ML20056E255
| ML20056E255 | |
| Person / Time | |
|---|---|
| Issue date: | 07/22/1993 |
| From: | Kopp L Office of Nuclear Reactor Regulation |
| To: | Rosalyn Jones Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9308230078 | |
| Download: ML20056E255 (16) | |
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UNITED STATES iQg[j NUCLEAR REGULATORY COMMISSION
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e W ASHINGTON, D.C. 20555-0001 July 22,1993 MEMORANDUM FOR:
Robert C. Jones, Chief Reactor Systems Branch Division of Systems Safety and Analysis THRU:
Laurence E. Phillips, Chief -
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Core Performance Section
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Reactor Systems Branch
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Division of Systems Safety and Analysis FROM:
Laurence I. Kopp, Sr. Reactor Engineer Core Performance Section Reactor Systems Branch Division of Systems Safety and Analysis
SUBJECT:
SUMMARY
OF MEETING WITH WOG ON BORON CREDIT IN SPENT FUEL P0OLS A meeting was held in the NRC Headquarters Building in Rockville, Maryland on July 21, 1993 with the Westinghouse Owners Group and NRC staff to discuss the safety implications of allowing credit for dissolved boron in spent fuel pool water under normal conditions. Although there is typically approximately 2000 parts per million (ppm) boron in the pool at all times, the present staff position allows credit for boron only under accident conditions (Double Contingency).
The Owners Group presented background information, including an overview and benefits which would be realized if credit for boron were allowed under normal as well as accident conditions.
These benefits include additional fuel storage due to closer center-to-center assembly spacing and lower fuel cycle costs due to increased enrichment and fewer fuel assemblies per cycle.
A generic topical report is planned for submittal to the NRC in August 1994 and a lead plant application in the third quarter of 1994.
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A copy of the presentation package for the meeting as well as the list of meeting attendees is attached.
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Laurence I. Kopp, Sr. Reactor Engineer Core Performance Section Reactor Systems Branch Division of Systems Safety and Analysis
Attachment:
As stated
-d' SRXB:DSSA[', LPHILLIPS LK0P.P 7/22/93' 7/ q 93 0FFICIAL RECORD COPY DOCUMENT NAME: G:\\MTGSUM.LK
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MEETING
SUMMARY
DISTRIBUTION
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WRussell (12G-18) t JPartlow (12G-18)
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BORON CREDIT IN SPENT FUEL POOL i
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ANALYSIS SUBCOMMITTEE 1
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AGENDA INTRODUCTION Lee Bush - CWE PROGRAM OVERVIEW Les Bencini - W PROGRAM BENEFITS Don Hill - W PLANT SPECIFIC ANALYSES Don Hill - E l
PROBABILISTIC EVALUATION Ed Dzenis - W l
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SUMMARY
Les Bencini - W DISCUSSION All l
I WOO 710/Page 2
PROGRAM OVERVIEW WHY IS THE PROGRAM NEEDED?
o Spent fuel pools are approaching limits BACKGROUND o
Standard Review Plan 9.1.2 requires:
K,,,.<_0.95 with nonborated water i
o Boron is typically at 2000 ppm in the spent fuel pool water o
Credit for soluble boron is allowed to meet criteria for accident conditions
'I WOO 7&l/Page 3
PROGRAM OVERVIEW WOG PROGRAM OBJECTIVES Phase 1 o
Meet with NRC staff to present the program and obtain feedback Phase 2 i
o Take credit for soluble boron in the spent fuel pool
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o Establish methodology for the evaluation o
Develop the required Tech Specs and/or required surveillance testing o
Provide the technical basis for a Tech spec amendment and/or required testing and/or other administrative controls for the WOG Lead Plant
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4 PROGRAM OVERVIEW BENEFITS o
Additional Fuel Storage o
Lower Fuel Cycle Costs o
Addresses Generic Spent Fuel Pool issues t
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PROGRAM BENEFITS o
Additional Fuel Storage Some Plants Have to Store Fuel in 3/4 Locations - Credit for about 400 ppm of Soluble Boron Permits 4/4 Storage Taking Credit for Soluble Boron Would Permit Closer Center-to-Center Rack Spacing With New Spent Fuel Pool (SFP) Racks Provides More Storage Every 50 Assemblies of Added Storage Saves $1 Million to i
S2 Million in Alternative Fuel Storage Cost o
Lower Fuel Cycle Costs Increasing the SFP Enrichment Limit from 4.5 to 5.0 w/o U-235 - Requires Credit for about 250 ppm of Soluble Boron Corresponds to increasing the Discharge Burnup Limit from 45,000 to 55,000 MWD /MTM Requires 8 to 12 Fewer Assemblies per Cycle Reduces Storage Requirements Saves = $750K to $1,000K per Cycle o
Reduces O&M Cost and Addresses Generic SFP issues - For Example l
Reduce Blackness Testing of Boraflex - $125K/yr.
