ML14162A520
| ML14162A520 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/11/2014 |
| From: | Eckholt G Xcel Energy |
| To: | Pamela Longmire NRC/NMSS/SFST/LID/LB |
| Longmire P | |
| Shared Package | |
| ML14162A504 | List: |
| References | |
| Download: ML14162A520 (42) | |
Text
Prairie Island Independent Spent Fuel Storage Installation License Renewal Application Discussion of Requests for Additional Information Rockville, Maryland June 16, 2014
Attendees - NSPM Mike Baumann - Director, Nuclear Fuel Supply Martin Murphy - Director, Nuclear Licensing and Regulatory Affairs Terry Pickens - Director, Regulatory Policy Gene Eckholt - Manager, Projects Licensing Oley Nelson - Engineer, Spent Nuclear Fuel Projects Sam Chesnutt - Engineer, Projects Licensing 2
Agenda
Introductions
Objective of Meeting
Background
Discussion of Requests for Additional Information and NSPM Proposed Responses
Closing Remarks 3
Acronyms ACI American Concrete Institute NRC Nuclear Regulatory Commission AMP Aging Management Program NSPM Northern States Power - Minnesota AMR Aging Management Review OE Operating Experience CAP Corrective Action Program PINGP Prairie Island Nuclear Generating Plant DOE Department of Energy PEO Period of Extended Operations EPRI Electric Power Research Institute RAI Request for Additional Information GALL Generic Aging Lessons Learned SAR Safety Analysis Report ISFSI Independent Spent Fuel Storage Installation TLAA Time Limited Aging Analysis LRA License Renewal Application TN Transnuclear 4
Objective Of Meeting
Ensure clear understanding of RAIs
Reach agreement on response strategies 5
Background
ISFSI Operations commenced - 1995
NSPM submitted PI ISFSI License Renewal Application (LRA) - October 2011
Requested 40 year extension beyond October 2013
Submitted Responses to Initial Round of Technical RAIs - July 2013
2nd Set of RAIs - May 2014 6
Discussion of RAI-12
RAI-12:
Provide an AMP for high burnup fuel addressing the 10 points in NUREG-1927; the AMP should be based on the DOE Cask Demonstration test plan.
7
Discussion of RAI-12 (Contd)
Response to RAI-12
Will provide an AMP based on DOE Demonstration plan
AMP will include Toll Gate Assessments
AMP will be included in revision to Appendix A of LRA, Aging Management Plan 8
Discussion of RAI-1
RAI-1:
Identify each instance in the safety analysis report (SAR) that refers to a limited storage system period -
explain and justify their disposition.
9
Discussion of RAI-1 (Contd)
Response to RAI-1:
Propose to provide markups of each instance in SAR that refers to a storage system period (e.g., 20 years)
SAR update categories:
Delete storage period if no technical basis
Revise storage period if new analysis
Clarify how storage period applies during PEO
Will provide complete list of SAR updates and justification of categorization 10
Discussion of RAI-2
RAI-2:
Provide a revised Aging Management Program (AMP) for the concrete pad, or provide detailed justifications for why five listed aging effects / mechanisms do not require an AMP, for both above-grade and below-grade areas, as applicable.
11
Discussion of RAI-2 Response to RAI-2:
Three of the listed aging effects / mechanisms for the concrete pad are addressed in the LRA, Table 3.4-1 (AMR) and A2.1-1 (AMP):
Cracking, Loss of Strength from cement aggregate reactions
Increase in porosity/permeability and Loss of Strength due to leaching of Ca(OH)2
Cracking due to Settlement 12
Discussion of RAI-2 (Contd)
Will provide site-specific technical justification for exclusion of:
Cracking, Loss of Material from chemical attack
Not exposed to aggressive chemical environment
Cracking, Loss of Material / Bond from corrosion of embedded steel
Good quality, well consolidated, properly cured concrete pads.
