NUCLEAR DATA FOR U-Pu FUEL CYCLE EVALUATION

E. FORT

CEA, CEN Cadarache, DRP/SPRC, 13108 ST PAUL-LEZ-DURANCE, FRANCE

The need for nuclear data for the U-Pu fuel cycle evaluation is reviewed for both thermal and fast reactors. It is interesting to note that the higher burn-up rates planned for future LMFBR's or already obtained for PWR have not so far significantly modified the requests lists.

The various methods used to derive the requests are also described. Some of them, which recently appeared, allow the use of integral data for the assessment of microscopic data requests. This is one way to stress the importance of the coupling of the microscopic and integral information.

The progress made during the past 10 years on the evaluation tools and associated parameter databases is impressive. It results from the accumulation of microscopic data of high quality and from the incorporation of more and more basic physics into the models.

The test of the evaluated files against integral data requires several conditions :

quality in the data processing,

cleanness of the experimental environment,

correctness of the neutronic calculations.

Such conditions are considered to have been met in consistent sets of integral data which have been used to check major data files in the thermal and the fast ranges concerning the Minacs, FP, structural materials. The quality of the evaluated data available for the U-Pu fuel cycle valuation is satisfying in most cases. The quality of the evaluation tools presently available is a guarantee that the last major requests will be satisfied within a reasonable time scale provided that a minimum of well targeted microscopic measurements are performed.

The long standing problem of the production of ²³⁶Pu via the (n,2n) process on ²³⁷Np is described in detail as an excellent example, possibly to be followed in the future, by that which can be obtained when looking at the possible convergence of the information from various sources : integral, microscopic, nuclear model.