DCL-15-093, 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2014

10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2014

ML15218A626
Person / Time
Site:	Diablo Canyon
Issue date:	08/06/2015
From:	Allen B Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-15-093
Download: ML15218A626 (9)

Text

Pacific Gas and Electric Company Barry S. Allen Diablo Canyon Power Plant Vice President, Nuclear Services Mail Code 104/6 P. 0. Box 56 August 6, 2015 Avila Beach, CA 93424 805.545.4888 Internal: 691.4888 PG&E Letter DCL-15-093 Fax: 805.545 .6445 U.S. Nuclear Regulatory Commission 10 CFR 50.46 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 Peak Cladding Temperature for 2014

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.46, "Acceptance criteria for emergency core systems for light-water nuclear power reactors," the enclosure to this letter is the 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's (PG&E's) Diablo Canyon Power Plant, Units 1 and 2. The attachments to the enclosure provide a summary of the PCT margin allocations and their bases.

PG&E will complete a reanalysis for both Units 1 and 2 using the Westinghouse FULL SPECTRUMTM loss-of-coolant accident (FSLOCA') methodology and provide the updated PCT results to the NRC by December 2018. This is a change to a previous regulatory commitment (as defined in NEI 99-04) made in PG&E Letter DCL-13-111, "Thirty-Day Notification Report of Significant Emergency Core Cooling System Evaluation Model Changes That Affect Peak Cladding Temperature," dated November 14, 2013, in which PG&E committed to complete the best estimate large break loss-of-coolant accident reanalysis for Units 1 and 2 and provide the updated PCT results to the NRC by December 2016. The reason for the change in commitment date is the current schedule for NRC approval of the methodology required to address fuel thermal conductivity degradation.

If you have questions regarding this submittal please contact Mr. Mark Sharp at 805-545-3031.

Sincerely, Jf7_5. AP--.

Barry S. Allen A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Document Control Desk PG&E Letter DCL-15-093 August 6, 2015 Page2 dqmg/6192/50795995 Enclosure cc/enc: Marc L. Dapas, NRC Region IV Administrator Siva P. Lingam, NRR Project Manager John P. Reynoso, Acting NRC Senior Resident Inspector Diablo Distribution A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Enclosure PG&E Letter DCL-15-093 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's (PG&E's) Diablo Canyon Power Plant (DCPP), Units 1 and 2. This report is based on changes described in Westinghouse Letter LTR-LIS-15-42, "Diablo Canyon Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2014," dated February 19, 2015.

Attachment A contains Unit 1 small-break loss-of-coolant accident (SBLOCA) and best-estimate, large-break loss-of-coolant accident (BELOCA) PCT Margin Utilization sheets. Attachment 8 contains the corresponding Unit 2 data. There have been no changes in the SBLOCA PCT or BELOCA PCT results for either Units 1 or 2 since the last annual update. The last annual update was provided in PG&E Letter DCL-14-070, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2013," dated August 7, 2014.

The net PCT values are listed below for each unit. 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.

SBLOCA BELOCA Reflood 1 Reflood 2 Unit 1: 1391 oF (no change) 2049°F (no change) 2124°F (no change)

Unit 2: 1288°F (no change) 2125°F (no change)

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

However, because Units 1 and 2 BELOCA have a total PCT margin allocation that is currently greater than 50°F, PG&E had proposed to complete a BELOCA reanalysis and provide the updated PCT results for both Units 1 and 2 to the NRC by December 2016, as stated in PG&E Letter DCL-13-111, "Thirty-Day Notification Report of Significant Emergency Core Cooling System Evaluation Model Changes That Affect Peak Cladding Temperature," dated November 14, 2013. However, in order to schedule compliance with methodology changes to address fuel Thermal Conductivity Degradation, PG&E will complete a reanalysis of both Units 1 and 2 using the Westinghouse FULL SPECTRUM' loss-of-coolant accident (FSLOCA') methodology and provide the updated PCT results to the NRC by December 2018.

1

Attachment A PG&E Letter DCL-15-093 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1391 OF DCL-09-057 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. None ooF

~Per=

C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None

~PCT= 0°F D. SUM OF 10 CFR 50.46 CHANGES

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

2. Absolute Sum of 10 CFR 50.46 PCT Changes ~PCT= ooF E. Analysis of Record PCT (Line A)

+ Line 0.1 Net Sum of 1391 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-15-093 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BELOCA PG&E Letter1 Reflood 1 Reflood 2 A. ANALYSIS OF RECORD 1900°F 1860°F DCL-05-146

~PCT ~PCT 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 ooF DCL-07-071 Error

3. Replacement Steam 75°F 71°F DCL-09-057 Generators

4. 230 kV Degraded Voltage Event ooF 39°F DCL-11-082

5. Performance and Design (PAD) -118°F -118°F DCL-12-102 4.0 Implementation

6. Fuel Thermal Conductivity 133°F 238°F DCL-12-102 degradation (TCD) and Peaking Factor Burndown

7. Revised Heat Transfer Multiplier 5°F -35°F DCL-13-111 Distributions

8. Changes to Grid Blockage and 24°F 24°F DCL-13-111 Porosity C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. Error in Burst Strain Application 15°F 40°F DCL-14-070 D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of PCT Changes 149°F 264°F

2. Absolute Sum of PCT Changes 385°F 570°F E. Analysis of Record PCT (Line A) +

Line 0.1 Net Sum of 10 CFR 50.46 2049°F 2124°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 remains less than 2200°F.

A-2

Attachment A PG&E Letter DCL-15-093 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-3

Attachment 8 PG&E Letter DCL-15-093 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SBLOCA PG&E Letter1 A." ANALYSIS OF RECORD PCT= 1288°F DCL-08-061 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. None LlPCT = OoF C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None ooF LlPCT =

D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT Changes LlPCT = OoF

2. Absolute Sum of 10 CFR 50.46 PCT Changes LlPCT = ooF E. Analysis of Record PCT (Line A)

+ Line 0.1 Net Sum of 1288°F 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.

8-1

Attachment B PG&E Letter DCL-15-093 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BELOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1872oF DCL-07-071 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS 2

1. HOTSPOT Fuel Relocation Error ~PCT= ooF DCL-07-071

2. 230 kV Degraded Voltage Event ~PCT= 16°F DCL-11-082

3. Fuel TCD and Peaking factor ~PCT= 209°F DCL-12-102 Burndown

4. Revised Heat Transfer Multiplier ~PCT= -17oF DCL-13-111 Distribution

5. Changes to Grid Blockage and ~PCT= 24°F DCL-13-111 Porosity C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. Error in Burst Strain Application ~PCT= 21oF DCL-14-070 D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT ~PCT= 253°F Changes

2. Absolute Sum of 10 CFR 50.46 ~PCT= 287°F PCT Changes E. Analysis of Record PCT (Line A)+ 2125°F 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.

8-2

Attachment B PG&E Letter DCL-15-093 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-3