used. Appendix II contains
a fuller description of the methodology of these recent studies and the
results of previous studies.
Ongoing and Planned Assessments:
Although NRC believes that the results of the federally sponsored
studies are valid, it has several evaluations ongoing and planned to
further assess its security and safety measures. To assess its existing
security measures following the September 11, 2001, terrorist attacks,
NRC initiated a commissionwide review. As part of this review, NRC
commissioned Sandia National Laboratory to examine more severe
terrorist attack scenarios involving spent fuel shipping containers.
For example, the laboratory will assess the effects of (1) a 20-
passenger aircraft loaded with explosives crashing into shipping
containers and (2) a sustained attack on these containers using a
variety of weapons in combination.
As part of an ongoing process to assess its safety measures, NRC has a
number of ongoing and planned studies. NRC commissioned Sandia National
Laboratory for further validation of computer models used to evaluate
the safety of shipping containers. To solicit comments on the scope of
its evaluation, NRC held a series of public meetings beginning in 1999.
It considered comments obtained during these meetings and issued an
interim report in 2002 that recommended several additional
studies.[Footnote 17] Although these studies are still being designed,
their preliminary objectives include (1) validating past computer-
based predictions of damage to containers resulting from collisions,
(2) validating past computer-based predictions of how well containers
withstand fires, and (3) identifying the response of fuel pellets, fuel
rods, and fuel assemblies in severe impacts. In contrast to past
analyses of severe accident scenarios, the studies are to include
physical tests of full-scale current model shipping containers. The
results of these physical tests will be compared to the predictions of
past computer-based analyses and serve to either validate or to correct
those results. The studies are also to address some of the technical
issues that were not adequately addressed by past accident analyses.
For example, while past studies relied on expert judgment to assess the
complex chain of variables involved in releasing respirable spent fuel
from containers--including fracturing spent fuel rods and pellets--the
planned studies will examine these events experimentally. According to
NRC officials, the studies are expected to be completed by 2006.
Widespread Release from Wet Storage Theoretically Possible
but Unlikely:
NRC studies have reported that a risk of widespread harm to human
health from spent fuel arises from the remote possibility of a
sustained loss of coolant in a spent fuel pool. Such a loss could
potentially lead to a fire that would disperse radioactive material
across a wide area. NRC's most recent published study of this risk,
released in 2001, found that, though the potential consequences of such
a fire could be severe--nearly 200 early fatalities and thousands of
latent cancer fatalities--the likelihood of such a fire is
low.[Footnote 18] The study estimated that a catastrophic earthquake or
a severe but unlikely accident, such as dropping a 100-to 150-ton
storage container into the pool, could precipitate a pool fire.
The study was conducted to assess the risks associated with accidents
at nuclear reactors that have been permanently shut down. According to
NRC, once the fuel is removed from the reactors, there is a risk
associated with the fuel stored in pools. NRC designed the study with
conservative assumptions to identify the most severe possible impact on
public health. The study assessed a variety of natural disasters and
accidents that could drain coolant and cause a fire. These events
included loss of electrical power, which would shut down the pool
cooling system; an event that would significantly damage the pool
cooling system; a drop of a heavy load, which could damage the pool
wall or floor; a severe earthquake; and an accidental aircraft crash.
The study found that a catastrophic earthquake and a heavy load drop
were the events most likely to significantly damage the pool, leading
to sustained loss of coolant and potentially causing a fire.
The study then calculated the amount of radioactive material that might
be released by a fire and the possible human health effects stemming
from exposure to this material. In making these calculations, the study
made various conservative assumptions to ensure that NRC identified the
most severe consequences possible. For example, the study assumed that
a pool fire would involve 100 percent of the spent fuel assemblies in
the pool, releasing large amounts of radioactive material into the
atmosphere. Two of the authors of the study noted that it was not
certain how many spent fuel assemblies would actually burn in a fire.
The uncertainty in the amount of radioactive material released depends
on the fuel age and distribution in the pool and the characteristics of
the accident scenario. The authors noted that some spent fuel
assemblies might not reach the high temperatures required to burn and
that some of the radioactive material might remain trapped in the pool
or building. Because spent fuel decays and thus becomes less dangerous
over time, the study evaluated scenarios in which the reactor had been
shut down for 30 days, 90 days, 1 year, 2 years, 5 years, and 10 years.
For each scenario, the study evaluated two levels of radioactivity
released from the fuel. NRC used the results of this study to calculate
the potential health effects of a fire in a spent fuel pool. These
results are shown in table 1.
Table 1: Potential Health Effects of Fire in a Spent Fuel Pool:
Time after shutdown of reactor: 30 days; Lower level of
radioactivity[A]: Number of early fatalities: 2; Lower level of
radioactivity[A]: Number of latent cancer fatalities: 3,500;
Higher level of radioactivity[A]: Number of early fatalities: 200;
Higher level of radioactivity[A]: Number of latent cancer fatalities:
15,000.
Time after shutdown of reactor: 1 year; Lower level of
radioactivity[A]: Number of early fatalities: 1; Lower level of
radioactivity[A]: Number of latent cancer fatalities: [B];
Higher level of radioactivity[A]: Number of early fatalities: 80;
Higher level of radioactivity[A]: Number of latent cancer fatalities:
[B].
Time after shutdown of reactor: 5 years; Lower level of
radioactivity[A]: Number of early fatalities: 0; Lower level of
radioactivity[A]: Number of latent cancer fatalities: [B];
Higher level of radioactivity[A]: Number of early fatalities: 1; Higher
level of radioactivity[A]: Number of latent cancer fatalities: [B].
Time after shutdown of reactor: 10 years; Lower level of
radioactivity[A]: Number of early fatalities: 0; Lower level of
radioactivity[A]: Number of latent cancer fatalities: [B];
Higher level of radioactivity[A]: Number of early fatalities: 0; Higher
level of radioactivity[A]: Number of latent cancer fatalities: 7,500.
Source: NRC.
[A] NRC assumed a low level and a high level of ruthenium in the
dispersed spent fuel. Ruthenium, found in higher levels in recently
discharged fuel, is a particularly lethal isotope when dispersed in
small particles.
[B] Information not available.
[End of table]
The study noted that the results are based on a natural disaster or an
accident severe enough to lead to a pool fire and that the risk of such
an event occurring is very low. NRC also noted that part of the reason
for the low probability is NRC's defense-in-depth policy, which states
that NRC establishes requirements to ensure that safety will not be
wholly dependent on any single system. Instead, NRC's requirements
ensure multiple or redundant safety systems. In the case of the storage
pool studied in the 2001 report, NRC noted that several factors combine
to make a pool fire unlikely, including the robust design of the pool;
the simple nature of the pool support systems; and the long time
required to heat up the fuel, which allows time for operators to
respond.[Footnote 19] For example, according to the 2001 report,
heating the least-decayed spent fuel to the ignition point--were it to
occur at all--would take hours, perhaps even days. Thus, NRC officials
explained that even if a massive loss of coolant occurred, plant
operators might still have time to react, depending on the extent of
the damage. NRC requires that nuclear power plants have a backup water
supply that can cool fuel in case of an accident, so, depending on the
extent of damage, plant operators might be able to keep the fuel
submerged.
The risk of a pool fire is also limited by the ability of some of the
fuel to be cooled by simple air ventilation if the coolant drains out.
According to NRC, completely draining a pool may allow enough air
ventilation among the stored fuel assemblies so that the spent fuel
would stay below the ignition point of a self-sustaining fire (about
1,650 degrees Fahrenheit). Furthermore, even if a fire did begin in one
assembly, there is considerable uncertainty about whether the fire
would spread to other assemblies. A 1987 study of spent fuel pools
found that spent fuel in pools with fewer assemblies, after being
cooled for just a few weeks, would not ignite if subjected to loss of
coolant.[Footnote 20] Under the dense storage conditions characterized
by most spent fuel pools today, however, air ventilation becomes less
effective.
