ML16365A006

Revised Applicability Matrix for Response to Request for Additional Information Questions APLA-1a and APLA-1b Regarding STP Risk-Informed GSl-191 Licensing Application

ML16365A006
Person / Time
Site:	South Texas
Issue date:	12/07/2016
From:	Rencurrel D South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-16003427, TAC MF2400, TAC MF2401
Download: ML16365A006 (4)

Text

South Texas Project Electric Ge!1erati!1g Statiof/ P.0 Sax 289 WadswO!th. Texas 77483 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 and 2 December 7, 2016 NOC-AE-16003427 10 CFR 50.90 Docket Nos. STN 50-498, STN 50-499 Revised Applicability Matrix for Response to Request for Additional Information Questions APLA-1a and APLA-1 b Regarding STP Risk-Informed GSl-191 Licensing Application (TAC Nos MF2400 and MF2401)

Reference:

Letter; J. Connolly to USNRC Document Control Desk; "Applicability of Application Supplement 1 Correspondence to Supplement 2 to STP Risk-Informed GSl-191 Licensing Application"; June 9, 2016; (NOC-AE-16003369) (ML16176A148).

In the above Reference, STP Nuclear Operating Company (STPNOC) provided information regarding request for additional information (RAI) responses that are no longer relevant to the STPNOC Risk-Informed GSl-191 application. Specifically, in Table 1 of Attachment 2 to the above Reference, STPNOC provided information related to the applicability of RAI Questions APLA-1 a and APLA-1 b for LOCA [Loss of Coolant Accident] Frequencies. A revised applicability basis for this item is provided in the Enclosure to this letter.

There are no commitments in this letter.

If there are any questions or if additional information is needed, please contact Drew Richards at (361) 972-7666 or me at (361) 972-7867.

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

Executed on __

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Senior Vice President - Operations amr/DWR

Enclosure:

Revised Applicability Matrix for RAI Questions APLA-1 a and APLA-1 b STI: 34416746

cc:

(paper copy)

Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 East Lamar Boulevard Arlington, TX 76011-4511 Lisa M. Regner Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (08H04) 11555 Rockville Pike Rockville, MD 20852 NRC Resident Inspector U.S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN116 Wadsworth, TX 77483 (electronic copy)

NOC-AE-16003427 Page 2 of 2 Morgan, Lewis & Bockius LLP Steve Frantz, Esquire U.S. Nuclear Regulatory Commission Lisa M. Regner NRG South Texas LP Chris O'Hara Jim von Suskil Skip Zahn CPS Energy Kevin Pollo Cris Eugster L. D. Blaylock City of Austin Elaina Ball John Wester Texas Dept. of State Health Services Helen Watkins Robert Free

ENCLOSURE Enclosure NOC-AE-16003427 Page 1of2 Revised Applicability Matrix for RAI Questions APLA-1a and APLA-1b

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Enclosure NOC-AE-16003427 Page 2 of 2 The Applicability Matrix is revised regarding the response to APLAB, CASA Grande, LOCA Frequencies: Question 1 a, 1 b to separate the responses. The response to APLAB, CASA Grande, LOCA Frequencies: Question 1 a is Not Applicable whereas the response 1 b is Applicable as revised below.

Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable APLAB, CASA Grande, The most accurate modeling of failure likelihood (Loss of Coolant Accident LOCA Frequencies:

(LOCA)) at any given location in the RCS pressure boundary would take into ML14149A434 Question 1a consideration failure mechanisms based on causal modeling of the underlying (Cover Letter phenomena thereby producing probabilities for each location. Theoretically, Ref.4) such values could be used in sums to estimate the (preferentially) frequency (or likelihood) of a LOCA of any particular size in a plant. The STP 2013 LAR used a weighting scheme that attempted to preserve the NU REG 1829 frequencies but additionally taking into account in-service data where cracks were observed and some consideration of the type of service. In Rovero, a bounding method, called top-down, was adopted that avoids the need to account for weighting by relying on the fact that locations where debris amounts exceed tested levels have been mitigated. That is, the problematic or "risk" locations have been mitigated and only the non-" risk" locations have not been. The Rovero methodology ignores the mitigation improvements and equally weights the NU REG 1829 exceedance frequencies for all locations thereby bounding local effects.

Applicable APLAB, CASA Grande, The conclusions described in the response to APLAB, CASA Grande - LOCA LOCA Frequencies:

Frequencies: RAI 1 b regarding preserving non-piping contribution to LOCA ML14149A434 Question1b frequency are applicable to the Rovero LOCA frequency analysis. Rovero (Cover Letter relies on using welds located with sufficient spatial resolution that contribution Ref.4) from components as are included in the NUREG 1829 frequency analysis are appropriately represented and preserved. Rovero also relies on the analysis that reactor vessel components otherwise relatively distant from weld locations are located in areas unimportant to generation of transportable debris (thereby conservatively shifting their frequency contribution to locations important to generation of transportable debris).