ML100740722
| ML100740722 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 07/21/2010 |
| From: | Jason Paige Plant Licensing Branch II |
| To: | Florida Power & Light Co |
| Paige, Jason C, NRR/DORL,301-415-5888 | |
| Shared Package | |
| ML100740721 | List: |
| References | |
| TAC ME3443 | |
| Download: ML100740722 (38) | |
Text
~.
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Agenda
~ Introduction
~ Background
~ Unit 3 License Amendment Request
- RACKLIFE and BADGER testing at Turkey Point for Boraflex management
- Proposed configurations, now evaluated using Amendment 234 method
~Current Situation &Unit-3 Commitment Letter of 12/31/09
~ Unit-4 License Amendment Request and Contingency LAR
~ Conclusions 1
-F=PL..
Purpose of Meeting
~ Discuss FPL's approach to addressing Boraflex degradation in the Turkey Point Unit 3 and 4 SFPs ana licensing compliance, including compensatory action.
2 fj FPL.
Background
~ Actions taken to address Boraflex degradation have ensured the Spent Fuel Pools have remained operable in a controlled safe configuration
- Commitments regarding Boraflex Management
- Implementation of conservative compensatory measures
- Long term program to address Boraflex degradation
- Additional recent actions taken 3
-FPL.
Background (can't)
~ Credit for 650 ppm soluble boron incorporated in 2000 with Amendments 206 & 200. Established TS requirement for the use of uncertainties in calculating keff.
~ In 2000 FPL provided a commitment for Boraflex surveillance program, including in-situ areal density testing (BADGER).
~ In 2000 FPL provided NRC with results of first BADGER test:
- Some Region II Boraflex panels degraded below the minimum analysis areal density of 0.006 gms-B lO/cm 2*
- Degraded and nonconforming condition addressed pursuant to RIS-2005-20 (GL-91-18) .
- Administrative controls established to limit the use of affected storage cells to assure TS keff requirements remain satisfied. Fundamental treatment of uncertainties consistent with that described in UFSAR.
- Boraflex degradation projected using RACKLIFE.
- Commitment for BADGER test frequency reduced from 5 years to 3 years.
4 fj I=PL.
Background (can't)
~ In 2001 the Unit 3 high duty Region II SFP storage rack was converted to a configuration that didn't credit Boraflex ("Sacrificial Module").
- 2-out-of-4 checkerboard with empty storage cells.
- Predominantly stored freshly offloaded fuel assemblies.
- Higher dose and higher heat load.
- After decay fuel moved to other modules to prepare for next refueling.
- Sacrifice Boraflex in this module and limit duty to remaining modules.
~ BADGER tests were performed in 2001,2004 and 2007 in the Unit 3 SFP.
- Boraflex racks were installed in the Unit 3 SFP in 1985.
- Boraflex racks were installed in the Unit 4 SFP in 1989.
- Tests in Unit 3 have covered a range of predicted Boraflex degradation up through near 500/0, covering the service life of Boraflex panels.
~ Since 2001, FPL has implemented administrative controls to:
- Ensure compliance with Technical Specifications and not rely on soluble boron in the pool beyond that allowed by 10 CFR 50.68.
- Prohibit the storage of a fuel assembly in any affected SFP storage cell unless an alternate storage configuration has been demonstrated to compensate for the loss of Boraflex.
- Satisfy criticality design basis requirements for keff using NRC approved methods.
5
-FPL..
Background (con't)
~ FPL developed use of alternate poisons (Metamic and RCCAs) and administrative controls (collectively referred to as Boraflex Remedy).
~ Boraflex Remedy approved by NRC in Amendments 234 and 229 (2007).
~ FPL was not able to implement the 2007 amendments by the implementation date despite significant efforts with FPL's vendor because:
- Vendor's inability to fabricate Metamic inserts within maximum specified dimensions;
- Long lead time to procure sufficient RCCAs and/or implement dry cask storage to create empty cells;
- Amendments preclude reliance on Boraflex.
~ FPL incorrectly assumed changes to implementation date would be administrative.
- Date for implementation was negotiated based on the expected poison fabrication schedule at the time the Boraflex Remedy amendments were issued.
6
- FPL.
Background (con't)
Region 2 Storage Cell Formed Cell Fuel Assembly Boraflex
......J - - - - Panel
.. 5.5.
5.5. Storage .. Wrapper Cell Plate Metamic Insert 7
- FPL..