NRC Continues to Study the Risks of Storing Spent Fuel in Pools:
To begin addressing some of the uncertainties regarding the risks of
storing spent fuel in wet storage pools, NRC has some ongoing work, and
recently completed some initial evaluations of sabotage attacks on
these pools, and has more work planned and ongoing at two DOE national
laboratories. Following the terrorist attacks of September 11, 2001,
NRC commissioned the U.S. Army Corps of Engineers to examine potential
effects of sabotage directed at spent fuel pools. The Corps conducted
several computer-based analyses of the potential effects of armor-
piercing weapons and high explosives on typical spent fuel pools. The
analyses found that the penetration of armor-piercing weapons and high
explosives could vary considerably, depending, among other things, on
the size of the weapon or explosive and the sophistication of the
attacker.
NRC is also conducting studies with less conservative assumptions to
more realistically evaluate the risks of spent fuel in a drained pool.
NRC has contracted with Argonne National Laboratory to study the
conditions necessary to ignite a pool fire. NRC has also contracted
with Sandia National Laboratory for a series of studies to define
potential threats, and to identify potential vulnerabilities,
regulatory improvements or legislative initiatives to improve security
and safety and better protect public health. The studies by Sandia
National Laboratory include a review of a variety of terrorist
scenarios, including attacks on fuel pools with aircraft and high
explosives. According to NRC, preliminary results of these studies
indicate that spent fuel may be more easily cooled than has been
predicted in some past studies and that off-site radiological releases
may be substantially reduced from previous worst-case estimates.
Predicted public health effects might also be substantially reduced for
the worst scenarios where coolant is lost and recovery actions are not
successful in cooling the fuel.
Dry Storage Containers Safeguard against Widespread Release:
Dry storage containers, like shipping containers, pose a considerable
barrier to releasing spent fuel. Used to store spent fuel when it is
removed from wet storage, dry storage containers are constructed of
layers of steel and radiation barriers such as concrete.[Footnote 21]
In establishing regulations for dry storage of spent fuel, NRC stated
in 1998 that dry storage containers are structurally similar to
shipping containers and that the results of sabotage studies on
shipping containers could reasonably be applied to dry storage
containers. Nevertheless, NRC is continuing to study potential risks of
releases from dry storage containers.
Studies by DOE and the Corps on dry storage containers have generally
reached the same conclusion--that the thick walls of the containers,
consisting of an inner steel container and an outer steel or concrete
container, could not be penetrated by airplane crashes and would result
in no significant release of radiation when attacked with advanced
weapons. Two DOE-sponsored reports, released in 1998 and 2001, found
that airplane crashes would not penetrate dry storage
containers.[Footnote 22] The reports focused on the most penetrating
components of the commercial jet aircraft: the engines and landing
gear. Both reports concluded that although airplane crashes could
damage the containers, no radioactive material would be released. The
analysis showed that the containers would break up the airplane,
spreading jet fuel over a wide area, causing the jet fuel to dissipate
or burn without affecting the spent fuel in the containers.
Two other studies, performed in 2001 by the Corps, found that the
containers would not release significant amounts of radioactive
material when attacked by armor-piercing weapons or high explosives.
The study examining the effect of armor-piercing weapons found that the
penetration to the containers was very limited. NRC and DOE officials
and independent experts told us that, based on a previous analysis and
similar studies involving shipping containers, the weapons would not
likely cause a significant release. The study examining the effects of
high explosives found that the explosives would not completely
penetrate the container. The study showed extensive exterior damage,
but no penetration to the spent fuel.
NRC Continues to Study Risks to Dry Storage Containers:
NRC is continuing to study potential risks to dry storage. NRC has
contracted with Sandia National Laboratory to assess the vulnerability
of dry storage containers to terrorist attacks, including a further
analysis of aircraft crashes and the effects of high explosives. In
addition, the laboratory will investigate measures to mitigate any
vulnerability identified through the assessment.
Options May Exist to Further Enhance Security and Safety:
As DOE develops its plans for shipping spent fuel to the Yucca Mountain
repository, the agency has several potential options for enhancing the
security of spent fuel during the Yucca Mountain shipping campaign.
Specifically, DOE could potentially minimize its total number of spent
fuel shipments, ship the fuel in an order that reduces risk, or
transport the fuel on railroad trains dedicated exclusively to hauling
spent fuel. Not all of these options may be feasible under the terms of
DOE's contracts with spent fuel owners, and some options for shipping
in a particular order would conflict with one another.
Minimizing Number of Shipments:
DOE could enhance the overall security of spent fuel by minimizing the
total number of shipments. Fewer shipments would present fewer
potential targets for terrorists and could also enhance safety because
there would be fewer chances for an accident. Representatives of the
nuclear power industry and nuclear safety experts that we contacted
agreed on these points. For example, a representative of a consortium
of nuclear utilities told us that shipping spent fuel by rail is
preferable to shipment by truck because spent fuel containers designed
for rail can carry about 5 times more spent fuel than truck containers.
This larger capacity translates to fewer shipments overall. Similarly,
a frequent critic of the safety of spent fuel shipments agreed that
fewer shipments would be better, noting that fewer, large shipments are
easier to protect and track. Beyond expressing a preference for
shipping spent fuel to Yucca Mountain mostly by rail, DOE has not yet
developed its plans to implement the shipping campaign.
In addition to providing security advantages, minimizing the number
of shipments by using rail provides safety and efficiency benefits.
According to a 1998 Department of Transportation report, rail was the
safer mode for shipping large amounts of spent fuel.[Footnote 23] The
report states that minimizing trips usually reduces total risk by
reducing risks associated with routine radiation exposure--such as the
incidental exposure experienced by transportation and plant workers
while shipping containers are being prepared--as well as accident-
related exposure and other nonradiation accident consequences.
DOE's ability to minimize the total number of shipments may be limited
by its contracts with owners of spent fuel. Under the contracts, DOE is
to establish a shipping queue, in which each utility has shipping
rights based on the date and quantity of fuel removed from a reactor.
In many cases, the places in the queue correspond to quantities of
spent fuel that would fill less than three large rail containers--an
amount that, according to the Association of American Railroads, would
be a reasonable size for a single rail shipment. If strictly followed,
the queue could result in many more shipments than necessary. For
example, the 12 spent fuel owners with the largest quantities of spent
fuel would make approximately 576 shipments based on the shipping
queue.[Footnote 24] On the other hand, if these 12 owners consolidated
all their shipments into rail containers and used 3 containers per
shipment, they could reduce their total shipments to 479, a 17 percent
reduction. If these same owners consolidated shipments into 5 rail
containers per shipment, which according to DOE is another possible
option, total shipments could be reduced to 287--a nearly 50 percent
reduction.
Order in Which Spent Fuel Is Shipped Could Enhance Security:
DOE could also enhance security by shipping spent fuel in an order
that minimizes risk. There are at least three shipping orders that
would potentially reduce risk: (1) shipping fuel from shutdown nuclear
reactors first, reducing the number of sites storing spent fuel;
(2) shipping the oldest and least radiologically dangerous fuel first
to reduce transportation risk; or (3) shipping fuel from storage pools
first, reducing the likelihood of a pool fire. Shipping fuel first from
shutdown nuclear reactors would be permissible under DOE's contracts
with fuel owners, but the contracts might preclude the other two
options. Further, to some extent, these options conflict with one
another. For example, an emphasis on shipping fuel from spent fuel
pools first could leave some older fuel in dry storage at current
storage facilities. Data are not available to determine which order
would provide the greatest risk reduction.
