ML11343A438
| ML11343A438 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/15/2011 |
| From: | Robert Kuntz License Renewal Projects Branch 1 |
| To: | Gallagher M Exelon Generation Co |
| Kuntz R | |
| References | |
| TAC ME6555, TAC ME6556 | |
| Download: ML11343A438 (7) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 December 15, 2011 Mr. Michael P. Gallagher Vice President License Renewal Projects Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348 SUB~IECT:
REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE LIMERICK GENERATING STATION LICENSE RENEWAL APPLICATION (TAC NOS. ME6555, ME6556)
Dear Mr. Gallagher:
By letter dated June 22,2011, Exelon Generation Company, LLC submitted an application pursuant to Title 10 of the Code of Federal Regulations Part 54, to renew the operating licenses for Limerick Generating Station, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review.
These requests for additional information were discussed with Christopher Wilson and a mutually agreeable date for the response is within 45 days from the date of this letter. If you have any questions, please contact me at (301) 415-3733 or bye-mail at Robert. Kuntz@nrc.gov.
Sincerely, License Renewal Branch RPB 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos: 50-352 and 50-353
Enclosure:
Requests for Additional Information cc w/encl: Listserv Robert. Kun:'~~roject Manager
LIMERICK GENERATING STATION LICENSE RENEWAL APPLICATION REQUESTS FOR ADDITIONAL INFORMATION RAI4.2.6-1
Background
License renewal application (LRA) Table 4.2.6-1 (page 4-50) summarizes the pertinent parameters for Limerick Generating Station (LGS), Units 1 and 2 to estimate the probability of failure for the circumferential welds.
The values for fluence at OT and shift in Reference Temperature ART NDT (OF) (without margin) do not agree with the corresponding values found in Tables 4.2.1-1 and 4.2.1-3 for fluence and Tables 4.2.3-1 and 4.2.3-3 for the temperature shift.
Request Justify the fluence values in LRA Tables 4.2.3-1 and 4.2.3-3 in light of the apparent discrepancy discussed above.
RAI4.6.5-1
Background
LRA Section 4.6.5 describes the time-limiting aging analysis (TLAA) for the jet pump auxiliary spring wedge assemblies. The LRA states that the original design analysis included an evaluation for relaxation of bolt preload due to integrated neutron fluence over 40 years. The applicant determined that the analysis remains valid for the period of extended operation based on the use of Radiation Analysis Modeling Application (RAMA) fluence projections for the jet pump riser brace weld, RS-9 location, which are bounding for all locations on the jet pump, including where the auxiliary spring wedge assembly is installed. The LRA states that the RS-9 weld attaches the riser brace to the riser pipe, located at approximately the 304 inch elevation, while the auxiliary spring wedge assembly is located at approximately the 230 inch elevation, where the fluence values are lower.
The applicant did not provide sufficient information to describe how it determined the existing analysis is valid for the period of extended operation. Specifically, the staffs review identified the following issues.
(a) The RS-9 weld is located on the riser brace, which, according to LRA Table 2.3.1-3, is part of the jet pump assembly of the reactor vessel internals. The NRC staff approved use of RAMA for boiling water reactor pressure vessel fluence projection applications, but use of RAMA for reactor internals applications is subject to NRC staff review on a ENCLOSURE
- 2 case-by-case basis. Therefore, it is not clear why use of RAMA is appropriate for fluence projections on the RS-9 weld, because it is part of the reactor vessel internals, not the reactor pressure vessel.
(b) It's not clear why the fluence values at the location of the auxiliary spring wedge assembly are lower than the fluence values at the location of the RS-9 weld.
Request
- 2. Justify why the fluence values at the RS-9 weld location are bounding for all locations on the jet pump, including the location lower on the jet pump where the auxiliary spring wedge assembly is installed.
RAI4.S.S-1
Background
LRA Section 4.6.6 describes the TLAA evaluation of the jet pump restrainer bracket pad repair clamps. The LRA states that the original design analysis included an evaluation for the decrease in the clamping bolts' preload due to thermal and radiation-induced relaxation over 40 years. The LRA projected this analysis to the end of the period of extended operation. The projection is based on the assumption that the bolt preload will decrease 5 percent over 20 additional years of operation, the same decrease predicted over 40 years in the original design analysis.
The projection of this analysis relies on the assumption that the preload will decrease by 5 percent over an additional 20 years of operation; however, the LRA did not justify this assumption.
Request Justify the assumption that the bolt preload will decrease by 5 percent over an additional 20 years of operation as a result of thermal and radiation-induced relaxation.
