Reprocessing LMFBR Fuels

Proceedings of the IAEA Meeting on LMFBR Fuel Reprocessing, Leningrad, 1976 , translated by ERDA. 

Plants in the UK, USSR and France are now reprocessing irradiated UO2/PUO2 fuels and LMFBR fuel reprocessing has been the subject of international conferences. " The plant at Cap la Hague, France, employs a 30% TBP solution and no U/Pu separation is undertaken, so that a mixed U/Pu product is obtained. Fluoride is added to the process feed to complex zirconium and suppress its extraction." The Dounreay plant in the UK employs a 20% TBP/OK solution and uses sulfuric acid to effect the U/Pu separation. TBP poorly extracts Pu or U from sulfuric acid solutions, but in mixed HNO3/H2SO4 the equilibria shown in equations (206) and (207) must be considered. The equilibrium constants for these reactions, Kj, and K i, are given... 

M3. Marm, S., and A. R. Irene A Study of Plutonium Polymer Formation and Precipitation as Applied to LMFBR Fuel Reprocessing, Report ORNDTM-2806, Dec. 22, 1969. 

The second approach, which represents a departure from previous Pur ex partitioning, provides for the quantitative reduction of Pu to Pu3 with HAN and N Hlf (as the holding reductant) prior to the introduction of the U- and Pu-containing feed into a second cycle extraction column (Fig. 2). This method was proposed for both the EXXON reprocessing plant in Tennessee (10) and the ORNL Reprocessing Facility for LMFBR fuel (11). HAN will continue to be an attractive reductant because, not only is the introduction of metallic cations avoided, but HAN is decomposed safely by heating at temperatures above 60°C, which simplifies the reoxidation of Pu to Pu prior to subsequent extraction cycles. 

Irvine, A. R., and Jones, F. J., "LMFBR Spent Fuel Reprocessing A Study of an Industrial-Scale Facility," Report... 

Baumgartner, F., Ochsenfeld, W., and Schmieder, H., "Development Work on Reprocessing of Oxidic LMFBR Fuel by the Purex Process," Paper presented at 82nd AIChE Mtg., Atlantic City, N.J., 1976. 

Tsujino, T. Advisory Group Meeting on Reprocessing of LMFBR fuels (Leningrad, USSR, 1976). 

Extraction Process Having Application to the Reprocessing of LMFBR Fuels, Report ORNL 746, 1972. 

To reduce the specific power somewhat in reprocessing, it is planned to combine irradiated fuel from the LMFBR core with irradiated fuel from the LMFBR blankets in proportion to the rates at which they are discharged from the reactor. Even so, the specific power of LMFBR fuel cooled ISO days is 1.4 times that of LWR fuel cooled the same length of time. 

Tfie concentration of plutonium in combined core and blanket fuel from the LMFBR is more than 10 times that of LWR fuel. This is the most significant difference between the two fuels with respect to reprocessing. Other important differences are the greater amounts of tritium and the 140 percent greater ruthenium activity, and the 60 percent greater overall specific activity of ISO-day cooled LMFBR fuel. 

The following discussion of reprocessing LMFBR fuels outlines the principal process steps, lists the main problem areas, and discusses possible solutions. Since 1973, international dissemination of reprocessing information has been restricted. This discussion of reprocessing LMFBR fuel is thus less complete and less up to date than would be desired. 

Figure 10.28 shows the principal steps in reprocessing LMFBR fuel. Feed quantities are for a plant fed with 5 MT/day of irradiated heavy metal (uranium plus plutonium). Feed is combined core and blanket assemblies from LMFBRs operated under conditions nearly the same as those on which Fig. 3.34 and Tables 8.8 and 10.20 were based. The head-end steps 1 through 6 follow one alternative of several sketched in Report ORNL-4422 [05]. 

Special problems in reprocessing LMFBR fuels compared with LWR fuels are as follows ... 

Figure 10.29 shows the principal steps in applying the Purex process to irradiated LMFBR fuel, step 7 of Fig. 10.28. The flow scheme and the compositions and locations of solvent, scrubbing, and stripping streams have been taken from the process flow sheet of a 1978 Oak Ridge report [Oil] describing a planned experimental reprocessing facility designed for 0.5 MT of uranium-plutonium fuel or 0.2 MT of uranium-plutonium-thoiium fuel per day. As that report gave process flow rates only for the uranium-plutonium-thorium fuel. Fig. 10.29 does not give flow rates for the uranium-plutonium fuel of present interest. This flow sheet shows the codecontamination step, in which flssion products are separated from uranium and plutonium the partitioning step, which produces an aqueous stream of partially decontaminated...

G16. Gronier, W. S. Calculation of the Transient Behavior of a Dilute-Purex Solvent Extraction Process Having Application to the Reprocessing of LMFBR Fuels, Report ORNL 746, Apr. 1972. 

The quantity of natural uranium to be mined for the production of the heavy metal reprocessed. This type of reference has already been used in Chap. 8 because it is the most general one with no special assumption about the form of the natural uranium involved. Its disadvantage is the strong dependence on fuel-cycle type. With an equilibrium LMFBR fuel cycle, for instance, the quantity of uranium to be mined becomes close to zero and, consequently, the period of significance of the waste hazard becomes extremely long. To maintain its applicability, the uranium equivalent must always be calculated on the virtual basis that all power has been generated from freshly mined uranium. 

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