scope:

This WRC Bulletin presents an overview developed by the ASME Section XI Task Group on Reactor Vessel Integrity Requirements of the methods for protection against brittle fracture of reactor vessels given in the ASME Code. The Task Group reviewed the basis of the current Code method for brittle fracture protection as defined in ASME Section III, Appendix G, the historical background of the method, and the current regulations for material reference toughness, assumed reference flaw size, and plant operating criteria. Based on the review, recommendations are provided for improving the requirements in the Code using present-day knowledge related to vessel integrity by considering the benefits of advanced technology in areas such as fracture mechanics and nondestructive evaluation and for determining plant operating pressure-temperature limits while maintaining the necessary requirements to assure vessel integrity. The focus is primarily on pressurized water reactors rather than boiling water reactors although information is provided for both. This Bulletin is a companion to WRC Bulletin 386 which includes papers prepared by international experts on nuclear plant safety issues. Publication of this document- WRC Bulletin No. 387 was sponsored by the WRC Pressure Vessel Research Council