ML120330124
| ML120330124 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 02/09/2012 |
| From: | Exelon Generation Co, Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML120330124 (33) | |
Text
Pre-Submittal Meeting Neutron Absorbing Inserts Exelon Generation Company, LLC Quad Cities Nuclear Power Station Units 1 and 2 February 9, 2012 PRELIMINARY
2 Agenda
Objectives Joe Bauer
LAR Overview Joe Bauer
NETCO-SNAP-IN Rack Inserts Rosanne Carmean Scot Leuenroth
Criticality Analysis Dr. Stefan Anton
Interim Actions Rosanne Carmean
Technical Specification Changes Rosanne Carmean
Summary, Questions, Joe Bauer NRC Feedback Preliminary
3 Objectives Provide the NRC with a clear summary of the LAR scope, content and analysis methodology Obtain NRC feedback LAR content Proposed dates for LAR submittal and approval Identify LAR gaps and follow-up actions Preliminary
4 LAR Overview
Purpose:
Submit a LAR to use NETCO-SNAP-IN inserts to permanently resolve the spent fuel pool (SFP) Boraflex degradation issue without crediting Boraflex
Submittal target date: June 2012
Approval target date: June 2013 (requested)
BADGER Testing and RACKLIFE model calculations being used to confirm TS compliance and trend Boraflex degradation
Clean pool insert installation tests scheduled for February 2012
Insert installation testing scheduled for summer 2012 at Quad Cities
Rack installation performed in accordance with 10 CFR 50.59
Installation schedule prioritized based on projected Boraflex degradation from RACKLIFE model. Preliminary installation periods have been established:
Unit 1: 2012 -
2015 Unit 2: 2013 -
2016
No credit taken for NETCO inserts until LAR approved by NRC Preliminary
5 LAR Overview - Lessons Learned
Peach Bottom submitted License Amendment Request (LAR) in June 2008 to address the spent fuel pool issues The long-term Criticality Analysis credited Boraflex; Unacceptable; LAR withdrawn
LaSalle submitted LAR to use NETCO-SNAP-IN neutron absorbing inserts on October 5, 2009 Did not submit an interim criticality analysis for Boraflex Resulted in a required accelerated insert installation LAR subsequently approved January 28, 2011 with License Conditions restricting use of SFP cells without NETCO inserts
Peach Bottom submitted new LAR on November 3, 2011 following LaSalles LAR (using NETCO-SNAP-IN inserts)
Submittal included interim criticality analysis for Boraflex Acceptance Review Supplemental Information requested to address seismic and structural issues Preliminary
6 LAR Overview - Lessons Learned (continued)
Criticality Analysis Holtec International will perform the Quad Cities interim Boraflex and NETCO insert criticality analyses Analysis will bound fuel conditions for the planned power uprate
Quad Cities LAR will:
Utilize the recent Peach Bottom LAR as a template Utilize NETCO-SNAP-IN inserts Include an interim criticality analysis crediting Boraflex
Appropriately model Boraflex parameters Include a revised criticality analysis crediting NETCO inserts Address seismic and structural issues Include License Conditions similar to the Peach Bottom LAR Preliminary
7 LAR Overview - Submittal Outline Technical Evaluation of Proposed Changes Mark-up of Proposed TS Pages Figure of NETCO-SNAP-IN Insert NETCO Report, Material Qualification of Alcan Criticality Analysis with Rack Inserts (proprietary and non-proprietary versions)
Criticality Analysis with Boraflex (proprietary and non-proprietary versions)
Example of Completed Rack Module with Inserts Summary of Commitments Preliminary
NETCO-SNAP-IN Rack Inserts: Neutron Poison Replacement for Fuel Storage Applications Quad Cities Pre-Submittal Meeting, 2/9/2012 K. Scot Leuenroth Principal Engineer
9 Replace Lost Reactivity Hold-Down What are NETCO-SNAP-IN Inserts?
Made of Al/B4 C
Composite Material Extends Useful Storage Rack Life Minimal Impact on Fuel Move Operations Preliminary
10 10 10 10 Project Overview
K. Lindquist Issued U.S. Patent 6,741,669 B2 in 2004 for Absorber Insert Design
Original Demonstration Program was a Joint Venture Between NETCO and Exelon Generation Company
Prototype Testing and On-Site Demonstration Performed for LaSalle and Peach Bottom
Testing Rigor to Continue for Quad Cities Inserts.
