Report on the EPRI pressurized thermal shock program

The long-term potential for neutron embrittlement of reactor vessels as been a recognized concern for a number of years. Recently, significant attention has been focused on the performance of certain vessels during overcooling transients. The Electric Power Research Institute (EPRI) has been supporting research on reactor vessel integrity for a number of years. This work in the past focused mainly on materials and dosimetry. In June 1981, thermal hydraulics research also was expanded and accelerated. In addition, a cooperative program with four utilities was initiated to evaluate reactor vessel thermal shock for four specific plants including one from each PWR vendor. The pressurized thermal shock issue is being addressed at EPRI using matrix management to coordinate and apply the program results. In its program, EPRI is: (1) developing the capability to accurately predict reactor vessel wall transient temperatures; (2) developing the capability to accurately determine vessel wall radiation exposure; (3) developing the capability to accurately determine reactor vessel toughness; (4) developing a linked set of analytical codes to that utilities or their contractors can independently assess the effects of reactor vessel thermal shock with high accuracy; and (5) investigating ways to extend a reactor vessel's life