Vessel Investigation Program of “CHOOZ A” PWR Reactor after Shutdown

Abstract

In October 1991 the CHOOZ A PWR plant, operated by the French and Belgian company SENA, was shut down after 24 years. It was the first PWR shutdown in France. According to the EDF life duration project it was decided to perform an examination program on samples taken from the wall of the vessel in order to complete the feedback. The results obtained show the following: • The embrittlement measured by the pressure vessel surveillance program is representative of that of the Shell determined at different axial and angular locations for the 1/4 of the internal thickness. This observation is consistent with the relative homogeneity of the embrittling elements (Cu, P, Ni) throughout the entire Shell, • The mechanical properties evolution through the wall thickness of the Shell measured after irradiation is interpreted in relation with fluence variation and unirradiated mechanical properties profile through the thickness, • The comparison of direct toughness measurement with the French code RCCM evaluation confirms the safety nature of the conventional approach. For the weld, after an irradiation damage of 2 1019 n.cm-2 (E>1MeV), a margin of the order of the irradiation effect seems to exist.

Current understanding of radiation-induced degradation in light water reactor structural materials

“…For example, molecular dynamics calculations of freely migrating point defects with a neutron transport calculation through pressure vessel steels revealed that the dpa attenuation trend was suitable to predict the attenuation of damage production [140]. Data from the decommissioned French PWR Chooz A pressure vessel demonstrated that the change in measured transition temperature shift was in agreement with the trend of the predicted shift assuming a dependence of (fluence) 0.48 [141]. The attenuation issue has been continued to be examined in the 2000s.…”

Local approach to fracture based prediction of the ΔT56J and shifts due to irradiation for an A508 pressure vessel steel

“…This will lead to higher computed stresses. Considering both the impact and fracture toughness properties, it is well known that irradiation embrittlement induces an increase of the DBT temperature and therefore of the index ) 2 1 2 3 [ 2,17,19,23,28,31]. As far as the upper shelf energy (USE) is concerned, most of the studies report a decrease with increasing irradiation level.…”

60th Anniversary of electricity production from light water reactors: Historical review of the contribution of materials science to the safety of the pressure vessel

“…It is widely accepted that the slight differences in irradiation conditions (neutron flux and shape of neutron spectrum) between the surveillance test specimens and the pressure vessel do not significantly modify the irradiation-induced evolution of mechanical properties. This point has been validated by destructive characterizations of pressure vessels from decommissioned reactors, (e.g., [9,10]).…”