ML20147F935
| ML20147F935 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 03/21/1997 |
| From: | Muench R WOLF CREEK NUCLEAR OPERATING CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| ET-97-0025, ET-97-25, NUDOCS 9703270275 | |
| Download: ML20147F935 (8) | |
Text
{{#Wiki_filter:' i l W@)NUCLEAROPERATING C ~ LF CREEK i Richard A. Muench Vice President Engineering March 21, 1997 i i ET 97-0025 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-137 Washington, D. C. 20555 j
Subject:
Docket No. 50-482: 10 CFR 50.46 Annual Report of ECCS Model Changes Gentlemen: This letter describes changes to the Emergency Core Cooling System (ECCS) ' Evaluation Models and the estimated effect on the limiting ECCS analysis for Wolf Creek Generating Station (WCGS) for 1996 in accordance with the criteria and reporting requirements of 10 CFR 50.46 (a) (3) (i) and (ii), as clarified in Section 5.1 of UCAP-13451, " Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting. The changes in calculated Peak Cladding Temperatures' (PCT) caused by the changes to Westinghouse ECCS Evaluation Models are reportable per 10 CFR 50.46 guidelines. Attachment I describes the impact of the ECCS Evaluation Model changes. Attachment II contains the calculated Large Break LOCA and Small Break LOCA PCT margin allocations resulting from the permanent changes to the evaluation models. Since the PCT values determined in the Small Break and Large Break i LOCA analyses of record, which, combined with all the PCT margin allocations, remain well below the 2200 OF regulatory limit, no reanalysis will be performed. l I l mmspmang l c.. r i I t / RO. Box 411/ Burhngton, KS 66839 / Phone: (316) 364-8831 An Equal Opportunity Employer M F HCVET
1 i 'ET 97-0025 s< Piga 2 of 2 l If you have any questions concerning this matter, _please call me at j (316) 364-8831, extensior. 4034, or Mr. Richard D. Flannigan at extension 4500. l Very truly yours, 1 ^ idf/ i Richard A. Muench RAM /jad Attachments cc: E. W. Merschoff (NRC), w/a l W. D. Johnson (NRC), w/a J. F. Ringwald (NRC), w/a J. C. Stone (NRC), w/a l 1 i l i i i l l i l l
'Attschm2nt I to ET 97-0025 Piga 1 of 3 ATTACHMENT I CHANGES TO THE WESTINGHOUSE EMERGENCY CORE COOLING SYSTEM EVALUATION MODELS I 1 j
___m m,.__... " Attachment I to ET 97-0025 I Page 2 of 3 -Changes To The Westinghouse 4 Emergency Core Cooling System Evaluation Models i Wolf Creek Nuclear Operating Corporation (WCNOC) has reviewed the annual 10 CFR 50.46 summary report of Emergency Core Cooling System'(ECCS) Evaluation i Model changes that were implemented by Westinghouse during 1996. The report f includes information concerning changes to and ' errors discovered in the j evaluation models. The review concludes that the cumulative effect of changes j to, or errors. in, the evaluation models on the limiting transient Peak -Cladding Temperature (PCT), is not significant. Therefore, reporting of the [ ECCS Evaluation Model changes may be submitted on an annual basis according to j the reporting requirements set forth in 10 CFR 50.46 (a) (3) (ii). Attachment II provides an update of PCT margin utilization for Wolf Creek l Generating Station (WCGS). The PCT margin utilization demonstrates that compliance with the requirements of 10 CFR 50.4i is maintained considering the l combined effects of the ECCS Evaluation Model changes with the plant design changes performed under 10 CFR 50.59. SBLOCTA FUEL ROD INITIALIZATION j
Background
i An error was discovered in the SBLOCTA code related to adjustments which are made as part of the fuel rod initialization process, which is used to obtain agreement between the SBLOCTA model and the fuel data supplied from the fuel thermal-hydraulic design calculations at full power, steady-state conditions. Specifically, an adjustment to the. power, which is made to compensate for adjustments - to the assumed pellet diameter, was incorrect. Additionally, updates were made to the fuel rod clad creep and strain model to correct logic errors that could occur in certain transient conditions. These model revisions also had a small affect on the fuel rod initialization process, and i can produce small effects during the transient. Due to the small magnitude of l effects, and the interaction between the two items, they are being evaluated i as a single, closely related effect. l This change is considered to be a Non-Discretionary Change as described in WCAP-13451. Affected Evaluation Model 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effects Previous representative plant calculations performed with the corrected model demonstrated that these revisions resulted in a predicted peak clad 0 temperature increase on the order of +10 F. The reanalysis with the latest revision of the SBLOCTA code resulted in a reduction of the PCT penalty for this item f rom 10*F to 2'F.
