RC-14-0014, V. C. Summer, Unit 1, Response to NRC Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns

V. C. Summer, Unit 1, Response to NRC Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns

ML14035A227
Person / Time
Site:	Summer
Issue date:	01/31/2014
From:	Gatlin T South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RC-14-0014
Download: ML14035A227 (5)

Text

Thomas D. Gatlin Vice-President Nuclear Operations (803) 345-4342 January 31, 2014 A SCANA COMPANY RC-14-0014 U.S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555-0001

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 SOUTH CAROLINA ELECTRIC & GAS (SCE&G) RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION ASSOCIATED WITH NEAR-TERM TASK FORCE RECOMMENDATION 2.3,. FLOODING WALKDOWNS

References:

1. NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 12, 2012 [ML12053A340]

2. NRC Letter, Endorsement of Nuclear Energy Institute (NEI) 12-07 "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," May 31, 2012 [ML12144A142]

3. SCE&G Letter, South Carolina Electric & Gas (SCE&G) Final Flooding Walkdown Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendations 2.3 of the Near-Term Task Force Review of Insights From the Fukushima Dai-ichi Accident, dated November 28, 2012 [RC-12-0189]

4. NRC Letter, Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns; dated December 23, 2013 [ML13325*A891]

On March 12, 2012, the NRC staff issued Reference 1 requesting information pursuant to Title 10 of the Code of Federal Regulations 50.54(f). Enclosure 4 of that letter contains specific Requested Information associated with Near-Term Task Force Recommendation 2.3 for Flooding. Per Reference 2, the NRC endorsed Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," dated Virgil C.Summer Station. Post Office Box 88. Jenkinsville, SC .29065 . F(803) 941-9776

Document Control Desk CR-12-01100 RC-14-0014 Page 2 of 2 May 31, 2012. By Reference 3, South Carolina Electric & Gas (SCE&G) submitted the final report in response to the request for information.

One of the requirements of NEI 12-07 is to identify the available physical margin (APM) associated with each applicable flood protection feature, determine if the margin provided is small, and evaluate any small margins that have potentially significant consequences through the corrective action process. The results of this effort were to be maintained on site for future NRC audits.

Following the NRC staff's initial review of the walkdown reports, regulatory site audits were conducted at a sampling of plants. Based on the walkdown report reviews and site audits, the staff identified additional information necessary to allow them to complete its assessments.

Accordingly, by Reference 4 the NRC staff has issued a request for addition information (RAI).

South Carolina Electric & Gas Company (SCE&G), acting for itself and as agent for South Carolina Public Service Authority is submitting this response to the request for additional information. SCE&G's response is provided within Enclosure I.

This letter contains no new regulatory commitments.

Should you have any questions concerning the content of this letter, please contact Bruce L.

Thompson at (803) 931-5042.

I declare under penalty of perjury that the foregoing is true and correct.

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Enclosure:

I. SCE&G Response to Request for Additional Information c: K. B. Marsh V. M. McCree S. A. Byrne S. A. Williams J. B. Archie K. M. Sutton N. S. Carns NRC Resident Inspector J. H. Hamilton NSRC J. W. Williams RTS (CR-12-01100)

W. M. Cherry File (815.07)

E. J. Leeds PRSF (RC-14-0014)

Document Control Desk CR-12-01 100 RC-14-0014 Enclosure I Page 1 of 3 VIRGIL C. SUMMER NUCLEAR STATION (VCSNS) UNIT I ENCLOSURE I SCE&G Response to Request for Additional Information RAI Number 1: Confirmation that the process for evaluating APM was reviewed.

SCE&G Response RAI-1:

SCE&G has completed a review of the process used at VCSNS to evaluate Available Physical Margins (APMs).

RAI Number 2: Confirmation that the APM process is now or was always consistent with the guidance in NEI 12-07 and discussed in this RAI.

SCE&G Response RAI-2:

VCSNS included consideration for APM during the performance of the Flooding Walkdowns conducted in accordance with NEI 12-07. The APMs were assessed against the current licensing basis values. Any low margin or no margin areas were documented in the station's CAP program for disposition of potential loss of safety function.

RAI Number 3. If changes are necessary, a general description of any process changes to establish this consistency.