Shipping Fuel from Shutdown Reactor Sites First:
DOE could potentially enhance the overall security of spent fuel by
first shipping fuel currently stored at shutdown nuclear reactor sites.
Currently, about 4,100 tons of spent fuel--about 8 percent of the total
stored nationwide--are stored at 14 shutdown nuclear reactors.[Footnote
25] Because nine of these sites will not be accumulating additional
spent fuel, clearing their spent fuel inventory would eliminate them as
potential targets of a terrorist attack.[Footnote 26]
DOE recognized the potential importance of removing spent fuel from
shutdown reactors when it established its contracts for disposal of
spent fuel. Although the contracts establish a shipping queue, the
contracts allow DOE to override the queue to make an exception for
spent fuel from shutdown reactors. Specifically, the contracts provide
that, notwithstanding the age of spent fuel, priority may be accorded
any spent fuel removed from a civilian nuclear power reactor that has
reached the end of its useful life or has been shut down for whatever
reason.
Shipping Oldest Fuel First:
DOE could lower the risk of transporting spent fuel by shipping the
oldest spent fuel first. Radioactivity emitted by some components of
spent fuel declines significantly over comparatively short periods of
time.[Footnote 27] For example, one of the more radioactive elements in
spent fuel--cobalt60--accounts for about 90 percent of the gamma
radiation emitted by spent fuel when it is first removed from the
reactor.[Footnote 28] However, after about 25 years, cobalt60 emits
about 3 percent of the gamma radiation it did when first removed from
the reactor. Similarly, the radioactivity of cesium137, a comparatively
volatile element that would be a major component of any accidental or
deliberate release, declines by half after 30 years. Shipping older
spent fuel first could therefore be preferable in the event of a
deliberate or accidental release during transit. For example, a release
of spent fuel that is 25 or 30 years old would be a lesser--though
still significant--threat to public health than fuel that is only 5 or
10 years old.
Analyses performed for DOE's environmental impact statement for the
Yucca Mountain repository illustrate the reduced impact that a release
of older spent fuel can have on public health. In the draft
environmental impact statement, DOE estimated that a particular release
due to a sabotage attack could result in about 16 latent cancer
fatalities. This scenario assumed that the shipped fuel was about
23 years old, which is approximately the average age of the inventory
of spent fuel. The final environmental impact statement analyzed the
same scenario, except that it assumed that the shipped fuel was about
15 years old. This analysis found that such a release would cause about
48 latent cancer deaths--3 times as many as the older fuel. The age of
the fuel was one of two major factors that resulted in the higher
estimate of latent cancer fatalities in the final statement. DOE noted
that the younger, more dangerous fuel, such as spent fuel discharged
5 years or less from a reactor, makes up a small percentage of the
total inventory of spent fuel. As a result, the youngest, hottest fuel
would be less likely to be shipped or would represent a small fraction
of the fuel that is shipped.
In discussions on security and safety issues surrounding the proposed
shipment of fuel to Yucca Mountain, some state and industry
representatives that we contacted also acknowledged the benefits of
shipping older spent fuel first. An analyst under contract with the
state of Nevada noted that shipping the oldest fuel first would be the
most important factor in protecting public health during transit. Not
only would older fuel have lower consequences if released in an
accident or a terrorist event, but it also would be safer for
transportation workers--drivers and handlers at intermodal transfer
points--and the general public. A representative of the National
Research Council's Board on Radioactive Waste Management told us that
shipping the oldest fuel first would help minimize potential human
health consequences in the event of a release during transit. However,
this representative said that if one assumes that the robust shipping
containers make a release unlikely, the potential risk reduction
associated with the age of the fuel becomes less important.
Regardless of the potential transportation-related security benefits,
DOE's contracts with spent fuel owners limit its ability to ship the
oldest fuel first. In addition to establishing a shipping queue, the
contracts allow each fuel owner discretion to decide which of its spent
fuel is actually delivered to DOE, commensurate with the quantity of
fuel associated with a particular spot in the queue. For example, the
Exelon company--the nation's largest nuclear power company--has a place
in the queue for about 35 tons of spent fuel removed from a reactor
located at its plant in Zion, Illinois. When the time comes to ship
this fuel to the repository, Exelon may deliver either this fuel or an
equal quantity of fuel--possibly much younger and more radioactive
fuel--from any of its facilities located at sites in Illinois and sites
in Pennsylvania and New Jersey.
Because owners have discretion to choose which fuel they will actually
ship under the terms of the contract, DOE does not have the ability
under the contract to require that oldest fuel be shipped first. Fuel
owners will likely select spent fuel for shipment based on their
operational needs. For example, representatives of Progress Energy, a
fuel owner with reactors in the Southeast, said they would will likely
ship from their pools first because their pools are reaching capacity.
Similarly, an Exelon official said that shipping from pools first would
minimize the need for dry storage facilities.
Shipping Fuel from Densely Packed Pools First:
As discussed in the first section of this report, a fire in a wet
storage pool, while highly unlikely, is theoretically possible.
Shipping spent fuel from densely packed spent fuel pools first could
have security benefits. Because DOE has not yet opened a permanent
repository, spent fuel has accumulated in quantities that pools were
not originally designed to contain. NRC officials noted that while a
few spent fuel pools have low density in at least part of the pools,
nearly all pools are densely packed. These densely packed pools contain
as much as 3.5 times more spent fuel on average than the pools were
originally designed to store. Reducing the density of spent fuel in the
pools would reduce the likelihood of a fire. Recent NRC and independent
studies show that lower-density configurations allow for greater
spacing between assemblies, which allows air to more efficiently
circulate in the event of coolant loss. According to these reports,
greater spacing could also help prevent a fire from spreading among
assemblies. Also, in the unlikely event of a fire, fewer assemblies in
the pool could result in reduced consequences.
As noted earlier, DOE's contracts limit its ability to influence the
order in which spent fuel is shipped. Some owners may prefer to ship
fuel from densely packed pools first because when the pools reach full
capacity, the fuel must be removed or the plant must shut down. To the
extent that, as Exelon and Progress Energy officials stated, utilities
are likely to ship from their wet pools first, the threat would be
reduced earliest at these pools. This would, however, result in a
relatively higher threat during transport from relatively younger, more
radioactive, spent fuel. It is not clear whether this will be a common
preference.
Shipping Fuel on Trains That Haul Only Spent Fuel:
According to some analysts, DOE could enhance the security of spent
fuel shipments by using trains dedicated to carrying only spent fuel.
Such trains would typically consist of three to five rail cars,
carrying one container of spent fuel per car. A truck shipment can
carry 1 to 2 tons of spent fuel. In contrast, depending on the
containers used, a 3-car train can carry from 50 to 65 tons of spent
fuel and a 5-car train can carry from about 80 to 110 tons of spent
fuel. Although dedicated trains could enhance the security and safety
of spent fuel shipments, these benefits would have to be weighed
against potential drawbacks. The benefits would also have to be weighed
against constructing a rail line to Yucca Mountain. Currently, no rail
line extends to Yucca Mountain.
Advocates of dedicated trains told us that such trains offer two
primary security and safety advantages. First, the use of dedicated
trains would significantly reduce the exposure of spent fuel shipments
to a terrorist attack by significantly shortening the trip duration
from its point of origin to the repository. A representative of the
Association of American Railroads, which recommended that DOE use
dedicated trains for the shipment of spent fuel, explained that a spent
fuel shipment from the East Coast to Nevada would take about 3 to
4 days by dedicated rail, while the same trip by regular rail would
take about 8 to 10 days. Specifically, spent fuel transported by
regular rail would spend significant amounts of time in rail yards
where trains are broken up and reconfigured. While in the rail yards,
spent fuel containers could be stationary targets.
