05000412/LER-2021-003, Indications Identified During Reactor Vessel Head Inspection

Indications Identified During Reactor Vessel Head Inspection

ML21354A405
Person / Time
Site:	Beaver Valley
Issue date:	12/17/2021
From:	Grabnar J Energy Harbor Nuclear Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-21-278 LER 2021-003-00
Download: ML21354A405 (5)

LER-2021-003, Indications Identified During Reactor Vessel Head Inspection

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded
4122021003R00 - NRC Website

text

energy harbor John J. Grabnar Site Vice President December 17, 2021 L-21-278 ATTN: Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 SUBJECT:

Beaver Valley Power Station, Unit No. 2 Docket No. 50-412, License No. NPF-73 LER 2021-003-00 10 CFR 50.73 Beaver Valley Power Station P.O. Box 4 Shippingport, PA 15077 724-682-5234 Fax: 724-643-8069 Enclosed is Licensee Event Report (LER ) 2021 -003-00, "Indications Identified During Reactor Vessel Head Inspection." This event is being reported in accordance with 10 CFR 50.73 (a)(2)(ii)(A).

There are no regulatory commitments contained in this submittal. Any actions described in this document represent intended or planned actions and are described for information only.

If there are any questions or if additional information is required, please contact Mr. Steve Sawtschenko, Manager, Regulatory Compliance and Emergency Response, at 724-682-4284.

Sincerely, John J. Grabnar Enclosure: Beaver Valley Power Station, Unit 2 LER 2021-003-00 cc: Mr. D. C. Lew, NRC Region I Administrator NRC Senior Resident Inspector Ms. J. Tobin, NRC Project Manager INPO Records Center (via INPO Industry Reporting and Information System )

Mr. L. Winker (BRP/DEP )

Enclosure L-21-278 Beaver Valley Power Station, Unit 2 LER 2021-003-00

Abstract

On October 22, 2021, during the Beaver Valley Power Station, Unit No. 2 (BVPS-2) twenty-second refueling outage (2R22), it was determined that the results of ultrasonic examinations performed on Penetrations 28 and 40 of the reactor vessel head did not meet the applicable acceptance criteria. The indications were not through-wall and there was no evidence of leakage at Penetrations 28 and 40 based on inspections performed on top of the reactor vessel head. Because the indications could not be dispositioned as acceptable per American Society of Mechanical Engineers (ASME) Code Section XI in a Reactor Coolant System pressure boundary, it was reported per Event Notification 55540 as a degraded condition per 10 CFR 50.72(b)(3)(ii)(A) and is being reported under 10 CFR 50.73(a)(2)(ii)(A).

Primary Water Stress Corrosion Cracking (PWSCC) of the Alloy 600 penetration tube material was determined to be the cause of the identified flaws. Reactor vessel head Penetrations 28 and 40 were repaired in accordance with the applicable embedded flaw repair methodology approved by the Nuclear Regulatory Commission (NRC) for use at BVPS-2. A weld overlay of PWSCC resistant material was performed to isolate the indications from the borated water. The safety significance of these indications was very low.

NRC FORM SSA U.S. NUCLEAR REGULA TORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 08/31/2023 (08-2020)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/read ing-rm/doc-colle ctions/nuregs/staff/sr1022/r3/)

05000-1 412 I G;J-1 NUMBER NO.

Beaver Valley Power Station, Unit 2 003 1-0

NARRATIVE

Energy Industry Identification System (EIIS) codes are identified in the text as [XX].

DESCRIPTION OF EVENT BVPS-2 was in a Defueled Mode. There were no systems, structures, or components that were inoperable at the start of the event that contributed to the event.

On October 2_2, 2021, during the BVPS-2 twenty-second refueling outage (2R22), it was determined that the results of ultrasonic examinations performed on Penetrations 28 and 40 of the reactor vessel head [AB-RPV] did not meet the applicable acceptance criteria. The indications were not through-wall and there was no evidence of leakage at Penetrations 28 and 40, based on inspections performed on top of the reactor vessel head. The examinations were being performed to meet the requirements of 10 CFR 50.55a(g)(6)(ii)(D) for reactor vessel head inspections. The intent is to identify potential flaws/indications well before the structural integrity of the reactor vessel head pressure boundary is significantly challenged.

The ultrasonic examination determined that the circumferential indication on Penetration 28 of the reactor vessel head was between the 25.5 to 30.0 degree location with a maximum depth of 0.223 inches into the penetration tube.

The ultrasonic examination determined that the axial indication on Penetration 40 of the reactor vessel head was at the 22.5 degree location with a maximum depth of 0.163 inches into the penetration tube.

The reactor vessel head inspection is a requirement of 10 CFR 50.55a(g)(6)(ii)(D) which invokes ASME Code Case N-729-6. Ultrasonic examinations or eddy current examinations (as applicable) are performed on each of the 66 vessel head penetrations on the BVPS-2 head during each refueling outage until head replacement activities are completed in the future. Head Penetrations 28 and 40 were repaired as required prior to plant startup from 2R22. Ultrasonic examination results for the other 64 vessel head penetrations were acceptable.

The indications identified on Penetrations 28 and 40 of the reactor vessel head were reported to the NRC per 10 CFR 50.72(b)(3)(ii)(A) on October 22, 2021. (Event Notification 55540).

CAUSE OF EVENT PWSCC of the Alloy 600 penetration tube material was determined to be the cause of the identified flaws. The failure mechanism is a known issue that is addressed by the requirements of 10 CFR 50.55a(g)(6)(ii)(D). The repairs to Penetrations 28 and 40 utilized an embedded flaw repair process that was approved under NRC Relief Request 2-TYP-4-RV-04.

ANALYSIS OF EVENT Indications that cannot be dispositioned as acceptable per ASME Code Section XI in a Reactor Coolant System (RCS)

[AB] pressure boundary are reportable under 10 CFR 50.73(a)(2)(ii)(A) as a degraded condition.

ANALYSIS OF EVENT (Cont.) 05000-1 412 n NUMBER I YEAR SEQUENTIAL

- I 003 REV NO. 1-0 The plant risk associated with the BVPS-2 ultrasonic indications identified on Penetrations 28 and 40 of the reactor vessel head is considered to be very low. This is based on the fact that the indications were not through-wall and there was no indication of RCS leakage. The change in core damage frequency derived using the conditional core damage probability, and the change in large early release frequency derived using conditional large early release probability for the observed condition, are very small. Therefore, the safety significance of the indications identified on Penetrations 28 and 40 was very low.

CORRECTIVE ACTIONS Completed Action Reactor vessel head Penetrations 28 and 40 were repaired in accordance with the applicable embedded flaw repair methodology approved by the NRC for use at BVPS-2. The repairs were completed by November 04, 2021.

Planned Action Additional surface examinations are planned for Penetrations 28 and 40 in the two following outages (2R23 and 2R24) in accordance with the requirements of relief request 2-TYP-4-RV-04.

PREVIOUS SIMILAR EVENTS Similar reactor vessel head indications were found and repaired during the previous BVPS-2 refueling outages in 2020, 2018, 2014, 2012, 2009, 2008, and 2006.

Condition Reports 2021-07969, 2021-07970