ML12355A161
| ML12355A161 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 12/18/2012 |
| From: | Andrachek J, Fink D, Gresham J, Schrader K, Sharp M, Summy J Pacific Gas & Electric Co, Westinghouse |
| To: | Plant Licensing Branch IV |
| Sebrosky J | |
| References | |
| TAC MF0313, TAC MF0315 | |
| Download: ML12355A161 (19) | |
Text
Diablo Canyon Power Plant Diablo Canyon Power Plant Use of Leak-before-break for Fuel Structural Analyses Jeff Summy Ken Schrader Mark Sharp Pacific Gas & Electric Co.
Jim Gresham Dave Fink Jim Andrachek Westinghouse December 18, 2012 1
Objectives Describe the Licensing Basis Verification Project Describe the Issue in the Corrective Action Program Describe the Emergency Core Cooling System (ECCS) l f
d i f 10CFR50 46(b)(1) (b)(2) analyses performed to satisfy 10CFR50.46(b)(1), (b)(2),
(b)(3), (b)(4), and (b)(5)
Describe the fuel assembly seismic and LOCA structural Describe the fuel assembly seismic and LOCA structural analysis and the interface with 10CFR50.46 (b)(4)
Actions going forward Questions and Feedback 2
Licensing Basis Verification Program PG&E is performing a Licensing Basis Verification Project (LBVP) for Diablo Canyon Licensing Basis Verification Program Diablo Canyon The LBPV is a comprehensive program to verify the Diablo Canyon licensing basis and to identify and correct deficiencies and inaccuracies inaccuracies The goal of the LBVP is to develop a clear and accurate licensing basis for Diablo Canyon 3
Description of Non Conforming Condition PG&E identified a potential deficiency in the way that the use of leak-before-break (LBB) methodology was incorporated into Description of Non-Conforming Condition leak before break (LBB) methodology was incorporated into licensing basis Specifically, PG&E did not perform a 10 CFR 50.59 review for a change where LBB methodology was implemented to exclude the change where LBB methodology was implemented to exclude the dynamic effects of a break in the main loop piping in the fuel assembly structural analyses performed to address Appendix A of SRP Section 4 2 Fuel System Design SRP Section 4.2, Fuel System Design The results of the fuel assembly structural analyses are used in part to demonstrate compliance with the 10 CFR 50.46(b)(4) fuel l bl t
i t
coolable geometry requirements On September 25, 2012, PG&E documented the deficiency as a non-conforming condition in the Diablo Canyon corrective action 4
program
Description of Non Conforming Condition An operability determination was performed and the fuel and ECCS was determined to be operable based on the current analysis Description of Non-Conforming Condition was determined to be operable based on the current analysis (WCAP-16946) conclusions being valid and previous NRC approval in licensing actions at two other plants PG&E has identified a significant amount of information on the PG&E has identified a significant amount of information on the existing Diablo Canyon licensing basis and how other plants have adopted use of LBB methodology in the fuel assembly structural analyses analyses A summary of the information is provided in this presentation for discussion 5
LOCA analyses performed to satisfy 10CFR50 46 to satisfy 10CFR50.46 The NRC approved Diablo Canyon large break LOCA Emergency Core Cooling System (ECCS) analysis for each unit is based on NRC approved Westinghouse best-estimate LOCA (BELOCA) evaluation models:
- Unit 1: WCAP-12945-P-A, Addendum 1-A
- Unit 2: WCAP-16009-P-A (ASTRUM)
A d bl d d ill ti l
b k LOCA i th i l A double-ended guillotine large break LOCA in the main loop piping is considered in the ECCS analysis.
