Reprocessing operations

Processing Chip Screen Rejects. Overlong chips are usually reprocessed in a smaller version of the disk-type roundwood chipper. Overthick chips are reprocessed in a chip sheer. The product from these reprocessing operations returns to the main chip flow ahead of the screens (see Eig. 10). The fines are sent to a hog boiler as fuel, or else rescreened. Pin chips are metered back into the main chip flow or sent to a fine-particle pulping system. 

Many reports on the hydrolysis of Pu(IV) and polymerization (aggregation) of the primary hydrolysis products exist in one form or another. The validity of some of the earlier data may be subject to question because the experimental conditions were not properly controlled. Therefore, these systems deserve further consideration for the sake of refinements. Nevertheless, the major area of interest for the future will remain with interactions between Pu(IV) hydrolysis products and other reactive species present in the solution. There is not only considerable promise of elucidating novel chemical interactions, but there is also a great practical need to fully understand the extent of these interactions in order to ensure the most complete control of plutonium in reprocessing operations. 

Effluent reduction using BAT, PSNS and PSNS for cathode reprocessing (operated with dry potline scrubbing commingled and not commingled with other process or nonprocess coaters 157.600 70.060 ... 

LENNEMANN, W.L. (1972). Management of radioactive aqueous wastes from U.S. Atomic Energy Commission s fuel reprocessing operations, page 357 in Proceedings of Symposium on the Management of Radioactive... 

The results are reported of a study of the influence of stabilisers and antioxidants (Irganox B900 and Sandostab P-EPQ) on the rheological and mechanical properties of recycled PP and PVC. The effects of the number of reprocessing operations, reprocessing conditions, molecular parameters of the polymers and the type and content of stabilisers on the properties of the recycled polymers are discussed. 8 refs. 

According to the report by Oi (1998) at the end of 1997, more than 130,000 tonnes of spent fuel from power reactors were estimated to be stored world-wide containing about 1000 tonnes of plutonium. Another 170 tonnes of separated plutonium were in storage from civilian reprocessing operations, and about 100 tonnes of excess plutonium from dismantled warheads no longer required for defense purposes were scheduled to be released from the military sector of Russia and United States. 

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. 

Cathode reprocessing (operating with dry potline scrubbing and not commingled)... 

The great improvement in performance of pulse columns over other column-type contactors, and the simple and reliable equipment involved, have led to the widespread use of pulse columns in many solvent extraction operations separating and purifying nuclear materials. In addition to their use in some fuel reprocessing operations, as mentioned above, pulse columns have been used in uranium purification plants at Femald, Ohio [Cl], and Gore, Oklahoma (cf. Chap. 5). 

The calculated elemental composition, radioactivity, and decay-heat rate for discharge fuel are shown in Table 8.7 for the uranium-fueled PWR (cf. Fig. 3.31), in Table 8.8 for the liquid-metal fast-breeder reactor (LMFBR) (cf. Fig. 3.34), and in Table 8.9 for the uranium-thorium-fueled HTGR (cf. Fig. 3.33). These quantities, expressed per unit mass of discharge fuel, are useful in the design of reprocessing operations. For the purpose of comparison, all quantities are calculated for 150 days of postirradiation cooling. 

Lennemann, W. L. Management of Radioactive Aqueous Waste from U.S. Atomic Energy Commission s Fuel Reprocessing Operations, Experience and Plaiming, Proceedings of the Management of Radioactive Wastes from Fuel Reprocessing, Paris, 1972, Report CONF-721107, Mar. 1973, p. 357. 

Reprocessing operations should be subjected to appropriate evaluation to show that these steps consistently perform the expected functions and result in batches that comply with ail established standards, specifications, and characteristics. 

Early Work. The irradiated fuel, upon discharge from the reactor, comprises the residual unbumt fuel, its protective cladding of magnesium alloy, zirconium or stainless steels, and fission products. The fission process yields over 70 fission product elements, while some of the excess neutrons produced from the fission reaction are captured by the uranium isotopes to yield a range of hew elements—neptunium, plutonium, americium, and curium. Neutrons are captured also by the cladding materials and yield a further variety of radioactive isotopes. To utilize the residual uranium and plutonium in further reactor cycles, it is necessary to remove the fission products and transuranic elements and it is usual to separate the uranium and plutonium this is the reprocessing operation. 

At present a total of about 750 m of high-level waste concentrate, containing about 4 X 10 Ci (beta) and having a radioactive decay heat of about 2 MW, is contained in special storage tanks at Windscale. This is the cumulative total from about 25 years of reprocessing operations. 

Magnox cladding, which has been removed mechanically from spent fuel rods at the start of reprocessing operations, is contaminated with small pieces of fuel and will require treatment before disposal to the environment. At present, this waste is stored under water (to eliminate any fire risk) in large concrete silos and processes are now under development for the conditioning of this waste to make it suitable for disposal. The favored processing route comprises the following operations ... 

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