ML25149A302
| ML25149A302 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/29/2025 |
| From: | Richard Guzman NRC/NRR/DORL/LPL1 |
| To: | Maynard N Dominion Energy Nuclear Connecticut |
| References | |
| Download: ML25149A302 (1) | |
Text
From:
Richard Guzman To:
nicholas.d.maynard@dominionenergy.com
Subject:
RE: Dominion Energy Query into Millstone 3 SPU SE Date:
Thursday, May 29, 2025 7:31:19 PM
- Nick,
The NRC staff has a shared understanding of the perspective provided in your message below and agrees with the statement:
Dominion's position is that the SE language was intended to convey that the flashing fraction assumed for the particulate nuclide groups was an arbitrary conservatism in an input that was not a significant factor in the NRC's approval of the analysis.
Please let me know if you need any additional clarification.
- Thanks, Rich Guzman Sr. PM, Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Phone: (301) 415-1030 Richard.Guzman@nrc.gov
From: nicholas.d.maynard@dominionenergy.com <nicholas.d.maynard@dominionenergy.com>
Sent: Monday, May 12, 2025 8:33 AM To: Richard Guzman <Richard.Guzman@nrc.gov>
Subject:
[External_Sender] Dominion Energy Query into Millstone 3 SPU SE
- Rich,
While scoping a project involving radiological dose consequence margins at Millstone Unit 3, Dominion identified the language presented below from the Stretch Power Uprate (SPU) Safety Evaluation (SE) for License Amendment No. 242 relevant to the Small Line Break Outside Containment (SLBOC) analysis (FSAR Section 15.6.2). This SE language cites a conservative flashing fraction of 1.0 (i.e.,100% flashing) for all other nuclide groups and states that the dose consequences are acceptable based on this flashing as a fraction (among other assumptions).
Dominion is planning to revise the SLBOC analysis to reduce the flashing fraction for the particulate nuclide groups (not including noble gases or iodines) from a value of 1.0 to a bounding value of 0.4. This would align the flashing fraction for the particulate nuclide groups
with the value for the iodine group already assumed in the analysis.
Dominion's position is that the SE language was intended to convey that the flashing fraction assumed for the particulate nuclide groups was an arbitrary conservatism in an input that was not a significant factor in the NRC's approval of the analysis. Thus, Dominion requests that the NRC provide their perspective in interpreting this SE language.
Excerpts from Section 2.9.2.7 of the SE (ADAMS Accession Number ML081640535) are attached and associated word document containing this writeup and excerpts from Section 2.9.2.7 from the SE.
Nick Maynard Associate Engineer - Nuclear Regulatory Affairs Dominion Energy nicholas.d.maynard@dominionenergy.com (804)-273-3910
While scoping a project involving radiological dose consequence margins at Millstone Unit 3, Dominion identified the language presented below from the Stretch Power Uprate (SPU) Safety Evaluation (SE) for License Amendment No. 242 relevant to the Small Line Break Outside Containment (SLBOC) analysis (FSAR Section 15.6.2). This SE language cites a conservative flashing fraction of 1.0 (i.e.,100% flashing) for all other nuclide groups and states that the dose consequences are acceptable based on this flashing as a fraction (among other assumptions).
Dominion is planning to revise the SLBOC analysis to reduce the flashing fraction for the particulate nuclide groups (not including noble gases or iodines) from a value of 1.0 to a bounding value of 0.4. This would align the flashing fraction for the particulate nuclide groups with the value for the iodine group already assumed in the analysis.
Dominions position is that the SE language was intended to convey that the flashing fraction assumed for the particulate nuclide groups was an arbitrary conservatism in an input that was not a significant factor in the NRC's approval of the analysis. Thus, Dominion requests that the NRC provide their perspective in interpreting this SE language.
Excerpts from Section 2.9.2.7 of the SE (ADAMS Accession Number ML081640535) are presented below.