13
Discussion of RAI-3
RAI-3:
Specify which materials properties are covered by the aging effect Change in Materials Properties when referring to the aging mechanism Leaching of Ca(OH)2 in the concrete pad and justify visual examination.
14
Discussion of RAI-3 (Contd)
Response to RAI-3:
Material properties that can be affected by leaching include:
Increase in porosity and permeability
Reduced strength
Lower pH
Visual examination can detect evidence of leaching such as white lime deposits 15
Discussion of RAI-4
RAI-4:
Revise the license renewal application (LRA) to include a water chemistry program as part of the AMP for the concrete pad, or provide justification for exclusion.
16
Discussion of RAI-4 (Contd)
Response to RAI-4:
Will revise AMP in Appendix A to LRA, to include groundwater chemistry
Proposed Frequency is every six months
Proposed acceptance criteria
Chloride 500 ppm
Sulfate 1500 ppm
pH 5.5 17
Discussion of RAI-5
RAI-5:
Revise inspection frequencies consistent with ACI 349.3R or justify discrepancies. Also, justify opportunistic inspections of below-grade areas.
18
Discussion of RAI-5 (Contd)
Response to RAI-5:
Inspection frequency for ISFSI concrete pad is proposed to be the same as other PINGP concrete structures
Above-grade - 5 years
Inaccessible - inspections of opportunity
Will clarify frequency in LRA Section A2.4.2
Inspection frequency consistent with GALL, NUREG-1801, Rev.2,Section XI.S6, Structures Monitoring 19
Discussion of RAI-6
RAI-6:
Describe the Corrective Action Program (CAP) and when inspection results of the concrete pad will initiate an Action Request, change to the AMP, or notification to the NRC. Also, address use of operating experience (OE) from other ISFSIs.
Explain monitoring and trending of identified but uncorrected aging effects.
20
Discussion of RAI-6 (Contd)
Response to RAI-6:
CAP Action Request initiated when acceptance criteria are exceeded:
Cracking - identified size limits
Change in material properties - calcium streaks and deposits (indicative of leaching)
Loss of material - identified size limits for surface scaling, spalling
Criteria are consistent with Tier 2 criteria in ACI 349.3R for conditions requiring evaluation 21
Discussion of RAI-6 (Contd)
CAP program is 10 CFR 50 Appendix B program
CAP evaluations include:
Extent of condition evaluation
Actions to accept or repair as appropriate, including possible increase in inspection frequency or expansion of sample population
Evaluation for NRC reportability
Determination if AMP needs to be revised 22
Discussion of RAI-6 (Contd)
Site OE program reviews issues identified by NRC and industry (e.g., INPO, Owners groups, TN cask users group)
Concrete OE issues are similar to other Plant concrete structure issues
OE reviews could lead to a CAP
CAP program evaluation will determine need for modifying the AMP
AMP includes monitoring and trending 23
Discussion of RAI-7
RAI-7:
Provide additional information in the AMP for the berm:
Define absence of aging effects
Provide basis for inspection frequency
Identify material properties that will change due to dessication and explain visible signs of change 24
Discussion of RAI-7 (Contd)
RAI-7 Discussion:
AMP for berm is consistent with PINGP AMP for earthen structures
Absence of aging effects for the berm includes:
(aging effects terminology from EPRI reports)
No loss of form - no indications of slope instability or settlement
No loss of material - no evidence of erosion
No change in material properties - no evidence of erosion 25
Discussion of RAI-7 (Contd)
Dessication is a drying of soils that results in a loss of soil adhesion - visible signs would include accelerated effects of erosion
Inspection frequency of 5 years is based on Plant structural inspections, also consistent with GALL report, NUREG-1801 Rev. 2 26
Discussion of RAI-8
RAI-8:
Provide a detailed technical basis for the acceptance criteria for visual examinations of the cask: the absence of any signs of aging, as indicated in LRA Section A2.6.2.
