ML14121A106
| ML14121A106 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/12/2014 |
| From: | John Lubinski Division of License Renewal |
| To: | Hackett E Advisory Committee on Reactor Safeguards |
| Daily J, 415-3873 | |
| References | |
| Download: ML14121A106 (6) | |
Text
May 12, 2014 MEMORANDUM TO: Edwin M. Hackett, Executive Director Advisory Committee on Reactor Safeguards FROM: John Lubinski, Director /RA/
Division of License Renewal Office of Nuclear Reactor Regulation
SUBJECT:
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS REVIEW OF THE CALLAWAY NUCLEAR PLANT LICENSE RENEWAL APPLICATION - SAFETY EVALUATION REPORT The purpose of this memorandum is to brief the Advisory Committee on Reactor Safeguards (ACRS) on the activities accomplished since the staff issued its Safety Evaluation Report with Open Items Related to the License Renewal of Callaway Plant, Unit 1 (SEROI) (ADAMS Accession No. ML13086A224), dated April 23, 2013, in view of the upcoming ACRS Subcommittee meeting for Callaway Nuclear Plant, Unit 1 (Callaway). The SEROI contains five open items, which will be discussed below.
Background
By letter dated December 15, 2011, Union Electric Company, (Ameren Missouri or the applicant), submitted a license renewal application (LRA) in accordance with Title 10 of the Code of Federal Regulations (10 CFR) Part 54, Requirements for Renewal of Operating Licenses for Nuclear Power Plants. Ameren Missouri requested renewal of the Callaway operating license (operating license NPF-30) for a period of 20 years beyond the current expiration at midnight, October 18, 2024.
The original ACRS Subcommittee meeting was scheduled for May 22, 2013. However, by letter dated May 10, 2013, Ameren Missouri requested postponement of the meeting to a later date due to delays in Callaways on-going refueling outage and the need to focus on its completion.
As a result, the schedule was changed to dates of to be determined.
CONTACT: J. Daily, NRR/DLR (301) 415-3873
E. Hackett By letter dated November 4, 2013, the staff completed its assessment of the challenges presented during Callaway's refueling outage and determined that there were no impacts on the license renewal safety review. However, the staff noted that to support a presentation to the ACRS Subcommittee, Ameren Missouri must provide complete responses to the staffs remaining requests for additional information (RAIs) in a timely manner. The RAIs pertained to three of the five open items from the SEROI: (1) National Fire Protection Association (NFPA) 805 gap analysis; (2) Reactor Vessel Internals Program action items 1, 7, 8, and the operating experience regarding clevis insert bolts; and (3) internal surfaces and coatings operating experience.
During the period from May 2013 until the present, the staff has continued its reviews of the open items and other emergent issues. The staff concludes that the applicant has proposed acceptable resolutions for each of the issues. The staff will present these to the ACRS Subcommittee and document the resolutions in the final SER.
Summary of SER Open Items On April 23, 2013, the staff issued an SEROI which contains five open items.
Open Item 2.3.3.20-1, Scoping of Fire Protection SSCs. This open item consists of two parts:
a) the staffs questions regarding exclusion of some fire suppression systems, structures, and components (SSCs) in the auxiliary boiler room and certain parts of the turbine building; and b) what impacts would be caused by the applicants conversion from traditional fire protection program to an NFPA 805-based program.
The applicant subsequently submitted RAI responses and supplemental information. The staff will present this open item and its review status to the ACRS Subcommittee. Pending completion of its review, the staff will close the open item and document it in the final SER.
Final closure will be presented to the ACRS full committee.
Open Item B2.1.3-1, Reactor Head Closure Studs. On multiple occasions, beginning with Callaways first refueling outage, the applicant had difficulties inserting/removing reactor vessel (RV) head closure studs. Multiple closure studs have become stuck at one time or another.
Because of these difficulties, some of the corresponding RV flange hole threads were damaged (10 of the 54 total). In addition, one stud (No. 18) became stuck partially inserted during the 1996 refueling outage, with the thread engagement being about 2.4 inches less than full engagement. Ameren Missouri performed engineering evaluations and determined that there was sufficient thread engagement to fully tension the partially inserted stud. The staff was concerned, based upon Callaways plant-specific operating experience, that the applicants proposed aging management program (AMP) may not be adequate to manage degradation of the flange hole threads and may not be adequate to detect and manage future wear or loss of material on closure stud No.18.