Unit 3 License Amendment Request (LAR)
>- The Unit 3 LAR will:
- Request NRC approval of a change to the Boraflex Remedy amendment to allow use of Boraflex in Region II until Amendment 234 is implemented.
- Approach similar to that used by other licensees.
- Provide information on RACKLIFE and BADGER testing
- Incorporate methodology, fuel classifications and configurations, already approved by NRC in Amendment 234.
- Cask Area Rack does not use Boraflex.
- Region I will not credit Boraflex after June 19, 2010.
- Temporary credit for Boraflex in Region II until 9/30/12 (Dry Cask storage implemented).
- Boraflex assumptions consistent with current licensing analysis
- Conservative shrinkage and gapping.
- Minimum areal density of 0.006 gms-B 1a1cm 2.
8
-I=PL.
Unit 3 LAR Boraflex Management Program
~Fundamentals of RACKLIFE
~Application of RACKLIFE /BADGER to assure actual varying conditions in the SFP remains bounded by licensing analysis on a 95/95 basis consistent with keff requirements.
9
- FPL..
Unit 3 LAR Boraflex Management Program
~ During the November interactions with the NRC staff several questions regarding RACKLIFE were raised.
~ 18 PWRs &7 BWRs are using or have used RACKLIFE to model Boraflex degradation.
~ RACKLIFE simulates the dissolution of Boraflex
- Utilizes a kinetics model based on a mass balance calculation of silica in SFPs to predict B4C loss from Boraflex.
- Silica concentration is tracked from its source (solubilization of the Boraflex matrix) through transit into the bulk pool volume and to its final removal via the SFP cleanup system.
- Kinetics equation parameters, such as silica release rate, were determined over a range of conditions (absorbed dose, temperature, ph) from a series of laboratory experiments.
- EPRI Topical Report TR-1 07333 discusses theory and operation of the code.
10
- FPL.
Unit 3 LAR Boraflex Management Program
~Developed for EPRI by NETCO, RACKLIFE has been successfully utilized to manage Boraflex degradation for over a decade:
- Several licensees have used RACKLIFE predictions and some have included as a part of NRC accepted submittals involving SFP criticality
- Mcquire Unit 1 & 2 and Indian Point 2
- Available data shows good correlation between RACKLIFE predictions and in-situ areal density measurements.
11 fj FPL.
Unit 3 LAR Boraflex Management Program
~ Licensees create RACKLIFE models based upon known SFP parameters (silica history, temperature history, cleanup system efficiency)
~ Models are modified to match actual SFP silica history by adjusting escape coefficient values.
SPEr'-lT FUEL POOL SILICA, 45 40 35 30 t:" ',1 C)
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0 1985 1988 1991 1994 1997 2000 2003 2006 2009 12 POOL ST.ATE, from 1985-01-05 to 2010-01-12
- Total - Reactive Ivleasured fiI=PL.
Unit 3 LAR - Boraflex Management Program
~ The relative conservatism of these models has been established post BADGER testing by comparing average predicted loss with average measured loss.
~ Under-predictions, therefore, are corrected and verified by subsequent BADGER campaigns.
Measured B4C loa. 'ill. Predlchd % B"C Loa*. PWR Awr;ou- of Imdlmd P.......s 50%,
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- PWR 4 Region 1 Red: 3rd Campaign 13 o PWR 2 Region 2 l:::, PWR4 Region 2 - - - _. Badger Uucertainty
-I=PL.
Unit 3 LAR Boraflex Management Program
~ RACKLIFE is conservatively applied to ensure that Keff < 1.0 on a 95/95 basis.
~ RACKLIFE is used to predict the varying degraded conditions of the areal density of the Boraflex panels in the SFP
~ The statistical analysis of the distribution of the difference between RACKLIFE predicted versus 2001, 2004, and 2007 BADGER test measured degradation shows that:
- Using the 95/95 minimum initial as-built areal density shows that compensatory action is conservatively taken at an areal density higher than 0.006 gms B101cm 2 when RACKLIFE predicts 50% degradation.
- There is a 95% probability with a 95% confidence that RACKLI FE is over predicting degradation for the four panels in any given storage cell in the SFP.
14
- FPL.
Unit 3 LAR Boraflex Management Program As-built areal density of Boraflex panels are higher than the degraded areal density assumed in the criticality analysis.
