Part 1: Development of Criteria for Assessment of Reactor Vessels with Low Upper Shelf Fracture Toughness: Development of Criteria and Analysis Methods

In 1982, the NRC published proposed procedures for the analyses required by 10CFR50 for operating reactor vessels, as NUREG-0744, and this led to further discussions on the issue. Many comments were received, and these were also published in revision 1 of NUREG-0744. Concurrently, the NRC officially requested the ASME Code to recommend criteria for the evaluation of reactor vessels that do not meet the Charpy upper-shelf requirements. This request was accepted by the Code and assigned to the Working Group on Flaw Evaluation of Section XI. This report presents the results of that effort.

Part 2: Development of Criteria for Assessment of Reactor Vessels with Low Upper Shelf Fracture Toughness: Implementation of Evaluation Procedures in ASME Code Section XI

Part 1 of this Bulletin described the development and formulation of the methodology and the criteria for the evaluation of reactor vessels that do not meet the Charpy upper-shelf requirements. The Working Group on Flaw Evaluation developed simplified evaluation procedures, which includes the effect of thermal stress for Level A and B Service Loadings. The acceptance criteria and evaluation procedures for Levels A and B were codified and adopted into the Code in 1993 as Code Case N-512 and as Appendix K to Section XI. The objective of Part 2 is to present the basis for the evaluation procedures in the Code Case and Appendix K.