ML21020A133

NRR E-mail Capture - Draft RAIs for Surry'S Request for Proposed Alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680)

ML21020A133
Person / Time
Site:	Surry
Issue date:	01/13/2021
From:	Stephanie Devlin-Gill NRC/NRR/DORL/LPL2-1
To:	Geoffrey Miller Dominion Generation
References
L-2020-LLR-0140
Download: ML21020A133 (4)

Text

From: Devlin-Gill, Stephanie Sent: Wednesday, January 13, 2021 2:55 PM To: Gary.D.Miller@dominionenergy.com Cc: Thomas, Vaughn; diane.aitken@dominionenergy.com

Subject:

Draft RAIs for Surry's Request for Proposed Alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680)

Attachments: Draft RAIs - Surry Alt Req for S1-I5-ISl-05 and S2-I5-ISl Final to Surry.doc

Gary, Attached are the NRC staffs draft RAIs for Surrys proposed alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680).

The draft questions are being transmitted to you to determine 1) If the questions clearly convey the NRC informational needs, 2) Whether the regulatory basis for the question is clear, and 3) If the information has already been provided in existing docketed correspondence. Additionally, review of the draft questions (within 5 days - COB 01/18/2021) will allow you to determine whether you are able to support a 30 day response time. If the licensee needs a clarification call within that timeframe, the staff will be available to participate on the call.

Thank you.

stephanie Stephanie Devlin-Gill Licensing PM, In-Training

w. 301-415-5301 U.S. NRC, NRR, DORL, LPL2-1

Hearing Identifier: NRR_DRMA Email Number: 976 Mail Envelope Properties (BLAPR09MB61305A0C81BC2AC993B6892CBDA90)

Subject:

Draft RAIs for Surry's Request for Proposed Alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680)

Sent Date: 1/13/2021 2:54:54 PM Received Date: 1/13/2021 2:54:54 PM From: Devlin-Gill, Stephanie Created By: Stephanie.Devlin-Gill@nrc.gov Recipients:

"Thomas, Vaughn" <Vaughn.Thomas@nrc.gov>

Tracking Status: None "diane.aitken@dominionenergy.com" <diane.aitken@dominionenergy.com>

Tracking Status: None "Gary.D.Miller@dominionenergy.com" <Gary.D.Miller@dominionenergy.com>

Tracking Status: None Post Office: BLAPR09MB6130.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 821 1/13/2021 2:54:54 PM Draft RAIs - Surry Alt Req for S1-I5-ISl-05 and S2-I5-ISl Final to Surry.doc 61496 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

REQUEST FOR ADDITIONAL INFORMATION OFFICE OF NUCLEAR REACTOR REGULATION Issue Date: TBD SURRY POWER STATION UNITS 1 AND 2 ASME SECTION XI INSERVICE INSPECTION PROGRAM REQUEST FOR NRC APPROVAL OF PROPOSED ALTERNATIVE S1-I5-ISl-05 AND S2-15-ISl-06 Virginia Electric & Power Co.

Dockets: 05000280-PWR-Surry 1,05000281-PWR-Surry 2 EPIDS: L-2020-LLR-0139, L-2020-LLR-0140

Background

By letter dated October 22, 2020, Dominion Energy Virginia, (DEV or the licensee) requested an alternative from the requirements of the American Society of the Mechanical Engineers (ASME) Boiler and Pressure Vessel for Surry Power Station (Surry) Units 1 and 2. The licensee proposed alternatives, S1-I5-ISI-05 and S2-I5-ISI-06, which would eliminate the volumetric examination of the reactor pressure vessel (RPV) threads in flange (i.e., Category B-G-1 examinations) during the ASME Code, Fifth 10-year inservice inspection (ISI) interval at Surry.

Regulatory Basis Title 10 of the Code of Federal Regulations (10 CFR) Part 50.55a(z) establishes a process for licensees to propose alternatives to codes and standard requirements. Specifically, as requested by the licensee, DEV must demonstrate that the proposed alternative would provide an acceptable level of quality and safety. The following requests for additional information (RAIs) are needed to reach a conclusion of acceptable level of quality and safety.

Question Number: 1 The licensee provided the following statement, in part, under the "Flaw Tolerance Evaluation" section of the submittal.

"As seen from the stress intensity factor (K) calculation documented in Table 6-1 Reference 1 (reproduced in Table 2 above), the maximum K is 19.8 ksi-in. The allowable K calculated in Section 6.2.2 of the report is 69.6 ksi-in, significantly higher than the calculated value. Assuming an RPV flange with 60 studs originally and one inoperable stud, the increase in K is approximately 1.7%

resulting in a maximum K of approximately 20.14 ksi-in which is still significantly less than the allowable value."

The NRC staff has concern that the above example does not appear to be applicable to Surry. As provided in Table 1 of the submittal, the licensee shows that Surry, Unit 1 and Unit 2, both have 58

studs. There is no mentioning of any inoperable studs for either Unit. The staff relies on a clear understanding of the RPV flange parameters (i.e., number of studs, stud hole diameter, etc.) and any factors affecting operability in order to complete an adequate review.

Please provide clarification regarding the state of the RPV flange:

(a) Clarify whether Surry, Unit 1 and 2, have any inoperable studs. If so, discuss the reason for its inoperability.

(b) Explain why an RPV flange of 60 studs with one inoperable stud is a bounding analysis for Surry, Unit 1 and 2.

Question Number: 2 Additional detail is needed regarding the lower bound fracture toughness (Kic) at preload conditions. A critical combination of applied Ki and Kic may occur at lower temperatures, such as the temperature at preload conditions since fracture toughness decreases with temperature, and therefore, the most limiting fracture toughness may exist at preload conditions.

Please provide a plant-specific evaluation that shows that the allowable fracture toughness of the flange is higher than the most limiting Ki value of 17.4 ksi-in, for a preload condition, as provided in Table 2 of the submittal.