Q: In the NOVA "Dirty Bomb" episode, the experts talked about
radioactive substances scattered all over the former Soviet Union
and that Russia has forgotten their locations or has failed to
recover these substances, leaving them as an easy capture for
possible terrorist "dirty bombs." Would it be conceivable that a
satellite with either thermal or some other way could take images
revealing these high concentrations of unrecovered radioactive
substances, which could then perhaps be retrieved by a United
Nations task force in this field? Or is this inconceivable due to
funding, technology, foreign relations, or some other reason?
Evan Lincolnshire, IL
A: This is an interesting question. The IAEA and various
governments have used helicopters equipped with radiation detectors
to track down radioactive sources in the former Soviet Union.
However, I'm not aware of any efforts to use thermal imaging
satellites as you suggested. Perhaps this is underway. I suspect,
though, that it may be difficult to discriminate the thermal signal
from highly radioactive sources from other non-radioactive thermal
sources.
Before investing funds in this method, I'd suggest that scientists
with expertise in thermal imaging satellites calculate whether these
satellites could unambiguously detect these signals. The signal
would depend on what type of radioisotope is in a source and how
much of the isotope is present in the source. In addition, the
thermal image produced would depend on the interaction of the
radiation emitted by a radioactive isotope with surrounding matter.
All these factors should be taken into account in determining
whether such satellites could help track down these radioactive
materials.
Q: What radioactive material or sources pose the greatest
threat for use in a Radiological Dispersion Device, based on the
inherent radiological risk and on their relative availability? That
is, over what sources in U.S. commerce is greater security and
oversight most urgently needed?
Thor Strong Lansing, MI
A: In the recently published report "Commercial Radioactive
Sources: Surveying the Security Risks," Occasional Paper No. 11,
Center for Nonproliferation Studies, by myself, Tahseen Kazi, and
Judith Perera (available at www.cns.miis.edu), we describe the top
seven radioisotopes that if present in large enough amounts in a
radioactive source would pose inherent radiological security risks.
These radioisotopes are americium-241, californium-252, cesium-137,
cobalt-60, iridium-192, plutonium-238, and strontium-90. These are
all produced in nuclear reactors. In addition, we would include
radium-226, a naturally occurring radioisotope that has been widely
used throughout the world.
Concerning U.S. export control and licensing rules for these
materials, radium-226 because it is naturally occurring is not
subject to the licensing rules governing the reactor-produced
radioisotopes. For the other radioisotopes, except for certain
restrictions on plutonium, americium, and californium, essentially
unlimited amounts of the other isotopes can be exported to almost
all countries (except those such as North Korea, Iran, and Iraq that
are under embargo). The licensing rules are such that there are
requirements for a detailed governmental review of the credentials
of end-users. After our report was published, we briefed some
government officials about this loophole. They are aware of it and
are taking steps to tighten the regulations.
Citizens should encourage their elected officials to become more
engaged in securing the high priority radioactive sources.
Currently, there are three bills before Congress that deserve
support. First, Senator Hillary Rodham Clinton and Senator Judd
Gregg have reintroduced legislation called the Dirty Bomb Prevention
Act of 2003. This bill aims to establish a task force consisting of
senior government officials charged to determine how best to secure
radioactive materials. Rep. Edward Markey is sponsoring a similar
bill in the House of Representatives. Second, Senator Richard Lugar,
Senator Joseph Biden, and Senator Pete Domenici are close to
reintroducing legislation from last October that would focus more on
the international dimension of radioactive source security. Third,
Senator Mary Landrieu has introduced legislation to provide for
increased port security. I urge Americans to contact their
congressional representatives to support these pieces of
legislation.
Q: Would not the radioactive storage room of a hospital or
nuclear lab be the perfect place to keep a dirty bomb until ready
for use? Sherlock Holmes once said that the perfect place to hide a
book was in a library. If I were the FBI, I would be doing
background checks on all employees with access or delivery to such
places.