6
LOCA analyses performed to satisfy 10CFR50 46 to satisfy 10CFR50.46 In the BELOCA ECCS evaluation models, no credit is taken for LBB to eliminate primary coolant main loop piping breaks when demonstrating that the acceptance criteria of 10CFR50.46 are met:
(b)(1) - Peak Cladding Temperature (b)(2) - Maximum Cladding Oxidation (b)(3) - Maximum Hydrogen Generation (b)(4) - Coolable Geometry
( )( )
y (b)(5) - Long Term Cooling 7
LOCA analyses performed to satisfy 10CFR50 46(b)(4) to satisfy 10CFR50.46(b)(4)
Coolable geometry is considered in the BELOCA ECCS g
y analyses by modeling the effects of individual rod or hot assembly fuel rod burst and blockage, and is satisfied by demonstrating compliance with 10CFR50 46 b(1) demonstrating compliance with 10CFR50.46 b(1) and b(2)
The BELOCA ECCS evaluation models, include additional evaluations to confirm coolable geometry, beyond rod burst/blockage, in the ECCS analysis when fuel assembly
/
g,
y y
grid deformation is determined to occur WCAP-12945-P-A, Volume 5 Rev 1 describes method Method depends on location of assemblies with grid 8
Method depends on location of assemblies with grid deformation, independent of break size
LOCA analyses performed to satisfy 10CFR50 46(b)(4) to satisfy 10CFR50.46(b)(4)
BELOCA ECCS grid deformation model g
Fuel assembly periphery grid deformation: No peak cladding temperature penalty assessed Fuel assembly in board (interior) grid deformation:
Fuel assembly in-board (interior) grid deformation:
Additional evaluations performed as defined in WCAP-12945-P-A, Volume 5 Rev 1 9
LOCA analyses performed to satisfy 10CFR50 46(b)(4) to satisfy 10CFR50.46(b)(4)
The fuel assembly seismic and LOCA structural analysis The fuel assembly seismic and LOCA structural analysis determine if fuel grid deformation occurs due to the impact forces exceeding the minimum grid test strength The DCPP BELOCA analyses do not need to address the The DCPP BELOCA analyses do not need to address the effect of grid deformation, since in-board (interior) grid deformation is not calculated to occur in the fuel assembly structural analyses assembly structural analyses Consistent with the WCAP-12945-P-A, Volume 5, Revision 1 methodology 10
Fuel assembly seismic and LOCA structural analysis LOCA structural analysis
Th t Di bl C f
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The current Diablo Canyon fuel assembly seismic and LOCA structural analysis is documented in WCAP-16946 that supported reactor head l
t replacement
The analysis is performed in accordance with Appendix A to SRP Section 4.2, Fuel System Design Appendix A to SRP Section 4.2, Fuel System Design
input for the fuel assembly response should include motions of the core plate, core shroud, fuel alignment plate, or other relevant structures (these motions should correspond to the break that produced the peak fuel assembly loadings in the primary coolant system and reactor internals analysis) 11
Fuel assembly seismic and LOCA structural analysis LOCA structural analysis
Th th d l f
th f l t t
l l
i
The methodology for the fuel structural analyses is based on the NRC approved method contained in WCAP-9401-P-A, Verification and Testing Analysis of th 17 17 O ti i
d F l A bl d t d A t
the 17x17 Optimized Fuel Assembly, dated August 1981 SRSS combination of LOCA and seismic loads Referenced in the Diablo Canyon LAR and associated Amendments 37/36 for the use of Vantage 5 Optimized Fuel Vantage 5 Optimized Fuel 12
Fuel assembly seismic and LOCA structural analysis LOCA structural analysis
Th f l t t
l l
i t i d i
The fuel structural analysis contained in WCAP-9401-P-A, Verification and Testing Analysis of the 17x17 Optimized Fuel Assembly, used a main loop i i b
k f ~ 1ft2 piping break of ~ 1ft2 Based on a reactor vessel inlet nozzle break being structurally limited to less than 1ft2 The same break size was assumed in a report for Diablo Canyon, Response to Combinations of Calculated Loads For Pipe Break and Earthquake, Calculated Loads For Pipe Break and Earthquake, submitted to the NRC on February 2, 1978 and referenced in Supplement 8 to the Safety Evaluation Report dated November 15, 1978 13 Evaluation Report dated November 15, 1978
