ML112010696

RAI, Related to Request to Exclude the Dynamic Effects Associated with Certain Postulated Pipe Ruptures from the Licensing Basis Based Upon Application of Leak-Before-Break Methodology

ML112010696
Person / Time
Site:	Prairie Island
Issue date:	07/22/2011
From:	Thomas Wengert Plant Licensing Branch III
To:	Schimmel M Northern States Power Co
Wengert, Thomas
References
TAC ME2976, TAC ME2977
Download: ML112010696 (5)

Text

UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 .July 22, 2011 Mr. Mark A. Schimmel Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company -Minnesota 1717 Wakonade Drive East Welch, MN 55089-9642 PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND REQUEST FOR ADDITIONAL INFORMATION RELATED TO REQUEST TO EXCLUDE THE DYNAMIC EFFECTS ASSOCIATED WITH CERTAIN POSTULATED PIPE RUPTURES FROM THE LICENSING BASIS BASED UPON APPLICATION OF LEAK-BEFORE-BREAK METHODOLOGY (TAC NOS. ME2976 AND ME2977)

Dear Mr. Schimmel:

By letter to the U.S. Nuclear Regulatory Commission (NRC) dated December 22, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML100200129), as supplemented by letters dated July 23, August 20, October 8,2010, and January 14, February 23, and April 6, 2011 (ADAMS Accession Nos. ML102040612, ML102320535, ML102810518, ML110140367, ML110550582 and ML110970101, respectively), Northern States Power Company (the licensee), a Minnesota corporation doing business as Xcel Energy, submitted a request for approval to exclude certain postulated pipe ruptures from the licensing basis based upon application of the leak-before-break methodology for Prairie Island Nuclear Generating Plant, Units 1 and 2. The NRC staff is reviewing your submittal and supplements and has determined that additional information is required to complete the review. The specific information requested is addressed in the enclosure to this letter. The NRC staff considers that timely responses to requests for additional information help ensure sufficient time is available for staff review and contribute toward the NRC's goal of efficient and effective use of staff resources.

M. Schimmel If circumstances result in the need to revise the requested response date, please contact me at (301 ) 4154037. Sincerely, Thomas J. We gert, Senior Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306 Request for Additional cc w/encl: Distribution via REQUEST FOR ADDITIONAL PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND DOCKET NOS. 50-282 AND Background The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the leak-before-break license amendment request dated December 22, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML100200129);

the responses to the requests for additional information dated July 23, August 20, October 8,2010, and January 14, February 23, and April 6, 2011 (ADAMS Accession Nos. ML102040612, ML102320535, ML102810518, ML110140367, ML110550582 and ML110970101, respectively), for the Prairie Island Nuclear Generating Plant, Units 1 and 2 (PINGP). Based on that review, the NRC staff has determined that the proposed leakage detection system configuration and operation would not satisfy certain regulatory guidelines for leak-before-break applications described in Section 3.6.3 of the NRC Standard Review Plan (SRP), NUREG-0800.

These guidelines specify that leakage detection systems credited for leak-before-break should satisfy the criteria of Regulatory Guide (RG) 1.45, "Reactor Coolant Pressure Boundary Leakage Detection Systems." Regulatory Positions 2 and 3 of RG 1.45, Revision 1, states the following: leakage detection systems should have a response time of no greater than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for a leakage rate of 1 gallon per minute (gpm) leakage detection systems should provide output and alarms in the main control room procedures to convert the instrument output to a leakage rate should be available to operators plant procedures should specify operator actions in response to leakage rates less than the limits set forth in the technical speCifications Based on its review of the information submitted to date, the NRC staff has determined that the proposed design and operation of the PINGP ReS leakage detection system is inadequate to fully satisfy the above criteria.

Specifically, the described detection sensitivity for the containment particulate radiation monitor was based on a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> trend reView, which would support self-masking of the type of slowly-developing leak associated with leak-before-break.

In addition, no procedure for converting particulate monitor readings to equivalent leakage rates was described and no suitable alarms for reactor coolant system leakage rates at or below one (1) gpm were identified.

Therefore, the staff is concerned that the proposed configuration and operation of the particulate radiation monitor would not provide a reliable, diverse indication of leakage. Finally, the proposed actions in response to leakage were not specific.

Enclosure

-Request for Additional Information (RAI) Accordingly, provide the following information to resolve the concerns with the proposed design and operation of the leakage detection system: Discuss PINGP's plans to develop and describe procedures that would allow operators to approximate the quantity of leakage in the range above 0.2 gpm based on indications from the particulate radiation monitor or other leakage monitor subject to a Technical Specification (TS) limiting condition for operation (LCO). Describe how masking of a slowly increasing leak rate would be avoided. Discuss PINGP's plans to develop and identify a reliable alarm that would be set to alarm at leakage rates less than 1 gpm. The instrument associated with the alarm should be subject to a TS LCO. Specify operator actions for leakage levels in excess of 0.2 gpm. Address entry conditions for abnormal or alarm response procedures, actions to verify actual leakage rates (avoid over-reliance on one instrument or process), identification of leak location, and any criteria for containment entry or plant shutdown more conservative than the TS LCOs. In preparing this RAI, the NRC staff acknowledges that methods and solutions that differ from those set forth in RG 1.45 and the SRP will be deemed acceptable if they provide a basis for findings required for the issuance of the leak-before-break license amendment.

M. Schimmel -2 If circumstances result in the need to revise the requested response date, please contact me at (301) 415-4037.

Sincerely, IRAJ Thomas J. Wengert, Senior Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306

Enclosure:

Request for Additional Information cc w/encl: Distribution via ListServ DISTRIBUTION:

PUBLIC RidsNRRPMPrairielsland Resource RidsAcrsAcnw_MailCTR Resource RidsRgn3MailCenter Resource LPL3-1 R/F RidsNrrLABTully Resource RidsOgcRp Resource RidsNrrDssSbpb Resource RidsNrrDorlLpl3-1 Resource RidsNrrDciCpnb Resource S. Jones, NRR ADAMS Accession Number' ML112010696 OFFICE LPL3-1/PM LPL3-1/LA NRR/DSS/SBPB/BC LPL3-1/BC NAME TWengert BTully/Rohrer GCasto RPascarelli DATE 07/21/11 07/21/11 07/22/11 07/22/11 OFFICIAL RECORD COpy