DCL-24-083, CFR Part 21 Notification: Commercially Dedicated Snubber Valve Not Properly Heat Treated

CFR Part 21 Notification: Commercially Dedicated Snubber Valve Not Properly Heat Treated

ML24255A090
Person / Time
Site:	Diablo Canyon
Issue date:	09/09/2024
From:	Peck A Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
DCL-24-083
Download: ML24255A090 (1)

Text

Pac ific Gas and Electric Company "'

Adam S. Peck Oia blo Can y on Po wer Plan t Site Vi ce President Mail cod e 10416/605 P.O. Bo x 56 Avila Bea c h, CA 93424

805.545. 6675 Adam. Pec k@pge.co m

PG&E Letter DCL-24-083 10CFR21.21

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001

Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 10 CFR Part 21 Notification: Commercially Dedicated Snubber Valve Not Properly Heat Treated

Dear Commissioners and Staff:

In accordance with the requirements of 10 CFR 21.21 (d)(3)(ii), Pacific Gas and Electric Company (PG&E) hereby submits the enclosed Diablo Canyon Power Plant (DCPP) written notification regarding a commercially dedicated snubber valve assembly. This information was initially reported to the Nuclear Regulatory Commission Operations Center on August 15, 2024 (Event Notification 57271 ).

PG&E makes no new or revised regulatory commitments (as defined by NEI 99-

04) in this report. Corrective actions identified in this letter will be implemented in accordance with the DCPP Corrective Action Program.

If you have any questions or require additional information, please contact Mr. James Morris, Manager, Regulatory Services, at (805) 545-4609.

Sincerely,

- ~ '>,...:.....,.::r.._,. _ -

September 9, 2024 Adam S. Peck Date

dqmg/51231137 Enclosure cc/enc: Diablo Distribution Mahdi 0. Hayes, NRG Senior Resident Inspector INPO Samson S. Lee, NRR Senior Project Manager John D. Monninger, NRC Region IV Administrator

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• Wolf Creek Internal Enclosure PG&E Letter DCL-24-083

10 CFR PART 21 NOTIFICATION

Commercially Dedicated Snubber Valve Not Properly Heat Treated Enclosure PG&E Letter DCL-24-083

10 CFR Part 21 Notification ALCO Snubber Valve

The following information is provided pursuant to 10 CFR 21.21 (d)(4).

i. Name and Address of the individual or individuals informing the Commission:

Adam S. Peck Site Vice President and Acting Chief Nuclear Officer Diablo Canyon Power Plant Mail code 104/6/605 P.O. Box 56 Avila Beach, CA 93424

ii. Identification of the facility, the activity, or the basic component supplied for such facility or such activity within the United States which fails to comply or contains a defect:

Facility: Diablo Canyon Power Plant (DCPP) Units 1 and 2 Docket No. 50-275 and 50-323 License No. OL-DPR-80 and OL-DPR-82 Basic Component: ALCO Snubber Valve Part Number 2402466

iii. Identification of the firm constructing the facility or supplying the basic component which fails to comply or contains a defect:

Pacific Gas and Electric (PG&E) Company Diablo Canyon Power Plant P.O. Box56 Avila Beach, CA 93424

iv. Nature of the defect or failure to comply and the safety hazard which is created or could be created by such defect or failure to comply:

On September 12, 2023, DCPP identified the apparent failure of a snubber valve assembly during a routine surveillance test. The snubber valve was removed and replaced. This condition did not impact the operability of any safety related systems or impact the health and safety of the public.

The failed snubber valve had originated from a specific lot of ALCO Snubber Valves (Part Number 2402466), which were purchased as a commercial-grade

Page 1 of 3 Enclosure PG&E Letter DCL-24-083

item and dedicated by PG&E solely for use at DCPP. The dedication of the subject lot (Part Number 2402466) was completed during July 2008.

PG&E performed a 10 CFR Part 21 evaluation and determined that reporting in accordance with Part 21.21 was required for these ALCO snubber valve assemblies. The upper body of the valves had been subjected to improper case hardening of the concave seating surface and were manufactured from incorrect material (AISI 1117 resulfurized carbon steel vs. AISI 8620/8630).

The improper case-hardening and the incorrect material application can result in micro-cracking in the tip of the snubber valve, which can expand and cause insufficient flow through the valve.

v. The date on which the information of such defect or failure to comply was obtained:

On May 28, 2024, PG&E informed the Nuclear Regulatory Commission (NRC) that it had initiated a 10 CFR Part 21 evaluation of a deviation concerning commercial-grade item dedicated at DCPP via an interim Part 21 report. After PG&E completed its evaluation, the reporting officer was subsequently informed on August 13, 2024. The defect was reported to the NRC telephonically on August 15, 2024 (Event Notification 57271 ).

vi. In the case of a basic component which contains a defect or fails to comply, the number and location of these components in use at, supplied for, being supplied for, or may be supplied for, manufactured, or being manufactured for one or more facilities or activities subject to the regulations in this part:

The snubber valve assemblies (Part Number 2402466) in question were removed from unrestricted spares and underwent further material analyses.

They were subsequently discarded. None of these snubber valve assemblies have been provided by PG&E to any other stations or vendors.

Two fuel snubber valve assemblies from the same material batch remain installed in the plant. PG&E has performed an assessment and determined they do not affect the operability of any safety related systems. There is no risk to the health and safety of the public.

vii. The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action:

Page 2 of 3 Enclosure PG&E Letter DCL-24-083 As stated in the response to question vi, the subject non-installed snubber valve assemblies have been discarded. The associated dedication package has been deleted and PG&E intends to purchase future snubber valve assemblies as safety-related.

viii. Any advice related to the defect or failure to comply about the facility, activity, or basic component that has been, is being, or will be given to purchasers or licensees:

This issue was documented in the DCPP corrective action program. As stated above, the subject snubber valve assemblies were purchased as a commercial grade item under ALCO Part No. 2402466 and dedicated for a safety-related application. Utilities that perform this dedication should consider specific tests for case-hardening and correct material verification.

Also note that similar issues have been reported to the NRG:

CORPORATION/ FACILITIY: Entergy/ Palisades NOTIFICATION DATE: March 13, 2008 EVENT NUMBER: 44059

- ALCO Part Number 240466

- AISI E 52100 material composition

CORPORATION/ FACILITIY: Fairbanks Morse I Not Applicable NOTIFICATION DATE: April 29, 2008 EVENT NUMBER: 44178

-ALCO Part Number 2402466-1

- Material composition not specified in report

Based on the snubber valve history supported by these two reports, licensees should review their purchase order and installation history for snubber valves purchased ahead of and during the 2008 timeframe for similar vulnerabilities.

ix. In the case of an early site permit, the entities to whom an early site permit was transferred:

Not applicable.

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