Fuel pyrochemical

Although the retention of selective fission products in fissile materials may not adversely affect the performance of fuel in a reactor, the intensity of the gamma radiation is such that the fissile material must be handled, transferred, and fabricated remotely. As a result, it is both technically difficult to divert the fissile material and fabricate a weapon, and nearly impossible to do so without detection. The levels of residual radioactivity in the product of some of the pyrochemical or dry processing methods is close to that found in spent unreprocessed fuel and hence the reprocessed product presents a risk to proliferation only trivially less than that of spent fuel. Pyrochemical and dry processing methods can be used that will... 

The oldest and still widely used in pyrotechnics and fireworks "first fire" and "starter" mixture is BkPdr. It belongs to mixts without metallic ingredients. Metallic mixts contain combustible powdered metals, such as Mg, Al, Zr etc. Metalloids B and Si are considered metallic fuels because of their similarity in pyrochemical behavior to metals. Although BkPdrs are described in Vol 2 of Encycl, pp Bl65ff, we are giving here as Table E compns of three formulations used in pyrotechnics, as described by Ellern (Ref 57, p 375)... 

Knighton, J.B. Baldwin, C.E. Pyrochemical Coprocessing of Uranium Dioxide-Plutonium Dioxide LMFBR Fuel by the Salt Transport Method, Rocky Flats Report RFP-2887, CONF-790415-29 (1979). 

IFR [Integral Fast Reactor] A pyrochemical process for processing the fuel from a fast nuclear reactor. The uranium metal fuel is dissolved in a fused melt of lithium and potassium chlorides and... 

PYRO-A A pyrochemical process proposed for use in nuclear reprocessing for separating transuranic elements from fission products, once the uranium has been removed by the UREX process. The spent fuel is dissolved in a molten salt bath and electrolyzed. The transuranic elements deposit on the cathode, and the fission products remain in the melt. Developed by the Argonne National Laboratory. See also PYRO-B. 

This Symposium has been organized about new concepts, new systems, and new developments in actinide separations methodology. Much of the work reported here is based on fundamental actinide chemistry developed since the Manhattan Project days. The chapters in this volume describe ion exchange, solvent extraction, precipitation, pyrochemical, photochemical, and other methods of actinide separations as well as application of these separation methods to power reactor fuel reprocessing and recovery of actinides from waste solutions. 

National Program for Pyrochemical and Dry Processing of Spent Reactor Fuel... 

Zinc Distillation Process ( 3, 4 ). A zinc distillation process was selected as a reference pyrochemical process that would have a sufficient degree of proliferation resistance that it could be used by nonweapons nations to reprocess spent fuel without significantly increasing their weapons production capability. The process has the inherent proliferation-resistant advantages of being a low decontamination process with limited plutonium enrichment in uranium-plutonium-zinc mixtures. The process chemistry flow sheet for this process is shown in Figure 1. 

Pyrochemical Coprocessing of Uranium Dioxide-Plutonium Dioxide LMFBR Fuel by the Salt Transport Method... 

The present work at Rocky Flats is an extension of the Argonne work and is directed to development of a proliferation resistant pyrochemical process for LMFBR fuels. This article describes a conceptual pyrochemical process and preliminary engineering concepts for coprocessing uranium and plutonium in spent LMFBR core-axial blanket and radial blanket fuels using the Salt Transport Process. 

Criteria used to develop the conceptual pyrochemical process for coprocessing uranium and plutonium from spent LMFBR fuel include the following ... 

The pyrochemical coprocessing of spent nuclear fuel by the Salt Transport Process appears to be a potentially viable reprocessing method, not only as an "exportable proliferation resistant technology," but as a domestic reprocessing operation. All operations are nonaqueous and waste generation is in solid form, thus requiring no conversion from aqueous solutions to solids. 

As indicated in the reference flow sheet for oxide fuels (Fig. 1) the processing of the fuel constituents requires a reduction step. Pyrochemical reduction of UO2 >(14) Pu02, (15) and... 

Brand, G. E. Murbach, E. W., "Experiments on Pyrochemical Reprocessing of Uranium Carbide Fuel" in "Symposium on Reprocessing of Nuclear Fuels, The Metallurgical Society of AIME, Ames, Iowa, August, 1969", Nucl. Metallurgy, Vol. 15, 1969. 

The use of molten nitrates as oxidants for nuclear fuel components has not been studied as much as other pyrochemical or pyrometallurgical processes. Previous studies of molten nitrate systems were primarily conducted in European laboratories, although some research was done in Japan and the United States. 

Based on available information, we believe that transfer of the uranate to a molten chloride system with electrolytic reduction is the most feasible method. Electrolytic deposition from molten alkali metal chlorides was an integral step in the pyro-chemical process known as the Hanford Salt Cycle. Documentation of this phase of the process was extensive and also represents one of the very few pyrochemical processes that has been carried through pilot-plant scale on irradiated fuel. Unknowns exist, such as the rate and conditions of uranate dissolution, but considerable use could be made of previously documented results. 

Wurm, J.G. Heylen, P.R. DeBeukelaer, R.C. DeConinck, A. "Pyrochemical Head-End Conception for Fast Breeder Fuel Processing", EUR-4614e, 1970. 

Brambilla, G. Caporali, G. "Process for the Pyrochemical Separation of Plutonium from Irradiated Nuclear Fuels", Ger. Offen. 2 611 333, 1976. 

To the melts containing a trivalent cation belong a great number of systems of alkali metal halide-rare earth metal halide systems. Lanthanide halides play an important role in the production of lanthanide metals by molten salt electrolysis and they are also used in a number of applications ranging from lighting to catalysis, through pyrochemical reprocessing of nuclear fuel. 

The three types of nonaqueous processes on which most development work has been done are (1) pyrometallurgical processes, involving high-temperature processing of metallic fuels (2) pyrochemical processes, involving high-temperature processing of oxide or carbide fuels and (3) fluoride volatility processes, in which elements in fuel are converted to fluorides, which are then separated by fractional distillation. 

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