Second, using dedicated trains would ensure that spent fuel was not
shipped with flammable hazardous materials. If spent fuel were released
from its containers in an accident or a terrorist attack, a fire fueled
by flammable materials could spread radioactive material over a wide
area. For example, NRC recently issued an analysis regarding a rail
tunnel fire that occurred in Baltimore in July 2001 that involved more
than 28,000 gallons of a flammable solvent. NRC estimated that
temperatures as high as 1,800 degrees Fahrenheit were reached at
certain locations in the tunnel during the course of the fire but found
that temperatures averaged 900 degrees in other parts of the fire. NRC
studied the potential effects of this fire on a spent fuel
transportation container carrying spent fuel and concluded that, when
subjected to similar fire conditions, the container would not release
radioactive material.[Footnote 29]
According to transportation officials we spoke to, dedicated trains can
also have safety and other benefits beyond sabotage prevention. For
example, officials of the Union Pacific Railroad and the Association of
American Railroads said that combining cars carrying fully loaded spent
fuel containers on trains with those carrying other cargo raises
operational and safety issues. Rail cars carrying spent fuel rail
containers are extraordinarily heavy--such a car weighs about
470,000 pounds compared to about 200,000 pounds for a standard loaded
rail car. This weight differential introduces difficulties in the
physical dynamics of a train carrying spent fuel and other cargo,
making derailments more likely.
On the other hand, it is not clear that the advantages of dedicated
trains outweigh the additional costs. In 1980, while considering
amendments to its security regulations, NRC examined the case for
requiring dedicated trains for rail shipments of spent fuel. NRC noted
the advantages of dedicated trains but also noted that dedicated trains
are no more capable of avoiding high-population areas than are regular
trains, that a regular train in a rail yard would be under surveillance
by escorts and railroad police, and that the necessary physical
protection measures can be as easily implemented on regular trains as
on dedicated trains. For these and other considerations, NRC declined
to require dedicated trains. Further, although DOE recognized the
possible advantages of shipping spent nuclear fuel by dedicated trains,
DOE also concluded in its final environmental impact statement that
available information does not indicate a clear advantage for the use
of either dedicated trains or general freight service.
Conclusions:
The events of September 11, 2001, elevated lingering public concerns
about the security of spent fuel, and in particular the security and
safety of large-scale shipping of spent fuel. NRC and DOE studies show
a low likelihood of widespread harm to human health from terrorist
attacks or severe accidents involving spent fuel. Nonetheless, DOE
could potentially take a number of measures to further enhance the
security and safety of the shipping campaign to Yucca Mountain. It is
not clear whether the additional security and safety benefits such
measures offer are worth the additional costs and effort--possibly
including a renegotiation of contracts that DOE has established with
the nation's utilities--that they would entail. In addition, it is not
clear which of these measures--some of which conflict with each other-
-would provide the greatest safety and security benefit. However, we
believe they should be explored.
Recommendations for Executive Action:
To ensure that all reasonable options to further enhance the security
and safety of spent fuel in storage at nuclear power plants and in
transit are explored, we recommend that the Secretary of Energy assess
the potential benefits and costs of (1) minimizing the total number
of shipments of spent fuel by consolidating shipments where possible,
(2) shipping spent fuel in an order that further minimizes risk, and
(3) emphasizing the use of trains dedicated to hauling spent fuel.
Agency Comments and Our Evaluation:
We provided DOE and NRC with drafts of this report for review and
comment. DOE generally concurred with the facts of the report, noting
that the information on transit was accurate and well balanced. DOE
also concurred with our recommendations, with one exception. DOE noted
that the Department of Transportation was expected to release a study
later this year on the safety and security implications of transporting
spent fuel by dedicated train. DOE stated that it preferred to wait for
the outcome of the study before beginning its own review. DOE also
provided technical comments, which we incorporated into the report.
NRC also generally concurred with the facts of the report, noting that
the information provides a reasonable characterization of the current
understanding of risks associated with spent fuel storage. However, NRC
stated that it does not consider the results of its most recently
published studies on spent fuel in a pool and spent fuel in transit, as
quoted in the report, to accurately reflect the consequences of a
potential terrorist attack. Rather, NRC indicated that the studies
started with overly conservative assumptions, resulting in
"unrealistically conservative" results. NRC noted that it is currently
conducting studies to assess the potential consequences of a terrorist
attack that use more realistic assumptions. NRC also noted in its
technical comments that preliminary results from these ongoing studies
show that potential consequences may be far less severe than reported
in the current publications.
We revised our report to account for NRC's preliminary findings from
ongoing work involving the risk associated with spent fuel pools. As
our report states, these findings indicate that risks from spent fuel
pools may be substantially reduced from previous estimates. We used
NRC's February 2001 report, Technical Study of Spent Fuel Pool Accident
Risk at Decommissioning Nuclear Power Plants, with the understanding
that the report received a high level of scrutiny both within and
outside NRC prior to its publication. As stated in the report,
"Preliminary drafts of this study were issued for public comments and
technical reviews in June 1999 and February 2000. Comments from
interested stakeholders, the Advisory Committee on Reactor Safeguards,
and other technical reviewers have been taken into account in preparing
this study. A broad quality review was also carried out at the Idaho
National Engineering and Environment Laboratory, and a panel of human
reliability analysis experts evaluated the report's assumptions,
methods, and modeling." The report also states that, based on the
comments received, "staff did further analyses and also added
sensitivity studies on evacuation timing to assess the risk
significance of relaxed offsite emergency preparedness requirements
during decommissioning." Given this level of review, we believe it to
be appropriate to report the results of this study.
NRC also took issue with our use of its report, Reexamination of Spent
Fuel Shipment Risk Estimates. NRC explained that the analyses in this
document are similarly overly conservative. This March 2000 study was
conducted by Sandia National Laboratory at the request of NRC to
reexamine the conclusions reached in previous studies regarding the
risks of spent fuel shipments. As with its February 2001 report, this
report also indicated a high level of review prior to publication.
Specifically, the report mentions a number of individuals who provided
comments to the report, including staff at Sandia National Laboratory,
Lawrence Livermore National Laboratory, and "a number of technical
experts at the NRC." Given the intent of this study and its level of
review, we believe it to also be appropriate to report the results of
this study.
Scope and Methodology:
We performed our review at DOE and NRC headquarters in Washington,
D.C., at NRC's Region III office near Chicago, Illinois, and at DOE's
Yucca Mountain Project office in Las Vegas, Nevada. We visited
several sites where spent fuel is stored, including operating nuclear
power plants, a decommissioned nuclear power plant, and independent
spent fuel storage sites. We conducted our review from April 2002 to
June 2003 in accordance with generally accepted government auditing
standards.
To determine the potential health effects of a terrorist attack or a
severe accident involving commercial spent nuclear fuel, we examined a
variety of federally sponsored studies, primarily conducted or
sponsored by DOE and NRC. We examined critiques of these studies
prepared by a variety of groups and individuals. We also spoke to many
of the authors of these federal studies, authors of critiques of these
studies, nuclear energy representatives, and other individuals
representing a variety of backgrounds, including academia and special
interest groups.
To identify options for DOE to enhance the security of spent fuel as it
develops its plans to ship the fuel to Yucca Mountain, we reviewed
documents analyzing DOE's plans and preferred alternatives, including
the environmental impact statement and many of its supporting
documents. We also interviewed DOE, NRC, and Department of
Transportation officials responsible for developing and coordinating
safe shipments of spent nuclear fuel. We also spoke to state and local
government officials in a number states, including Nevada; nuclear
energy representatives; and a variety of groups and individuals
representing a spectrum of viewpoints on the shipment of spent nuclear
fuel.