WOO 7PJ/Page 6 i
PLANT SPECIFIC ANALYSES o
All Analyses Will Employ Standard Codes and Methods o
Determination of Boron Credit Concentration Establish Benefits to Be Obtained with Boron Credit Perform Calculations to Determine Amount of Boron Credit Needed for Each Benefit 1
Establish Reference Boron Needed for Benefits o
Criticality Analyses Taking Credit for Boron Perform Reference K,,, Calculation with Reference Boron Determine Reactivity Equivalence Limits with Boron Burnup and/or integral Absorber Repeat above Computations for Each Storage Region I
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i W(XIE/Page 7
PLANT SPECIFIC ANALYSES o
Evaluation of Postulated Fuel Handling Accidents Determine Delta Boron to Mitigate Postulated Accident Reactivity increaso 1
o Determination of Minimum Baron Concentration Minimum Boron Concentration is the Sum of The Boron Credit Concentration Delta Boron to Mitigate Postulated Fuel Handling Accidents Delta Boron for Measurement Uncertainty in Boron Concentration A
1 WOO 78J/Page 8
PROBABILISTIC EVALUATION o
Objective Demonstrate that Frequency of Off-Normal Events is
" Acceptably Low" Without impact on Soluble Boron Credit, Pool Design, or Surveillance If Necessary, Identify Surveillance or Design Changes to Reduce Frequency of Selected Off-Normal Events if Necessary m
W(Kr70/Page 9
PROBABILISTIC EVALUATION o
Reference Risk Perspective NUREG-0933 - Issue 82 Beyond Design Basis Accidents in Spent Fuel Pools NUREG-1353 Regulatory Analysis for the Resolution of Generic issue 82 Quantified Accident Sequences Reactor Cavity / Transfer Gate Pneumatic Seal Failures Inadvertent Draining Loss of Cooling /Make-up Structural Failure Missiles Aircraft Crashes Heavy Loads Beyond DB Earthquake o
Reference Risk Goals Inherently Low Public Risk of Fuel Pool Low Probability of Having Sufficient Number of Failures to Cause Release Leading to Public Risk Concept of Acceptability of Minimizing Event Frequencies to Point of " Insignificance" Relative to Other Risks WOO 7M/Page 10
PROBABILISTIC EVALUATION o
Estimate Frequency of "Off-Normal" Events Leading to Adverse Reactivity impacts Select List of Events for Refueling Normal Plant Operation Estimate Frequencies for Each Category of Event Based on Existing Surveillance and Design Frequencies Based on Available Data or Judgement t
Features and Surveillance Based on Typical Pool i
Identify any "Important" Scenarios Screen Out Very Low Frequency Events Identify and Focus on Events for Which Frequency Cannot be Claimed to be insignificant Establish Credit for increased Surveillance or Enhanced Mitigative Features of Fuel Pool Design Recalculate Sequence Frequency including Credit for Enhancements I
WOU7&JfPage 11
SUMMARY
The Program will provide Technical Justification for Boron Credit.
Utilities have expressed the need for increased fuel storage while containing O&M costs.
W/WOG will complete a Topical in August,1994.
The Lead Plant will submit 3" Otr of 1994.
WOO 7EJ/Page 12
WOG BORON CREDIT IN SPENT FUEL POOL MEETING ATTENDANCE July 21, 1993 NAME ORGANIZATION TELEPHONE Larry Kopp NRR/SRXB (301) 504-2879 Larry Phillips NRR/SRXB (301) 504-3232 Howard Richings NRR/SRXB (301) 504-2888 Les Bencini Westinghouse (412) 374-5699 Edward Dzenis Westinghouse (412) 374-5216 Earl Novendstern Westinghouse (412) 374-2219 Lee Bush Commonwealth Edison (708) 746-2084 x2890 Ravi Joshi Northeast Utilities (203) 665-3844 Dave Campbell Westinghouse (412) 374-6206 George Konopka Westinghouse (412) 374-4506 Vince San Angelo Bechtel (301) 417-8828 Don Hill Westinghouse (412) 374-2275
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