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Terrorism and Nuclear Power:
What are the Risks?
by Gerald E. Marsh and George S. Stanford Synopsis: In view of how difficult it is to create widespread havoc by
attacking nuclear power plants, sophisticated terrorists will not see them as
attractive targets. A determined group, however, could cause some disruption and
garner a lot of public attention - but they would be unlikely to cause any
civilian casualties. Nevertheless, a significant portion of what vulnerability
there is could be removed by transferring spent fuel to underground storage at
Yucca Mountain. * * * * America has lost its innocence. But in responding to this loss we must not
lose those facets of our society that have made us a guiding light for much of
the rest of the world. One facet is the dynamism of the American economy, driven
in large measure by the abundant and relatively cheap energy. Unfortunately,
much of that energy today comes to us in the form of imported oil. There is a
very simple and prudent means of keeping the energy supply growing in an
environmentally acceptable way namely, by relying increasingly on nuclear
power. (Currently nuclear power plants provide only 20% of electric energy
nationally; 40% in Illinois, the most nuclearised state.) We should not allow
panic, politics, or political correctness to curtail the use of nuclear power. Is nuclear power's potential jeopardized by the heightened awareness of the
threat of terrorism? The short answer is, "No, because nuclear plants are
not attractive targets for terrorists." There are many targets that would
have a higher payoff. [1] Storage ponds should
promptly be hardened, if at all feasible. [2] As much spent fuel as
possible should be moved into the less vulnerable dry-storage type of cask. [3] The Yucca Mountain
repository should immediately be opened as an interim storage facility,
with spent fuel currently in collocated pools moved as quickly as possible to
storage pools installed in this secure, underground location. The first pools to
be emptied should be the ones that are not below-grade. Moving the spent fuel in
"wet" transportation casks would be a very low-risk operation: the
casks can withstand severe accidents, although probably not enough are currently
available to allow a timely transfer of the relatively large amount of spent
fuel now located at reactor sites throughout the country-hence points [1] and
[2]. [4] Once the current storage
pools have been emptied, the fuel now in surface dry-cask facilities could also
be moved to Yucca Mountain. The public thinks the vulnerability
of nuclear plants is much worse than it really is. This creates the potential
for widespread panic should these plants or their associated facilities be
attacked by terrorists. To make such an event less likely, the suggestions
listed above should be put into effect immediately. The
Vulnerability Of Nuclear Power Plants Without question, sophisticated and
well-organized terrorists could do damage to nuclear power plants, and such
attempts cannot be ruled out. However, to be appealing to a suicidal terrorist
cell, a potential mission must offer the prospect of appreciable havoc
with a high probability of success. We show below that nuclear power plants do
not offer that combination: scenarios that are likely to succeed will do minimal
damage, and those where serious damage could theoretically result have a very
small chance of success. There are two classes of reactor
accident that have the potential of leading to serious off-site consequences: super criticality
(Chernobyl) and loss of coolant (Three Mile Island). This does not mean that
serious consequences are inevitable: at Three Mile Island, where coolant was not
completely lost, the off-site release of radioactivity was negligible and there
were no casualties, although the utility suffered a significant financial loss
and there was some panic due to the lack of credible and timely information on
the potential consequences of the accident. At Chernobyl there was a steam
explosion, but it took a persistent graphite fire to inject the radioactivity
into the atmosphere. The health consequences of that accident have been grossly
exaggerated in the popular press [see endnote ]. Even so, the Chernobyl
