NL-18-0211, Response to Request for Additional Information Regarding Alternative HNP-181-ALT-05-05 to Adopt Code Case N-702

Response to Request for Additional Information Regarding Alternative HNP-181-ALT-05-05 to Adopt Code Case N-702

ML18051A170
Person / Time
Site:	Hatch
Issue date:	02/20/2018
From:	Wheat J Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-18-0211
Download: ML18051A170 (4)

Text

~ Southern Nuclear Justin T. Wheat Nuclear Ltcenstng Manager 40 Imemes' C~!nter Parh.way Post Olficc l.lnx 1295 Airmingham. AI 3'i2-12 205 992 5998 tel 205 992 71i01 fax Jl wheat (iil,outhcrnco.com FEB 2 0 2018 Docket Nos.: 50-321 NL-18-0211 50-366 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Units 1 and 2 Response to Request for Additional Information Regarding Alternative HNP-181-ALT-05-05 to Adopt Code Case N-702 Ladies and Gentlemen:

By letter dated June 5, 2017, Southern Nuclear Operating Company (SNC) submitted Alternative HNP-ISI-ALT-05-05 to allow a reduced percentage requirement for nozzle-to-vessel weld and inner radius examinations based on the applicability criteria of Code Case N-702. On September 9, 2017, the Nuclear Regulatory Commission (NRC) staff notified SNC that additional information is needed for the staff to complete their review. The Enclosure provides the SNC response to the NRC staff's request regarding the probability of failure (PoF) per reactor year due to normal operation for the reactor pressure vessel (RPV) nozzle-to-shell weld and RPV nozzle blend radii in the reactor recirculation outlet (N1) and inlet (N2) nozzles.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at 205.992.7369.

Respectfully submitted, Nuclear Licensing Manager JTW/RMJ

Enclosure:

Structural Integrity Associates Report No. 1800072.401.RO Cc: Regional Administrator, Region II NRR Project Manager- Hatch Senior Resident Inspector- Hatch RTYPE: CHA02.004

Edwin I. Hatch Nuclear Plant Units 1 and 2 Response to Request for Additional Information Regarding Alternative HNP-ISI-ALT-05-05 to Adopt Code Case N-702 Enclosure Structural Integrity Associates Report No. 1800072.401.RO

~Structural Integrity Associates, Inc.

5215 Hellyer Ave Suite 210 San Jose, CA 95138-1025 Phone: 408-978-8200 Fax: 408-978-8964

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wwong@structinlcom February 8, 2018 Report No. 1800072.401.RO Quality Program: ~ Nuclear D Commercial

Subject:

Normal Operating Probability of Failure for Code Case N-702 Using VIPERNOZ SI Calculation No. 1500231.303 Revision 0 determined that probability of failure (PoF) per reactor year due to a Low Temperature Over Pressure (L TOP) event for the RPV nozzle-to-shell-weld and RPV nozzle blend radii in the Hatch reactor recirculation outlet (N 1) and inlet (N2) nozzles are below the acceptance criterion of 5 x 1o- 6 per year. The work was performed using the same methodology used in BWRVIP-108, which is the technical basis for ASME Code Case N-702 and similar to the work in BWRVIP-05.

In the NRC staff's request for additional information (RAI), sent September 9, 2017 the PoF due to normal operation was requested to complete their review for Southern Nuclear Operating Company's relief HNP-ISI-AL T-05-05 .

In response to the RAI, the PoF due to normal operation was calculated for both the RPV nozzle-to-shell-weld and RPV nozzle blend radii in the Hatch N I and N2 nozzles. For theN I nozzles, the maximum PoF per year due to normal operation is 2.5x 1o-s compared to 1.31 x 1o-7 due to an LTOP event. For the N2 nozzles, maximum PoF per year due to normal operation is 8.0x 1o- 9 compared to 1.31 x 1o-7 due to an LTOP event. These are below the PoF for each corresponding RPV nozzle due to an LTOP event and the acceptance criterion of 5 x 1o-6 per year. The normal operation PoF was calculated using the same methodology as the normal operation PoF number reported in the Safety Evaluation ofBWRVIP-108.

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February 8, 2018 Report No. 1800072.401.RO Page 2 of2 Prepared by: Verified by:

2/8/18 2/8/ 18 Wilson Wong Date S. S. Tang Date Senior Engineer Associate Reviewed by:

2/8/ 18 Terry J. Herrmann, P .E. Date Senior Associate Approved by:

2/811 8 Wilson Wong Date Senior Engineer eStructural Integrity Associates, Inc.*