Reactor fuel reprocessing, potential

Mason, G.W. Griffin, H.E. Demonstration of the potential for designing extractants with preselected extraction properties possible application to reactor fuel reprocessing, In Actinide Separations, J.D. Navratil and W.W. Schulz (Eds.), American Chemical Society, Washington, DC (1980), pp. 89-99. 

Demonstration of the Potential for Designing Extractants with Preselected Extraction Properties Possible Application to Reactor Fuel Reprocessing... 

The americium and curium isotopes formed during irradiation of nuclear reactor fuels are diverted into the high-level waste (HLW) stream during fuel reprocessing. The HLW is thus the biggest potential source for these elements, and R+D activities to develop a process for the recovery of Am and Cm from HLW were started in 1967. A major condition was that the process to be developed must not essentially increase the waste amount to be processed further, must not use strongly corrosive reagents, and must be compatible with the final waste solidification procedure. 

At the moment, a standard once-through fuel cycle using low enriched (up to 10% of by weight) uranium fuel without spent nuclear fuel reprocessing is considered as basic for the MARS reactor. It is assumed that MARS spent nuclear fuel will be placed in long-term storage until a decision is made on further use of the energy potential of actinides contained in this spent fuel. 

An assessment of the potential hazard due to the release of radioactive material has to take account of the following parts of the nuclear fuel cycle (i) mining and fabrication of fuel, (ii) operation of power reactors, (iii) reprocessing of fuel (if desired), and (iv) disposal of wastes. 

Since nearly all of the fission products generated in nuclear fuels are retained within the fuel cladding until the fuel is chemically reprocessed, the principal potential environmental sources of are the effluents from nuclear fuel reprocessing plants rather than those from nuclear reactors. 

Nuclear reactors are the prime producers of 1, but fuel reprocessing plants are the prime potential sources of environmental releases. Releases, however, can be minimized by careful design, operating procedures, and installation of efflcient treatment systems. 

Concern about the potential diversion of separated reactor-grade plutonium has led to a reduction ia U.S. governmental support of development of both plutonium recycle and the Hquid metal reactor. This latter ultimately depends on chemical reprocessing to achieve its long-range purpose of generating more nuclear fuel than it bums ia generating electricity. 

In plutonium-fueled breeder power reactors, more plutonium is produced than is consumed (see Nuclearreactors, reactor types). Thus the utilisa tion of plutonium as a nuclear energy or weapon source is especially attractive to countries that do not have uranium-enrichment faciUties. The cost of a chemical reprocessing plant for plutonium production is much less than that of a uranium-235 enrichment plant (see Uranium and uranium compounds). Since the end of the Cold War, the potential surplus of Pu metal recovered from the dismantling of nuclear weapons has presented a large risk from a security standpoint. 

Indications from both microscopic analyses of metallic particles from corrosion tests and evidence from the Oklo natural reactors indicate that performance assessment calculations should not assume 99Tc is easily mobilized. It is entirely inappropriate to use "Tc release as a marker for fuel corrosion because Tc is not located in the fuel matrix. The TEM examinations of corroded e-particles have shown that Mo is preferentially leached from these phases, a behaviour that is similar to the one observed at Oklo. It is interesting to note that laboratory dissolution of billion-year old 4d-metallic particles for a chemical analysis required a corrosive mix of peroxide and acid (Hidaka Holliger 1998) similar to the experience at SNF reprocessing plants. It is doubtful that the oxidation potential at the surface of an aged fuel will be sufficient to move Tc(0) from the e-metal particles. 

---