Session: CS-36-01 Combined Session: Master Curve Method and Applications, and Improvement of Flaw Characterization Rules for Fitness for Service

Paper Number: 61969

Start Time: Thursday, July 15, 2021, 09:00 AM

61969 - Effect of Neutron Irradiation on the Mechanical Properties of an A508 CL2 and 15Kh2NMFA Irradiated in the NOMAD_3 Rig in the BR2 Cooling Water 

The typical operating temperatures of a nuclear reactor pressure vessel in a PWR is typically between ~290°C and 300°C. However, many BWRs and some PWRs operate at slightly lower temperatures down to ~260°C. Most of the literature and neutron irradiation damage is therefore focused on those irradiation temperatures. It is well-known that the lower the irradiation temperature, the more neutron irradiation damage occurs, because no appreciable annealing occurs below approximately 230°C.

The previous NOMAD-0 irradiation campaign at the BR2 was a preliminary irradiation specifically designed to determine the appropriate irradiation conditions that result in specific irradiation damage levels of an A508 Cl.2 grade at lower temperatures than the usual PWR operating temperature window. The BAMI capsules with controlled He gas gap were used for this irradiation. The hardening and the SiC temperature monitors showed however that the real irradiation temperature was close to 280°C. The fast fluence range was between 2.1 and 6.6 x 10¹⁹ n/cm² (E>1MeV). The hardening Ds_y was up to 155 MPa. The embrittlement-to-hardening ratio,  DT₀ /Ds_y, was around 0.43 °C/MPa.

The NOMAD_3 irradiation consisted in total of 24 Charpy sized samples from an A508 Cl.2 forging and a 15kH2NMFA material. They were irradiated to three various fluences between 1.55 and 7.90 x 10¹⁹ n/cm² (E>1MeV). The hardening of the A508 Cl.2 was between 260 and 400 MPa which was much higher than the NOMAD_0 properties. The radiation embrittlement derived from Charpy impact tests, DT_41J, is up to ~156°C for the highest fluence. For this irradiation, the embrittlement to hardening ratio was also around 0.43 +/- 0.2 °C/MPa as it was found in the previous campaign. First results indicate that the neutron irradiation temperature is between ~150°C-180°C.

This paper discusses the tensile, hardness and impact properties of the NOMAD_3 irradiation campaign. It is compared to the NOMAD_0 with respect to effect of irradiation temperature and annealing recovery.

Presenting Author: Inge Uytdenhouwen SCK CEN The Belgian Nuclear Research Centre

Authors:

Rachid Chaouadi SCK CEN The Belgian Nuclear Research Centre
Inge Uytdenhouwen SCK CEN The Belgian Nuclear Research Centre