DCL-08-061, CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2007, Affect Peak Cladding Temperature (PCT) Calculations

CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2007, Affect Peak Cladding Temperature (PCT) Calculations

ML082140615
Person / Time
Site:	Diablo Canyon
Issue date:	07/23/2008
From:	Becker J Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PG&E Letter DCL-08-061
Download: ML082140615 (9)

Text

PacificGas and ElectricCompany' James R. Becker Diablo Canyon Power Plant Site Vice President and Mail Code 104/5/502 Station Director P.0. Box 56 Avila Beach, CA 93424 July 23, 2008 805.545.3462 Internal: 691.3462 Fax: 805. 545.4234 PG&E Letter DCL-08-061 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2007

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.46, this letter provides an annual report of changes in the Westinghouse emergency core cooling system (ECCS) evaluation models that affect peak cladding temperature (PCT) calculations for Pacific Gas and Electric Company (PG&E) Diablo Canyon Power Plant (DCPP), Units 1 and 2.

There have been no changes in the Unit 1 small-break loss-of-coolant accident (SBLOCA) PCT results or the large break best estimate loss of coolant accident (BELOCA) PCT results since the last annual update. The last update was provided in PG&E Letter DCL-07-071, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2006," dated July 23, 2007.

Replacement Steam Generators (RSGs) were recently installed during the Unit 2 fourteenth refueling outage which concluded in April of this year. In support of this design change, a new SBLOCA analysis was performed using the previously approved NOTRUMP methodology. This new analysis of record for Unit 2 has been implemented in accordance with 10 CFR 50.59.

As reported last year in DCL-07-071, a new BELOCA analysis of record was performed for Unit 2 using the ASTRUM methodology and implemented per License Amendment 192. This BELOCA analysis already conservatively bounds the RSGs and remains the analysis of record for Unit 2.

A summary of the updated PCT margin allocations and their bases are provided in the enclosure. The Unit 1 SBLOCA and BELOCA PCT Margin Utilization sheets are provided in Attachment A. The Unit 2 SBLOCA and BELOCA PCT Margin Utilization Sheets are provided in Attachment B. The ECCS evaluation model A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Cattaway e Comanche Peak

• Diabto Canyon

• Palo Verde - South Texas Project

• Wolf Creek ,4'662._

Document Control Desk PG&E Letter DCL-08-061 July 23, 2008 Page 2 changes that. have occurred since the last annual report are summarized in Attachment C.

The new PCT values remain within the 2200°F limit specified in 10 CFR' 50.46.

There are no new or revised regulatory commitments in this report.

If you have questions regarding this submittal please contact Mr. Nozar Jahangir at 805-545-4674.

Sincerely JamesR.Be r Site Vice Presidentand Station Direc ddm/2254/A0674893 Enclosure cc/enc: Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Alan B. Wang, NRR Project Manager Diablo Distribution 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-08-061 ANNUAL REPORT OF EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL CHANGES FOR PEAK CLADDING TEMPERATURE Pursuant to 10 CFR 50.46, this enclosure provides an annual report of changes in the Westinghouse emergency core cooling system (EGOS) evaluation models that affect peak cladding temperature (PCT) calculations for Pacific Gas and Electric Company.(PG&E) Diablo Canyon Power Plant (DCPP), Units 1 and 2.

This report is based on changes described in the following Westinghouse 10 GFR 50.46 notification letters:

Westinghouse Letter LTR-LIS-08-45, "10 CFR 50.46 Annual Notification and Reporting for 2007," dated January 31, 2008.

Attachment A to this enclosure provides DCPP Unit 1 small-break loss-of-coolant accident (SBLOCA) and best estimate large-break loss of coolant accident (BELOCA) PCT Margin Utilization Sheets. Attachment B to this enclosure provides DCPP Unit 2 SBLOCA and BELOCA PCT Margin Utilization Sheets.

There have been no changes in the Unit 1 SBLOCA PCT results or the large break BELOCA since the last annual update. The last update was provided in PG&E Letter DCL-07-071, "10 CFR 50..46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2006," dated July 23, 2007.

Replacement Steam Generators (RSGs) were recently installed during the Unit 2 fourteenth refueling outage which concluded in April of 2008. In support of this design' change, a new SBLOCA analysis was performed using the previously approved NOTRUMP methodology. This new analysis of record for Unit 2 has been implemented in accordance with 10 CFR 50.59.

As reported last year in DCL-07-071, a new BELOCA analysis of record was performed for Unit 2 using the ASTRUM methodology and implemented per License Amendment LA 192. This BELOCA analysis already conservatively bounds the RSGs and remains the analysis of record for Unit 2.

The summary of the updated PCT margin allocations and their bases are provided in the attachments, and the final net PCT values are listed below for each unit. It should be noted that two PCT values are reported for the Unit 1 BELOCA consistent with the current Westinghouse PCT tracking methodology.

The two BELOCA PCT values are labeled Reflood 1 and Reflood 2, as they represent the two distinctive PCT peaks that occur during the reflood phase for the Unit 1 BELOCA methodology, while.the Unit 2 ASTRUM methodology reports only one PCT value.

1

Enclosure PG&E Letter DCL-08-061 Small-Break LOCA Large-Break Best Estimate LOCA Reflood 1 Reflood 2 Unit 1: 1352 0 F (no change) 1915OF (no change) 1865 0 F (no change)

Unit 2: 1288 0 F 1872 0 F (no change)

The new PCT values remain within the 2200°F limit specified in 10 CFR 50.46.

