ML13301A678
| ML13301A678 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 07/30/2013 |
| From: | Simpson L Exelon Generation Co |
| To: | Nicholas Difrancesco Division of Operating Reactor Licensing |
| References | |
| MF0500 | |
| Download: ML13301A678 (7) | |
Text
NRR-PMDAPEm Resource From: Lisa.Simpson@exeloncorp.com Sent: Tuesday, July 30, 2013 2:52 PM To: DiFrancesco, Nicholas Cc: David.Gullott@exeloncorp.com; Bowen, Jeremy
Subject:
Responses to Questions Regarding Review of LaSalle Unit 1 Evaluation of Reactor Vessel Capsule Surveillance (MF0500)
Attachments: Responses to NRC Questions on ISP letter.docx
- Nick, In an email dated July 1, 2013, you provided informal questions regarding the LaSalle submittal dated January 10, 2013.
Included in the attached file are the responses to those questions.
Please contact me if you have any questions regarding these responses.
Lisa Simpson Exelon Corporate Licensing 630-657-2815 lisa.simpson@exeloncorp.com From: DiFrancesco, Nicholas [1]
Sent: Monday, July 01, 2013 1:37 PM To: Simpson, Lisa A.:(GenCo-Nuc)
Cc: Gullott, David M.:(GenCo-Nuc); Bowen, Jeremy
Subject:
Request for Additional Information Re: Review of LaSalle Unit 1 Evaluation of Reactor Vessel Capsule Surveillance (MF0500)
Ms. Lisa Simpson, In response to Exelon Generation Company, LLC, letter dated January 10, 2013 (Agencywide Document Access and Management System [ADAMS] No. ML13011A005), the staff is reviewing capsule surveillance requirements pursuant to 10 CFR 50 Appendix H, Reactor Vessel Material Surveillance Program Requirements. The following questions relate to clarifying interim actions taken prior to the planned submittal of license amendment revising Technical Specifications associated with Pressure-Temperature (P-T) limit curves.
Q 1.
The NRC staff understands that the current P-T limit curves have been re-evaluated to extend their applicability to 26.5 EFPY using the RAMA fluence methodology to re-evaluate the neutron fluence on which the P-T limit curves are based. NRC-approved Boiling Water Reactor Vessel Internals Project (BWRVIP) Licensing Topical Reports BWRVIP-114, -115, -117, and -121 comprise the NRC-approved methodology. The NRC staff SE approving this methodology imposes the following conditions of approval:
- 1) To apply the RAMA methodology to plant groups which have geometries that are different than the cited BWR-IVs, at least one plant-specific capsule dosimetry analysis must be provided to quantify the potential presence of a bias and assure that the uncertainty is within the RG 1.190 limits, and
- 2) Justification is necessary for a specific application based on geometrical similarity to an analyzed core, core shroud, and RPV geometry. That is, a licensee who wishes to apply the 1
RAMA methodology for the calculation of RPV neutron fluence must reference, or provide, an analysis of at least one surveillance capsule from an RPV with a similar geometry.
The approved methodology was originally limited to calculation of fluence for BWR-IV plants. The use has subsequently been expanded to additional plants including those of the BWR-III and Westinghouse PWR designs, based on submittal and NRC staff review and approval of appropriate qualification data.
Please demonstrate that this condition is satisfied for LSCS.
Q 2.
The 26.5 EFPY applicability period that is claimed for the current PT curves assumes the implementation of an anticipated power uprate, according to Exelons January 10, 2013, letter.
Explain how the fluence re-evaluation addresses the effects of this uprate.
Q 3.
Given the delay in reviewing the withdrawn reactor vessel surveillance capsule from February 12, 2010, please confirm that Unit 1 P-T limits operability evaluation was completed prior to reaching 21 EFPY (understood as prior to the fluence re-evaluation) for Unit 1.
A copy of this email will be placed in ADAMS as an official record.
Please advise if a clarification call is needed to support a response to the questions.