Region 2 Areal Density 120 Limiting value used in criticality Starting value used in criticality analysis 95/95 minimum as-built value II analysis wI Boraflex Degradation before any degradation (Minimur:n (0.015 gms-B 1O/cm 2 )
(0.006 gms-B 1O/cm 2 ) Certified) (0.012 gms-B10/cm2) ....... I 100
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- Areal Density (gms-B 10/cm 2 )
15 fj I=PL.
Unit 3 LAR Boraflex Management Program
>- BADGER testing confirms conservative nature of RACKLIFE compared to SFP conditions.
>- This graph shows the distribution of the difference between degradation measured with BADGER and predicted by RACKLIFE for individual panels.
Predicted* Measured Distribution 9
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16 FPL.
Unit 3 LAR Boraflex Management Program
~ Based on the as-built areal density data, there is a 95%
probability, with 95% confidence, that a given Boraflex panel had an areal density of 0.015 gms-B 101cm 2 or higher.
~ Therefore, when RACKLIFE predicts that a panel has 50%
degradation, that means there's a 95/95 that the panel will be at 0.0075 gms-B 101cm 2 or higher.
- Considerable margin to 0.006 gms-B H/cm 2.
17
- I=PL.
Unit 3 LAR Boraflex Management Program
~ From the RACKLIFE / BADGER comparison data, there is a 95% probability with 95% confidence that RACKLIFE will under-predict degradation by a maximum of 23.1 %.
~ That means that if RACKLI FE is predicting 50% degradation for a panel, it could be 73.1 % degraded.
~ However, the impact on keff must consider the other panels in a SFP storage cell.
18 fj I=PL.
PTN-3 LAR - Managing Boraflex Degradation
~ FPL takes action when one panel in a cell is predicted to reach 50% degradation.
~ Therefore, the limiting case would be when RACKLIFE predicts that all four panels in one cell reach 50°k> degradation at once, with one under-predicted (in % degradation) 50%
500~ 50%
73.10/0 19
-FPL.
PTN-3 LAR - Managing Boraflex Degradation
~Using the RACKLIFE / BADGER comparison data, there is a 95% probability, with a 95% confidence, that the four panels in one cell will be over-predicted by RACKLIFE by a cumulative total of 10.4% *
~ Therefore, if one panel is under-predicted by 23.1 %, there's a 95/95 that the other three are over-predicted by 33.5%.
38.8%
38.8% 38.80/0 73.10/0 20 fj FPL.
PTN-3 LAR - Managing Boraflex Degradation
~Converted to areal densities (in gms-B 101cm 2), based on the 95/95 minimum value of 0.015 gms-B 101cm 2 0.0092 0.0092 0.0092 0.0040
~ This limiting case is bounded by the case with all panels at 0.006 gms-B 1oIcm 2.
21
-FPL.
Unit 3 Commitment Letter of 12/31/09
~Continue to credit Boraflex as a neutron absorber and administratively restrict with compensatory measures the use of storage cells that have Boraflex panels whose B-1 0 areal density have degraded below 0.006 gms-B 101cm 2.
~ Update the UFSAR describe compensating measures.
~ Provide additional margin beyond that already afforded by FPL's historical treatment of Boraflex degradation until Amendment 234 is implemented.
22 fj F=PL.
Compensatory Actions for Boraflex Loss
>- To ensure margin to criticality is maintained and the keff requirements of the TS are satisfied compensatory actions are taken when a Boraflex panel is predicted to reach 50% degradation.
>- Prohibit storage of fuel assembly in any affected SFP storage cell unless an alternate configuration has been demonstrated to compensate for the loss of Boraflex.
>- Alternate configurations analyzed using NRC approved methodology.
- KENO-Va and PHOENIX-P as used in WCAP-14416 for SFP criticality analysis.
- MCNP4a and CASMO-4 as used in the Turkey Point Cask Area Rack and Boraflex Remedy criticality analysis.
23
- I=PL.
Compensatory Actions for Boraflex Loss
~ Alternate configurations accommodate a conservative allowance for uncertainties as described in UFSAR.
- UFSAR Section 9.5.2.3 describes this methodology for the treatment of uncertainties as:
- "A final 95/95 Keff was developed by statistically combining the individual tolerance impacts with the calculational and methodological uncertainties and summing this term with the temperature and method biases and the nominal KENOVa [or MCNP4a]
reference reactivity [multiplication factor (K)]."
- "The 95/95 basis is defined as the upper limit, with a 95 percent probability at a 95 percent confidence level, of the effective neutron multiplication factor Keff of the fuel assembly array, including uncertainties and manufacturing tolerances."
