ML17265A824
| ML17265A824 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/26/2017 |
| From: | Martin Z Tennessee Valley Authority |
| To: | Andrew Hon Plant Licensing Branch II |
| Hon A | |
| References | |
| Download: ML17265A824 (14) | |
Text
Watts Bar Unit 2 Tritium Production License Amendment Pre-Application Meeting Spent Fuel Pool Criticality Analysis Z. I. Martin September 26, 2017
Agenda Introduction and Background Overview of Current Analysis Overview of New Analysis Technical Specification Changes Neutron Absorber Material Monitoring l 2 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Introduction and Background Watts Bar (WBN) Spent Fuel Pool (SFP)
Racks WBN SFP contains a single type of BORALTM racks containing flux traps Installed in WBN SFP in 1997 Originally resided in Sequoyah Nuclear Plant (SQN)
SFP from 1980-1995 Original design had seal welded cavity for BORALTM BORALTM cavity vented during WBN installation No monitoring program required at time of licensing (either at SQN or WBN) l 3 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Overview of Current Analysis Performed by Holtec in 2000 using Kopp guidance SFP Criticality Analysis credits Storage cell spacing, i.e., flux traps between storage cells Fixed neutron absorbers: BORALTM panels Burnup using Burnup - Enrichment Curves
- Addressed TPBARs in depletion analysis Integral Fuel Burnable Absorber (IFBA) in New Fuel Administrative Controls (Loading Patterns) l 4 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Overview of New Analysis (1/2)
Performed by Holtec Follows ISG 2010-01 and NEI 12-16 Guidance SFP Criticality Analysis credits Storage cell spacing, i.e., flux traps between storage cells Fixed neutron absorbers: BORALTM panels Soluble Boron (500ppm) l 5 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Overview of New Analysis (2/2)
Criticality calculations qualify the BORALTM storage racks uniformly loaded with fresh fuel assemblies with an initial enrichment up to 5 wt%
235U Bounding fuel density of all types of fuel assemblies is considered Bounding approach provides analysis simplicity and adequate margin Neutron absorber monitoring program will be implemented following the NRC-approved guidance in NEI 16-03-A l 6 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Comparison of Current and Proposed New Analyses Parameter Current Analysis Proposed New Analysis Impact Burnup Credit Burnup versus enrichment curves Not used - Fresh fuel only Simplifies implementation by reduction of administrative controls IFBA Credit for Fresh Fuel Minimum number of IFBA rods required Not used Simplifies implementation by reduction of administrative controls Soluble Boron Credit Not Used 500 ppm Now credited at all times Boral' Monitoring Program None Propose to Implement NEI 16-03-A Increased ability to determine material performance Boral' Blister Impact Not addressed Assumes void on every panel over entire panel surface Bounds Boral' blistering Analytical Guidance Kopp Memo guidance used Consistent with DSS-ISG-2010-01 and NEI 12-16 Analysis consistent with industry best practices l 7 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Technical Specification Changes (1/2)
Proposed change revises the Units 1 and 2 TSs affected by the new spent fuel rack criticality analysis TS 3.7.15, Spent Fuel Assembly Storage, revised to simplify the fuel storage limitations on fuel assemblies by eliminating burnup-related criteria TS 3.7.18, Fuel Storage Pool Boron Concentration, added to specify minimum fuel storage pool boron concentration when fuel is stored in the pool TS 3.9.9, Spent Fuel Pool Boron Concentration, revised to modify the minimum fuel storage pool boron concentration during refueling operations when fuel is stored in the pool l 8 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Technical Specification Changes (2/2)
Proposed change revises the Units 1 and 2 TSs affected by the new spent fuel rack criticality analysis (continued)
TS 4.3, Fuel Storage, revised to replace the storage limitations on fuel assembly initial enrichment, burnup, and storage location limitations with a single requirement to maintain a specified boron concentration in the spent fuel pool TS 5.7.2.21, Spent Fuel Storage Rack Neutron Absorber Monitoring Program, added to incorporate the NRC-approved NEI 16-03-A guidance l 9 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Neutron Absorber Monitoring Program (1/4)
Current WBN Spent Fuel Storage Racks have never had Boral' coupons Monitoring industry OE including SQN and BFN Participating in Industry Groups Monitoring Fuel Movements for Issues Monitoring SFP chemistry pH Aluminum l 10 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Neutron Absorber Monitoring Program (2/4)
Future Implement Boral' Monitoring Program per NEI 16-03-A NEI 16-03-A Options In-situ testing (BADGER)
Coupon program Continue to monitor SFP chemistry l 11 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Neutron Absorber Monitoring Program (3/4)
Future (contd)
IF TVA decides on a coupon program, the following are issues to resolve Generate coupons from existing rack panels Harvest enough coupons for life of plant plus life extension Use rack periphery panel Circular coupons - approximately 4 inch diameter Pre-characterize coupons For 10B areal density use actual panel data (if available) or neutron attenuation testing l 12 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Neutron Absorber Monitoring Program (3/3)
Future (contd)
IF TVA decides on a coupon program, the following are issues to resolve (contd)
Place coupons on coupon tree in SFP Accelerate exposure Perform periodic Areal Density Measurements per NEI 16-03-A Re-insert coupons, when applicable l 13 Tritium Production License Amendment Pre-Application Meeting - Criticality l September 26, 2017
Watts Bar Unit 2 Tritium Production License Amendment Pre-Application Meeting Spent Fuel Pool Criticality Analysis Z. I. Martin September 26, 2017