ML23067A021
| ML23067A021 | |
| Person / Time | |
|---|---|
| Site: | 99902049 |
| Issue date: | 12/02/2022 |
| From: | Carolyn Lauron NRC/NRR/DNRL/NRLB |
| To: | Hawkins J Holtec International SMR |
| References | |
| Download: ML23067A021 (1) | |
Text
From:
Carolyn Lauron To:
Justin Hawkins Cc:
Greg Cranston; Michael Dudek; Andrew Brenner
Subject:
NRC Staff Response to SMR (Holtec) Clarification Question re: Turbine Missiles - 2nd question on PRA scope Date:
Friday, December 2, 2022 5:52:00 AM Hi Justin -
Please find the staffs response to the second question submitted on the topic. A response to the first question was previously provided.
If you have questions or need additional information, please let us know.
- Thanks, Carolyn
Question:
- 2. If an applicant adequately justifies an unfavorable turbine orientation using RG1.115, does that mean that the applicant can screen a turbine-generated missile external hazard out of their design PSA/PRA?
If the orientation of the turbine is unfavorable for essential SSCs and the applicant does the analysis in RG 1.115 to ensure the probability of failure is below RG1.115 and associated SRP 3.5.1.3 criteria (1x10-7 per year), can the applicant screen out the turbine generated missile hazard from the plant design PRA?
Note that RG 1.115 considers plants designed with no essential SSCs within the low-trajectory hazard zone to have a favorable turbine orientation. Unfavorable turbine orientation has essential SSCs within the low-trajectory hazard zone. RG 1.115, Section C, Position 5 states that, The NRC will review turbine designs that are significantly different from the current 1,800-rpm machines on a case-by-case basis to determine the applicability of the strike zones.
NRC Staff Response:
- 2. An advanced LWR applicant has the option of screening out a hazard, such as turbine generated missiles, from its PRA or include the hazard in the PRA and demonstrate its impact on risk insights and PRA results. The NRC staff expects detailed technical justification supporting the selected option, especially if the orientation of the turbine is unfavorable for essential SSCs. The applicant should include key assumptions from the analysis in Chapter 19 of the FSAR, as necessary.
The applicant should note that Regulatory Guide (RG) 1.200, Revisions 2 and 3, states that it is recognized that for those new reactor designs with substantially lower risk profiles (e.g., internal events [core damage frequency] CDF below 1x10-6 per year), the quantitative screening value should be adjusted according to the relative baseline risk value.
References:
- 1. RG 1.200, Revision 2, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities, dated March 2009, ADAMS Accession No. ML090410014.
- 2. RG 1.200, Revision 3, Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities, dated December 2020, ADAMS
Accession No. ML20238B871.