ML091810934
| ML091810934 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/16/2009 |
| From: | Jennifer Fisher Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation |
| Hughey J, NRR/DORL, 301-415-3204 | |
| Shared Package | |
| ml091810857 | List: |
| References | |
| Download: ML091810934 (9) | |
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Exelon@
Generation
Background
../ Spent fuel racks in both pools contain Boraflex neutron absorber material for criticality control
../ Existing licensing basis k(inf-cold core) < 1.362 (approved 5/93)
../ 10% pool average Boraflex B-1 0 areal density loss
../ BADGER testing and RACKLIFE analyses performed to monitor condition of Boraflex
- Condition of Boraflex in individual cells dependent upon numerous factors, including gamma exposure, water chemistry and temperature
- Unit 2 racks showing slightly faster degradation than Unit 3
../ RACKLIFE analyses indicated 10
% threshold would be exceeded in Fall 2008
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Exelon@
Generation LAR Submittal - Summary
~---.._-,
../ Submitted License Amendment Request (LAR) in June 2008, requesting change in Tech Spec 4.3.1.1.a
../ Determine in-rack impact of using less reactive bundle
- Choose reasonable point in time when mitigation strategy can be implemented - May 2012
- Identify design basis Reactivity Equivalent Beginning of life (REBOl) assembly that bounds future assembly designs
- Based upon RACKll FE projections, determine pool average Boraflex areal density loss
- Using REBOl, determine reactivity penalty (NETCO criticality analysis)
Exelen, Generation LAR Submission - Summary (cont.
../ Determine Tech Spec impact of using less reactive bundle
- Determine k(inf-cc) for REBOL assembly (GNF criticality analysis)
- k(inf-cc) < 1.318
- Confirm REBOL design bounds all previous fuel designs either stored or in-use at site (GNF criticality analysis)
Exelon@
Generation RAls
../ NRC Request for Additional Information (RAI) issued January 2009
../ RAI significant questions included:
- Use of RACKLIFE for determination of Boraflex degradation at PBAPS (NETCO criticality analysis)
- Use of CASMO for in-core and in-rack criticality analyses (NETCO criticality analysis)
- Use of k(eff) 0.95 for off-normal conditions (NETCO criticality analysis)
- Numerous questions regarding GNF criticality analysis
../ NRC requested 45 day response
Exelon@
Generation RAI Responses
./ Exelon removed conservatisms to meet criticality criterion of k(eff) < 0.95 without defining a new REBOL assembly
- Corrections required to criticality analyses in response to NRC RAls necessitated using lower peak reactivity bundle
./ Challenge for Exelon was to determine if pool average Boraflex B-1 0 areal density loss is compatible with chosen REBOL design
./ Using REBOL analyzed, Exelon determined B-10 areal density loss is limit for keeping k(eff) < 0.95
./ Based upon RACKLIFE analysis, NETCO determined this loss corresponded to May 201 0
Exelen.
Generation RAI Responses (cont.)
~ May 201 0 date does not allow sufficient time to procure and install new spent fuel racks
~ Exelon determined additional step required (new, lower peak reactivity REBOl) was necessary to meet May 2012
~ Exelon indicated in RAI response that additional lAR with new, lower peak reactivity REBOl would be resubmitted
Exelon@
Generation RAI Responses (eont.)
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v" Responding to questions raised by NRC Staff regarding GNF criticality, Exelon:
- Reviewed and determined GNF could not support evaluating new REBOl lattice in time to respond to RAls
- Determined that inclusion of duplicate, in-pool criticality analyses was confusing
- Identified that the GNF criticality analysis was not a necessary component of the original lAR
- The only datum required from GNF was the determination of k(inf cc) < 1.318, which was necessary for the lAR submission v" In the RAI responses, Exelon indicated that the GNF document has been withdrawn
Exelon Generation Status of Boraflex Management
../ BADGER testing scheduled for both pools in 1Q201 0
../ Additional RACKLIFE calculations underway (based upon previous BADGER testing) to project Boraflex degradation through 2016
../ Budgetary estimate and estimated schedule for new, spent fuel racks obtained
../ Alternative methods of criticality control under investigation for PBAPS