Sincerely, Nick DiFrancesco Project Manager - LaSalle and Power Uprate Program U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Division of Operating Reactor Licensing nicholas.difrancesco@nrc.gov l Tel: (301) 415-1115 2
Hearing Identifier: NRR_PMDA Email Number: 890 Mail Envelope Properties (B89765C774C10B4992D8F5806597A58A015E2223)
Subject:
Responses to Questions Regarding Review of LaSalle Unit 1 Evaluation of Reactor Vessel Capsule Surveillance (MF0500)
Sent Date: 7/30/2013 2:51:41 PM Received Date: 7/30/2013 2:51:46 PM From: Lisa.Simpson@exeloncorp.com Created By: Lisa.Simpson@exeloncorp.com Recipients:
"David.Gullott@exeloncorp.com" <David.Gullott@exeloncorp.com>
Tracking Status: None "Bowen, Jeremy" <Jeremy.Bowen@nrc.gov>
Tracking Status: None "DiFrancesco, Nicholas" <Nicholas.DiFrancesco@nrc.gov>
Tracking Status: None Post Office: cccmsxch13.energy.power.corp Files Size Date & Time MESSAGE 3963 7/30/2013 2:51:46 PM Responses to NRC Questions on ISP letter.docx 24227 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
NRC Questions on EGC letter RA13-002, Evaluation of LaSalle County Station Unit 1 120° Capsule Surveillance Data Question 1 The NRC staff understands that the current P-T limit curves have been re-evaluated to extend their applicability to 26.5 EFPY using the RAMA fluence methodology to re-evaluate the neutron fluence on which the P-T limit curves are based. NRC-approved Boiling Water Reactor Vessel Internals Project (BWRVIP) Licensing Topical Reports BWRVIP-114, -115, -117, and -121 comprise the NRC-approved methodology. The NRC staff SE approving this methodology imposes the following conditions of approval:
- 1) To apply the RAMA methodology to plant groups which have geometries that are different than the cited BWR-IVs, at least one plant-specific capsule dosimetry analysis must be provided to quantify the potential presence of a bias and assure that the uncertainty is within the RG 1.190 limits, and
- 2) Justification is necessary for a specific application based on geometrical similarity to an analyzed core, core shroud, and RPV geometry. That is, a licensee who wishes to apply the RAMA methodology for the calculation of RPV neutron fluence must reference, or provide, an analysis of at least one surveillance capsule from an RPV with a similar geometry.
The approved methodology was originally limited to calculation of fluence for BWR-IV plants. The use has subsequently been expanded to additional plants including those of the BWR-III and Westinghouse PWR designs, based on submittal and NRC staff review and approval of appropriate qualification data. Please demonstrate that this condition is satisfied for LSCS.
EGC Response to Question 1 Reference 1: BWRVIP Letter 2011-206 from David Czufin (Chairman, BWR Vessel and Internals Project) to Andrew Hon (U. S. Nuclear Regulatory Commission),
"Project No. 704 - BWRVIP-250NP: BWR Vessel and Internals Project, Testing and Evaluation of the LaSalle Unit 1 120° Surveillance Capsule,"
dated November 18, 2011 (ADAMS Accession No. ML11326A290)
Reference 2: BWRVIP Letter 2008-235 from Rick Libra (Chairman, BWR Vessel and Internals Project) to Vanice Perin (U. S. Nuclear Regulatory Commission),
Project No. 704 - BWRVIP-189: BWR Vessel and Internals Project, Evaluation of RAMA Fluence Methodology Calculational Uncertainty, dated August 28, 2008 (ADAMS Accession No. ML082480312)
The current LaSalle Unit 1 P-T limit curves are valid until 32 EFPY, and the station has used the RAMA fluence methodology to limit their applicability to 26.5 EFPY.
The NRC imposed two conditions for the use of the RAMA fluence methodology, and the LaSalle method for satisfying the conditions is discussed below.
