ML070160169

Columbia Generating Station - Clarification of Alternative Source Term Amendment

ML070160169
Person / Time
Site:	Columbia
Issue date:	02/05/2007
From:	Terao D NRC/NRR/ADRO/DORL/LPLIV
To:	Parrish J V Energy Northwest
Fields M B, NRR/DORL/LP4, 415-3062
References
TAC MC4570
Download: ML070160169 (4)

Text

February 5, 2007Mr. J. V. Parrish Chief Executive Officer Energy Northwest P.O. Box 968 (Mail Drop 1023)

Richland, WA 99352-0968

SUBJECT:

COLUMBIA GENERATING STATION - CLARIFICATION OF ALTERNATIVESOURCE TERM AMENDMENT (TAC NO. MC4570)

Dear Mr. Parrish:

On November 27, 2006, the Nuclear Regulatory Commission (NRC) issued AmendmentNo. 199 to Facility Operating License No. NPF-21 for the Columbia Generating Station (CGS).

The amendment replaced the previous accident source term used in design-basis radiological analyses with an alternative source term pursuant to Title 10 of the Code of FederalRegulations, Section 50.67 (10 CFR 50.67), "Accident source term." The related SafetyEvaluation (SE) provided the details of the NRC staff's review of this license amendment. Energy Northwest, the CGS licensee, verbally requested the NRC staff provide clarification ofthe section of this SE that discussed the design basis of the secondary containment.

Specifically, the licensee requested confirmation of its understanding of the requirements for assuring the secondary containment is being maintained in a sufficiently leak-tight condition to preclude exfiltration. The details of the licensee's understanding of this issue were provided in its September 11, 2006, letter.The September 11, 2006, letter provides clarification on what Energy Northwest considersrelevant to providing reasonable assurance of secondary containment integrity. It states:In addition, it is understood that the value of greater than or equal to 0.25 inchesof vacuum water gauge is an indication of pressure at one location in the secondary containment and not a value maintained at every surface within the secondary containment. The instrument used to perform this surveillance measures pressure at reactor building elevation 572' in an area that has open communication with the rest of the secondary containment volume. The NRC staff discussed this issue in Section 3.1.1.3 of the SE, "Secondary ContainmentDrawdown," and concluded that secondary containment integrity is ensured in part by Technical Specification (TS) 3.6.4.1, "Secondary Containment" and its associated surveillance requirements (SRs). The design basis dose modeling, which assumes that (1) either all or none of the leakage fromthe primary containment volume is released to the environment depending upon whether secondary containment integrity is assumed, and (2) conservative modeling of meteorological conditions, is a very conservative approach. It is the NRC staff's engineering judgment that the J. V. Parrish-2-containment drawn down to a negative 0.25 inch water gauge (w.g.), as determined by a singlerepresentative location, is sufficient to demonstrate adequate performance of the SRs in TS 3.6.4.1. Minor amounts of exfiltration under these conditions are expected to have a minimal impact on the radiological consequences and does not present a safety concern. SR 3.6.4.1.4 is intended to demonstrate that the standby gas treatment system (SGTS) has thecapability of drawing down the secondary containment to a negative 0.25 inch w.g. in a 2-minute period of time. The NRC staff finds the acceptance criteria for this SR to be adequate, since a 2-minute draw down will adequately demonstrate the functional capability of the SGTS and because 20 minutes is used as the draw-down time in the loss-of-coolant accident (LOCA) analysis. The significant margin between the SR acceptance criteria of 2 minutes and the assumption of 20 minutes used in the LOCA analysis is sufficient to account for the potential increase in draw-down time due to accident and meteorological conditions. SR 3.6.4.1.5 is intended to demonstrate that the SGTS is capable of maintaining a negativepressure in the secondary containment for a period of time at a reduced SGTS fan flow rate of 2,240 cubic feet per minute (cfm). SR 3.6.4.1.5 confirms that the SGTS can maintain the negative pressure of 0.25 inch w.g. for an extended period with reduced SGTS flow under test conditions and provides reasonable assurance that the negative pressure can continue to be maintained under adverse conditions when the SGTS would be operating at its full design flow of 4,800 cfm.Successful completion of these SRs provides reasonable assurance of secondary containmentintegrity. Changes which reduce required integrity would be detected by increases in draw-down time in successive testing until ultimately the test would fail. An increase in inleakage above the fan flow rate would cause the test to fail and indicate that integrity had degraded.If you have any questions regarding this letter, please contact me at (301) 415-3317.Sincerely,/RA/David Terao, ChiefPlant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor RegulationDocket No. 50-397 cc: See next page

ML070160169OFFICENRR/LPL4/PMNRR/LPL4/LANRR/AADBNRR/ACVBNRR/LPL4/BCNAMEMFieldsLFeizollahiMKotzalasRDennigDTerao DATE2/5/071/25/071/24/071/25/072/5/07 August 2006Columbia Generating Station cc:Mr. W. Scott Oxenford (Mail Drop PE04)

Vice President, Technical Services Energy Northwest P.O. Box 968 Richland, WA 99352-0968Mr. Albert E. Mouncer (Mail Drop PE01)Vice President, Corporate Services/

General Counsel/CFO Energy Northwest P.O. Box 968 Richland, WA 99352-0968ChairmanEnergy Facility Site Evaluation Council P.O. Box 43172 Olympia, WA 98504-3172Mr. Douglas W. Coleman (Mail Drop PE20)Manager, Regulatory Programs Energy Northwest P.O. Box 968 Richland, WA 99352-0968Mr. Gregory V. Cullen (Mail Drop PE20)Supervisor, Licensing Energy Northwest P.O. Box 968 Richland, WA 99352-0968Regional Administrator, Region IVU.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-4005ChairmanBenton County Board of Commissioners P.O. Box 190 Prosser, WA 99350-0190Senior Resident InspectorU.S. Nuclear Regulatory Commission P.O. Box 69 Richland, WA 99352-0069Mr. Dale K. Atkinson (Mail Drop PE08)Vice President, Nuclear Generation Energy Northwest P.O. Box 968 Richland, WA 99352-0968Mr. William A. Horin, Esq.Winston & Strawn 1700 K Street, N.W.

Washington, DC 20006-3817Mr. Matt SteuerwaltExecutive Policy Division Office of the Governor P.O. Box 43113 Olympia, WA 98504-3113Ms. Lynn AlbinWashington State Department of Health P.O. Box 7827 Olympia, WA 98504-7827Technical Services Branch ChiefFEMA Region X

130 228 th Street, S.W.Bothell, WA 98201-9796Ms. Cheryl M. Whitcomb (Mail Drop PE03)Vice President, Organizational Performance & Staffing/CKO Energy Northwest P.O. Box 968 Richland, WA 99352-0968 Assistant DirectorNuclear Safety and Energy Siting Division Oregon Department of Energy 625 Marion Street, NE Salem, OR 97301-3742