Fuel assembly seismic and LOCA structural analysis and LOCA structural analysis
Th NRC d th LBB l
i (WCAP 13039) f
The NRC approved the LBB analysis (WCAP-13039) for the Diablo Canyon main loop piping in a Safety Evaluation dated March 2, 1993 S
ff l
i Th ff l d h
h li
' LBB Staff conclusion: The staff concludes that the licensee's LBB analysis is consistent with the criteria in NUREG-1061, Volume 3, and draft SRP 3.6.3.; therefore, the analysis complies with GDC-4. Thus, the probability of large pipe breaks with GDC 4. Thus, the probability of large pipe breaks occurring in the RCS line is sufficiently low that the dynamic effects associated with postulated pipe breaks need not be a design basis 14
Fuel assembly seismic and LOCA structural analysis and LOCA structural analysis
Th i
t l
d d i th f l
bl
The pipe rupture loads used in the fuel assembly structural analyses (WCAP-16946), are based on the most limiting of an accumulator, pressurizer surge line, d RHR b h li b
k and RHR branch line breaks
Limitation of breaks to branch line breaks (exclusion of main loop breaks) is based on application of the LBB main loop breaks) is based on application of the LBB methodology in accordance with the 1987 revision to GDC-4 Allows exclusion of dynamic effects from the design basis Allows exclusion of dynamic effects from the design basis analyses when LBB analyses are approved by the Commission 15
Fuel assembly seismic and LOCA structural analysis
The NRC Leak-Before-Break Knowledge Management Document (page 3) provides additional information on (p g
) p the dynamic effects that can be excluded when LBB is approved Only local dynamic effects Only local dynamic effects Discharging fluids The NRC Leak-Before-Break Knowledge Management
(
)
l Document (page 3) provides permitted plant activities Decompression waves within the intact portion of the piping system 16
Fuel assembly seismic and LOCA structural analysis and LOCA structural analysis
WCAP-16498-NP, 17x17 Next Generation Fuel (17x17 NGF), dated March 2008, has stated fuel qualification NGF), dated March 2008, has stated fuel qualification analyses are performed postulating the rupture of branch lines connected to the main coolant loop (page 61):
Currently, all Westinghouse designed US PWR primary coolant main loop piping has been excluded from consideration for dynamic effects associated with postulated pipe rupture under Reference 61 or postulated pipe rupture under Reference 61 or subsequent LBB analyses. As a result, all current fuel qualification analyses are performed on the basis of postulated rupture of branch lines connected to the i
l t l
primary coolant loop.
WCAP-16498-NP was approved in an NRC Safety Evaluation dated March 16, 2011 17
Fuel assembly seismic and LOCA structural analysis and LOCA structural analysis
The Staff recently approved the use of LBB for fuel assembly seismic and LOCA structural analyses as part assembly seismic and LOCA structural analyses as part of the Turkey Point Units 3 and 4 Extended Power Uprate Licensing Amendment Request in a letter dated June 15, 2012 (ML11293A356)
Section 2.8.1 of the NRC Safety Evaluation reflected use of WCA-9401-P-A methodology and use of largest branch line breaks The licensee evaluated seismic and LOCA loading using the approved methodology described in WCAP-9401-P-A The largest branch line breaks, either the accumulator line (ACC) break, surge line break, or RHR line break, were considered when generating LOCA hydraulic forcing functions used as input to the analysis 18 forcing functions used as input to the analysis
Resolution of Issue Resolution of Issue
PG&E is prepared to take the actions necessary to resolve the non-conforming condition and improve the g
p licensing basis
PG&E is determining what conservative approach is i
d dd h
f i
di i d
required to address the non-conforming condition and close the operability determination
PG&E plans to work collaboratively with the Staff to PG&E plans to work collaboratively with the Staff to understand and resolve the issue 19