The Toughness of Irradiated Pressure Water Reactor (PWR) Vessel Shell Rings and the Effect of Segregation Zones

Abstract

To establish the integrity of pressure water reactor (PWR) vessels it is necessary to determine the toughness of A508C1.3 steel at the end of its life, that is after thermal ageing and irradiation embrittlement. In safety analyses the toughness can be deduced from a reference curve set forth in the code (ASME or RCC-M). The validity of the reference curve has been verified for several years for unirradiated French reactor vessels. Tests were performed on specimens taken from materials having heterogeneities in chemical composition. For most of the test results the reference curve is a lower bound. To solve the problem of determining the toughness of SA 508 C1.3 steel after irradiation and in the presence of possible heterogeneities, the toughness results were gathered. The synthesis shows that the RCC-M code curve is conservative.

Application of criterion for A-segregation in steel ingots

“…However, the A-segregation observed appears to begin at a lower value than the lowest limit of the 17¡8 range suggested by Torabi Rad et al Closer inspection revealed this to be when Ra. 6.…”

“…The enriched steel contained within A-segregate channels has often been found to deliver poor mechanical properties, [4][5][6][7] and the discovery of A-segregates can result in material rejection. Hence, it is useful for the manufacturers of large ingots to predict the location and severity of these defects.…”