Anonymous
A: That's an interesting observation. Could there be a
"rogue" element at these facilities surreptitiously building dirty
bombs? Owners and operators of these facilities are required by
federal regulation to conduct regular inspections and ensure that
their facilities are secure. It is my understanding that the Nuclear
Regulatory Commission is considering background checks for the
highest risk facilities. The NRC has been coordinating security
activities with the FBI, but I'm not sure if the FBI is conducting
such checks.
Q: Comparing the dirty bomb with the depleted uranium that
has been extensively used by the U.S. in Kosovo, Bosnia, and
Afghanistan, which one is more dangerous from the standpoints of
chemical poisoning, radiation-caused diseases, and half-life?
Jim Charlotte, NC
A: Depleted uranium would not be an effective material for a
radiological dirty bomb because it has a very long half-life and is
not very radioactive. There are several other radioactive materials
that pose higher radiological security risks. Nonetheless, because
depleted uranium is a heavy metal, it could present a chemical
poisoning risk in large enough doses, especially to the kidneys.
Q: In the event of a "dirty bomb" detonation, is there any
program or resources available to citizens to predict the path of
the fallout? Would it be possible to calculate the rads per minute
as the cloud progresses based on, perhaps, government or university
sensors, initial radiation readings, etc.? Thank you.
Anonymous
A: Lawrence Livermore National Laboratory has developed a
computer code called HOTSPOT, which is available for free on the
Internet. This code can be used to get a rough estimate of the
amount of contamination, the plume (cloud) progression, etc.
Government officials can use computer tools such as HOTSPOT to
determine quickly what emergency steps should be taken. More
sophisticated modeling codes can be used to make more accurate
determinations of contamination in the intermediate to long terms.
Citizens if they are so inclined could learn to use HOTSPOT, but I
feel that it makes the most sense to listen to authorities, because
they will have the equipment to determine quickly and in sufficient
detail where plumes are headed and what type of radioactive material
is involved.
Q: How is low-level radiation good for your health?
Anonymous
A: Thank you for your question. Answering it gives me an
opportunity to refute the notion that I may have appeared to endorse
on the NOVA show the idea of a hormesis effect. Hormesis posits that
exposing people to low-level doses of ionizing radiation greater
than the inescapable background radiation will lead to health
benefits. Based on my readings of this subject, I believe that this
notion mainly comes from a false reasoning by analogy. It is known
that small doses of certain chemicals, such as selenium, are
essential for good health, but large doses are surely harmful.
Similarly, proponents of hormesis argue that low-level doses of
ionizing radiation stress the body enough to stimulate an "adaptive
response," which could result in protective effects for the body.
The reasoning by analogy is false because ionizing radiation
interacts with living tissue differently than the way bacteria,
viruses, or chemicals typically interact with the body.
Health studies—with proper control groups in place and that
consider whether the group under study is generally healthier than
other populations because of increased access to health care or
access to adequate nutrition and exercise—have not shown
evidence for a hormetic effect. In sum, there is no clear evidence
that low-level ionizing radiation is good for your health. For now,
I believe that the safe response is to keep radiation exposure "as
low as reasonably achievable," known by the acronym ALARA in the
radiation safety field.
Q: What length of time would pass between the detonation of a
dirty bomb and the public notification of the event? It seems that
it would take some time to determine that radiological material was
present in a terrorist bomb attack. Are we prepared to test any and
all blast sites for the presence of radioactive material?
Scott Nice Dallas, PA
A: These are all vital questions. The short answer is that I
don't know how long it would take for public notification. The
actual response would strongly depend on the answer to your second
question. That is, if authorities are prepared to test any and all
blast sites for the presence of radioactive material, then they
would have the information in a short period of time in order to
notify the public. I've read press accounts that emergency
responders are gearing up to be able to conduct these tests. But I
do not know the actual extent and depth of these efforts.
Q: What solutions/products do you use to clean up radioactive
materials? Sorry I missed the show; I learned a lot from the
Q&A.
