Measurements of power profile of the BN-600 commercial fast reactor by gamma-scanning and analytical studies of experimental data

During 25 years of operation of BN-600 fast reactor at the Beloyarsk NPP, complex of analytical and experimental measurements has been developed for control of power rate distribution in the reactor core. Continuous control is performed by computational accompaniment based on three-dimensional multi-group analysis in hexagonal geometry in diffusion approximation. Periodical control is made by measuring of power rate profile in the standard fuel subassemblies of the BN-600 reactor by gamma scanning method on the stages of updating of the reactor core. By now, two cycles of such measurements have been performed when changing for the new reactor core design 01M2 providing 4-fold refueling mode and max fuel burn-up increased up to ∼11.1% h.a. In the paper given are brief description of analytical and experimental methods of monitoring of power profile of the BN-600 reactor, results of their comparison and estimation of their precision based on the results of the above studies. It has been demonstrated that the use of 26-group diffusion approximation and GEFEST, JARFR and TRIGEX codes with ABBN-93 nuclear data gives adequate description of power rate distribution among the SAs of the BN-600 reactor core. Conservative estimation of calculation error is 5%. The main concern is evaluation of power profile of peripheral areas of the radial blanket and in-vessel storage, if achieved accuracy of 10-15% is insufficient. (authors)