IP-2's 144.6 MWt Power Uprate Request: uses proprietary Westinghouse analysis of 'Best Estimate Small Break LOCA Methodology'
Docket review by Steve Schulin, nuclear.com
(Rockville, April 11) -- IP-2 is the first plant to seek NRC approval for power uprate based on a Westinghouse methodology with implications for many other plants. And based on Westinghouse's request to keep some proprietary information withheld from public disclosure during NRC's evaluation, the methodology seems likely to have implications for other vendors' plants, too.
NRC's project manager, Patrick D. Milano of NRR, in his summary of a February 13, 2003 meeting with Entergy, noted that the utility requested NRC "review and approval of the proposed methodology in order to apply the methodology to support a possible power increase to about 3216 megawatts thermal (MWt) from the current licensed power level of 3071.4 MWt."
Milano told Entergy that NRC review of such a request could generally be expected to take 18-24 months (if programming code is provided) and up to 36 months if code is not provided. He also noted that NRC would also be interested in generic implications during the review.
A pdf version of Milano's meeting report is available here. A copy of the presentation slides used by Entergy in February 13, 2003 meeting were released by NRC via ADAMS on April 11. (accession number ML030930466). Here's a transcription:
BEST ESTIMATE SMALL BREAK LOCA METHODOLOGY FOR IP2
PRESENTED BY ENTERGY NUCLEAR OPERATIONS AND WESTINGHOUSE
FEBRUARY 13, 2003, ROCKVILLE, MARYLAND
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AGENDA
¥ Introduction
¥ Background and Schedule
¥ Overview BE SBLOCA Methodology
¥ Technical Approach for WCAP-14936 (PROPRIETARY)
- Code Scaling, Applicability, and Uncertainty (CSAU) methodology
- Comparison to Best Estimate Large Break LOCA Methodology (previously reviewed and approved by NRC)
- Code Revisions and Validation
- Results for Indian Point 2
- Statistical Methodology
- Conclusions
- Questions and Discussion
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BACKGROUND
¥ 1996
- NRC approves BE LBLOCA methodology (June)
- Con Ed contracts Westinghouse to develop BE SBLOCA methodology (June)
¥ 2001
- Westinghouse completes BE SBLOCA development (August)
- Con Ed submits WCAP-14936 for NRC review and approval (August)
- Entergy suspends request for NRC review (September)
¥ 2002
- Entergy initiates project for Power Uprate of IP2 to 3216 MWt (November)
¥ 2003
- Entergy re-submits WCAP-14936 for NRC review and approval (January)
- Kick-off meeting with the NRC (February)
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Appendix K versus Best Estimate
¥ Appendix K SBLOCA at 3O71MWt
PCT = 2116¡F
¥ BE SBLOCA at 3216 MWt
PCT = 1328¡F
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[BESBLOCA Overview, p. 1]
[report cover] Best Estimate Small Break LOCA Methodology Overview
by Robert M. Kemper, Advanced Technical Engineer, Westinghouse Electric Company (412) 374-4579
[BNFL and Westinghouse logos]
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[BESBLOCA Overview, p. 2]
Best Estimate Small Break LOCA Program
¥ Westinghouse received approval of its best estimate large break LOCA methodology in 1996.
¥ The same advanced T/H code WCOBRA/TRAC, has been applied to small break LOCA analysis.
Program Major Objectives
¥ Develop and license a best estimate small break methodology generically applicable to conventional Westinghouse 3- and 4-loop PWRs.
¥ Perform a plant specific application for Indian Point Unit 2.
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[BESBLOCA Overview, p. 3]
Code scaling, applicability and uncertainty (CSAU) approach followed:
¥ Westinghouse review of NUREG/CR-5249 concluded that the CSAU approach is generically applicable to many types of problems.
¥ NRC has provided some guidance applicable to SBLOCA events in Reg. Guide 1.157.
- Specific concerns (Reg. Guide 1.157) include consideration of system-wide inventory distribution, break location & orientation, operating state of RCPs.
- Some important phenomena also identified in Reg. Guide 1.157, including level swell, "reflux," and heat transfer to uncovered core.
---
[BESBLOCA Overview, p. 4]
PIRT Process for Best Estimate Small Break LOCA
1. Initial PIRT developed by Westinghouse
2. Preliminary PWR calculations performed for the scenario
- PIRT and PWR Results Presented
3. W PIRT reviewed by independent external review team [P. Griffith (MIT), Y. Hassan (Texas A&M), T. Fernandez (EPRI), D. Speyer (Consultant)]
- Comments & Recommendafions
4. Final PIRT for SBLOCA
---
[BESBLOCA Overview, p. 5]
PIRT for Small Break Processes
SBLOCA transient is composed of five periods:
¥ Blowdown Period: Short initial period as RCS depressurizes to near-equilibrium condition with the secondary.
¥ Natural Circulation Period: Break flow continues to be low quality and system drains from top - down. Heat transfer is from primary to secondary.
¥ Loop Seal Clearance Period: Loop seal(s) begin to vent and break quality becomes high. Heat transfer reverses, as secondary becomes a heat source.
¥ Boil-Off Period: Vessel inventory boils away and core uncovery can occur while RCS depressurization continues. Minimum inventory and PCT typically occur at the end of boil-off period.
¥ Recovery Period: Vessel inventory increases as SI flows exceed break flow. PCT is decreasing.
Rankings assigned as:
H (high), M (medium), L (low), N/A (not applicable)
---
[BESBLOCA Overview, p. 6]
Indian Point 2 BE SBLOCA Analysis
3-INCH CL BREAK WITH LOOP
Reactor Vessel Mass
[graph showing fluid mass at times out to approximately 2400 seconds]
Figure 27-2-5. Reactor Vessel Mass, 3-Inch Break with LOOP
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[BESBLOCA Overview, p. 7]
Indian Point 2 BE SBLOCA Analysis
3-INCH CL BREAK WITH LOOP
Peak Cladding Temperature
[graph showing Temperature at times out to approximately 2400 seconds]
Figure 27-2-6. PCT, 3-Inch Break With LOOP
--- END OF TRANSCRIPTION OF PRESENTATION SLIDES
The above is based on records released to public by NRC on April 11, 2003