Highly enriched uranium

Supply Projections. Additional supphes are expected to be necessary to meet the projected production shortfall. A significant contribution is likely to come from uranium production centers such as Eastern Europe and Asia, which are not included in the capabihty projections (27). The remaining shortfall between fresh production and reactor requirements is expected to be filled by several alternative sources, including excess inventory drawdown. These shortfalls could also be met by the utili2ation of low cost resources that could become available as a result of technical developments or pohcy changes, production from either low or higher cost resources not identified in production capabihty projections, recycled material such as spent fuel, and low enriched uranium converted from the high enriched uranium (HEU) found in warheads (28). 

HEU De-Enrichment. Highly enriched uranium (HEU), initially enriched to >93% U, for use in research, naval reactors, and nuclear weapons, may be de-enriched and fabricated into fuel for civihan nuclear reactors. An estimate of the world inventory of highly enriched uranium in the nuclear weapons states is provided in Table 6 (34). 

The recycle weapons fuel cycle rehes on the reservoir of SWUs and yellow cake equivalents represented by the fissile materials in decommissioned nuclear weapons. This variation impacts the prereactor portion of the fuel cycle. The post-reactor portion can be either classical or throwaway. Because the avadabihty of weapons-grade fissile material for use as an energy source is a relatively recent phenomenon, it has not been fully implemented. As of early 1995 the United States had purchased highly enriched uranium from Russia, and France had initiated a modification and expansion of the breeder program to use plutonium as the primary fuel (3). AH U.S. reactor manufacturers were working on designs to use weapons-grade plutonium as fuel. 

The first reactor, SM-1, was operated at Fort Belvoir, Virginia. Others were located ia Wyoming, Greenland, Alaska, and Antarctica. The fuel consisted of highly enriched uranium as the dioxide, dispersed ia stainless steel as plates or rods. Details are available ia Reference 18. 

The determination of critical si2e or mass of nuclear fuel is important for safety reasons. In the design of the atom bombs at Los Alamos, it was cmcial to know the critical mass, ie, that amount of highly enriched uranium or plutonium that would permit a chain reaction. A variety of assembhes were constmcted. Eor example, a bare metal sphere was found to have a critical mass of approximately 50 kg, whereas a natural uranium reflected 235u sphere had a critical mass of only 16 kg. 

The NRC also imposes special security requirements for spent fuel shipments and transport of highly enriched uranium or plutonium materials that can be used in the manufacture of nuclear weapons. These security measures include route evaluation, escort personnel and vehicles, communications capabiHties, and emergency plans. State governments are notified in advance of any planned shipment within their state of spent fuel, or any other radioactive materials requiring shipment in accident-proof. Type B containers. 

The political problems with profound economic impact could include, for example, the significance of the continuing worldwide growth of nuclear power, with such issues as the use of Highly Enriched Uranium (HEU) and Plutonium obtained from tire dismantling of U.S. and former USSR nuclear weapons the urgency of nonproliferation the disposal of civilian and military nuclear waste nuclear power alternatives. 

Notwithstanding the Iraqi lesson learned that the possibility of undeclared nuclear activities must be taken seriously and their possible existence sought out, the concern with undeclared activities as a proliferation risk is not new and their possible existence has always been recognized, indeed, presumed, in ary serious analysis of safeguards. Even purified plutonium or highly enriched uranium metals are harmless in bulk form. Further steps, specifically fabrication into weapons components, are necessary before these materials can result in proliferation and these steps, while perhaps not demanding, are not trivial. They are necessarily presumed to exist if the diversion of separated plutonium or HEU is discovered, since no reliable means for their detection are available. 

Nuclear Materials. The United States has deployed sensors both nationwide and overseas for the detection of nuclear materials. Although the presence of highly enriched uranium (an indication of a functional or potential nuclear weapon) would present the greatest threat, currently deployed sensors are unable to detect this material because of its low radioactivity. The Department of Homeland Security alone spent more... 

High-energy irradiation, silicone network preparation via, 22 567 High energy ruminant feeds, 10 864-865 High enriched uranium (HEU), 17 526 Higher aliphatic alcohols aldol process, 2 41-43 analysis, 2 9-10, lOt chemical reactions, 2 4-6 economic aspects, 2 7-9 health and safety factor, 2 6 manufacture from fats and oils, 2 12-19 oxo process (odd-numbered alcohols), 2 1, 10, 36-41... 

In fast (neutron) reactors, the fission chain reaction is sustained by fast neutrons, unlike in thermal reactors. Thus, fast reactors require fuel that is relatively rich in fissile material highly enriched uranium (> 20%) or plutonium. As fast neutrons are desired, there is also the need to eliminate neutron moderators hence, certain liquid metals, such as sodium, are used for cooling instead of water. Fast reactors more deliberately use the 238U as well as the fissile 235U isotope used in most reactors. If designed to produce more plutonium than they consume, they are called fast-breeder reactors if they are net consumers of plutonium, they are called burners . 

For the purpose of this discussion, radiological materials that could be used in a terrorist attack are divided into three categories (1) bomb-grade nuclear material, (2) nuclear reactor fuel and associated waste products, and (3) industrial sources. Bomb-grade nuclear material includes concentrated plutonium and/or highly enriched uranium (>20% U-235) that may be used to build a nuclear weapon, assuming a terrorist group cannot or has not already secured an assembled weapon. 

Highly enriched uranium is uranium composed of >20% by weight of the U-235 isotope. 

Cases Involving Thefts of Highly Enriched Uranium and Plutonium... 

Democratic Republic of Congo. It contained low-enriched uranium with a U-235 content of 19.9% —just below the 20% threshold defining highly enriched uranium. It is uncertain whether the rod was ever recovered. 

Albright, E., Berhout, F., and Walker, W., World Inventory of Plutonium and Highly Enriched Uranium, Oxford University Press, New York, 1993. 

HELP HEU HFO HFR HLW HREE HRL HT HTGR HWR Hydrological evaluation of landfill performance Highly enriched uranium Hydrous ferrous oxide or ferric hydroxide Hot fractured-rock High-level nuclear waste Heavy rare earth elements (Gd-Lu) Hard rock laboratory High temperature High-temperature gas-cooled reactor Heavy water reactor... 

Albright. D. and F. Berkhout Plutonium and Highly Enriched Uranium, 1996 World Inventories, Capabilities, and Policies, Oxford University Press, Inc., New York, NY, 1996. 

However, at this time all such LMRs have been shut down and are being decommissioned. Programs are also underway to use conventional uranium dioxide fuel containing blended down highly enriched uranium... 

Although the fission products could be recovered as byproducts from the waste from spent nuclear reactor fuel, special-purpose neutron irradiation of highly enriched uranium (isotopically separated uranium-235) followed by chemical separation is the normal production method. The major products, molybdenum-99 and iodine-131 with fission yields of 6.1 and 6.7 percent, respectively, have important medical applications. Mo-99,... 

The fuel which was used in these SSBNs is based on a UZr metallic alloy with highly enriched uranium for which no reprocessing process has been developed. 

---