Evaluation of the fission cross-section within the multi-modal fission approach for 235U(n, f) Original Research Article

The need for nuclear data of increased accuracy for nuclear technologies represents a permanent challenge to find powerful methods for data evaluation. One of the most important isotopes for reactor physics, whose data must be known with a high degree of accuracy is 235U. Despite the fact that it was intensively studied the evaluation of the fission process in the frame of the multi-modal model is a challenge. The branching ratios of the three most dominant fission modes, the two asymmetric standard I (S1) and standard II (S2) modes and the symmetric super-long (SL) mode are taken into account. Deconvoluted fission cross-sections for S1, S2 and SL modes for 235U(n, f), based on experimental fission mode branching ratios, were calculated for the first time in the incident energy range 0.01 to 5.5 MeV providing good agreement with the experimental fission cross-section data. Including the concept of multi-modal fission into nuclear reaction models could lead to a better understanding and provides a more consistent description of the fission process.