As agreed with your office, unless you publicly announce the contents
of this report earlier, we plan no further distribution of it until
30 days from the date of this letter. At that time, we will send copies
of this report to other interested parties and make copies available to
others who request them. In addition, the report will be available at
no charge on GAO's Web site at http://www.gao.gov/.
If you or your staff have any questions about this report, please call
me at (202) 512-3841. Key contributors to this report are listed in
appendix V.
Sincerely yours,
Robin M. Nazzaro
Director, Natural Resources and Environment:
Signed by Robin M. Nazzaro:
[End of section]
Appendix I: Nuclear Regulatory Commission Requirements for Safety and
Security of Spent Fuel:
As the regulating agency responsible for spent fuel, the Nuclear
Regulatory Commission (NRC) must adequately protect the public health
and safety against accidents or acts of sabotage. To provide this
assurance, NRC uses a "defense-in-depth" philosophy. Consistent with
this philosophy, NRC designs its safety and security requirements to
ensure that public safety and health are not wholly dependent on any
single element of the design, construction, maintenance, or operation
of a nuclear facility. More specifically, NRC designs multiple or
redundant measures to mitigate areas of known risk or to increase
confidence in areas of uncertainty. Listed below are some of the
primary requirements NRC has recognized as protecting spent fuel while
in transit, in wet storage, and in dry storage.
Requirements for Preventing Release of Spent Fuel in Transit:
NRC requires that transporters of spent fuel (1) contain the fuel in
NRC-certified shipping containers that must meet stringent durability
performance requirements and (2) comply with requirements designed
to impede an act of sabotage on the fuel.
NRC regulations for spent fuel shipping containers dictate that the
containers prevent releases of significant amounts of radiation under
both normal operating conditions and in hypothetical accident
scenarios. The containers include shielding to ensure that persons near
a container are not exposed to significant amounts of radiation. In
addition, the containers must remain intact after a series of simulated
accident conditions, including:
* an impact test, in which containers are dropped from 30 feet onto a
flat, unyielding surface;
* a puncture test, in which containers are dropped from 40 inches onto
a 6-inch diameter steel bar at least 8 inches long;
* a fire test, in which containers are engulfed in a 1,475-degree
Fahrenheit fire for 30 minutes; and:
* an immersion test in which containers are submerged in 3 feet of
water for 8 hours.
The containers must survive each of these tests in succession, without
significant levels of surface radiation or release of spent fuel.
Containers must also be shown to survive water pressure equivalent to
immersion under nearly 670 feet of water for 1 hour.
Because of these requirements and the dimensions of the spent fuel
assemblies they contain, spent fuel shipping containers are massive and
robust. A typical train container is about 25 feet long and 11 feet in
diameter, weighs about 100 tons empty, and about 120 tons fully loaded-
-thus the container can account for over 80 percent of the total weight
of a shipment. Though truck containers have significantly less capacity
than rail containers, both types have similar basic designs. As figure
2 indicates, they are generally composed of several layers of shielding
material, totaling about 5 to 15 inches in thickness, including a
radiation barrier consisting of lead or depleted uranium.
Figure 2: Cutaway Graphic of a Spent Fuel Truck Transportation Cask:
[See PDF for image]
[End of figure]
When in transit, each end of the container is made of material that is
designed to absorb much of the force of an impact. Figures 3 and 4 show
a spent fuel rail container and a truck container, respectively.
Figure 3: Spent Fuel Rail Container:
[See PDF for image]
[End of figure]
Figure 4: Spent Fuel Truck Container on a Trailer:
[See PDF for image]
[End of figure]
Although the shipping container is the most important component in
preventing release and dispersal of spent fuel in transit, NRC also
requires transporters of the spent fuel to implement measures designed
to further protect spent fuel shipments from sabotage. For example,
transporters of spent fuel must ensure that shipments are under
surveillance, that arrangements have been made with local law
enforcement agencies for their response in the event of an emergency,
and that rail and highway routes have been approved by NRC. NRC had
also required that armed escorts be either aboard the shipping vehicle
or in a following vehicle in areas of high population; NRC has since
strengthened the security required of shipments following the September
11, 2001, terrorist attacks.
Requirements for Preventing Release of Spent Fuel in Wet Storage:
Spent fuel pool designs must meet specific performance criteria before
NRC can issue a license for construction or operation. The requirements
focus on ensuring that the safety features of the pool survive certain
natural phenomena or accidents to ensure that, among other things, the
pool will retain water and keep the stored fuel sufficiently cool.
Spent fuel in wet storage is also protected by the physical security
measures in place at the storage site.
As part of the licensing process prior to construction and operation,
utilities must submit reports that analyze the likelihood of certain
natural phenomena, such as earthquakes, hurricanes, floods, and tidal
waves. Using probability analyses, historical information, and current
information on seismology, geology, meteorology, and hydrology, the
utilities must determine the risks of certain types of natural
phenomena. Then the utilities must show that the proposed pool designs
would survive the most severe natural phenomena or combinations of less
severe phenomena expected for that particular area. The utilities must
also perform the same exercise for the likelihood and severity of
certain accidents, including airplane crashes. For example, pools
constructed near airports may have to be designed to withstand certain
types of accidental airplane crashes.
Consequently, although the specific designs of wet storage pools vary
from site to site, they are massive, robust structures. Pools are
typically 30 to 60 feet long, 20 to 40 feet wide, and 40 feet deep.
Pools could nearly hold three semi-truck tractor-trailers parked side-
by-side and stacked three deep. The pool is contained by a structure
consisting of a 1/8 inch to 1/4 inch stainless steel liner, and 4-to 6-
foot thick walls of steel-reinforced concrete. Generally, the pools are
contained in other buildings. The roofs of some of these buildings may
be made from industrial-type corrugated steel. The assemblies, stored
vertically in racks, must be immersed at least 20 feet below the
surface of the water in order to keep the fuel cool and to provide a
sufficient radiation barrier. See figure 5 for a photograph of a wet
storage pool.
Figure 5: A Wet Storage Pool:
[See PDF for image]
[End of figure]
Spent fuel pools are also protected by the physical security measures
in place at the facilities where they are located. About 95 percent of
the spent fuel inventory is stored in pools, most of which are located
at operating nuclear reactors. The perimeters of these reactor sites
are secured by fences topped with barbed wire, vehicle barriers, and
intrusion detection systems--including perimeter cameras and motion
detection technology--that are monitored 24 hours per day. Access to
the building containing the wet storage pools is impeded by locked
steel doors capable of surviving armed assault and security checkpoints
where a person's identity must be verified and where security searches
take place. Finally, these facilities are manned by a force of armed
guards.
In addition, nuclear power plants are required to coordinate an
emergency response to the site in the event of a terrorist or sabotage
event. The coordination requires contingency plans and joint exercises
with local law enforcement agencies to ensure an adequate and timely
response to an event. Since the terrorist attacks of September 11,
2001, NRC has added additional requirements, including additional armed
guards and vehicle barriers.
Requirements for Preventing Release of Spent Fuel in Dry Storage:
NRC requires that spent fuel in dry storage be stored in containers
that protect workers and other nearby persons from significant amounts
of radiation, and that can survive operational accidents at the storage
site, as well as extreme meteorological and other natural events. In
addition, fuel in dry storage is protected by physical security
measures in place at the storage site.