E. Hackett The applicant proposed two commitments to be completed prior to the period of extended operation (PEO) in order to resolve the staffs concerns: (a) the first is associated with inspection of the locations with the most missing threads; and (b) the second is associated with removal of stud No.18. The staffs position is that completion of the activities in the proposed commitments is necessary to make a determination regarding the adequacy of the applicants Reactor Head Closure Stud AMP to effectively manage the effects of aging during the PEO.
The staff will present this open item and its review status to the ACRS Subcommittee. Pending completion of its review, the staff will close the open item and document it in the final SER.
Final closure will be presented to the ACRS full committee.
Open Item B2.1.6-1, Materials Reliability Program 227-A Report Applicant/Licensee Action Items. This issue concerns the applicants [Pressurized-Water Reactor (PWR)] Vessel Internals Program and conformance with industry-recommended inspection and evaluation guidelines for PWR design reactor vessel internal components in Materials Reliability Program 227-A (MRP 227-A), PWR Reactor Internals Inspection and Evaluation Guideline. The applicants plant-specific responses to action items, conditions, and limitations identified in the NRC Safety Evaluation (December 16, 2011) for the MRP are covered by this issue. While the applicants AMP, as originally proposed in the LRA, did not address the applicable action items, Ameren Missouri supplied responses to staff RAIs that allowed for resolution of most of the items. The staff found that additional information was required in order to resolve four portions of the MRPs applicant/licensee action items (A/LAIs) A/LAIs 1, 5, 7, and 8 (subpart 5). The applicant also needed to address an industry operating experience issue with clevis insert bolt cracking and assess whether a change to the frequency for performing ASME inservice visual inspections of the clevis insert bolts will be needed at Callaway.
During the period May 2013 through April 2014, Ameren Missouri submitted several RAI responses and additional, supplemental information to cover these items. The staff has reviewed the applicants responses to these A/LAIs and the basis for addressing the applicable clevis insert bolt operating experience and has found them to be acceptable.
The staff will present this open item and its review status to the ACRS Subcommittee. Pending completion of its review, the staff will close the open item and document it in the final SER.
Final closure will be presented to the ACRS full committee.
Open Item B2.1.20-1, ASME Code Class 1 Small-Bore Socket Welds. Ameren Missouri originally stated in its LRA that Callaway had 19 Class 1 small-bore socket welds of ASME Code Class 1 piping of from 1 to 4 inches nominal pipe size. Based on experience with previous LRA reviews of similar PWRs, the staff noted that this population seemed considerably smaller than the typical quantity of in-scope socket welds; therefore, the staff requested the applicant to explain the reason for this low count. The applicant conducted a recount and indicated that there were actually 23 Class 1 small-bore socket welds within the scope of the One-Time Inspection of ASME Code Class 1 Small-Bore Piping Program; it also provided an amendment to the LRA, accordingly. Noting that even this new quantity of 23 socket welds was still a considerably low number, the staff continued to pursue the issue of ascertaining the correct number of small-bore welds at Callaway. Subsequent revisions by the applicant raised that count to 77 and then 80 small-bore socket welds. The staff was also concerned that Ameren Missouri may have had errors in its evaluation processes.
E. Hackett In responses dated April 16, 2013, and August 2, 2013, the applicant explained that its erroneous counts occurred due to incorrect queries of its database, it entered the issue into its corrective action program, and it identified that the error also occurred when counting the in-scope small-bore butt weld population. The applicant also stated that it conducted thorough re-verifications and supplemented its searches with drawing reviews to arrive at final within-scope counts of 80 small-bore socket welds and 343 small-bore butt welds. The staff found the applicants responses acceptable.
The staff will present this open item and its review status to the ACRS Subcommittee. Pending completion of its review, the staff will close the open item and document it in the final SER.
Final closure will be presented to the ACRS full committee.
Open Item 4.3.4-1, Effects of the Reactor Coolant System Environment on Fatigue Life of Piping and Components. As part of its evaluation of the effects of a reactor water environment on the fatigue life [environmentally-assisted fatigue (EAF)] of piping and components, Ameren Missouri performed a review of all applicable reactor coolant pressure boundary components with a Class 1 fatigue analysis to show that the locations identified in staff guidance (NUREG/CR-6260, Application of NUREG/CR-5999 Interim Fatigue Curves to Selected Nuclear Power Plant Components) are bounding. In addition, the applicant stated that it reviewed its components to identify whether there were other, more limiting plant-specific components to be evaluated for EAF. However, the staff identified additional information that was required on the applicants approach taken in screening EAF of piping and components.