l
- AttachmLnt I to ET 97-0025 Page 3 of 3 TRANSLATION OF FLUID CONDITIONS FROM SATAN TO LOCTA
Background
An error was discovered in the coding related to the translation of fluid conditions between the SATAN blowdown hydraulics code and the LOCTA code used for subchannel analysis of the fuel rods. In performing axial interpolations to translate the SATAN fluid conditions onto the mesh nodalization used by the LOCTA code, the length of the lower core channel fluid connection to the lower plenum node was incorrectly calculated. This change is considered to be a Non-Discretionary Change as described in WCAP-13451. Affected Evaluation Models 1981 Westinghouse Large Break LOCA Evaluation Model 1981 Westinghouse Large Break LOCA Evaluation Model with BART 1981 Westinghouse Large Break LOCA Evaluation Model with BASH Estimated Effects Representative plant calculations with the corrected model demonstrated that l this correction resulted in approximately a 115'F effect on the BASH large break LOCA evaluation model. Evaluations based on these studies conclude that the effect on the BART and 1981 evaluation models was a 5'F benetit. Therefore, the following estimated effects are assigned: BASH EM 15'F penalty BART and 1981 EM 5'F benefit I l l i i ? I i i I
i 'Attrichment II to ET 97-0025 Paga 1 of 3 ATTACHMENT II ECCS EVALUATION MODEL PEAK CLAD TEMPERATURE (PCT) MARGIN ASSESSMENTS l l 4 1 i j i 4 _j
4 .-___.__.________m .~___..____._-__.~m I 1 4
- Attachment II to ET 97-0025 i
Page 2 of 3 ] l l
- SMALL BREAK PEAK CLAD TEMPERATURE (PCT) MARGIN UTILIZATION ***
I I j Evaluation Model: 1985 EM with NOTRUMP I j Fuel: 17X:7 V5H w/IFM, non-IFBA 275 psig l 1 Peaking Factor: FQ=2.50, FdH-1.65 i SG Tube Plugging: 10% i j Power Level: 3565 MWth j Limiting transient: 3-inch Break i 1 A. ANALYSIS OF_ RECORD (Rerating 8/92) { Peak Cladding Temperature (PCT): 1510 F I B. PRIOR PERMANENT ECCS MODEL ASSESSMENTS APCT = 2 9 F f ,( C. 10 CFR 50.59 SAFETY EVALUATIONS
- 1. Loose Parts APCT = 4 5'F i
2. Cycle 10 Fuel Assembly Design Changes APCT = 1*F III
- 3. Reduced Feedwater Inlet Temperature APCT =
10*F l f TOTAL 10 CFR 50.59 SMALL BREAK ASSESSMENTS APCT = 56*F I D. 1996 10 CFR 50.46 MODEL ASSESSMENTS j l (Permanent Assessment of PCT Margin) l ] 1. SBLOCTA Fuel Rod Initialization Error APCT - 2F l i!' E. TEMPORARY ECCS MODEL ISSUES l
- 1. None APCT = 0F l
i i i l I F. OTHER MARGIN ALLOCATIONS 1. Cold Leg Streaming Temperature Gradient APCT = 7F I t -{ LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 1604 F I 4 i Notes: j (1) A detailed evaluation of the impacts of fuel design changes on the small break LOCA analysis was provided in WCNOC's license amendment application to revise 1 WCGS Technical Specification Section 5.3.1, Fuel Assemblies, to allow the use of l an alternate zirconium-based fuel cladding material, ZIRLO (Letter ET 97-0020 ' dated March 18, 1997). i-l 1
- Attachmant II to ET 97-0025 Pega 3 of 3 j
t a 1 1
- LARGE BREAK LOCA PEAK. CLAD TENPERATURE (PCT) MARGIN UTILIZATION ***
( l [ Evaluation Model: 1981 EM with BASH Fuels 17X17 V5H w/IFM, non-IFBA 275 psig Peaking Factor: FQ=2.50, FdH=1.65 l SG Tube Plugging: 10% j Power Level: 3565 MWth Limiting transient: Cp=0.4, Min. SI, Reduced Tavg I A. ANALYSIS OF RECORD (Rerating 8/92) j J l Peak Cladding Temperature (PCT) : 1916 F i B. 'RIOR PERMANENT ECCS MODEL ASSESSMENTS APCT = -15 F l C. 10 CFR 50.59 SAFETY EVALUATIONS l
- 1. Loose Parts APCT = 2 0'F
- 2. Containment Purge Evaluation APCT =
0'F
- 3. Cycle 10 Fuel Assembly Design Changes APCT =
95'F I3) TOTAL 10 CFR 50.59 LARGE BREAK ASSESSMENTS APCT = 115 F i D. 1996 10 CFR 50.46 MODEL ASSESSMENTS I (Permanent Assessment of PCT Margin)
- 1. Translation of Fluid Conditions from SATAN to LOCTA APCT = 15 F E. TEMPORARY ECCS MODEL ISSUES APCT =
0F F. OTHER MARGIN ALLOCATIONS I2)
- 1. Transition Core (STD to V5H)
APCT = 50 F III
- 2. Cold Leg Streaming Temperature Gradient APCT =
0F LICENSING BASIS PCT + MARGIN ALLOCATIONS PCT = 20B1 F Notes: (1) A PCT benefit of < 2.5 F was assessed, however, a benefit of O'F will be tracked for reporting purposes. i2) Transition core penalty applies on a cycle-specific basis for reloads utilizing both V5H (with IFMs) and STD fuel until a full core of V5H is achieved. (3) A 95'F PCT margin was allocated to Fuel Assembly Design Changes which will be implemented in Cycle 10. A detailed evaluation of the impacts of fuel design changes on the large break LOCA analysis was provided in WCNOC's license amendment application to revise WCGS Technical Specification Section 5.3.1, Fuel Assemblies, to allow the use of an alternate zirconium-based fuel cladding I material, ZIRLO (Letter ET 97 0020 dated March 18, 1997). I l ._.=., m '}}