Calculation and measurement of neutron flux in the VVER-1000 mock-up on the LR-0 research reactor

The neutron fluence load on a reactor pressure vessel is an important physical quantity affecting material degradation and consequently reliable assessment of pressure vessel integrity and lifetime prolongation beyond designed conditions. This degradation is influenced by mixed neutron–photon source from the core periphery as well as by material parameters of the reactor pressure vessel. Computational procedures and experimental determination of neutron fluxes in the VVER-1000 mock-up internal structures as well as the results achieved are described in this paper. The calculation were performed with the MCNPX code with different nuclear data libraries. Nuclear data were processed using NJOY code.The neutron spectra measurements were performed with a two-parameter stilbene spectrometer.

► Measurement of neutron fluxes behind reactor pressure vessel of VVER-1000 mock-up. ► Calculations of neutron fluxes behind reactor pressure vessel using various data libraries. ► Discrepancies between calculation and experiment of neutron fluxes behind reactor pressure vessel.