The applicant stated that it performed a systematic review to determine the locations to be monitored by the Fatigue Monitoring Program for EAF. This review involved ranking and comparisons of environmental fatigue usage. However, in justifying its review, Ameren Missouri did not demonstrate that its methodology to rank or compare EAF cumulative usage factors (CUFs) was appropriate and conservative. The staff identified questions in the applicants underlying assumptions which required additional information about the consistency in the level of rigor; questions on how EAF CUFs were compared that were calculated with or without lumped transients; and questions on the validity of comparisons of EAF CUFs across multiple thermal zones.
Ameren Missouris responses in April, 2013, and August, 2013, provided additional information regarding these assumptions and demonstrated that its evaluations for screening and ranking EAF CUFs were sufficiently rigorous and appropriate for Callaway. In addition, the applicant enhanced its Fatigue Monitoring Program to ensure that EAF-susceptible locations are updated appropriately and remain bounded consistent with any updated or refined analysis. Therefore, the staff has concluded that the applicant has justified its approach and the locations that require monitoring for EAF of the reactor coolant pressure boundary during the PEO.
The staff will present this open item and its review status to the ACRS Subcommittee. Pending completion of its review, the staff will close the open item and document it in the final SER.
Final closure will be presented to the ACRS full committee.
E. Hackett Emergent Issues Since the issuance of the SEROI in April 2013, several emergent issues arose which also necessitated the staffs review. In each case the staff issued RAIs and will address the resolutions in the final SER.
Fire water system alternative testing and inspection proposals. LR-ISG-2012-02, Aging Management of Internal Surfaces, Fire Water Systems, Atmospheric Storage Tanks, and Corrosion Under Insulation, which was issued to address flow blockage issues identified in the industry, added recommended inspections and tests from industry standards and augmented inspections for wetted but normally dry piping that cannot be drained to the GALL Reports Fire Water System AMP. Ameren Missouri is in the process of responding to clarification questions from the staff to ensure that its testing and inspection protocols will effectively manage this aging effect for fire water system piping. The staff will present this issue to the ACRS Subcommittee and will document the resolution in the final SER.
Effective aging management for bolting associated with submerged pumps. Ameren Missouris recent identification of the need to manage aging for bolting associated with submerged pumps in several systems raised an issue with how to manage aging effects for normally submerged, inaccessible bolted connections. The applicant is in process of responding to clarification questions from the staff to ensure clarity on what parameters would be monitored, what inspection techniques would be used, and what the frequency of those inspections would be.
The staff will present this issue to the ACRS Subcommittee and will document the resolution in the final SER.
Clarification of issues related to aging management of mechanical components with loss of coating integrity. License renewal interim staff guidance, LR-ISG-2013-01, Aging Management of Loss of Coating Integrity for Internal Coatings on In-Scope Piping, Piping Components, Heat Exchangers, and Tanks, and an associated new AMP were issued to address loss of coating integrity issues identified in the industry. Ameren Missouri is in the process of responding to clarification questions from the staff to ensure its AMPs can adequately manage this new aging effect. The staff will present this issue to the ACRS Subcommittee and will document the resolution in the final SER.
Conclusion As discussed above, all of the open items and the emergent issues identified to-date have been discussed with the applicant. The staff concludes that Ameren Missouri has proposed acceptable resolutions for these issues. The applicant will formally submit any remaining requested information in a timely manner to support closure. The staff will present these issues to the ACRS and document the resolutions in the final SER. The staff recommends that the ACRS Subcommittee meeting be held as currently planned.
If you have any questions, please contact John Daily, the license renewal Safety Project Manager for this application, at 301-415-3873 or by email at John.Daily@NRC.Gov.
Docket No. 50-483
ML14121A106 *concurred via email OFFICE LA:DLR* PM:DLR:RPB1 BC:DRA:AFPB BC:DLR:RARB BC:DLR:RPB1 D:DLR NAME IKing JDaily JRobinson (AKlein DMorey YDiaz-Sanabria JLubinski for)
DATE 5/1/14 5/5/14 5/5/14 5/6/14 5/6/14 5/12/14