SCE&G Response RAI-3:

As stated above, the original walkdown effort was consistent with the guidance provided in NEI 12-07. The APMs were assessed against the current licensing basis values. Any low margin or no margin areas were documented in the station's CAP program for disposition of potential loss of safety function.

RAI Number 4: As a result of the audits and subsequent interactions with industry during public meetings, NRC staff recognized that evaluation of APM for seals (e.g., flood doors, penetrations, flood gates, etc.) was challenging for some licensees. Generally, licensees were expected to use either Approach A or Approach B (described below) to determine the APM for seals:

a) If seal pressure ratings were known, the seal ratings were used to determine APM (similar to example 2 in Section 3.13 of NEI 12-07). A numerical value for APM was documented. No further action was

Document Control Desk CR-12-01100 RC-14-0014 Enclosure I Page 2 of 3 b) performed if the APM value was greater than the pre-established small-margin threshold value. If the APM value was small, an assessment of "significant consequences" was performed and the guidance in NEI 12-07 Section 5.8 was followed.

c) If the seal pressure rating was not known, the APM for seals in a flood barrier is assumed to be greater than the pre-established small-margin threshold value if the following conditions were met: (1) the APM for the barrier in which the seal is located is greater than the small-margin threshold value and there is evidence that the seals were designed/procured, installed, and controlled as flooding seals in accordance with the flooding licensing basis. Note that in order to determine that the seal has been controlled as a flooding seal, it was only necessary to determine that the seal configuration has been governed by the plant's design control process since installation. In this case, the APM for the seal could have been documented as "not small".

As part of the RAI response, state if either Approach A or Approach B was used as part of the initial walkdowns or as part of actions taken in response to this RAI. No additional actions are necessary if either Approach A or B was used.

If neither Approach A or B was used to determine the APM values for seals (either as part of the walkdowns or as part of actions taken in response to this RAI), then perform the following two actions:

• Enter the condition into the CAP (note: it is acceptable to utilize a single CAP entry to capture this issue for multiple seals). CAP disposition of "undetermined" APM values for seals should consider the guidance provided in NEI 12-07, Section 5.8. The CAP disposition should confirm all seals can perform their intended safety function against floods up to the current licensing basis flood height.

Disposition may occur as part of the Integrated Assessment. If an Integrated Assessment is not performed, determine whether there are significant consequences associated with exceeding the capacity of the seals and take interim action(s), if necessary, via the CAP processes. 'These actions do not need to be complete prior to the RAI response.

" Report the APM as "undetermined" and provide the CAP reference in the RAI response.

SCE&G Response RAI-4:

Approach B, as described above, was used to determine APM values for seals at VCSNS. Per NEI 12-07 [Rev. 0-A], "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," May 2012 (NEI Guidelines), Section 3.8, a deficiency exists when a flood protection feature is unable to perform its intended flood protection function when subject to a design basis flooding hazard. The Flooding Walkdown Credited Features Checklist (Checklist) was prepared to define the current license basis (CLB) flood protection features at VCSNS. The Checklist did not specifically list any penetration seals as a flood protection feature. However, exterior building walls are defined as CLB flood protection features, and flooding walkdowns were performed on these features. Part of the inspection for these features was to verify that

Document Control Desk CR-12-01100 RC-14-0014 Enclosure I Page 3 of 3 visible penetrations are sealed, and that the seal is not degraded. Section 5.6 of the NEI Guidelines further explains that it is sufficient to confirm that the seals are appropriate, installed as designed, and not damaged; it is not necessary to test the pressure rating of the seal.

VCSNS FSAR Section 3.4.1.2 states below grade penetrations are provided with a waterproofing seal. These below grade and buried seals are not expected to experience a significant pressure increase during design basis flood event, which for VCSNS is the local intense precipitation (LIP) and has a short duration pooling. The south walls of Control building, Intermediate building, and Diesel Generator building between column line 12.5 and 1.8 are open to the Turbine building and could experience significant hydrostatic pressure increase during design basis flood. The seals in subject walls were designed to withstand specified hydrostatic pressure per VCSNS Specification 227 and architectural drawings, and were determined to be installed as designed and free of damage during flood protection verification walkdowns.