RAI4.S.S-2
Background
LRA Section 4.6.6 describes the applicant's TLAA evaluation of the jet pump restrainer bracket pad repair clamps. The LRA states that the original design analysis included an evaluation for fatigue, but it was determined that the fatigue usage would be insignificant because the stress amplitude for cyclic loads was well below the American Society of Mechanical Engineers (ASME) Code stress limit of 13,600 psi for 10 11 cycles and less than the 10,000 psi lower limit considered for flow-induced vibration stress cycles.
- 3 The staff reviewed LRA Section 4.6.6 and determined that it includes separate analyses involving two aging effects: (1) decrease in preload due to thermal and radiation-induced relaxation, and (2) fatigue. The applicant provided one disposition for LRA Section 4.6.6, stating that it projected the analysis to the end of the period of extended operation. However, for the evaluation of fatigue, it is not clear how the applicant projected the analysis because it did not describe changes to any parameters of the original analysis. Therefore, for its analysis of fatigue for the jet pump restrainer bracket pad repair clamps, the applicant has not provided a disposition in accordance with 10 CFR 54.21 (c)(1).
Request For the fatigue analysis of the jet pump restrainer bracket pad repair clamps, provide one of the demonstrations required by 10 CFR 54.21(c)(1):
If demonstrating that the analysis remains valid for the period of extended operation in accordance with 10 CFR 54.21 (c)(1 )(i), describe and justify why the analysis is bounding during the period of extended operation. Include in this demonstration the applicable materials and their properties, the value of the stress amplitude for cyclic loads, and the specific sources of the 13,600 and 10,000 psi stress limits to which the stress amplitude was compared.
If demonstrating that the analysis has been projected to the end of the extended period of operation in accordance with 10 CFR 54.21 (c)(1 )(ii), describe and justify how the original analysis was revised.
If demonstrating that the effects of aging on the intended function(s) will be adequately managed for the period of extended operation in accordance with 10 CFR 54.21 (c)(1)(iii), provide an aging management program and justify how it adequately manages fatigue.
RAI4.6.6-3
Background
LRA Section 4.6.6 describes the TLAA evaluation of the jet pump restrainer bracket pad repair clamps, and LRA Section A.4.6.6 provides a summary description of this TLAA for the UFSAR supplement. As discussed in RAI 4.6.6-2, the staff determined that LRA Section 4.6.6 describes separate analyses involving two aging effects: (1) decrease in preload due to thermal and radiation-induced relaxation, and (2) fatigue.
LRA Section A.4.6.6 describes the analysis for the decrease in preload, but it does not address the analysis for fatigue.
-4 Request Consistent with the response to RAI 4.6.6-2, provide for the UFSAR supplement a summary description of the TLAA evaluation for fatigue of the jet pump restrainer bracket pad repair clamps.
RAI4.6.9-1
Background
LRA Section 4.6.9 describes the TLAA evaluation of the jet pump slip joint repair clamps, which are subject to a loss of preload due to neutron fluence. The LRA states that the loss of preload will be managed through periodic inspections under the reactor vessel internals program. LRA Section 8.2.1.9 describes the BWR vessel internals program as consistent, with enhancements, with GALL Report AMP XI.M9, "BWR Vessel Internals."
The staff reviewed GALL Report AMP XI.M9 and found that this aging management program does not manage loss of preload; therefore, it is not clear how the applicant's BWR vessel internals program will manage this aging effect.
Request Specific to the jet pump slip joint repair clamp components subject to a loss of preload, address the following:
- 1. Describe the parameters that are monitored or inspected to detect the presence and extent of loss of preload. Justify how monitoring or inspecting these parameters will ensure that this aging effect is adequately managed.
- 2. Describe how loss of preload is detected or identified. Include in this description the method or technique, frequency, and timing of inspections, and provide justification, including references to any codes or standards, that these measures are adequate to detect loss of preload before loss of the jet pump slip joint repair clamps' intended function.
- 3. Describe the monitoring and trending activities and justify how they are used to predict the extent and rate of degradation so that corrective or mitigative actions can be taken or so that future inspections will occur before a loss of intended function.
- 4. Describe and justify the acceptance criteria for the jet pump slip joint repair clamp inspections for loss of preload, so that corrective actions are taken before loss of the components' intended function. In addition, describe and justify the corrective actions taken when the acceptance criteria are not met, such that a future recurrence is prevented.
!PM:RPB1 :DLR BC:RPB1 :DLR PM: RPB1 :DLR LA:DLR OFFICE DMorey RKuntz SFigueroa IRKuntz NAME 12113111 DATE 12/15/11 12/12/11 112/12/11
Letter to M. Gallagher from R. Kuntz dated December 15, 2011
SUBJECT:
REQUESTS FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE LIMERICK GENERATING STATION LICENSE RENEWAL APPLICATION (TAC NOS. ME6555, ME6556)
DISTRIBUTION:
E*MAIL:
PUBLIC RidsNrrDlr Resource RKuntz DMorey MSmith,OGC