ML20127H816
| ML20127H816 | |
| Person / Time | |
|---|---|
| Issue date: | 05/06/2020 |
| From: | NRC/RES/DE |
| To: | |
| J. Poehler | |
| References | |
| RG-1.099 | |
| Download: ML20127H816 (1) | |
Text
Key Messages for RG 1.99 Public Meeting The NRC conducted an analysis based on an 80-year life to evaluate the change in risk due to the embrittlement prediction differences between RG 1.99 Rev 2 and E900-15 based on a smart sample of the US fleet.
Based on the staffs analysis, the staff expects it will be acceptable for most plants to continue to use RG 1.99, Rev. 2 ETC to determine the adjusted reference temperature (ART), and the pressurized thermal shock (PTS) reference temperature (RTPTS).
Therefore, based on the risk analysis results, consideration of fleetwide implementation of a revised RG is not expected.
In a few cases plants with large deltas between the reference temperatures estimated by the two ETCs, the staffs analysis identified questions for certain transients, specifically PWR cooldowns on licensed pressure-temperature limits, and BWR leak tests with higher cooldown rates. The NRC staff would like to work with industry to obtain information to address these questions to provide assurance that the risk remains low.
The NRC has developed the framework of a revised RG 1.99 incorporating the ASME E900-15 embrittlement trend correlation (ETC), which also includes specific guidance on use of surveillance data, margins, limitations, and default values.
There may be a potential reduction in burden for some plants resulting from implementation of a RG based on the framework described above. The NRC staff desires input from industry and licensees on whether they could benefit from a revised regulatory guide.