Frank von Hippel

Explosive Properties of Reactor-Grade Plutonium

The following discussion focuses on the question of whether a terrorist organization or a threshold state could make use of plutonium recovered from light-water-reactor fuel to construct a nuclear explosive device having a significantly damaging yield. Questions persist in some nonproliferation policy circles as to whether a bomb could be made from reactor-grade plutonium of high burn-up, and if so, whether the task would be too difficult for a threshold state or terrorist group to consider. Although the information relevant to these questions is in the public domain, and has been for a considerable time, it is assembled here for use by policy makers and members of the public who are concerned about preventing the spread of nuclear explosives.

U-232 and the Proliferation- Resistance of U-233 in Spent Fuel

The factors influencing the level of U‐232 contamination in U‐233 are examined for heavy‐water‐moderated, light‐water‐moderated and liquid‐metal cooled fast breeder reactors fueled with natural or low‐enriched uranium and containing thorium mixed with the uranium or in separate target channels. U‐232 decays with a 69‐year half‐life through 1.9‐year half‐life Th‐228 to T1–208, which emits a 2.6 MeV gamma ray upon decay. We find that pressurized light‐water‐reactors fueled with LEU‐thorium fuel at high burnup (70 MWd/kg) produce U‐233 with U‐232 contamination levels of about 0.4 percent. At this contamination level, a 5 kg sphere of U‐233 would produce a gamma‐ray dose rate of 13 and 38 rem/hr at 1 meter one and ten years after chemical purification respectively. The associated plutonium contains 7.5 percent of the undesirable heat‐generating 88‐year half‐life isotope Pu‐238. However, just as it is possible to produce weapon‐grade plutonium in low‐burnup fuel, it is also practical to use heavy‐water reactors to produce U‐233 containing only a few ppm of U‐232 if the thorium is segregated in “target” channels and discharged a few times more frequently than the natural‐uranium “driver” fuel. The dose rate from a 5‐kg solid sphere of U‐233 containing 5 ppm U‐232 could be reduced by a further factor of 30, to about 2 mrem/hr, with a close‐fitting lead sphere weighing about 100 kg. Thus the proliferation resistance of thorium fuel cycles depends very much upon how they are implemented.

The radiological and psychological consequences of the Fukushima Daiichi accident

The release of radioactivity into the atmosphere from the Fukushima Daiichi accident has been estimated by Japan’s government as about one-tenth of that from the Chernobyl accident. The area in Jap...The release of radioactivity into the atmosphere from the Fukushima Daiichi accident has been estimated by Japan’s government as about one-tenth of that from the Chernobyl accident. The area in Japan contaminated with cesium-137—at the same levels that caused evacuation around Chernobyl—is also about one-tenth as large. The estimated number of resulting cancer deaths in the Fukushima area from contamination due to more than 1 curie per square kilometer is likely to scale correspondingly—on the order of 1,000. On March 16, 2011, the Nuclear Regulatory Commission advised Americans in the region to evacuate out to 50 miles (NRC 2011a). If the Japanese government had made the same recommendation to its citizens, it would have resulted in the early evacuation of about two million people instead of 130,000. Because contaminated milk was interdicted in Japan, the number of (mostly non-fatal) thyroid cancer cases will probably be less than 1 percent of similar cases in Chernobyl. Unless properly dealt with, however, fear of ionizing radiation could have long-term psychological effects on a large portion of the population in the contaminated areas.

Nuclear Waste Management in the United States—Starting Over

The debate has begun again over the disposition of nuclear fuel and waste. The recent action to shelve Yucca Mountain as the potential geologic repository for U.S. “spent” (i.e., no longer usable) nuclear fuel (SNF) and high-level nuclear waste (HLW) (1) brings to a close a 30-year effort to develop and implement a policy for nuclear wastes in the United States. Selection by Congress in 1987 of Yucca Mountain in Nevada as the only site to be investigated condemned the United States to pursue a policy that had no backup if Yucca Mountain failed politically or technically.