The cited BWR-IV plants were Hope Creek and Susquehanna. The reactor internal geometries of these two plants were compared to the geometry of LaSalle Unit 1, and the geometries were identical. Specifically, Susquehanna, Hope Creek and LaSalle all
contain 764 fuel assemblies, all have a shroud with an outside diameter of 207 inches, and have 20 jet pumps in the downcomer area.
In addition to the identical geometries, at least one plant-specific capsule dosimetry analysis exists to quantify the potential bias and confirm that the uncertainty is within the RG 1.190 limits. The Integrated Surveillance Program (ISP) data from the LaSalle Unit 1 ISP capsule at 120° is contained in EPRI Technical Report BWRVIP-250NP, Testing and Evaluation of the LaSalle Unit 1 120°Surveillance Capsule. BWRVIP-250NP was transmitted to the NRC in the Reference 1 letter. Section 3.5.3 of this report, Combined Uncertainty, determined that the combined uncertainty (1) for the LaSalle capsule fluence is 10.0% with energy > 1.0 MeV. The combined uncertainty limit prescribed in RG1.190 is 20%. This section of the report also notes that the bias terms are less than their constituent uncertainty values, concluding that no statistically significant bias exists. Therefore, since the LaSalle geometry is identical to the BWR-IV plants, no bias term is necessary for LaSalle, and the LaSalle uncertainty is within the limit of the RG, the two NRC conditions for use of the RAMA code are satisfied.
Additionally, EPRI prepared Technical Report BWRVIP-189, BWR Vessel and Internals Project, Evaluation of RAMA Fluence Methodology Calculational Uncertainty. BWRVIP-189 was transmitted to the NRC in the Reference 2 letter. The report states that compliance with the provisions of Regulatory Guide 1.190 requires that RAMA be qualified using comparisons to plant-specific measurement data and industry benchmark problems. Data comparisons from several plant specific surveillance capsule and simulator benchmark problems have been performed in order to qualify RAMA for use in RPV fluence evaluations for BWRs. The plant and benchmark data that have been evaluated with RAMA are presented in the report, and the calculated-to-measured (C/M) ratio for various BWR class reactors is reported as 0.98 with a standard deviation of
+/-8%, indicating no significant variation in the predictive capability of RAMA for the various BWR classes. Comparisons of the predicted activations to measured values from the Pool Critical Assembly Pressure Vessel Facility and the VENUS-3 vessel simulation benchmarks results in a C/M ratio of 1.03 and a standard deviation of +/-5%.
BWRVIP-189 concludes that the RAMA fluence evaluations do not have a statistically significant bias. The overall calculational uncertainty of the RAMA fluence evaluations is on the order of 9% to 11%, depending upon the plant-specific analytic uncertainty component. The overall calculational uncertainty is well within the uncertainty guidelines provided in Regulatory Guide 1.190.
Question 2 The 26.5 EFPY applicability period that is claimed for the current PT curves assumes the implementation of an anticipated power uprate, according to Exelons January 10, 2013, letter. Explain how the fluence re-evaluation addresses the effects of this uprate.
EGC Response to Question 2 During the time period in which the LaSalle 120° surveillance data was being analyzed, EGC was performing the analyses necessary to support a possible Extended Power Uprate (EPU). Included in the scope of the EPU tasks were evaluations of the LaSalle Unit 1 EPU flux and the impact of the EPU on the LaSalle Unit 1 PT curves. When the ISP report was issued, this information was shared with the EPU team for evaluation.
Rather than revise the PT curves only due to the ISP results, and then revise the PT curves again to incorporate the EPU flux, it was decided to combine the ISP results and the EPU flux in one PT curve revision. This would result in conservative PT curves with respect to only the ISP data, and eliminate one revision and review of the PT curves.