- The analysis of the alternate configurations included an allowance for uncertainties consistent with this fundamental methodology for the treatment of uncertainties described in the UFSAR.
24 FPL.
Compensatory Actions for Boraflex Loss
~ In 2001 the high duty Region II SFP storage rack was converted to a configuration that didn't credit Boraflex ("Sacrificial Module").
~ Additional alternate configurations use RCCAs to compensate for Boraflex degradation.
~ Other alternate configurations use higher burnup requirements and empty cells.
~ In addition, going forward the configurations of Amendment 234 (Boraflex Remedy) will be used to compensate for the loss of Boraflex.
- Consistent with commitments in 12/31/09 letter.
- Region I of the Unit 3 SFP to comply with Amendment 234 by June 19, 2010.
- One storage rack in Region II to comply with Amendment 234 by June 19, 2010.
- Additional storage racks will be configured to comply with Amendment 234 as Metamic inserts, RCCAs or empty storage cells become available.
~
25 FPL.
Summary Compensatory Actions for Boraflex Loss
~ Compensatory actions taken in response to the degraded and nonconforming condition of some of the Boraflex panels in the Unit 3 SFP.
- Actions taken use administrative controls and configurations similar to those approved in Amendment 234.
- Empty storage cells.
- RCCAs.
- Higher fuel assembly burnup configurations.
- Actions taken enhance the reactivity control capability of the SFP and satisfy the requirements of T5 5.5.1.1.a and 5.5.1.1.b.
- The compensatory measures were analyzed using NRC-approved methodology and are conservative to accommodate a conservative allowance for uncertainties as described in the UFSAR.
- Implementation of the Boraflex Remedy Amendment intended to be final corrective action for the degraded and nonconforming condition.
~ Given length of time compensatory actions in place, UFSAR should have been.
updated.
~ Compensatory measures taken are more conservative than TS requirements and require action to bring TS into conformance per NRC Administrative Letter 98-10.
- Implementation of the Boraflex Remedy Amendment intended to address this issue.
26 fj FPL.
Unit 4 LAR
~ NRC approved Unit 4 Boraflex remedy extension to 2/28/11 with license conditions (BADGER test by 5/1/10, 2100 ppm SFP boron, 10%
burnup penalty and no additional fuel to SFP).
~ License conditions have been implemented providing additional margin.
~ BADGER testing to start in 3/10/10.
~ Based on BADGER test results FPL will subsequently submit a LAR to NRC requesting Boraflex Remedy extension to 2012.
- Similar to the Unit 3 LAR, the Unit 4 LAR is to be based on the Boraflex Remedy amendment methodology.
~ FPL is preparing a contingency LAR for Unit 4 to have available to submit in the unlikely event we have to offload the core prior to the next refueling outage.
27
- FPL.
Conclusions
~ The Turkey Point SFPs remain operable in a controlled safe configuration.
- Actions taken and going forward conservatively manage Boraflex degradation to assure adequate reactivity margin in the SFP.
~ Actions taken in SFPs are in compliance with TS.
~FPL will update Turkey Point UFSAR to include compensatory measures by 3/15/10.
~ The proposed Unit 3 LAR will address SFP conditions until the Boraflex Remedy Amendment can be implemented.
28
- FPL.
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Definitions
~ Resultant cells: Region II storage cell that contains Boraflex panels.
~ 95/95 lower tolerance limit: The value in a statistical population which has a 95 percent pro6a6ITfty that the population is greater than at a 95 percent confidence level.
~ Metamic Insert: A chevron shaped SFP storage cell insert composed of an aluminum and B4C metal matrix composite.
~ Administrative controls: Those actions established to restrict stor~e of ue assem les an t e placement of neutron absorbers in the SF? to assure that the SFP keff requirements are satisfied.
~ Boraflex Remedy: License Amendments 234 and 229.
30
- F=PL.
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'TEMPORARY CASK AREA I TEMPORARy CASKAREA FUEL FUEL STORAGE RACK STORAGE RACK 31 Unit 3 SFP Layout
- FPL.
Unit 3 SFP
- FPL.
U3 SFP Projected Degradation
~ Status of the Boraflex in the Unit 3 SFP
- 10% of the Region II Boraflex panels conservatively projected to be below the minimum analysis areal density of 0.006
.. 12 gms-B1O"cm2 by 9/27/10.
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I=PL.
