L-25-025, Supplement to 10 CFR 50.55a Request BV-ISI-2025-01, Quench Spray Pinhole Leak
| ML25018A001 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 01/18/2025 |
| From: | Hicks J Vistra Operations Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| L-25-025 | |
| Download: ML25018A001 (1) | |
Text
L-25-025 January 18, 2025 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Jack C. Hicks Senior Manager, Fleet Licensing Vistra Operations Company LLC P.O. Box 1002 6322 North FM 56 Glen Rose, TX 76043 Office: 254.897.6725 10 CFR 50.55a Supplement to 10 CFR 50.55a Request BV-ISI-2025-01, Quench Spray Pinhole Leak By letter dated January 17, 2025 (ADAMS Accession No. ML25017A395), Vistra Operations Company LLC (VistraOps) requested Nuclear Regulatory Commission (NRC) approval of relief request BV-ISI-2025-01 for the Beaver Valley Power Station, Unit No. 1 (BVPS-1) pursuant to 10 CFR 50.55a(z)(2). Subsequent to the submittal of the letter on January 17, 2025, the NRC requested clarification information. The information is provided below to supplement the January 17, 2025 request.
In performing the review of the Generic Letter (GL) 90-05 "through-wall" flaw evaluation criteria, the NRC staff requested clarity on the acceptable surface size of the flaw during the augmented examinations. Since volumetric examination to determine flaw size at tnun is not available, what will the licensee use for a total allowable flaw length on the surface of the weld during these future examinations? VistraOps provides the following response.
VistraOps will use the 0.125-inch through wall defect size assumed in the evaluation as the allowable measured surface flaw length for monitoring exams. Being an acceptable through wall flaw size makes use of this value for a surface flaw length conservative. This value bounds the current surface flaw measurement of approximately 0.031-inch and also provides margin to the calculated maximum value of 0.158-inch. If the daily qualitative assessment of leakage determines there is potential additional degradation of structural integrity, VistraOps will measure the flaw on the surface of the pipe to compare to the acceptance criteria.
The NRC staff indicated that it is the staffs understanding from the phone call [held at 2:30 p.m. EST on January 17, 2025] that the current surface size of the flaw is ~0.031-inch, and the conservatively chosen total flaw length at tnun is 0.125-inch from page 5 of 6 of the request. Additionally, the calculated total allowed flaw length of 0.158-inch was calculated at a depth of tnun. The NRC staff also noted the calculated tnun is 0.012-inch of a nominal thickness of 0.180-inch pipe wall. The licensee was asked to confirm the current surface size of the flaw and correct any of the NRC staff's statements, if necessary. VistraOps provides the following response.
The NRC staff has correctly stated the current status relative to total current measured flaw length and the bounding number used to support the acceptability calculation.
6555 SIERRA DRIVE IRVING, TEXAS 75039 o 214-812-4600 VISTRACORP.COM
Beaver Valley Power Station, Unit No. 1 L-25-025 Page2 The code-required minimum wall thickness (tmin=0.012) was calculated based on internal pressure, sustained loading, thermal expansion, and safe shutdown earthquake as stipulated in GL 90-05. This minimum required thickness is low as a result of the calculated stresses being unusually low for this pipe segment as seen on page 1 of Attachment 2 of the request.
The tmin and the calculated stresses were used with the GL 90-05 "Through-Wall Flaw Approach" to calculate the maximum acceptable through-wall flaw size of 0.158-inch (page 2 of Attachment 2 of the request). Thus, the calculated total allowed flaw length of 0.158-inch was the allowable through-wall defect. This is described mathematically in Attachment 2 of the request.
There are no regulatory commitments contained in this submittal. ff there are any questions, or if additional information is required, please contact Jack Hicks, Senior Manager, Licensing, at (254) 897-6725 or jack.hicks@luminant.com.
Sincerely, iJack H-ickr Ja_fk Hicks (Jan 18, 202510:16 CST)
Jack C. Hicl<s cc: NRC Region I Administrator NRC Resident Inspector NRC Project Manager Director BRP /DEP Site BRP /DEP Representative