Radiation damage and yield strength calculations in the pressure vessel of WWER-1000 reactor and sensitivity analysis of neutron spectrum on the shield of vessel

Radiation damage calculation is very important for estimating the lifetime of nuclear power plant instruments. The purpose of the present study is to evaluate the sensitivity of the damage values to the neutron group energy, where the neutron flux rate is maximum. In the present study, we propose three neutron group energy (WIMS, CINDER, and OPENMC) to evaluate the sensitivity of radiation damage calculations. The obtained result from SPECTER code shows that the differences between these results and the standard values (ASTM E-693) for three group energy WIMS, CINDER and OPENMC are respectively 0.25E-04, 0.75E-04, and 1.74E-04 in the ¼ diameter of reactor pressure vessel (RPV). Therefore, the WIMS energy group is the most accurate spectrum compared to other spectrums in this region. Also, these differences are respectively 0.43E-04, 0.52E-04, and 1.86E-04 in the ¾ diameter of RPV. Moreover, the WIMS group energy is the most accurate spectrum in this region. This result shows that increasing the number of neutron energy group cause to reduce the difference between calculation of damage and its standard values. According to the results of calculated damage that induced by WIMS group energy in ¼ diameter of RPV, the values of yield strength at 1, 5, 10, 15, 20, 25, 30, 35 and 40 years are calculated by SPECOMP and SPECTER codes.