ML091810934

Hand-outs for June 16, 2009 Public Meeting with Exelon

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: ML091810891 ML091810934
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

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../ 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