consequences were much worse than what reasonably could happen in the United
States. One reason is that current Western power reactors do not use graphite -
there can be no fire, and without a fire there is no plausible way to put such a
large amount of radioactivity into the atmosphere, even with a steam explosion
that somehow breaches the containment. Steam explosion. A
hypothetical reactor accident that is getting a lot of publicity is a steam
explosion that sends the top of the pressure vessel upward through the
containment, releasing radioactivity to the atmosphere in a Chernobyl-size
disaster. That is a scary scenario, but - as we just pointed out, and for
further reasons given below - it is not a realistic one. Super criticality. Achieving
gross super criticality is not as easy as throwing a switch or two to withdraw
control rods. The terrorists must first disable a variety of automatic safety
systems that will scram the reactor if the power level rises too fast. More
obstacles to be overcome, and the consequences of succeeding in that difficult
task, are mentioned below. Loss of cooling. The
possibility of an explosion following loss of cooling has been the subject of
much research in the United States and the rest of the world for several
decades. The current expert consensus is that, while a steam explosion with
oxide fuel (the type used in current power reactors) cannot be ruled out as a
theoretical possibility, it is highly improbable. This accident is no longer
considered realistic by the NRC, even when evaluating "worst case"
scenarios. Attack scenarios and likely
outcomes. There are three potential targets at a typical reactor site: the
reactor itself, a spent-fuel storage pool, and, in some cases, a dry-cask
spent-fuel storage facility. One can imagine various modes of attack against one
or the other of the three targets, such as: 1. A truck bomb that explodes
beside a critical structure Attack Scenario #1: A truck
bomb is probably the least effective of the above options. It would be expected
to do minimal damage to a reactor containment building or a fuel-storage
facility. This would not be a terrorist's weapon of choice, if he were after
more than publicity. Attack Scenario #2: A small,
explosive-laden airplane could be crashed into any of the three targets.
Crashing into the reactor containment would do little damage, and the
dry-storage casks are highly resistant, being of heavy concrete. Because the
airplane can come in from above, it might do some damage to a storage-pool
facility, so that is probably the most vulnerable of the three. However, some years ago General
Electric did a comprehensive study of the consequences of a terrorist attack on
a fuel-storage pool, using high explosives. The conclusion was that the
potential for off-site release of radioactivity was negligible. Even a thousand
pounds of high explosive delivered by a small plane crashing into the pool would
not seriously disrupt the fuel assemblies, which sit under nine or more feet of
water - especially since the explosive would probably be triggered when the
plane hit the roof of the building, well above the pool. Attack Scenario #3: A
small-arms assault would give time for an orderly shutdown of the reactor, or at
least a scram, and for outside assistance to arrive. From a terrorist's
viewpoint, successful penetration to commit significant sabotage would be very
uncertain, at best. In particular, we understand that bringing a shut-down
reactor immediately back to full power and beyond would be extremely difficult,
if not impossible. See a Attack Scenario #6, below, for more
considerations. Attack Scenario #5. It might
be relatively easy to topple the power lines leading into a nuclear plant - in
fact, a severe ice storm can have the same effect. For this reason, all nuclear
plants have redundant backup systems to permit an orderly shutdown if external
power is lost. Specifically, there are two independent, separately-located
diesel generator systems, each with enough fuel to provide operational power for
thirty days or more. In addition, there are batteries that can provide emergency
power long enough to achieve a safe shutdown, with a cushion of some hours to
get the diesels restarted. Thus the first five of the above
attack modes are unattractive to terrorists who want to inflict major damage.