Current TS Requirements
~ TS 3.9.14 SPENT FUEL STORAGE The following conditions shall apply to spent fuel storage:
- The maximum enrichment loading for the fuel assemblies in the spent fuel racks shall not exceed 4.5 weight percent of U-235.
- The minimum boron concentration in the Spent Fuel Pit shall be 1950 ppm.
- Storage in Region II of the Spent Fuel Pit shall be further restricted by burnup and enrichment limits specified in Table 3.9-1.
~ TS 5.5.1.1 DESIGN FEATURES - FUEL STORAGE - CRITICALITY The spent fuel storage racks are designed to provide safe subcritical storage of fuel assemblies by providing sufficient center-to-center spacing or a combination of spacing and poison and shall be maintained with:
- Keff equivalent to less than 1.0 when flooded with unborated water, which includes a conservative allowance for uncertainties as described in UFSAR Appendix 14D.
- A Keff equivalent to less than or equal to 0.95 when flooded with water borated to 650 ppm water, which includes a conservative allowance for uncertainties as described in UFSAR Appendix 14D.
- A nominal 10.6 inch center-to-center distance for Region I and 9.0 inch center-to-center distance for Region II for the two region spent fuel pool storage racks. A nominal 10.1 inch center-to-center distance in the east-west direction and a nominal 10.7 inch center-to-center distance in the north-south direction for the Region I cask area storage rack.
- The maximum enrichment loading for fuel assemblies is 4.5 weight percent of U-235.
34
- FPL.
Compensatory Actions for Boraflex Loss
~ 2001: 2-out-of-4 checkerboard with empty storage cells (Sacrificial Module).
- NRC approved methods
- Codes: KENO-Va
- Uncertainties: Accommodates conservatively applied biases & uncertainties
- Calculational bias and uncertainty appropriate for the 44-energy group KENO-Va model
- Remaining biases and uncertainties are those used in the licensing basis analysis in the UFSAR Affected FA with Boraflex Metamic Fuel Water Hole RCCA Panel L-Insert Assembly No Boraflex in any cells I
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r * *
- 35
- FPL.
Compensatory Actions for Boraflex Loss
~ 2008: Location specific (SFP Location H15) use of Amendment 234 (Boraflex Remedy) configurations.
- NRC approved methods
- Codes: MCNP4a and CASMO-4
- Unborated keff consistent with Amendment 234 licensing basis analysis.
- Uncertainties: Biases & uncertainties conservatively applied consistent the UFSAR methodology for the treatment of uncertainties.
~ 2009: Location specific (SFP Location L38) use of specific higher burnup fuel assemblies.
- NRC approved methods
- Codes: PHOENIX-P
- Use consistent with WCAP-14416 defined the use of PHOENIX-P for SFP criticality analysis
- Target multiplication factor (K) was established (base case) using this model with the limiting fuel assembly allowed by Technical Specification (TS)
- Analysis performed assuming Boraflex neutron absorber removed from one SFP storage cell and the actual enrichment / burnup cnaracteristics of the fuel stored in and around L38 to compensate for the K impact of the loss of the Boraflex
- Analysis determined the no Boraflex case K was less than base case K.
- Uncertainties: Biases & uncertainties conservatively applied
- Comparative analysis inherently applies the calculated biases and uncertainties from the licensing basis analysis.
- Increased axial burnup shape bias appropriate for the higher burnup fuel assemblies used in the compensatory measure configuration consistent with the licensing basis analysis methodology.
36
- FPL.
Compensatory Actions for Boraflex Loss
~ 2003: RCCAs used to compensate for the loss of Boraflex.
- NRC approved methods
- Codes: PHOENIX-P
- Use consistent with WCAP-14416 defined the use of PHOENIX-P for SFP criticality analysis
- Target multiplication factor (K) was established (base case) using this model with the limiting fuel assembly allowed by Technical Specification (TS)
- Analysis performed assuming Boraflex neutron absorber removed from one SFP storage cell and used RCCAs to compensate for the K impact of the loss of the Boraflex.
- Analysis determined the no Boraflex case Kwas less than base case K.
- Uncertainties: Accommodates conservatively applied biases & uncertainties
- Comparative analysis inherently applies the calculated biases and uncertainties from the licensing basis analysis.
- Uncertainty associated with RCCA easily accommodated by conservative results.
111111 II II_ II .. ... Affected Boraflex Metamic Fuel FA with 11111111 1111 II Water Hole RCCA Panel L-Insert Assembly 111111 II II II I
I I
r * *
- 37
- FPL.