First Installation at Exelons LaSalle Station in 2007 (Three inserts installed in Demonstration Program)
Full Scale Insert Installation at LaSalle Unit 2 Completed in 2011 with 4022 Spent Fuel Assembly Storage Locations Preliminary
11 11 11 11 Description
Al-1100/B4 C Composite, Provided by Rio Tinto Alcan, Formed Into a Chevron Shaped Rack Sleeve
Installed via Custom Tool from the Refueling Bridge
Chevron is Compressed During Installation; Friction and Compression Forces Hold it in Place Preliminary
12 12 12 12 Key Features
Simplicity of NETCO-SNAP-IN Standard fabrication methods used to form Al/B4 C composite material
Simplicity of Installation Tool Installation force provided by tool weight alone; no electrical or hydraulic systems
Once Installed, NETCO-SNAP-IN Inserts are an Integral Part of the Rack Modules Preliminary
13 13 13 13 Application
When Placed in Each Storage Location, the NETCO-SNAP-IN Inserts Supplement the Neutron Poison in the Existing Racks
Once Installed, Fuel Can Be Moved In and Out of the Storage Locations as Usual
Insert Installation Complete at LaSalle Unit 2
Prior Installation Experience and Lessons Learned are Being Applied at Quad Cities Preliminary
14 14 14 14 LaSalle Installation
No clearance issues were encountered during installation; further use has validated acceptable clearance with irradiated fuel
Same manufacturing technique used to fabricate the Quad Cities inserts Preliminary
15 15 Company Confidential 15 Insert Being Installed in Location B17 of the LaSalle Unit 2 Spent Fuel Pool
16 16 16 16 16 Borated Aluminum Material
Material Qualification of Alcan Through Accelerated Corrosion Testing Pre-test characterization Post-test characterization Accelerated corrosion environment 2000, 4000, 6000 and 8000-hour test results
Results Show Corrosion Rates Within Measurement Uncertainty of Zero for 8000-hr Tests
Stability of B-10 Areal Density Values Throughout Test
Fast-Start Results Show Consistency with Accelerated Test Predictions, Showing No Negative Change in Areal Density Preliminary
17 17 17 17 Material Performance (LaSalle)
Alcan Material Shows Consistent Performance in Neutron Attenuation Tests Preliminary
18 18 18 Material Surveillance
Coupon Surveillance program will be similar to LaSalle
Fast Start Program Results of the LaSalle Program eliminate need for fast start program at Quad Cities
Long Term Surveillance Program General, Bend and Galvanic coupons will be included in surveillance program Pre-Characterizations will include visual, dimensional, weight and areal density testing
Removal Inspection Insert with the highest fuel move frequency will be removed every 10 years to inspect for wear and overall performance Preliminary
Quad Cities Spent Fuel Pool Criticality Analysis NRC Pre-Submittal Meeting Dr. Stefan Anton February 9, 2012 19 Preliminary
95
.0
)
95
/
95
(
max K
Guidance and Regulations GDC 62: Prevention of Criticality in Fuel Storage & Handling Criticality in the fuel storage and handling system shall be prevented by physical systems or processes, preferably by use of geometrically safe configurations.
The k-effective of the spent fuel storage racks loaded with fuel of the maximum fuel assembly reactivity must not exceed 0.95, at a 95 percent probability, 95 percent confidence level, if flooded with unborated water.
20 Preliminary
Basic Analysis and Requirements All storage rack locations assumed to contain identical fuel assemblies at their most reactive state as a function of exposure Consideration given to all credible abnormal conditions, manufacturing tolerance implications, and computational uncertainties y
Uncertaint Tolerance Bias Nominal
)
95
/
95
(
K K
K Kmax
1 i
Bi Bias K
K
1 2
1 2
int i
Ui i
Ti y
Uncerta Tolerance K
K K
Contribution from Biases Contribution from Independent Tolerances and Uncertainties 21 Preliminary
Computational Tools and Validation CASMO-4 Studsvik 2-D lattice physics code Determines exposure dependent, pin-by-pin isotopic fuel compositions Utilizes ENDF/B-V cross-section data Not used for k-inf calculations MCNP5 LANL code Calculates in-rack k-calc values Uses CASMO-4 pin-specific isotopic specifications to establish peak reactivity Utilizes ENDF/B-VII cross section data 95/95 Bias and bias uncertainty quantified and applied standard benchmark experiments (including HTC)
Uncertainties applied consistent with previous Holtec analyses, including:
Depletion Isotopics Uncertainty Fission Product/Lumped Fission Product Uncertainty 22 Preliminary
