DCL-17-075, Transmittal of 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2016

Transmittal of 10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2016

ML17249A541
Person / Time
Site:	Diablo Canyon
Issue date:	09/06/2017
From:	Welsch J Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-17-075
Download: ML17249A541 (9)

Text

Pacific Gas and Electric Company James M. Welsch Diablo Canyon Power Plant Vice President, Nuclear Generation Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.3242 Internal: 691. 3242 September 6, 2017 Fax: 805.545.4884 PG&E Letter DCL-17-075 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 2016

Reference:

1. PG&E Letter DCL-15-093, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2014," .dated August 6, 2015.

(ADAMS Accession No. ML15218A626)

Dear Commissioners and Staff:

Pursuant to 10 CFR 50.46, 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.

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 remains within the 2200°F limit specified in 10 CFR 50.46. Because the Unit 1 and Unit 2 best-estimate, large-break loss-of-coolant accident analyses each have a cumulative sum of PCT changes and errors greater than 50°F, PG&E has proposed to complete a reanalysis of both units using the Westinghouse FULL SPECTRUMTM LOCA (FSLOCA') methodology and will provide the updated PCT results by December 2018 per Reference 1. The FSLOCA'will include code methodology changes that address fuel thermal conductivity degradation.

PG&E makes no new or revised regulatory commitments (as defined by NEI 99-04) in this letter.

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

A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Document Control Desk PG&E Letter DCL-17-075 September 6, 2017 Page 2 Vice President, Nuclear Generation bnsm/4540/50871345 Enclosure cc: Diablo Distribution cc/enc: Scott A. Morris, NRC Region IV Administrator (Acting)

Christopher W. Newport, NRC Senior Resident Inspector Balwant K. Singal, NRC Senior Project Manager A member of the STARS Alliance Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Enclosure PG&E Letter DCL-17-075 ANNUAL REPORT OF EMERGENCY CORE COOLING SYSTEM EVALUATION MODEL CHANGES FOR PEAK CLADDING TEMPERATURE

Enclosure PG&E Letter DCL-17-075 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-17 -32, "Diablo Canyon Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2016," dated February 8, 2017.

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 results or BELOCA PCT results for either Unit 1 or Unit 2 since the last annual update. The last annual update was provided in PG&E Letter DCL-16-105, "10 CFR 50.46 Annual Report of Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2015," dated October 18, 2016.

The final 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.

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

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

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 remains within the 2200°F limit specified in 10 CFR 50.46. However, because the Unit 1 and Unit 2 BELOCA analyses each have a cumulative sum of PCT changes and errors greater than 50°F, PG&E has proposed to complete a reanalysis of both Units using the Westinghouse FULL SPECTRUM' LOCA (FSLOCA') methodology and provide the updated PCT results to the NRC by December 2018, per PG&E Letter DCL-15-093, "10 CFR 50.46 Annual Report of 1

Enclosure PG&E Letter DCL-17-075 Emergency Core Cooling System Evaluation Model Changes for Peak Cladding Temperature for 2014," dated August 6, 2015. The FSLOCA' will include code methodology changes that address fuel Thermal Conductivity Degradation.

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Attachment A PG&E Letter DCL-17-075 DCPP UNIT 1 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1391°F DCL-09-057 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS

1. None

~PCT= ooF C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None OoF

~PCT=

D. SUM OF 10 CFR 50.46 CHANGES

1. Net Sum of 10 CFR 50.46 PCT Changes ~PCT= ooF

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

A-1

Attachment A PG&E Letter DCL-17-075 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

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

9. Error in Burst Strain Application 15°F 40°F DCL-14-070 C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None ooF ooF 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 For those issues that have been previously reported under 10 CFR 50.46, a PG&E letter number is listed.

A-2

Attachment B PG&E Letter DCL-17-075 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION SMALL-BREAK LOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1288°F DCL-08-061 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS

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

1. None ooF

~PCT=

D. SUM OF 10 CFR 50.46 CHANGES

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

2. Absolute Sum of 10 CFR 50.46 PCT Changes ~PCT=

E. Analysis of Record PCT (Line A)

+ Line 0.1 Net Sum of 10 CFR 50.46 PCT Changes For those issues that have been previously reported under 10 CFR 50.46, a PG&E Letter number is listed.

B-1

Attachment 8 PG&E Letter DCL-17-075 DCPP UNIT 2 PEAK CLADDING TEMPERATURE MARGIN UTILIZATION BELOCA PG&E Letter1 A. ANALYSIS OF RECORD PCT= 1872°F DCL-07-071 B. PRIOR 10 CFR 50.46 ECCS MODEL ASSESSMENTS

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

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

3. Fuel Thermal Conductivity ~PCT= 209°F DCL-12-102 Degradation (TCD) and Peaking Factor Burndown

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

5. Changes to Grid Blockage and ~PCT= 24°F DCL-13-111 Porosity

6. Error in Burst Strain Application ~PCT= 21oF DCL-14-070 C. 10 CFR 50.46 ECCS MODEL ASSESSMENTS THIS YEAR

1. None ~PCT= ooF 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 For those issues that have been previously reported under 10 CFR 50.46, a PG&E letter number is listed.

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