Reactors, fast

Fast reactor fuel assembhes are shrouded with a relatively heavy metal envelope. This envelope is removed before shearing by either laser cutting (14) or stress cracking (15). 

The fifth component is the stmcture, a material selected for weak absorption for neutrons, and having adequate strength and resistance to corrosion. In thermal reactors, uranium oxide pellets are held and supported by metal tubes, called the cladding. The cladding is composed of zirconium, in the form of an alloy called Zircaloy. Some early reactors used aluminum fast reactors use stainless steel. Additional hardware is required to hold the bundles of fuel rods within a fuel assembly and to support the assembhes that are inserted and removed from the reactor core. Stainless steel is commonly used for such hardware. If the reactor is operated at high temperature and pressure, a thick-walled steel reactor vessel is needed. 

Full advantage of the neutron production by plutonium requires a fast reactor, in which neutrons remain at high energy. Cooling is provided by a hquid metal such as molten sodium or NaK, an alloy of sodium and potassium. The need for pressurization is avoided, but special care is required to prevent leaks that might result in a fire. A commonly used terminology is Hquid-metal fast-breeder reactor (LMFBR). 

Most fast reactors that use Na or NaK as coolant utilize an intermediate heat exchanger (IHX) that transfers heat from the radioactive core coolant to a nonradio active Hquid-metal coolant loop, which has the reactor s steam generator. This helps minimize the spread of contamination in the event of a leak or fire. 

K. Wh t2, Eectures on Fast Reactors, American Nuclear Society, La Grange Park, lU., 1978. 

C. E. TiU, The Riquid-Metal Reactor. Overview of the Integrated Fast Reactor Rationale and Basis for Its Development, Presented to National Academy Sciences Committee on Future Nuclear Power, Argonne National Laboratory, Chicago, lU., Aug. 1989. 

A more recently developed pyrometaHurgical process is that of the proposed integral fast reactor, which would use metallic fuel (U—Pu—Zr alloy) and a molten salt electrorefiner as follows ... 

Pnictides. Plutonium nitride, PuN, has been studied as a possible fast-reactor fuel. It can be prepared by reaction of PuH with NH at 600—650°C or N2 above 230°C. The pnictides ate also interesting for their soHd-state magnetic and electrical properties. For the latter reason they also have been prepared as single crystals (165). 

Uranium and mixed uranium—plutonium nitrides have a potential use as nuclear fuels for lead cooled fast reactors (136—139). Reactors of this type have been proposed for use ia deep-sea research vehicles (136). However, similar to the oxides, ia order for these materials to be useful as fuels, the nitrides must have an appropriate size and shape, ie, spheres. Microspheres of uranium nitrides have been fabricated by internal gelation and carbothermic reduction (140,141). Another use for uranium nitrides is as a catalyst for the cracking of NH at 550°C, which results ia high yields of H2 (142). 

Fullwood, R. and R. C. Erdman, 1974, On the Use of Leak Path Analysis in Fault Tree Construction for Fast Reactor Safety, CONF-74040I-P3. 

Figure takes into account fast reactors. It is stated in original document that predictions are particularly speculative. 1971 consumption rates were taken as oil 2500 Mtoe gas 900 Mtoe coal 1500 Mtoe. 

Nuclear Niobium finds use in some nuclear reactors on account of its compatibility with uranium and liquid sodium/potassium at fast reactor temperatures. 

Hurst, P. and Cowen, H. C., Proc. Conf. Ferritic Steels for Fast Reactor Steam Generators, British Nuclear Energy Society, London, (1977)... 

Klueh, R. L., in Proc. Int. Conf. Sodium Technol. Large Fast Reactor Design, Nov. 7-9 1968 ANL-7520, Pt. 1, 171, Argonne National Laboratory Klueh, R. L., Corrosion, 25, 416 (1969)... 

Solar energy, 6, 488 surface modified electrodes, 6, 30 Sol-Gel process fast reactor fuel, 6, 924 Solid state reactions, 1, 463-471 fraction of reaction, 1, 464 geometric, 1, 464 growth, 1, 464 nucleation, 1, 464 rate laws, 1,464 Solochrome black T metallochromic indicators, 1,555 Solubility... 

Pu-239 is used as a fast reactor fuel, in nuclear weapons, and frequently in chemical research where production grade material of mixed isotopic content is suitable. Available enrichments range from 99.99+% to 97%. 

Pu-240 is principally used in flux monitors for fast reactors. Available enrichments range from 99+% to 93%. 

Since the largest scale usage of Na is as a coolant in nuclear fast reactors, purity information on this Na is included as a separate section. 

R. A. Davies, C. M. Robertson, Proc. Conf. on Fast Reactor Power Stations, British Nucl. Energy Soc., London (1974) Oiem. Abstr., 83, 169,809 (1975). 

Further away in time are possibilities of using fast reactors, though, at least for some decades, not as breeders. The Soviet navy has been using such reactors, using a lead/bismuth eutectic mixture as coolant, for some decades in some of their high performance submarines and it is understood that work is now going on to see whether this design could be made suitable for small commercial power production... 

The fact that fast reactors are an essential component of good nuclear non-proliferation practice since they destroy through beneficial use, nuclear material and source materials that could be used to make weapons. 

In addition it may be helpful to set up, or at least approve, a number of worid specialized manufacturing facilities for example, quality facilities to manufacture the hundred pressure vessels needed each year. Laboratories should be available to expeditiously solve reactor operating problems which may arise worldwide, and to improve reactor performance. And there should be an international program to develop the Fast Reactor which generates some sixty to a hundred times as much energy from a pound of uranium than do our present commercial reactors. 

With the expansion of nuclear power, the Fast Reactor is likely to be needed in the next half century as supplies of uranium for the present reactor types become scarce. Because of its efficiency in utilizing uranium the Fast Reactor can supply the world s energy needs indefinitely. 

Perhaps there should be centralized areas for storage of spent fuel from present reactor types. These storage areas should be adjacent to reprocessing plants which would be built to process the spent fuel to provide the new fuel for the Fast Reactors going on line. 

The fast reactor high level waste is accumulated at the reprocessing plants and retains its toxicity for only a few hundred years, rather than the tens of thousands of years ofthe spent fuel wastes from our present reactors,. Thus, the nuclear waste disposal problems are minimal and arrangements for disposal could be made on a global basis. 

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