Anonymous
A: Presently, clean up or decontamination is mainly at a
low-tech stage—so-called "muck and truck." Techniques include
sand-blasting buildings to remove the layers of contamination and
removing the layers of contaminated soil and trucking it away. I
understand from talking to some U.S. national laboratory scientists
that more advanced research and development to find effective
decontamination methods are underway. As Michael Levi said on the
NOVA program, we really can't eliminate radioactivity; we can only
transfer it from one place to another. I would add that then we
would have to wait until the radioactive materials decay. For a
substance such as cesium-137 with a 30-year half-life, we would have
to wait at least six or seven half-lives or about 200 years until
the material has decayed to very small amounts.
Q: Do you think there is any value to the Red
Cross/government guide to terrorism disaster plans? Is there
anything else you recommend we do?
Anonymous
A: In general, the Federal Emergency Management Agency (FEMA)
guide and the Department of Homeland Security's www.ready.gov Web
site provide useful general information that can be helpful for most
emergencies, such as hurricanes, tornadoes, etc. In particular,
these sources of information usefully discuss the three principles
to minimize excess radiation exposure. These principles are time,
distance, and shielding. Minimize the time of exposure. Maximize the
distance between you and the radiation source. Maximize the amount
of shielding between you and the source.
However, the government has to be able to detect ionizing radiation
from a dirty bomb in a rapid enough fashion to give people proper
instructions as to the particular event. As my colleague Michael
Levi has said, smoke detectors in homes help provide the alert
system that people need to be able to remove themselves from
possible danger in a calm but expeditious manner. Similarly, we need
the equivalent of a smoke detector for radiation. Perhaps the
government has adequate radiation detectors in place, but I'm not
sure.
Q: Cs-137 was illustrated as dirty bomb material in the NOVA
special. I understand Cs-137 poses a great threat because of its
physical form (powder) and availability, however other isotopes have
been widely produced and distributed. Do other easily exploitable
isotopes such as Co-60 have the same potential for dispersion, or
does the physical form of most of the other exploitable isotopes
make wide dispersion unlikely? Additionally if you would name
several other isotopes that have high potential to be exploited, it
would be very helpful, as I am involved in preparations being made
to respond to a RDD. Thank you for providing accurate information
regarding this horrible threat.
Curtis Liddle Boston, MA
A: If you don't mind, I'm copying part of an answer to an
earlier question to answer part of your question: In the recently
published report "Commercial Radioactive Sources: Surveying the
Security Risks," Occasional Paper No. 11, Center for
Nonproliferation Studies, by myself, Tahseen Kazi, and Judith Perera
(available at www.cns.miis.edu), we describe the top seven
radioisotopes that if present in large enough amounts in a
radioactive source would pose inherent radiological security risks.
These radioisotopes are americium-241, californium-252, cesium-137,
cobalt-60, iridium-192, plutonium-238, and strontium-90. These are
all produced in nuclear reactors. In addition, we would include
radium-226, a naturally occurring radioisotope that has been widely
used throughout the world.
Concerning the dispersibility of radioisotopes other than
cesium-137, cobalt-60, for example, is usually in a solid metal
form, so in that form it would be difficult to disperse. However, it
is not impossible to make cobalt-60 more dispersible, but in doing
so even suicidal terrorists could risk exposing themselves to a
lethal dose of radioactivity in a very short period of time. In the
report cited above, my co-authors and I recommend that radioactive
source producers should strive to make sources that are relatively
difficult to disperse. One way to do this would be to reduce the
production of powdered cesium chloride.
Q: After watching the program about dirty bombs, I had a
question. I live near Lake Michigan, and I was wondering what effect
a dirty bomb would have on the ecosystem of a large body of water?
What about a pond or stream, and would these bombs eventually effect
ocean life?
Anonymous
A: Again, if you don't mind, I'll quote from an earlier
answer: "Because contaminating large water supplies to levels beyond
acceptable health limits would require an enormous amount of
radioactive material, this method is not likely to succeed.
Moreover, certain radioisotopes, such as Pu-238 [plutonium-238], are
not even water soluble and would tend to sink to the bottom of
reservoirs, thereby presenting an essentially insignificant danger
to human health." (Source: "Commercial Radioactive Sources:
Surveying the Security Risks," Occasional Paper No. 11, Center for
Nonproliferation Studies, p. 19.) Perhaps small ponds could become
highly contaminated if there is enough radioactive material and if
the radioactive material is soluble.
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