Even a "successful" attack would cause little more than damage to
physical structures at the plant, and perhaps a temporary shutdown of the
reactor, but would not in any credible scenario lead to a major radiation
release. The remaining three scenarios
deserve more careful consideration, as loss of cooling or super criticality
could occur. Attack Scenario #6. The
primary protection against sabotage from within lies in the stringent clearance
and screening procedures that are in place. Nevertheless, a group of technically
sophisticated and ruthless infiltrators could do serious damage, if they could
disable most or all of the non-collaborating employees (operators, security
forces, maintenance technicians, and on-site NRC monitors). Given enough time
and materials, such a group could presumably create a criticality accident, or
loss of cooling, or both, leading to destruction of the reactor. As far as we
know, such an attack cannot be completely ruled out, but it would be many times
harder to plan and execute than the World Trade Center attack, and would require
far greater technical expertise, along with detailed inside knowledge. Off-site release of some
radioactivity would seem to be a distinct possibility in this scenario, but is
by no means assured (as explained above, the Chernobyl dispersal mechanism is
not available). The radiological consequences might well be similar to those of
TMI - i.e., negligible. Difficulty in infiltrating the power-plant organization,
combined with uncertain infliction of major damage, should motivate terrorists
to seek easier routes to their goal. Attack Scenario #7: Nuclear
Regulatory Commission News Release No. 01-112 reports that "detailed
engineering analyses of a large airliner crash have not yet been
performed." Pending such an analysis, a reasonable speculation is that only
a direct hit on the reactor building by one of the heavy engines of the incoming
airplane could crack the thick concrete containment. This would require
extremely precise guidance of the aircraft by the hijacking pilot. Whether the
engine would enter the containment is an open question. Even if it does, the
reactor vessel is unlikely to be breached, because it is a heavy steel shell
surrounded and protected by thick concrete radiation shielding. We know of no credible way, in this
scenario, that the reactor could go supercritical to cause a steam explosion.
The chain reaction would shut down, for a number of reasons, but cooling could
be lost. If so, and if, as is likely, the reactor had been operating for some
time, the decay heat could melt the core. Since a steam explosion following loss
of cooling is unlikely (see Loss of cooling, above), the hot fuel might
melt through the reactor vessel after a few hours, and spread out in the
substructure, where it would eventually freeze in a sub critical configuration. Some fraction of the more volatile
fission products (such as iodine, cesium, and the noble gases) might escape to
the atmosphere. With a timely and orderly evacuation of nearby residents, in
accordance with the site's emergency plan, no serious off-site irradiation of
the public should occur. The burning jet fuel would scarcely
aggravate the situation - it would have been distributed over a considerable
area, and would have burned off well before the molten reactor fuel penetrated
the reactor vessel. Attack Scenario #8: A
jetliner could be crashed into spent-fuel storage. Typically, used reactor fuel
is allowed to cool for five or ten years under nine or more feet of water in
storage pools, and then, pending final disposition, is transferred to interim
dry-cask storage. Both of those facilities tend to be on-site, near the reactor.
Such a building, being just one of several low buildings in the complex, would
be even trickier for the terrorist-pilot to identify and hit than the reactor
containment. While this event may not yet have
been fully analyzed, in light of the World Trade Center disaster, informed
speculation can give a reasonable picture of the potential consequences. The dry casks are made of concrete
or thick steel, providing good protection of their contents. If the dry-storage
facility were directly hit by the jetliner, a few of those casks might be
broken, but the ensuing fire could not disperse a large amount of radioactivity.
Nevertheless, local evacuation might be called for. A lesson to be learned from
Chernobyl is that the only significant off-site exposure to the public was due
to food contaminated with iodine-131, which seeks the thyroid. Since I-131 has a
half-life of only eight days, there is very little of it remaining in spent fuel
that has been stored for more than a few weeks. Therefore - especially with
evacuation of nearby residents - radiological risk to the populace would be very
small. The storage pools are somewhat more
vulnerable, although they are not pushovers. For one thing, much of their water
would have to be removed if a significant release of radioactivity were to
occur, and many such pools are largely below-grade. The burning jet fuel by
itself will not remove the water, since it will float on top as it burns,
without boiling off much water. For a limiting, worst-case event,
