Results on Attenuation of Neutron Embrittlement Effects

A carefully designed irradiation experiment was conducted in which a 180-mm thick reactor pressure vessel (RPV) wall has been simulated using eighteen 10-mm slices of some key RPV steels and irradiated under test reactor conditions to investigate the through wall attenuation of neutron embrittlement. Results from two of the irradiated materials (a low copper content plate and a high copper content Linde 80 flux weld) were reported in 2006. Another RPV plate, the international reference steel, JRQ, was also extensively irradiated in the simulated RPV wall. Comparisons of predicted attenuation changes in toughness properties using measured Charpy V-notch results are presented for the JRQ steel and compared to the results from the low copper content plate and the high copper content Linde 80 weld metal. Also, Charpy V-notch and Master Curve fracture toughness test results are compared for the low copper plate and the high copper weld. Predictions are made of through-wall attenuation following the practice defined in ASTM E 900-02 and Regulatory Guide 1.99, Revision 2, in which the attenuation of high energy neutron fluence (E > 1 MeV) is projected based upon an approximate displacements per atom (dpa) change through the wall thickness.. The resultant degree of material damage using this dpa-based fluence change is estimated using the ASTM E 900–02 embrittlement correlation model and compared to the experimental data.