Volume 2, Issue 7 (July 2005)
Recent Surveillance Data and a Revised Embrittlement Correlation
The mechanistically-guided embrittlement correlation model adopted in ASTM E 900-02 was based on U.S. surveillance results current through calendar year 1998. There now exists an extensive amount of new surveillance data that includes a large amount of boiling water reactor (BWR) results from a supplemental surveillance program designed to augment the plant-specific BWR surveillance programs. These recent data allow a statistical check of the ASTM E 900-02 embrittlement correlation, as well as the NRC correlation model currently being used in the pressurized thermal shock (PTS) re-evaluation effort and the older Regulatory Guide 1.99, Revision 2 correlation. Even though the ASTM E 900-02 embrittlement correlation is a simplified version of the NRC model, a comparison of the two embrittlement correlation models utilizing the new database has proven to be revealing. Based on the new BWR data, both models are inadequate in their ability to predict BWR results. Other aspects of the two models are presented, as well as plans to develop a revised embrittlement correlation.