The Current Licensed Thermal Power (CLTP) for LaSalle Unit 1 is 3546 MWt, and the proposed EPU was 3988 MWt. The proposed EPU was estimated to be implemented on Unit 1 at the start of the 17th operating cycle, or in March of 2016. To minimize the shift in the PT curves, the fluence calculated using the RAMA code was used for the first 13 cycles of operation, corresponding to the time the 120° surveillance capsule was removed from the Unit 1 reactor. Then the currently licensed General Electric-Hitachi (GEH) flux methodology was used to calculate the fluence between the 13th and 17th operating cycles, and then EPU fluence was calculated from the beginning of the 17th operating cycle until 32 EFPY.
On June 11, 2013, EGC announced the cancellation of its EPU project for LaSalle, but the conservative EPU flux input into the CLTP PT curve development will not be changed. Including the EPU fluence in the CLTP calculation is conservative in that it yields a higher shift in the Adjusted Reference Temperature for the limiting material.
Question 3 Given the delay in reviewing the withdrawn reactor vessel surveillance capsule from February 12, 2010, please confirm that Unit 1 P-T limits operability evaluation was completed prior to reaching 21 EFPY (understood as prior to the fluence re-evaluation) for Unit 1.
EGC Response to Question 3 A limited timeline of events is provided below:
- The surveillance capsule was removed from the reactor on February 12, 2010.
- BWRVIP-250NP provided the ISP test results in January 2012.
- The revised ART table, using the revised fluence and BWRVIP-250NP data, was completed in October 2012.
- Initially determined current PT curves expiration dates:
o Using only GEH fluence for 32 EFPY, the current curves would expire in 21.0 Effective Full Power Years (EFPY);
o Using RAMA fluence for cycles 1-13 and GEH fluence for the remaining 32 EFPY, the current curves would expire in 27.0 EFPY; and o Using RAMA fluence for cycles 1-13, GEH fluence up until the planned EPU, and using the GEH fluence at EPU conditions for the remaining 32 EFPY, the current curves would expire at 26.5 EFPY.
At this same approximate time, EGC announced that the implementation of the LaSalle EPU would be deferred beyond the original schedule, and since the fluence calculation is a time-based calculation, the fluence calculation was revised to reflect the EPU deferral.
- The corrected ART values reflecting deferral of EPU were issued in December 2012, and later in the same month the revised PT curves based on the revised fluence and ART calculations were completed.
- In January 2013, the site completed the owners review of the new PT curves and confirmed that the report accurately incorporated the appropriate design inputs, and confirmed that based on the results, the current curves were non-conservative. At this point, the Operability Evaluation process was entered, because the site had confirmed that the curves are non-conservative. An issue report was initiated to communicate the facts, an Operability Evaluation was initiated, and a letter sent to the NRC.
- On January 1, 2013, LaSalle Unit 1 had operated for approximately 21.59 EFPY.
So at the time the site confirmed that the PT curves were non-conservative, Unit 1 had operated for greater than 21 EFPY. Note however, that the 21.0 EPFY limit for the current curves was based on the current power level, and without using the RAMA fluence. Removing conservatism in the fluence calculation by using RAMA for cycles 1-13 provides a more realistic estimate of fluence, and can be used to support operability. Using the more realistic fluence, the current curves do not expire until 27.0 EFPY. To efficiently use resources in the future, the final fluence calculation is based on the proposed EPU fluence, the RAMA fluence for cycles 1-13, and the GEH fluence for up to 32 EFPY. Although EGC has determined to cancel the EPU project for LaSalle, the use of the EPU fluence is conservative. Using the EPU fluence, the current LaSalle Unit 1 curves expire at 26.5 EFPY.
LaSalle is currently processing revised PT curves for submittal to the NRC for review and approval. Although EGC has decided not to implement the EPU on LaSalle Unit 1, the conservative EPU flux input into the CLTP PT curve development will not be changed. Including the EPU fluence in the CLTP calculation is conservative in that it yields a higher shift in the Adjusted Reference Temperature for the limiting material, and yields higher PT limits.