Among other things, dry storage containers must be capable of
surviving:
* a drop test, in which containers are tested by a drop from the height
to which it would be lifted to during operations;
* a tip-over test, testing containers against seismic, weather, and
other forces or accidents that could knock over 100-to 150-ton
containers,
* an explosion test, in which containers are tested against nearby
explosions and the resulting pressures created by the blasts;
* a tornado and tornado missile test, in which high winds and tornado
missiles are simulated;
* a seismic test, in which containers are tested against the seismic
motions that might be expected to occur in its geologic area
(certification requirements may differ from region to region);
* a flood test, in which containers are analyzed for floods; and:
* a fire test, in which containers are engulfed at temperatures up to
1,475 degrees Fahrenheit for 30 minutes.
Manufacturers must provide NRC with information on how well a container
design meets these performance requirements. NRC does not require
physical tests of the containers, but it accepts information derived
from scaled physical tests and computer modeling.
As with shipping containers, to meet these performance requirements,
certified dry storage containers are massive and robust. A typical dry
storage container consists of a 1-inch thick steel container housing
the spent fuel. At some facilities, the containers are placed
horizontally in garage-sized bunkers constructed of concrete. The
concrete protects nearby workers and the public from radiation. At
other facilities, the container is encased in an outer cask. The outer
cask typically is constructed of steel-reinforced concrete, 18 or more
inches thick. Like the concrete bunkers, the outer cask shields workers
and the public from radiation. The free-standing, upright units, stored
on concrete pads, can weigh from 100 to 150 tons each with nearly
90 percent of that consisting of the container weight. A dry storage
container can store between 7 and 68 assemblies, depending on the size
of the container. See figure 6 for an illustration of a dry storage
container.
Figure 6: A Spent Fuel Dry Storage Container:
[See PDF for image]
[End of figure]
In addition to the physical performance requirements of dry storage
containers, the containers are protected by the physical security
measures in place at the facilities where they are stored. Dry storage
containers at operating nuclear power plants generally benefit from the
physical security measures already in place at the sites. The large
majority of spent fuel in dry storage is located at operating nuclear
power plants. For dry storage containers situated away from a reactor
site, NRC requires vehicle barriers, fences, intrusion detection
systems, and guards. The guards are also able to contact local law
enforcement agencies for assistance, if required. NRC requires that dry
storage facilities coordinate response plans with local law enforcement
agencies to ensure assistance can be readily provided, if needed. In
the wake of the September 11, 2001, terrorist attacks, NRC issued
orders to dry storage facility licensees that required enhanced
security measures, including additional protections against a vehicle
bomb threat.
[End of section]
Appendix II: Additional Information on Studies on the Safety and
Security of Spent Fuel in Transit:
The human health implications of sabotage events and accidents
involving spent nuclear fuel shipments described in the report are
based on computer-based engineering and other analytic models that
rely, in part, on physical experiments. In addition, these studies are
the most recent in a series of studies that date back to the 1970s.
According to NRC and DOE, better data and improved analytic tools over
the years have significantly enhanced the agencies' confidence in the
results of these studies. This appendix provides an overview of the
methodology of the most recent studies, as well as the approach and
results of previous studies.
Sabotage Studies:
Methodology of Most Recent Studies. The 1999 Sandia National Laboratory
study was undertaken at the request of DOE for use in its preparation
of an environmental impact statement for the Yucca Mountain
repository.[Footnote 30] The study relied on computer models to
estimate how the two selected armor-piercing missiles would damage
shipping containers. Although no physical tests or experiments were
conducted in this study, the study used computer models that were
validated using the results of previous studies that included
experimental data.
Two of the most important factors considered in designing the study
were the types of shipping containers and the weapons selected for
analysis. For the shipping containers, the study used truck and rail
containers considered representative of those that would be used to
transport the spent fuel likely to be shipped in the early decades of
the 21st Century. NRC's performance standard for these containers
requires that they prevent release of significant amounts of radiation
under normal operating conditions and in accident scenarios. For
example, radiation levels at the exterior of the container must remain
below specified minimal levels after a series of tests to simulate
accident conditions, including an impact test, in which the container
is dropped from 30 feet onto a flat, unyielding surface.
In selecting the weapons used in the analysis, the authors researched
the latest information available and chose weapons they believed
represented the two weapons that would penetrate spent fuel shipping
containers, and which could also be available to terrorists.[Footnote
31]
To ensure that the analysis would represent the upper limit of possible
damage, the authors made conservative assumptions, including the
following:
* No security measures were in place, such as armed guards who travel
with spent fuel shipments and who are required to have the capability
to contact local law enforcement personnel in the event of an attack.
* The weapons would be employed at a distance from these containers
that would result in maximum damage to the container and that the
weapon would strike the container dead center; if the missile were to
strike higher or lower, it could be deflected by the cylindrical shape
of most containers, and penetration of the container would be lessened
or not occur at all.
Previous Studies. The 1999 Sandia study is the most recent in a series
of federally sponsored studies dating back to the 1970s that have
examined the ability of armor-piercing weapons to penetrate spent fuel
containers. A draft version of a Sandia study from 1978, for example,
concluded that a successful sabotage attack on a spent fuel container
would not cause prompt fatalities but could cause several hundred
latent cancer fatalities in a densely populated urban area.[Footnote
32] The final version of this study reduced the total latent cancer
fatalities to fewer than 100, based on a re-evaluation of the quantity
of radioactive material released.[Footnote 33] Based largely on the
initial draft of this study, NRC established its regulations for
security of spent fuel in transit. Because this study was based on a
conservative set of analytical assumptions instead of on experimental
data, there was a high degree of uncertainty regarding the quantities
of radioactive material released, and the human health consequences.
Consequently, in 1983, DOE commissioned Sandia National Laboratory to
conduct physical tests, in which armor-penetrating missiles were fired
at shipping containers containing mock spent fuel assemblies.[Footnote
34] The study found that, under the worst-case scenario, about 24 ten-
thousandths (0.0024) of 1 percent of the total solid fuel inventory in
the container could be released as respirable particles.[Footnote 35]
To estimate the human health impact, the study included conservative
assumptions, including that the attacks occurred in Manhattan, in New
York City, on a business day, that the fuel had been removed from the
reactor for only 150 days (and thus was comparatively more
radiologically dangerous), and that no evacuation took place to limit
human exposure. Based on these results and assumptions, the study
predicted no early deaths and between two and seven long-term latent
cancer fatalities.
Accident Studies:
Methodology of Most Recent Studies. According to NRC, the 2000 Sandia
National Laboratory study was conducted to address three developments-
-the likelihood that spent fuel shipments would be increasing as a
result of the progress on the Yucca Mountain repository, the use of
containers and transportation routes that differed from those
considered in previous studies, and the increased effectiveness in risk
assessment and computer modeling of spent fuel containers.[Footnote 36]
The overall objective of the study was to determine the degree of risk
involved in shipping spent fuel by truck and rail.
The study examined the effects of severe collisions and fires on four
types of shipping containers--a lead-lined steel truck container, a
depleted uranium-lined steel truck container, a lead-lined steel rail
container, and a monolithic steel container. The study relied on
computer analysis to estimate the probability of such events and the
quantity of radioactive material that might be released. The analysis
developed 19 representative truck accidents and 21 representative rail
accidents.
The study simulated the effect on each of the truck and rail containers
after slamming them into a rigid surface from a variety of angles at
30, 60, 90, and 120 miles per hour. None of the cases modeled showed
that the body of the container would fail. Moreover, the modeling
showed that the seals around the lid at each end of the truck container
would not allow a release at 30, 60, and 90 miles per hour, although
they may leak at 120 miles per hour. The results from modeling the two
different rail containers, however, showed that the seals may leak, for
some collisions at a speed of 60 miles per hour, depending on the angle
of impact.
