Creation and evaluation of the VVER-1000 Balakovo-3 ex-vessel dosimetry benchmark for the NEA SINBAD data base

A new neutron dosimetry benchmark of the NEA SINBAD Data Base is described. This full-scale reactor benchmark, based on VVER-1000 ex-vessel neutron activation measurements performed at the Balakovo NPP, Unit 3 (Balakovo-3), is a result of several years of thorough measurements and calculations. With regard to evaluation of measured and calculated results an international intercomparison study played a key role. This interlaboratory comparison produced the reference measured data expressed as end-of-irradiation activities of reaction products of the reactions: 237Np(n,f), 238U(n,f), 93Nb(n,n'), 58Ni(n,p), 54Fe(n,p), 46Ti(n,p) and 63Cu(n,a). A comprehensive analysis of reactor data used for creating the computational models has been performed. Special attention was paid to the analysis of the reliability of the absolute neutron source distributions. Results of calculations performed by various discrete ordinates and Monte Carlo codes have been used for the benchmark evaluation. It turned out that these calculation results are in agreement within 12 % with the reference measured data. The experience gained by creation and evaluation of the full-scale power reactor benchmark is discussed in the paper.