27
Discussion of RAI-8 (Contd)
Response to RAI-8
Acceptance criteria of the absence of any of the aging effects listed in Table A2.1-1 ensures conservative initiation of an Action Request in the CAP program
Aging effect listed in Table A2.1-1 for casks is Loss of Material due to various corrosion mechanisms
Acceptance criteria are not met if Inspector observes any corrosion 28
Discussion of RAI-8 (Contd)
Any observed corrosion is evaluated in the CAP program
CAP Program relies on engineering evaluations to determine actions
Calculation referred to in the RAI provides basis for inspection frequency - is not a quantitative or actionable operation criterion 29
Discussion of RAI-9
RAI-9:
Provide conclusive evidence to support no observable loss of material statement regarding the lead cask examination. Also, clarify photographs of the inspection and address observations regarding pits and measurable loss of material.
30
Discussion of RAI-9 (Contd)
Response to RAI-9:
Use of visual examinations is consistent with NUREG 1927, Appx E, Component Specific Aging Management
Only conclusive evidence is inspection report with documented observations by the inspector
Inspector documented no observable depth to corrosion (including pitting corrosion)
AMP will be revised to clarify no measureable loss of material should be no observable loss of material
Discussion of photos and annotations 31
Discussion of RAI-11
RAI-11:
Provide a TLAA to support position that there will be no buildup of flammable hydrogen based on radiolytic degradation of the neutron shield polymer. Provide AMP for the relief valve if needed.
32
Discussion of RAI-11 (Contd)
Response to RAI-11:
Will provide analysis:
Calculation of potential flammable gas generation based on methodology in NUREG/CR-6673
Conservatively includes energy deposition in resin from both gamma and neutron radiation
The amount of gas generated is less than solubility capacity of resin
Analysis concludes that the amount of flammable gas released from resin would be negligible 33
Discussion of RAI-10
RAI-10:
Provide an AMP to detect degradation of cask neutron shield. The current radiation monitoring program does not adequately address detector selection, measurement location selection, resolution of measurement data, time dependency of the decaying source term, or detection of cracks or unexpected degradation of the shield.
34
Discussion of RAI-10 (Contd)
Response to RAI-10:
NSPM will provide additional support for position that there is no aging effect for neutron shield that could result in a loss of shielding intended function
Aging effects such as embrittlement, cracking, loss of elasticity do not affect intended function
Calculation discussed in response to RAI 11 shows hydrogen generated by radiolytic degradation will remain absorbed in the poly material
No loss of shielding 35
Discussion of RAI-10 (Contd)
Will provide clarification that current surveys can detect degradation before loss of intended function
Intended function is to provide shielding for compliance with offsite dose regulations, as demonstrated by Safety Analysis
Loss of intended function would be defined as a reduction in shielding effectiveness that results in actual dose rates that exceed those based on the Safety Analysis 36
Discussion of RAI-10 (Contd)
Neutron survey meters
Will discuss neutron energy spectrum used during survey meter calibration
Will explain that meter readings are conservatively higher than actual due to different neutron energy spectra in calibration source vs. casks
Shielding degradation could result in a shift to higher energy neutrons which would produce even higher measured values 37
Discussion of RAI-10 (Contd)
Measurement Locations
Survey measurements at consistent locations
Measurements taken approximately 2 m from casks
- at a point straight out from each cask
Approximately 1 m above ground
Minimizes impact of dose from adjacent casks 38
Discussion of RAI-10 (Contd)
Measurement resolution
Meter scale is analog, 1 to 10 mr/hr; data typically recorded to nearest 1 mr
Elevation is at point of high dose rate
Consistent measurement locations provide representative sample of casks 39
Discussion of RAI-10 (Contd)
Trending
Trending of 2-meter survey data shows dose rates below dose rates based on Safety Analysis
Increases in dose rate trends will detect degradation before loss of intended function 40
Closing Remarks 41
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