NL-14-1100, Response to Request for Additional Information Regarding Technical Specification 3.7.5. Control Room Air Conditioning (AC) System

Response to Request for Additional Information Regarding Technical Specification 3.7.5. Control Room Air Conditioning (AC) System

ML14203A160
Person / Time
Site:	Hatch
Issue date:	07/22/2014
From:	Pierce C Southern Co, Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-14-1100
Download: ML14203A160 (5)

Text

Charles R. Pierce Southern Nuclear Regulatory Affairs Director Operating Company. Inc.

40 Inverness Center Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205.992.7872 Fax 205.992.7601 SOUTHERN A COMPANY JUL 2 2 2014 Docket Nos.: 50-321 NL-14-1100 50-366 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Response to Request for Additional Information Regarding Technical Specification 3.7.5. Control Room Air Conditioning <AC) System Ladies and Gentlemen:

By letter dated January 16, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14016A202) Southern Nuclear Operating Company (SNC), licensee of Edwin I. Hatch Nuclear Plant (HNP),

Units 1 and 2, submitted a license amendment request (LAR) to modify the Technical Specifications (TSs) for HNP. The requested amendment will revise the existing HNP TS 3.7.5, Control Room Air Conditioning (AC) System, to provide new Required Actions for one, two, or three main control room (MCR) AC subsystems inoperable, and make other required corresponding changes.

By letter dated June 23, 2014, the Nuclear Regulatory Commission sent a Request for Additional Information (RAI) letter with two questions. The Enclosure provides the SNC response to the NRC questions.

This letter contains no NRC commitments. If you have any questions, please contact Ken McElroy at (205) 992-7369.

U.S. Nuclear Regulatory Commission NL-14-1100 Page2 Mr. C. R. Pierce states he is Regulatory Affairs Director of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and, to the best of his knowledge and belief, the facts set forth in this letter are true.

Respectfully submitted,

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C. R. Pierce Regulatory Affairs Director CRP/RMJ My commission expires: ld/i/zot1 I I

Enclosure:

SNC Response to NRC RAis cc: Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bast, Executive Vice President & Chief Nuclear Officer Mr. D. R. Vineyard, Vice President - Hatch Mr. B. L. lvey, Vice President- Regulatory Affairs Mr. D. R. Madison, Vice President - Fleet Operations Mr. B. J. Adams, Vice President- Engineering Mr. G. L. Johnson, Regulatory Affairs Manager - Hatch RType: CHA02.004 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager- Hatch Mr. D. H. Hardage, Senior Resident Inspector- Hatch State of Georgia Mr. J. H. Turner, Environmental Director Protection Division

Edwin I. Hatch Nuclear Plant Response to Request for Additional Information Regarding Technical Specification 3.7.5, Control Room Air Conditioning (AC) System Enclosure SNC Response to NRC RAis to NL-14-1100 SNC Response to NRC RAis NRC RAJ #1 What is being gained or avoided (benefit) by having a CR temperature limit of go oF versus an ambient temperature limit of 65°F?

SNC Response to NRC RAJ #1 Using a direct measure of the main control room (MCR) temperature is a more reliable and appropriate method to maintain MCR habitability than establishing an estimated MCR temperature based on the ambient temperature. The measure of the ambient temperature only provides an indirect estimate of the MCR temperature. The MCR temperature is dependent on many variables, including the ambient temperature, the MCR surrounding temperature, and the service water temperature to the water cooled condensing unit (among other variables). The MCR surrounding temperature is dependent on the ambient temperature, while the service water temperature is dependent on the ambient temperature and on seasonal variations. The current measure of the ambient temperature at 65°F is correlated to an estimated maximum MCR temperature of 105°F with one MCR AC system operable. Based on the amount of variables associated with correlating the MCR temperature to the ambient temperature, this does not provide an accurate way to assess actual MCR area temperature.

NRC RAI #2 What would be the safety impact of operating for 7 days with a CR temperature at gooF versus the current ambient 65°F limit?

SNC Response to NRC RAI #2 The existing Hatch TS require both Units to be in MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and MODE 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, if two MCR AC subsystems are inoperable during MODE 1, 2, or 3, and the outside air temperature has been greater than 65°F anytime during the previous 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, if even for an instant. The very limited time allowed to shutdown both units results in a small likelihood that the Nuclear Regulatory Commission (NRC) will be able to grant a Notice of Enforcement Discretion (NOED) prior to Hatch commencing a dual unit shutdown. This requirement is irrespective of the fact that the actual MCR temperature rise due to loss of cooling may be acceptable. The requirement to monitor MCR area temperature ensures the environment for the MCR equipment and people is maintained. This license amendment request realigns the requirements for a dual unit shutdown with the actual parameter of safety significance (i.e. the MCR area temperature).

The current ambient 65°F limit is based on one MCR AC subsystem maintaining MCR area temperature less than 105°F, and allows up to 30 days in this configuration. The proposed RAs will only allow the MCR area temperature to reach gooF, and will only allow 7 days of MODE 1 operation with one operable MCR AC subsystem. The proposed RAs are therefore more conservative than the current RAs in this regard. However, based on the current RAs, a dual unit shutdown will be required if the ambient area temperature reaches 65°F, or if it had reached 65°F in the previous 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, even if for an instant. This can result E-1 to NL-14-1100 SNC Response to NRC RAis in an unnecessary plant transient that affects both Unit 1 and Unit 2, and could cause the plant to incur more risk by shutting down than would be incurred by continued operation. Requiring a dual unit shutdown can result in a large grid instability from the loss of roughly 1800 megawatts electric.

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