ML21020A132
| ML21020A132 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 01/19/2021 |
| From: | Stephanie Devlin-Gill NRC/NRR/DORL/LPL2-1 |
| To: | Geoffrey Miller Dominion Generation |
| References | |
| L-2020-LLR-0139 | |
| Download: ML21020A132 (4) | |
Text
From:
Devlin-Gill, Stephanie Sent:
Tuesday, January 19, 2021 8:37 AM To:
gary.d.miller@dominionenergy.com Cc:
Thomas, Vaughn
Subject:
RAIs for Surry's Request for Proposed Alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680)
Attachments:
RAIs to Surry - Surry Alt Req for S1-I5-ISl-05 and S2-I5-ISl-06.doc Gary, Attached are the NRC staffs requests for additional information (RAIs) for Surrys proposed alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680).
Via email, you confirmed that Virginia Electric and Power Company (Dominion Energy Virginia) could respond within 30 days to these RAIs. The NRC staff anticipates your response to the attached RAIs by Thursday, February 18, 2021.
Thank you.
stephanie Stephanie Devlin-Gill Licensing PM, In-Training
Hearing Identifier:
NRR_DRMA Email Number:
975 Mail Envelope Properties (BLAPR09MB6130E77349E29DE906BDA357BDA30)
Subject:
RAIs for Surry's Request for Proposed Alternative S1-I5-ISl-05 and S2-I5-ISl-06 (ML20296A680)
Sent Date:
1/19/2021 8:37:18 AM Received Date:
1/19/2021 8:37:18 AM From:
Devlin-Gill, Stephanie Created By:
Stephanie.Devlin-Gill@nrc.gov Recipients:
"Thomas, Vaughn" <Vaughn.Thomas@nrc.gov>
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 526 1/19/2021 8:37:18 AM RAIs to Surry - Surry Alt Req for S1-I5-ISl-05 and S2-I5-ISl-06.doc 61440 Options Priority:
Normal Return Notification:
No Reply Requested:
No Sensitivity:
Normal Expiration Date:
REQUEST FOR ADDITIONAL INFORMATION OFFICE OF NUCLEAR REACTOR REGULATION Issue Date: January 19, 2021 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.