The hazard posed by depleted uranium munitions

This paper assesses the radiological and chemical hazards resulting from the use of depleted uranium (DU) munitions. Due to the low radioactivity of DU, radiological hazards to individuals would become significant in comparison to natural background radiation doses only in cases of prolonged contact—for example, when shards of a DU penetrator remain embedded in a soldiers body. Although the radiation doses to virtually all civilians, would be very low, the cumulative “population dose” resulting from the dispersal of hundreds of tons of DU, as occurred during the Gulf War, could result in up to ten cancer deaths. It is highly unlikely that exposures of persons downwind from the use of DU munitions or consuming food or water contaminated by DU dust would reach the estimated threshold for chemical heavy‐metal effects. The exposures of soldiers in vehicles struck by DU munitions could be much higher, however, and persons who subsequently enter such vehicles without adequate respiratory protection could potentially be at risk. Soldiers should be trained to avoid unnecessary exposure to DU, and vehicles struck by DU munitions should be made inaccessible to curious civilians.

Fission Power: An Evolutionary Strategy

Motivated by concerns about the difficulty of safeguarding the large flows of plutonium in a breeder reactor fuel cycle, we explore the resource and economic implications of a strategy in which there is no nuclear weapons-usable material in fresh reactor fuel. The strategy involves the deployment of already developed types of advanced converter reactors which, unlike the breeder, can be operated effectively on proliferation-resistant once-through fuel cycles. Advanced converter reactors could be much more uranium-efficient on once-through fuel cycles than current systems and therefore could compete economically with breeders up to very high uranium prices. If necessary, the uranium requirements of an advanced converter reactor system could be reduced much further with the recycling of isotopically denatured uranium, but any commitment to a closed fuel cycle would be unnecessary for many decades.

Ending the production of highly enriched uranium for naval reactors

Chunyan Ma is a Researcher in Weapon System Development and Arms Control Studies in China’s Defense Science and Technology Information Center. Work on this paper was done while she was a Fellow at the Monterey Institute of International Studies (January-June 2000) and a Visiting Researcher at Princeton University’s Center for Energy and Environmental Studies (July 2000-January 2001). Frank von Hippel is a Professor of Public and International Affairs at Princeton University. His articles focus broadly on the technical basis for new nuclear disarmament and nonproliferation initiatives, including: deep cuts in the nuclear arsenals, taking U.S. and Russian missiles off hairtrigger alert, banning the production of fissile materials for weapons, and assisting Russia in down-sizing its nuclear weapon production complex.

Nuclear proliferation: Time to bury plutonium

Recycling plutonium is dangerous and costly. Britain should take the lead on direct disposal, say Frank von Hippel, Rodney Ewing, Richard Garwin and Allison Macfarlane.

Limited Proliferation-Resistance Benefits from Recycling Unseparated Transuranics and Lanthanides from Light-Water Reactor Spent Fuel

Keeping LWR plutonium mixed with other transuranics and with lanthanide fission products other than 154Eu does not make it significantly more self protecting or more difficult to fabricate into a nuclear weapon. Gamma-ray and neutron doses at one meter, heat generation, and spontaneous-neutron emission are calculated from 1-kg metal balls of weapon-grade plutonium, reactor-grade plutonium, and the full mix of transuranics in high-burnup light-water-reactor (LWR) spent fuel with and without the lanthanide fission products from the spent fuel. The total radiation dose rate from transuranics without the lanthanides is more than three orders of magnitude lower than the IAEAs threshold for self-protection, 1 Sv/hr (100 rems/hr) at 1 meter. Inclusion of either of two lanthanide fission products, 144Ce and 154Eu, could increase the dose rate above the self-protection threshold. However, 144Ce has a half-life of only 0.8 years and has already decayed away in all but the most recently discharged LWR spent fuel. 154Eu has a half-life of nine years but is not recycled with the transuranics in the pyroprocessing fuel cycle that was developed for the Integrated Fast Reactor.

Fissile Material Security in the Post‐Cold‐War World

During the cold war, the US and the Soviet Union each produced enough fissile material to make tens of thousands of nuclear weapons—between 100 and 200 metric tons of plutonium and about 1000 tonnes of highly enriched uranium (uranium enriched to more than 20% in U‐235). This weapons‐usable fissile material seemed invulnerable to theft until the collapse of the Soviet Union in 1991. Since then, subkilogram quantities of plutonium and multikilogram quantities of highly‐enriched uranium have been intercepted in Russia, the Czech Republic and Germany—apparently stolen from Russian nuclear facilities and intended for sale. the old Soviet security system for fissile material, which focused on the surveillance and control of those in contact with such material, has been largely swept away. Gone too is the economic security of nuclear workers, who may now be tempted or threatened by predatory criminal groups. the situation poses a grave risk to global security, because the biggest obstacle facing non‐nuclear‐wea...