one can visualize the hijackers achieving such a precise hit that the aircraft
splashes out most of the water and crushes an appreciable fraction of the fuel
elements stored there. Perhaps the shock wave lifts some radioactive debris out
of the pool and scatters it near the building. Jet fuel runs into the pool and
burns. The fire is not hot enough even to melt the reactor fuel pellets, but
radioactive fission products, especially the more volatile ones, could escape
from the disrupted fuel assemblies and be transported into the atmosphere by hot
gases from the jet-fuel fire. A local evacuation would undoubtedly
be ordered. However, such dispersal of radioactivity from a storage pool would
in no way be comparable to what happened at Chernobyl; the stored fuel is five
or ten times less radioactive than fuel from an operating reactor, and most
important, as mentioned above, the iodine-131 would be largely or entirely
missing because of its short half-life. No significant irradiation of members of
the public would be expected, the most serious consequences probably being
anxiety and possibly panic. Since the storage-pool building is
not nearly as hardened as a reactor containment, a jetliner considerably smaller
than a 767 might be sufficient to disrupt it. This fact alone might make the
pool a more attractive target than the reactor itself. Summary: A terrorist
assault on a nuclear power plant would attract a lot of attention, and some
types of attack could conceivably prompt a limited evacuation. However, the
chance of dangerous release of radioactivity to the atmosphere is remote, and
there seems to be no credible way that any members of the public could be
seriously irradiated. Many easier and more lucrative targets (where damage could
be comparable to the World Trade Center disaster) are available for terrorists
to attack. Our ultimate protection against terrorism will lie in lack of
terrorists, not in scarcity of targets. * *
* * Postscript: We have
suggested that the Yucca Mountain repository be immediately opened as an interim
storage facility. We say "interim" because the question of
reprocessing spent reactor fuel should be reopened. Past objections were based
on the association of reprocessing with separated plutonium, which many believe
could be used in nuclear weapons. The current method of reprocessing,
known as PUREX, does indeed result in separated plutonium. However, there are
other technologies, such as "pyroprocessing," that cannot produce the
chemically pure plutonium required for nuclear weapons, although this much
safer, reprocessed fuel is excellent feed for new "fast" reactors. Reusing spent reactor fuel in fast
reactors is very attractive, because what otherwise would need to be stored for
ten thousand years is now consumable fuel. The waste from fast reactors will be
much easier to store, since its radioactivity is almost gone in less than 500
years. The new, pyroprocessed fast-reactor
fuel is far more proliferation-resistant than today's unreprocessed
"spent" fuel. In both cases, further chemical processing would be
needed to extract the plutonium, but the fuel in a fast-reactor plant with a
collocated reprocessor is much more inaccessible. And, in both cases, the
resulting reactor-grade plutonium makes very poor bomb material. No nation
spending the enormous amount of money needed for a nuclear weapons program would
use reactor-grade plutonium - there always are easier options.
Footnotes: 1 A
note on the after-effects of the Chernobyl accident. According to a United
Nations Scientific Committee study issued in 2000, popular reports of the
off-site effects have been grossly exaggerated. The "UNSCEAR 2000"
document says that the accident caused
the deaths, within a few days or weeks, of 30 workers and radiation injuries to
[a hundred] others. It also brought about the immediate evacuation, in 1986, of
about 116,000 people from areas surrounding the reactor and the permanent
relocation, after 1986, of about 220,000 people from Belarus, the Russian
Federation, and the Ukraine. . . . There have been about 1,800 cases of thyroid
cancer in children who were exposed at the time of the accident, and if the
current trend continues, there may be more cases during the next decades. Apart
from this increase, there is no evidence of a major public health impact
attributable to radiation exposure fourteen years after the accident.
[Emphasis added] Reports
of tens of thousands of deaths are pure speculation - completely unsupported by
any evidence. # #
# Gerald Marsh is a physicist who
served with the U.S. START delegation and was a consultant to the Office of the
Chief of Naval Operations on strategic nuclear policy and technology for many
years. He is an advisory board member of The National Center for Public Policy
Research's John P. McGovern, MD Center for Environmental and Regulatory Affairs.
He can be contacted at gmarsh@nationalcenter.org. George Stanford is a nuclear
reactor physicist, now retired from Argonne National Laboratory after a career
of experimental work pertaining to power-reactor safety. Reprinted from The
National Centre for Public Policy Research November 2001 |
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