DOE's study that predicted the health effects of these releases used a
computer code. The code calculated the dispersion of radioactive
particles and the resultant dose to the population. To estimate latent
cancer deaths, DOE made a number of key assumptions. DOE's analysis
assumed the accident occurred in the most populous center of an urban
area and that the population distribution from the accident site in the
urban center to the outer fringes was similar to the average
populations--projected to the year 2035--of the 20 largest U.S.
metropolitan areas, plus Las Vegas, Nevada. Stable weather conditions-
-with comparatively slow wind speeds--were assumed to prevail at the
time of the accident.[Footnote 37] Finally, the population was assumed
to be exposed to remnants of the release for 1 year after the accident,
with no evacuation or cleanup.
Previous Studies. The 2000 Sandia study reexamined the risks
associated with the transport of spent fuel by truck and rail and
compared the results to two previous studies--one conducted by NRC in
1977 and one performed by DOE's Lawrence Livermore National Laboratory
in 1987. According to NRC, the 2000 Sandia study extended the methods
used in the 1987 report for container analysis and used improved risk
assessment methods.
The 2000 Sandia study found that previous NRC-commissioned studies
overestimated the risks of human exposure due to transportation
accidents. According to NRC and Sandia officials, they have become more
confident in their results as analytical techniques and data have
improved. In 1977, NRC examined the risks of shipping a variety of
radioactive materials, including spent fuel.[Footnote 38] At that time,
NRC determined that the risks of accidental releases involved in
shipping spent fuel and other radioactive materials were quite small--
specifically, the study estimated latent cancer deaths to be about 3 in
200 years of shipping spent fuel at estimated rates for 1985. The study
concluded that the existing NRC requirements were adequate to protect
public health. Partly because this study was based on conservative
engineering judgments and did not include physical tests of shipping
containers in severe accidents, NRC subsequently commissioned a study
published in 1987 that found that the risks of spent fuel releases
under transportation accident conditions were much smaller.[Footnote
39] Performed by Lawrence Livermore National Laboratory for NRC, this
study included a more sophisticated analysis than the 1977 study, using
historical data on past transportation accidents to determine the
likelihood of specific accident scenarios. The study then used a
computer-based analysis of accident scenarios involving collisions and
fire temperatures exceeding NRC standards. The 1987 study found that in
99.4 percent of all rail and truck accidents, the container would
experience no significant damage, and no radioactive material would be
released.
[End of section]
Appendix III: Comments from the Department of Energy:
Department of Energy Washington, DC 20585:
JUN 06 2003:
Ms. Robin M. Nazzaro
Director:
Natural Resources and Environment U. S. General Accounting Office
Washington, DC 20548:
Dear Ms. Nazzaro:
The Office of Civilian Radioactive Waste Management (OCRWM) has
reviewed the General Accounting Office's (GAO) draft report, "Spent
Nuclear Fuel: Low Risk of Harm from Terrorist Attacks and Severe
Accidents, but Potential Options Exist to Further Enhance Security"
(GAO-03-426). In its draft report, GAO recommends that, as the
Department develops its plans for transporting spent nuclear fuel to
Yucca Mountain, it assess potential benefits and costs of options to
enhance the safety and security of spent nuclear fuel shipments. GAO
cited the following potential enhancements: 1) minimizing the total
number of shipments, 2) shipping spent nuclear fuel in an order that
further minimizes risk, and 3) transporting spent nuclear fuel on
trains dedicated to hauling exclusively spent nuclear fuel.
OCRWM concurs with GAO's recommendation to perform such an assessment,
with the following exception. In his April 25, 2002, testimony before
the House Subcommittees on Railroads and Highways and Transit, Mr.
Allan Rutter, Administrator of the Federal Rail Administration (FRA),
stated that the FRA is conducting a thorough study of the safety and
security implications of transporting spent nuclear fuel by dedicated
trains versus general freight. Mr. Rutter stated that FRA expects to
issue their report this year. We believe that it is appropriate to
await the outcome of this evaluation and be informed by FRA's results,
rather than duplicate their efforts. Since it will be approximately
seven years before OCRWM begins transporting spent nuclear fuel, we
have the ability to incorporate relevant recommendations in our
operational plans.
We believe that the draft report is an accurate and balanced
representation of the issues associated with the in-transit security of
spent nuclear fuel, and we have enclosed specific comments that we
believe would enhance the technical accuracy of the draft report.
We appreciate the opportunity to offer comments on your draft report.
Sincerely,
Dr. Margaret S. Y. Chu,
Director Office of Civilian Radioactive Waste Management:
Signed by Margaret S. Y. Chu:
Enclosure:
[End of section]
Appendix IV: Comments from the Nuclear Regulatory Commission:
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C.
20555-0001:
June 20, 2003:
Ms. Robin M. Nazarro
Director, Science Issues
Natural Resources and Environment
United States General Accounting Office 441 G Street, NW:
Washington, DC 20548:
Dear Ms. Nazarro:
I would like to thank you for the opportunity to review and submit
comments on the draft report, "SPENT NUCLEAR FUEL: Low Risk of Harm
from Terrorist Attacks and Severe Accidents, but Potential Options
Exist to Further Enhance Security" (GAO-03-426). The U.S. Nuclear
Regulatory Commission (NRC) appreciates the time and effort that you
and your staff have taken to review this important topic. Overall, the
report provides a reasonable characterization of the current
understanding of risks associated with spent fuel storage.
The NRC does not consider the results of NUREG-1738, "Technical Study
of Spent Fuel Pool Accident Risk at Decommissioning Nuclear Power
Plants," to be appropriate for characterizing the consequences of
terrorist attacks at spent fuel pools as it was prepared for a very
different purpose. The results of this study, which was not endorsed by
the Commission and which several commenters asked be peer-reviewed in
light of its obvious over-conservatisms, are considered to be
unrealistically conservative. That is one of the reasons why we are
reevaluating the predicted results of such events. It is very important
when discussing the results of these analyses that the report clearly
state that these analyses were overly conservative. The report also
references the results of NUREG/CR-6672, "Reexamination of Spent Fuel
Shipment Risk Estimates." The analyses in this document are similarly
overly conservative. We have enclosed a recent letter the Commission
received from the Chairman of the Advisory Committee on Nuclear Waste
(ACNW). The ACNW's review stated that NUREG-6672 overestimates the
radiological releases by several orders of magnitude. The Committee
also states that it "believes that it is unfortunate that such
overestimates of consequences are published by NRC in NUREG reports,
because they get separated from the caveats and are used as though they
were valid best estimates." The Commission agrees with the ACNW. The
enclosure provides some specific comments on the draft report which we
hope help to clarify these points.
Specific comments relative to factual accuracy, clarity, and
completeness of the report are provided in Enclosure 2. In addition, we
have communicated separately with the GAO review team relative to minor
editorial comments.
Should you have any questions about these comments, please contact
either Mr. William Dean at (301) 415-1703, or Ms. Melinda Malloy, at
(301) 415-1785, of my staff.
Sincerely,
William D. Travers
Executive Director for Operations:
Signed for William D. Travers:
Enclosures:
1. ACNW Letter dated 6/4/03:
2. Specific Comments on Draft Report GAO-03-426:
cc: Daniel Feehan, GAO (Denver) Robert Sanchez, GAO (Denver):
[End of section]
Appendix V: GAO Contact and Staff Acknowledgments:
GAO Contact:
Daniel J. Feehan (303) 572-7352:
Acknowledgments:
In addition to the individual named above, Doreen Feldman, Michael
Hartnett, Gary Jones, Cynthia Norris, Robert Sanchez, Amy Stewart,
Barbara Timmerman, and Dwayne Weigel made key contributions to
this report.
