DCL-12-070, 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2011

10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2011

ML12202A793
Person / Time
Site:	Diablo Canyon
Issue date:	07/19/2012
From:	Becker J Pacific Gas & Electric Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
DCL-12-070
Download: ML12202A793 (8)

Text

Pacific Gas and Electric Company James R. Becker Diablo Canyon Power Plant Site Vice President Mail Code 104/6 P. O. Box 56 Avila Beach, CA 93424 805.545.3462 Internal: 691. 3462 July 19, 2012 Fax: 805.545.6445 PG&E Letter DCL-12-070 U.S. Nuclear Regulatory Commission 10 CFR 50.46 ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-BO Docket No. 50-323, OL-DPR-B2 Diablo Canyon Units 1 and 2 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2011

Dear Commissioners and Staff:

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

There have been no changes in the small-break loss-of-coolant accident (SBLOCA) PCT results or the large-break, best-estimate loss-of-coolant accident (BELOCA) PCT results for either Unit 1 or Unit 2 since the last annual update. The last update was provided in PG&E Letter DCL-11-0B2, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2010,"

dated July 19, 2011.

A summary of the PCT margin allocations and their bases are provided in the enclosed attachments. 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 PCT values remain within the 2200 degree Fahrenheit (F) limit specified in 10 CFR 50.46. However, because the Unit 1 BELOCA has a total PCT margin allocation that is currently greater than 50 degrees F, and in order to coordinate with the 24-month fuel cycle project schedule, PG&E expects to complete the .

Unit 1 BELOCA reanalysis and provide the updated PCT results to the NRC by December 2016, as stated in PG&E Letter DCL-11-0B2, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2010,"

dated July 19, 2011.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• San Onofre

• South Texas Project

• Wolf Creek

Document Control Desk PG&E Letter DCL-12-070 July 19, 2012 Page 2 PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this report.

If you have questions regarding this submittal please contact Mr. Steve Baker at 805-545-6742.

Sincerely,

~~vJJr-I- ~

Jame\lR. Becker Site Vice President wrl8/6980/64059110 Enclosure cc/enc: Elmo E. Collins, NRC Region IV Michael S. Peck, NRC Senior Resident Inspector Joseph M. Sebrosky, NRR Senior Project Manager Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• San Onofre

• South Texas Project

• Wolf Creek

Enclosure PG&E Letter DCL-12-070 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 (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.

This report is based on changes described in the following Westinghouse 10 CFR 50.46 notification letter:

Westinghouse Letter LTR-LlS-12-116, "Diablo Canyon Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2011 ," dated February 20,2012 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 SBLOCA PCT results or the BELOCA PCT results for either Unit 1 or Unit 2 since the last annual update.

The last update was provided in PG&E Letter DCL-11-082, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2010," dated July 19, 2011.

A summary of the PCT margin allocations and their bases are provided in the attachments.

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 results. 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 Code Qualification Document methodology. The Unit 2 BELOCA reports only one PCT value consistent with the BELOCA ASTRUM methodology.

Small-Break LOCA Large-Break, Best-Estimate LOCA Reflood 1 Reflood 2 Unit 1: 1391°F (no change) 1990°F (no change) 1975°F (no change)

Unit 2: 1288°F (no change) 1888°F (no change)

The PCT values remain within the 2200 degree Fahrenheit (F) limit specified in 10 CFR 50.46. However, because the Unit 1 BELOCA has a total PCT margin allocation that is currently greater than 50 degrees F, and in order to coordinate with the 24-month fuel cycle project schedule, PG&E expects to complete the 1

Enclosure PG&E Letter DCL-12-070 Unit 1 BELOCA reanalysis and provide the updated PCT results to the NRC by December 2016, as stated in PG&E Letter DCL-11-082, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for 2010,"

dated July 19, 2011.

2

Attachment A PG&E Letter DCL-12-070 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL*BREAK LOCA PG&E Letter1 A. ANAL YSIS OF RECORD PCT= 1391°F DCL-09-057 B. PRIOR 10 CFR 50.46 ECCS MODELASSESSMENT~

1. None L1PCT = O°F C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None L1PCT = O°F D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT Changes L1PCT = O°F

2. Absolute Sum of 10 CFR 50.46 PCT Changes L1PCT = O°F E. Analysis of Record PCT - Line A

+ Line 0.1 Net Sum of 10 CFR 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 remains less than 2200°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-12-070 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BEST-ESTIMATE z LARGE-BREAK LOCA PG&E Letter1 Reflood Reflood 1 2 A. ANAL YSIS OF RECORD 1900°F 1860°F DCL-05-146 L1PCT L1PCT B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. Revised blowdown heatup 5°F 5°F DCL-05-086 uncertainty distribution.

2. HOTSPOT Fuel Relocation 10°F OaF DCL-07-071 Error.

3. Replacement Steam 75°F 71°F DCL-09-057 Generators C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. 230kV Degraded Voltage OaF 39°F DCL-11-082 Event Evaluation D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT 90°F 115°F Changes

2. Absolute Sum of 10 CFR 50.46 90°F 1156°F PCT Changes E. Analysis of Record PCT - Line A +

Line 0.1 Net Sum of 10 CFR 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 remains less than 2200°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-12-070 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= DCL-08-061 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. None ilPCT =

C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

2. None ilPCT =

D. SUM OF 10 CFR 50.46 CHANGES

3. Net Sum of 10 CFR 50.46 PCT Changes ilPCT = OaF

4. Absolute Sum of 10 CFR 50.46 PCT Changes ilPCT = OaF E. Analysis of Record PCT - Line A + Line 0.1 Net Sum of 10 CFR 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 remains less than 2200°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-1

Attachment 8 PG&E Letter DCL-12-070 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BEST-ESTIMATE, LARGE-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= DCL-07-071

8. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. HOTSPOT Fuel Relocation llPCT= DCL-07-071 Error.

C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. 230kV Degraded Voltage llPCT= DCL-11-082 Event Evaluation D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT llPCT=

Changes

2. Absolute Sum of 10 CFR 50.46 llPCT=

PCT Changes E. Analysis of Record PCT - Line A +

Line 0.1 Net Sum of 10 CFR 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 remains less than 2200°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.

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