RC-17-0067, Regulatory Commitment Change Related to Best Estimate Large Break Loss of Coolant Accident Analysis That Explicitly Accounts for Thermal Conductivity Degradation

Regulatory Commitment Change Related to Best Estimate Large Break Loss of Coolant Accident Analysis That Explicitly Accounts for Thermal Conductivity Degradation

ML17153A219
Person / Time
Site:	Summer
Issue date:	06/01/2017
From:	Lippard G South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RC-17-0067
Download: ML17153A219 (4)

Text

George A. Lippard Vice President, Nuclear Operations 803.345.4810 A SCANA COMPANY June 1, 2017 RC-17-0067 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 REGULATORY COMMITMENT CHANGE RELATED TO BEST ESTIMATE LARGE BREAK LOSS OF COOLANT ACCIDENT ANALYSIS THAT EXPLICITLY ACCOUNTS FOR THERMAL CONDUCTIVITY DEGRADATION

Reference:

Letter from T. D. Gatlin, SCE&G, to U.S. Nuclear Regulatory Commission, "ECCS Evaluation Model Revisions 30-Day Report," dated October 16, 2012

[ML12293A071]

In accordance with 10 CFR 50.46(a)(3)(ii), South Carolina Electric & Gas Company, acting for itself and as agent for South Carolina Public Authority, hereby submits a request to change the commitment made in the referenced letter listed above and the commitment due date. The commitment pertains to VCSNS's Best Estimate Large Break Loss of Coolant Accident (BE LBLOCA) analysis, and the effects of fuel pellet Thermal Conductivity Degradation (TCD) on that analysis.

The original commitment, with a due date of June 15, 2017, is changed from:

SCE&G will submit to the NRC for review and approval a BE LBLOCA analysis that applies NRC-approved methods that include the effects of fuel TCD To:

SCE&G will submit to the NRC for review and approval a LOCA analysis that applies NRC-approved methods that include the effects of fuel TCD Additionally, the reference listed above also mentioned including the effects of peaking factor burndown and facilitating an upgrade to a later version of the PAD fuel thermal performance code. A correction to an evaluation for the Transverse Momentum Cells for Zero Cross-Flow Boundary Condition is also mentioned. These remain included with the commitment.

SCE&G had planned to address the above issues by providing a BE LBLOCA analysis; however, the approach changed to employ the Full Spectrum LOCA (FSLOCA) method described in WCAP-16996. VCSNS participated as a pilot plant for the FSLOCA's method development. As with the BE LBLOCA, the FSLOCA method predicts the response of a LOCA V. C. Summer Nuclear Station

• P. 0. Box 88

• Jenkinsville, South Carolina

• 29065

• F (803) 941-9776

• www.sceg.com

USNRC DCD CR-11-06265 RC-17-0067 Page 2 of 3 using a combination of deterministic thermal-hydraulics and a statistical treatment of results, thus demonstrating the qualification of a plant's Emergency Core Cooling System (ECCS) in accordance with 10 CFR 50.46. However, unlike the BE LOCA, the FSLOCA method is not limited to the Large Break LOCA portion of the break spectrum. Rather, it extends the applicability of best estimate methods to the Intermediate Break (IBLOCA) and Small Break LOCA (SBLOCA), which have required different methods to compute system and fuel responses. With one approach for the entire break spectrum, the commitment is changed to reflect the departure from the BE LBLOCA method to a more general one.

As with other LOCA analysis methods, FSLOCA relies upon a fuel thermal performance code for providing fuel-related initial conditions for transient and accident analyses. The PAD 5.0 code is the state-of-the-art fuel performance code for Westinghouse fuel. It is intended to replace PAD 3.4 and 4.0, which were the codes originally used in the BE LBLOCA analysis and the estimation of TCD effects, respectively. PAD 5.0 is described in topical report WCAP-17642-P/NP explicitly addresses TCD effects.

As stated earlier, a due date of June 15, 2017, was set to fulfill the commitment. Two factors warrant the commitment due date change:

• The FSLOCA topical report remains under review.

• PAD 5.0 is planned for review by the Advisory Committee for Reactor Safeguards (ACRS) in May 2017.

The change in commitment date does not degrade or otherwise alter the ability of the plant to operate safely. The current analyses of record for VCSNS's LOCA analyses show that peak clad temperature for the LOCA events remain acceptable. Further, a change in date would provide the opportunity for VCSNS to demonstrate compliance with the anticipated 10 CFR50.46c rule. Once the rule is issued, this then could become a one-time effort that efficiently utilizes licensee and regulator resources. Therefore, the changes in commitment and date from June 15, 2017, to June 15, 2020, are justified.

This letter contains no new regulatory commitments. The revised commitment is listed in this submittal's Enclosure.

USNRC DCD CR-11-06265 RC-17-0067 Page 3 of 3 If you have any questions about this submittal, contact Mr. Bruce L. Thompson at (803) 931-5042.

Very truly yours, George A. Lippard TS/GAL/rp

Enclosure:

Revised Regulatory Commitment cc:

K. B. Marsh S. A. Byrne J. B. Archie N. S. Cams J. H. Hamilton S.M. Shealy W. M. Cherry C. Haney S. A. Williams NRC Resident Inspector K. M. Sutton NSRC RTS (CR-11-06265)

File (818.02-17)

PRSF (RC-17-0067)

USNRC Enclosure CR-11-06265 RC-17-0067 Page 1 of 1 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 ENCLOSURE REVISED REGULATORY COMMITMENT The following table identifies the revised action committed to by the Virgil C. Summer Nuclear Station (VCSNS) in this document. Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments. Please direct questions regarding this revised commitment to Mr. Bruce L. Thompson at (803) 931-5042.

COMMITMENT DUE DATE SCE&G will submit to the NRC for review and approval a LOCA analysis that applies NRC-approved methods that include the June 15, 2020 effects of fuel Thermal Conductivity Degradation (TCD).