The ECCS evaluation model changes that have occurred since the last annual report are summarized in Attachment C.

2

Attachment A PG&E Letter DCL-08-061 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter' A. ANALYSIS OF RECORD PCT = 1304°F DCL-99-096 B. PRIOR 10 CFR 50.46 ECCS 2 MODEL ASSESSMENTS

1. NOTRUMP Mixture Level Tracking/Region Depletion Errors APCT = 130 F DCL-00-107

2. NOTRUMP Bubble Rise/Drift Flux Model Inconsistency Corrections APCT = 35°F DCL-04-094 C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None APCT = OoF D. SUM OF 10 CFR 50.46 CHANGES

1. NetSumoflOCFR50.46 PCT Changes APCT = 480 F

2. Absolute Sum of 10 CFR 50.46 PCT Changes APCT = 480F E. Analysis of Record PCT - Line A

+ Line D.1 Net Sum of 10 CFR 1352 0 F 50.46 PCT Changes The sum of the PCT from the most recent analysis of record using an acceptable evaluation model and the estimates of the net PCT effect for changes and errors identified since this analysis remain less than 2200 0 F.

For those issues that have been previously reported under 10 CFR 50.46, a PG&E letter number is listed.

2 Only permanent assessments of PCT margin are included. Temporary PCT allocations that address current LOCA model issues are not considered with respect to 10 CFR 50.46 reporting requirements.

A-1

Attachment A PG&E Letter DCL-08-061 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BEST ESTIMATE LARGE-BREAK LOCA PG&E Letter1 Reflood Reflood 1 2 A. ANALYSIS OF RECORD 1900OF 1860oF DCL-05-146 APCT APCT B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. Revised blowdown heatup uncertainty distribution.

50 F 50F DCL-05-086

2. HOTSPOT Fuel Relocation 100 F O0 F DCL-07-071 Error.

C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None 0oF 0OF D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT 150 F 50 F Changes

2. Absolute Sum of 10 CFR 50.46 150 F 50 F PCT Changes E. Analysis of Record PCT - Line A +

Line D.1 Net Sum of 10 CFR 50.46 1915°F 1865 0 F PCT Changes The sum of the PCT from the most recent analysis of record using an acceptable evaluation model and the estimates of the net PCT effect for changes and errors identified since this analysis remain less-than 2200 0 F.

For those issues that have been previously reported under 10 CFR 50.46, a PG&E letter number is listed.

2 Only permanent assessments of PCT margin are included. Temporary PCT allocations that address current LOCA model issues are not considered with respect to 10 CFR 50.46 reporting requirements.

A-2

Attachment B PG&E Letter DCL-08-061 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter 1 This letter in A. ANALYSIS OF RECORD PCT = 1288 0 F Attachment C B. PRIOR 10 CFR 50.46 ECCS 2

MODEL ASSESSMENTS

1. None APCT= 00 F C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

2. None APCT = 0°F D. SUM OF 10 CFR 50.46 CHANGES

3. Net Sum of 10 CFR 50.46 PCT Changes APCT = 0°F

4. Absolute Sum of 10 CFR 50.46 PCT Changes APCT'= 0°F E. Analysis of Record PCT - Line A

+ Line D.1 Net Sum of 10 CFR 12880 F 50.46 PCT Changes The sum of the PCT from the most recent analysis of record using an acceptable evaluation model and the estimates of the net PCT effect for changes and errors identified since this analysis remain less than 22000 F.

For those issues that have been previously reported under 10 CFR 50.46, a 1

PG&E Letter number is listed.

2 Only permanent assessments of PCT margin are included. Temporary PCT allocations that address current LOCA model issues are not considered with respect to 10 CFR 50.46 reporting requirements.

B-1

Attachment B PG&E Letter DCL-08-061 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BEST ESTIMATE LARGE-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1872 0 F DCL-07-071 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. HOTSPOT Fuel Relocation APCT= 0°F DCL-07-071 Error.

C. 10 CFR50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None APCT= 00 F D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT APCT= 0°F Changes

2. Absolute Sum of 10 CFR 50.46 APCT= 0°F PCT Changes E. Analysis of Record PCT - Line A +

Line D.1 Net Sum of 10 CFR 50.46 1872°F PCT Changes The sum of the PCT from the most recent analysis of record using an acceptable evaluation model and the estimates of the net PCT effect for changes and errors identified since this analysis remain less than 2200 0 F.

For those issues that have been previously reported under 10 CFR 50.46, a PG&E letter number is listed.

2 Only permanent assessments of PCT margin are included. Temporary PCT allocations that address current LOCA model issues are not considered with respect to 10 CFR 50.46 reporting requirements.

B-2

Attachment C PG&E Letter DCL-08-061 CURRENT EMERGENCY CORE COOLING SYSTEM MODEL CHANGES AND ERRORS Best Estimate Loss-of-Coolant Accident (BELOCA)

None.

Small-Break Loss-of-Coolant Accident (SBLOCA)

Unit 2 SBLOCA Analysis with Replacement Steam Generators (RSGs)

In support of the installation of RSGs during the recent Unit 2 fourteenth refueling outage, a new SBLOCA analysis was performed using the previously approved NOTRUMP methodology. This new SBLOCA analysis explicitly modeled the RSGs and incorporated the ECCS model changes previously reported in DCL-07-071 such that there are currently no outstanding PCT assessments for this new SBLOCA analysis of record for Unit 2 which has been implemented in accordance with 10 CFR 50.59.

C-1