No credit taken for B4 C in Boraflex Panels are modeled as water No credit taken for lateral neutron leakage Design basis analyses assume a single lattice design at peak reactivity for full bundle height in every storage location Stainless steel rack cell modeled explicitly Assumes a single rack insert with a minimum (95/95) areal density of 0.0116 g B-10/cm2 in every accessible storage cell Rack Insert Schematic Spent Fuel Rack Cell Model -
Rack Inserts MCNP Rack Model Preliminary 23
Credit taken for degraded Boraflex model includes various degradation mechanisms Only used for racks without inserts No credit taken for lateral neutron leakage Design basis analyses assume a single lattice design at peak reactivity for full bundle height in every storage location Stainless steel rack cell and degraded Boraflex modeled explicitly Spent Fuel Rack Cell Model -
Boraflex MCNP Rack Model Preliminary 24
Design Basis Bundle Selection Optima 2 fuel is shown to bound all past and current fuel types in the Quad Cities SFP Each Optima 2 lattice is analyzed independently The lattice resulting in the highest in-rack k-eff is used to:
Define nominal in-rack k-eff value Perform bias, tolerance, uncertainty sensitivity, interface, accident evaluations 25 Preliminary
Credible Normal Conditions Final Pool Configuration (Inserts only)
Interim Pool Configuration (Inserts and Degraded Boraflex)
Fuel Assembly Channeling (except for Optima 2 assembly)
- Eccentric Positioning
- Moderator Temperature
- Bundle Orientation Credible Abnormal Conditions Dropped Fuel Assembly Mislocated Fuel Assembly Missing Rack Insert Storage Scenarios Addressed 26 Preliminary
Manufacturing Tolerances, Including
- Fuel Enrichment
- Fuel Pellet Density
- Gadolinium Content
- Rod Cladding Thickness
- Rack Wall Thickness
- Rack Pitch
- Rack Insert Thickness
- Rack Insert B-10 areal density Interface Effects Racks with Inserts Adjacent to Storage Modules without Inserts Storage Cells without a Poison Panel on Every Side (on module edge or next to an inaccessible location)
Storage Scenarios Addressed 27 Preliminary
Compliance with ISG and IN DSS-ISG-2010-01
- Fuel Assembly Selection
- Depletion Analysis
- Criticality Analysis
- Criticality Code Validation Information Notice 2011-03
- Monte Carlo Bias Uncertainty
- Depletion Uncertainty 28 Preliminary
Analysis performed will fulfill requirements of 10 CFR 50.68 and GDC 62 with consideration given to DSS-ISG-2010-01 and IN-2011-03 Consideration given to all credible abnormal conditions, manufacturing tolerance implications, and computational uncertainties in determining maximum in-rack eigenvalue Spent fuel racks will be demonstrated to remain >5%
subcritical for storage of current and previous fuel types with defined enrichment and Gadolinium distribution Analyses will include final and interim SFP configuration Summary 29 Preliminary
30 Interim Actions
RACKLIFE model revised every year to incorporate updated assembly power history, fuel movement, and pool chemistry RACKLIFE model is also benchmarked against BADGER results following each BADGER campaign Current RACKLIFE model conservatively bounds peak degradation values from most recent 2009 BADGER testing
RACKLIFE results compared against minimum allowable areal density
BADGER testing is performed every three years to validate the RACKLIFE model BADGER results are compared against minimum allowable areal density Most recent BADGER tests performed in November 2009 (both units)
BADGER campaign performed in January; results pending Preliminary
31 Interim Actions
Interim Boraflex analysis Similar to interim analysis performed for Peach Bottom Will address Boraflex degradation mechanisms and issues
Undetected Cracking
Shrinkage and Edge Dissolution
Gaps
Experimental and Measurement Uncertainties (from BADGER and RACKLIFE methodology)
Boraflex particle self-shielding
Non-uniform panel thinning
Effects of a seismic event on degraded Boraflex
Analysis will establish the degradation acceptance criteria and confirm TS compliance RACKLIFE and BADGER results will be compared to the minimum acceptable areal density analyzed Preliminary
32 Technical Specification Changes
Unit 1 and Unit 2 TS will be the same
Proposed TS similar to LaSalle with inserts
include rack inserts as part of design
TS 4.3.1.1.a. -
in-rack keff
0.95, including allowance for uncertainties described in the UFSAR (no change)
TS 4.3.1.1.b. -
nominal center-to-center distance between assemblies of 6.22 inches (no change)
TS 4.3.1.1.c. (new) -
rack inserts will have a minimum certified B-10 areal density of 0.0116 g/cm2
License Conditions -
will establish restrictions on using SFP storage cells without NETCO Inserts Preliminary
33 Summary Questions NRC Feedback Preliminary