DCL-06-006, Response to Request for Additional Information Regarding License Amendment Request 06-02, Revision to Technical Specification 5.6.5, 'Core Operating Limits Report (Colr)'.

Response to Request for Additional Information Regarding License Amendment Request 06-02, Revision to Technical Specification 5.6.5, 'Core Operating Limits Report (Colr)'.

ML062860065
Person / Time
Site:	Diablo Canyon
Issue date:	09/29/2006
From:	Becker J Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-06-006, DCL-06-114, LAR 06-02, WCAP-16009-P-A
Download: ML062860065 (4)

Text

Pacific Gas and Electric Company' James R. Becker Diablo Canyon Power Plant Vice President P.0. Box 56 September 29, 2006 Diablo Canyon Operations and Avila Beach, CA 93424 Station Director 805.545.3462 PG&E Letter DCL-06-114 Fax: 805.545.4234 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Docket No. 50-323, OL-DPR-82 Diablo Canyon Unit 2 Response to Request for Additional Information Reqarding License Amendment Request 06-02, "Revision to Technical Specification 5.6.5, 'Core Operatinq Limits Report (COLR)"

Dear Commissioners and Staff:

Pacific Gas and Electric Company Letter DCL-06-006, dated January 13, 2006, submitted License Amendment Request (LAR) 06-02, "Revision to Technical Specification 5.6.5, 'Core Operating Limits Report (COLR)."' LAR 06-02 proposes to revise Technical Specification (TS) 5.6.5, "Core Operating Limits Report (COLR),"

by adding WCAP-1 6009-P-A, "Realistic Large-Break LOCA Evaluation Methodology Using the Automated Statistical Treatment of Uncertainty Method (ASTRUM)," dated January 2005, as an approved analytical method for determining core operating limits for Unit 2.

On July 14, 2006, the NRC staff requested additional information required to complete the review of LAR 06-02. The enclosure provides the requested information.

The response provided in this submittal does not affect the results of the technical evaluation or the no significant hazards consideration determination previously transmitted in DCL-06-006.

PG&E makes no regulatory commitments or revisions to regulatory commitments in this letter. If you have any questions or require additional information, please contact Stan Ketelsen at (805) 545-4720.

I declare under pena erjury that the foregoing is true and correct.

Exe uted on Fp. 920 James R. Becker A member of the STARS (Strategic Teaming and Resource Sharing) Alliance 7)/

Callaway o Comanche Peak

• Diablo Canyon

• Palo Verde

• South Texas Project

• Wolf Creek

Document Control Desk PG&E Letter DCL-06-114 IPJ.

E-I September 29, 2006 Page 2 jerl /3664 Enclosure cc: Edgar Bailey, DHS Terry W. Jackson Bruce S. Mallett Diablo Distribution cc/enc: Alan B. Wang A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• South Texas Project

• Wolf Creek

Enclosure PG&E Letter DCL-6-114 Response to Request for Additional Information Regarding License Amendment Request 06-02, "Revision to Technical Specification 5.6.5,

'Core Operating Limits Report (COLR)"'

NRC Question No. I Confirm that performing the Unit 2 BELOCA [best estimate loss of coolant loss-of-coolant accident]analysis with an assumed nominal core power level of 3468 MWt [megawatt, thermal]and an associateduncertaintyof 0.3 percent is conservatively bounding.

PG&E Response to Question No. I The BELOCA methodology used in WCAP-1 6009-P-A, "Realistic Large-Break LOCA Evaluation Methodology Using the Automated Statistical Treatment of Uncertainty Method (ASTRUM)," performs a statistical treatment of key parameter uncertainties in order to calculate a ninety fifth percentile peak cladding temperature (PCT) value. The core power level is one of the key input parameters, which is randomly sampled for each of the 124 WCOBRA/TRAC cases, which are analyzed to establish the ninety fifth percentile PCT result. A greater core power level results in increased initial fuel temperatures and decay heat for a given case analysis and thus generates a more limiting PCT result. In order to conservatively bound any future potential increase in the licensed maximum core power level associated with a measurement uncertainty recapture (MUR) power uprate, the Unit 2 BELOCA analysis was performed with an assumed core power level of 3468 MWt. This analyzed core power level represents a 1.7 percent increase with respect to the current Unit 2 licensed maximum core power level of 3411 megawatt, thermal (MWt). The ASTRUM BELOCA statistical analysis was then performed based on a uniform probability distribution corresponding to 0.3 percent uncertainty about the assumed value of 3468 MWt.

Figure 1 shows example plots of the uniform probability distribution for a core power level of 3411 MWt analyzed with a 2 percent uncertainty, and the Unit 2 ASTRUM BELOCA assumed core power level of 3468 MWt with a 0.3 percent analyzed uncertainty. The figure shows the core power probability distribution analyzed for the Unit 2 ASTRUM BELOCA results in a significant shift and increase in the probabilistic power level compared to the 3411 MWt case with a 2 percent uncertainty. Since an increase in the analyzed core power level results in a larger PCT value, the Unit 2 ASTRUM BELOCA analyzed a more limiting core power level probability distribution and generated PCT results that are conservatively bounding for the current Unit 2 licensed maximum core power level of 3411 MWt with a 2 percent uncertainty.

1

Enclosure PG&E Letter DCL-6-114 NRC Question No. 2 Confirm that PG&E is not implementing any core power level changes for Unit 2 as part of this COLR amendment and any such core power uprate will only be implemented in a separatelicense amendment.

PG&E Response to Question No. 2 PG&E is not implementing any core power level changes as part of this COLR license amendment. The assumed nominal core power level for the ASTRUM BELOCA analysis was increased to preclude having to perform a BELOCA re-analysis should a MUR power uprate be implemented for Unit 2. Any such calorimetric power uprate would only be implemented following NRC approval of a separate license amendment request that evaluates the applicable license and design basis changes.

Figure 1: Examples of Uniform Probability Distributions for Assumed for BELOCA Power Levels 0.05 3411 MWt wI 2% uncertainty

- 3468 MWt w/ 0.3% uncertainty 0.03 0.02 0 0.02 0.01-3300 3350 3400 3450 3500 Power Level 2