FOOTNOTES
[1] A boiling water reactor uses slightly radioactive steam that is
generated in the reactor to drive a turbine that generates electricity.
The water is returned to the reactor core where it is reheated to
steam, driving the turbines as the cycle is repeated. Pressurized
reactors send slightly radioactive pressurized water to a steam
generator, which creates steam from nonradioactive water kept separated
by tubes. The steam drives the turbine and the slightly radioactive
water returns to the reactor where it is reheated and the cycle
repeated.
[2] This other waste is the result of nuclear activities from DOE--
90 percent of the volume of waste expected to be shipped to the Yucca
Mountain repository is expected to be spent fuel and the other
10 percent is expected to be DOE waste.
[3] Yucca Mountain, Nevada, is located approximately 100 miles
northwest of Las Vegas, Nevada.
[4] U.S. General Accounting Office, Nuclear Waste: Technical, Schedule,
and Cost Uncertainties of the Yucca Mountain Repository Project, GAO-
02-191 (Washington, D.C., Dec. 21, 2001).
[5] Spent fuel rods recently discharged from a reactor also contain
some radioactive gases that are a by-product of the nuclear fission
process--these gases account for a small fraction of the total quantity
of radioactive material in spent fuel rods, but because of the short
half lives of the material, the gases decay quickly and may not be
present in older spent fuel.
[6] A micron is one millionth of a meter in length--by comparison, one
micron is about 1/70 the thickness of a human hair.
[7] At the present time, there is no direct rail service to Yucca
Mountain and the closest rail line is 100 miles away. Until a branch
rail line is established, intermodal transfer stations with interim
storage may need to be established to transfer shipping containers from
rail to truck for the final trip to Yucca Mountain.
[8] See appendix I for a more detailed description of the NRC-certified
spent fuel shipping containers.
[9] Sandia National Laboratory, Projected Source Terms for Potential
Sabotage Events Related to Spent Fuel Shipments, SAND 99-0963, a report
prepared at the request of the Department of Energy, Albuquerque,
N.Mex., June 1999.
[10] Rather than focus on the entire amount of material released, this
and other studies focused on the amount of respirable particles--these
particles can potentially become airborne, transported to densely
populated areas, and inhaled. By comparison, the nonrespirable material
would be a more localized problem that could be more easily contained
and controlled.
[11] Jason Technologies Corporation, Transportation Health and Safety
Calculation/Analysis Documentation in Support of the Final EIS for the
Yucca Mountain Repository, a report prepared at the request of the
Department of Energy, Las Vegas, Nev., December 2001.
[12] The respirable particles include solid particles of spent fuel,
radioactive gases released from the fuel rods, and particles of
radioactive deposits that accumulate on the exterior of the fuel
assemblies.
[13] Appendix II contains a summary of the methodology of both the 1999
Sandia National Laboratory study and the subsequent DOE analysis.
[14] U.S. Nuclear Regulatory Commission, Reexamination of Spent Fuel
Shipment Risk Estimates, NUREG/CR-6672, Washington, D.C., March 2000.
[15] Jason Technologies Corporation, Transportation Health and Safety
Calculation/Analysis Documentation in Support of the Final EIS for the
Yucca Mountain Repository, a report prepared at the request of the
Department of Energy, Las Vegas, Nev., December 2001.
[16] According to DOE, this accident involved a high-temperature, long
duration fire that fully engulfed a rail container.
[17] Sandia National Laboratory, Spent Nuclear Fuel Transportation
Package Performance Study Issues Report, NUREG/CR-6768, a report
prepared for the Nuclear Regulatory Commission, June 2002.
[18] U.S. Nuclear Regulatory Commission, Technical Study of Spent Fuel
Pool Accident Risk at Decommissioning Nuclear Power Plants, NUREG-1738,
Washington, D.C., February 2001.
[19] See appendix I for a description of the NRC-certified wet storage
pools.
[20] Brookhaven National Laboratory, Severe Accidents in Spent Fuel
Pools in Support of Generic Safety Issue 82, NUREG/CR-4982, a report
prepared for the U.S. Nuclear Regulatory Commission, July 1987.
[21] See appendix I for a description of the of the NRC-certified dry
storage containers.
[22] Jason Technologies Corporation and Pacific Northwest National
Laboratory, Accident Analysis for Continued Storage, a report prepared
for the U.S. Department of Energy, October 27, 1998. Jason Technologies
Corporation, An Evaluation of the Consequences of a Commercial Aircraft
Crash into the Yucca Mountain Repository, a report prepared for the
U.S. Department of Energy, December 2001.
[23] Identification of Factors for Selecting Modes and Routes for
Shipping High-Level Radioactive Waste and Spent Nuclear Fuel, U.S.
Department of Transportation, Research and Special Programs
Administration, April 1998.
[24] These figures are based on our analysis of DOE's 1995 Acceptance
Priority Ranking (U.S. DOE Office of Civilian Radioactive Waste
Management), the most recent version published.
[25] In addition to permanently shutdown reactor sites, a limited
quantity of spent fuel is stored at an independent storage facility in
Morris, Illinois.
[26] Four of the shutdown reactors are co-located with operating
reactors.
[27] Some components of spent fuel remain deadly for thousands or
millions of years. For example, uranium235 requires about 704
million years for its radiation output to be cut in half.
[28] As mentioned previously, gamma radiation can damage critical
organs of the body.
[29] Evaluation of the Effects of the Baltimore Tunnel Fire on Rail
Transportation of Nuclear Fuel. Nuclear Regulatory Commission, January
6, 2003.
[30] Sandia National Laboratory, Projected Source Terms for Potential
Sabotage Events Related to Spent Fuel Shipments, SAND 99-0963, a report
prepared at the request of the Department of Energy, Albuquerque,
N.Mex., June 1999.
[31] According to NRC, information on the types of weapons used in this
analysis is classified.
[32] Sandia National Laboratory, Transport of Radionuclides in Urban
Environs: Working Draft Assessment, SAND 77-1927, Albuquerque, N.Mex.,
1977.
[33] Sandia National Laboratory, Transport of Radionuclides in Urban
Environs: Draft Environmental Assessment NUREG/CR-0743, Albuquerque,
N.Mex., July 1980.
[34] According to Sandia National Laboratory officials, in addition to
the high cost, environmental and health regulations generally prevent
the use of actual spent fuel that leads to the use of mock fuel--a
nonradioactive material--that generally displays enough of the same
properties as spent fuel for purposes of these analyses.
[35] Sandia National Laboratory, An Assessment of the Safety of Spent
Fuel Transportation in Urban Environs, Albuquerque, N.Mex., June 1983.
[36] U.S. Nuclear Regulatory Commission, Reexamination of Spent Fuel
Shipment Risk Estimates, NUREG/CR-6672, Washington, D.C., March 2000.
[37] Higher wind speeds would result in faster dispersion and hence a
lower population dose.
[38] U.S. Nuclear Regulatory Commission, Final Environmental Statement
on the Transportation of Radioactive Material by Air and Other Modes,
NUREG-0170, Washington, D.C., 1977.
[39] Lawrence Livermore National Laboratory, Shipping Container
Response to Severe Highway and Railway Accident Conditions, NUREG/CR-
4829, a report prepared at the request of the Nuclear Regulatory
Commission, 1987.
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Automated answering system: (800) 424-5454 or (202) 512-7470:
Public Affairs:
Jeff Nelligan, managing director, NelliganJ@gao.gov (202) 512-4800 U.S.
General Accounting Office, 441 G Street NW, Room 7149 Washington, D.C.
20548:
