ML20282A732
| ML20282A732 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 10/27/2020 |
| From: | Jennifer Dixon-Herrity Plant Licensing Branch IV |
| To: | Sawatzke B Energy Northwest |
| Chawla M | |
| References | |
| EPID L-2020-LLR-0035 | |
| Download: ML20282A732 (9) | |
Text
October 27, 2020 Mr. Bradley J. Sawatzke Chief Executive Officer Energy Northwest 76 North Power Plant Loop P.O. Box 968 (Mail Drop 1023)
Richland, WA 99352-0968
SUBJECT:
COLUMBIA GENERATING STATION - PROPOSED ALTERNATIVE REQUEST NO. 4ISI-08 APPLICABLE TO THE FOURTH INSERVICE INSPECTION INTERVAL (EPID L-2020-LLR-0035)
Dear Mr. Sawatzke:
By letter dated February 26, 2020 (Agencywide Documents Access & Management System (ADAMS) Accession No. ML20057E954), Energy Northwest (the licensee), submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code)Section XI requirements at Columbia Generating Station (Columbia). The proposed alternative in Relief Request 4ISI-08 would eliminate the vessel interior examination requirement and redefine ASME Section XI, Division 1, Table IWB-2500-1, Examination Category B-N-1, Item No. B13.10 as an examination of interior welded attachments within the beltline region for the fourth inservice inspection interval at Columbia.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(z)(1), the licensee requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1) and demonstrated that the proposed alternative provides an acceptable level of quality and safety. Therefore, the NRC staff authorizes the use of the proposed alternative in Relief Request 4ISI-08 at Columbia for the remainder of the fourth inservice inspection interval for ASME Section XI, Examination Category B-N-1, Item No. B13.10 and Examination Category B-N-2, Item Nos. B13.20, B13.30, and B13.40.
All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact the Project Manager, Mahesh Chawla at 301-415-8371 or via e-mail at Mahesh.Chawla@nrc.gov.
Sincerely,
/RA/
Jennifer L. Dixon-Herrity, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-397
Enclosure:
Safety Evaluation cc: Listserv
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE RELIEF REQUEST NO. 4ISI-08 FOURTH INSERVICE INSPECTION INTERVAL ENERGY NORTHWEST COLUMBIA GENERATING STATION DOCKET NO. 50-397
1.0 INTRODUCTION
By letter dated February 26, 2020 (Agencywide Documents Access & Management System (ADAMS) Accession No. ML20057E954), Energy Northwest (the licensee), submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to certain American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code)Section XI requirements at Columbia Generating Station (Columbia). The proposed alternative in Relief Request 4ISI-08 would eliminate the vessel interior examination requirement and redefine ASME Section XI, Division 1, Table IWB-2500-1, Examination Category B-N-1, Item No. B13.10 as an examination of interior welded attachments within the beltline region for the fourth inservice inspection (ISI) interval at Columbia.
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(z)(1), the licensee requested to use the proposed alternative on the basis that the alternative provides an acceptable level of quality and safety.
2.0 REGULATION EVALUATION Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), Inservice inspection standards requirement for operating plants, which states, in part, that ASME Code Class 1, 2, and 3 components will meet the requirements, except the design and access provisions and the pre-service examination requirements, set forth in Section XI of the ASME Code.
Section 50.55a(z) of 10 CFR, Alternative to codes and standards requirements, states, in part, that:
Alternatives to the requirements of paragraphs (b) through (h) of [10 CFR 50.55a]
or portions thereof may be used when authorized by the Director, Office of
Nuclear Reactor Regulation.... A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that:
(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety, or (2) Hardship without a compensating increase in quality and safety.
Compliance with the specified requirements... would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request, and for the NRC to authorize, the alternative requested by the licensee.
3.0 TECHNICAL EVLAUATION 3.1 Licensees Proposed Alternative 3.1.1 ASME Code Component Affected The affected components at Columbia belong to Examination Category B-N-1, Interior of Reactor Vessel, under Examination Item No. B13.10, and Examination Category B-N-2, Welded Core Support Structures and Interior Attachments to Reactor Vessel, under Examination Item Nos. B13.20, B13.30, and B13.40.
3.1.2 Applicable Code Edition and Addenda This alternative request applies to the fourth ISI interval, in which the licensee has adopted the 2007 Edition with 2008 Addenda of the ASME Code Section XI as the Code of Record.
3.1.3 Applicable Code Requirements ASME Section XI, Table IWB-2500-1, Examination Category B-N-1, Examination Item No. B13.10 requires a visual examination of accessible areas of the vessel interior.
ASME Section XI, Table IWB-2500-1, Examination Category B-N-2, Examination Item No. B13.20 requires a visual examination of accessible welds of interior attachments within the beltline region.
ASME Section XI, Table IWB-2500-1, Examination Category B-N-2, Examination Item No. B13.30 requires a visual examination of accessible welds of interior attachments beyond the beltline region.
ASME Section XI, Table IWB-2500-1, Examination Category B-N-2, Examination Item No. B13.40 requires a visual examination of accessible surfaces of the core support structure.
3.1.4 Licensees Reason for Request for Alternative The licensee proposed to implement ASME Code Case N-885, Alternative Requirements for Table IWB-2500-1, Examination Category B-N-1, Interior of Reactor Vessel, Category B-N-2, Welded Core Support Structures and Interior Attachments to Reactor Vessels, Category B-N-3, Removable Core Support Structures,Section XI, Division 1, in lieu of ASME Section XI, Division 1, Table IWB-2500-1, Examination Category B-N-1, Item No. B13.10 and Examination Category B-N-2, Item Nos. B13.20, B13.30, and B13.40. This alternative eliminates the VT-3 visual examination of the vessel internal spaces (Item No. B13.10) while retaining the VT-1 examination requirement for the accessible interior attachment welds within the beltline region (Item No. B13.20), the VT-3 visual examination of the interior attachment welds outside the beltline region (Item No. B13.30), and the VT-3 visual examination of the welded core support structure each 10-year ISI interval (Item No. B13.40).
Code Case N-885 redefines the ASME item numbers, but with the exception of the vessel interior (B13.10), it does not alter the components required to be examined, the examination method, or the examination frequency.
3.1.5 Licensees Basis for Use of Alternative The licensee stated, in part, in its submittal that: Adoption of ASME Code Case N-885 provides an acceptable level of quality and safety because: 1) the B-N-1 examinations are for foreign material which is not required for vessel integrity; 2) examination of the vessel cladding is not required to support vessel integrity; 3) alternative guidance and practices are in place to address foreign material and debris in the reactor vessel; and 4) the remaining B-N-2 examinations applicable to Columbia are continued under the Code Case as shown in [the]
comparison table at the end of this section. The licensee provided further discussion for each of these reasons in its submittal.
Examinations for Foreign Material and Debris Are Not Required for Vessel Integrity The licensee stated in its submittal that the purpose of the ASME Section XI Examination Category B-N-1 requirement is to detect foreign material and debris, which is supported by the Table IWB-2500-1, Note 1, stating that these examinations are specific to the accessible spaces above and below the reactor core. The licensee also stated in its submittal that this position is further supported by ASME Interpretation XI-1-95-27, which states that the B-N-1 examination is intended to look for loose or missing parts and debris, but does not include the components within the space. The licensee further stated that the purpose of the current ASME Section XI Examination Category B-N-1, Item No. B13.10 examination is not to address vessel integrity, but to detect foreign material and debris.
Examination of the Vessel Cladding Is Not Required to Support Vessel Integrity The licensee stated in its submittal that early versions of ASME Section XI contained a requirement for cladding examinations under Examination Category B-I-1, but were removed with issuance of the Summer 1976 Addenda. The licensee stated that the visual examination of the accessible spaces above and below the core are not necessary to detect corrosion or cracking of the low-alloy steel vessel. The licensee also stated that relevant cladding degradation mechanisms include general corrosion, localized corrosion, wear, and cracking of the underlying low-alloy steel. Based upon evaluations of industry operating experience, the licensee stated that boiling-water reactors implement various activities to mitigate corrosion,
such as effective hydrogen water chemistry and adherence to industry water chemistry guidelines. The licensee further stated that Columbia has implemented design and operational changes to mitigate thermal fatigue cracking and have calculated reactor vessel integrity assessments in accordance with fracture toughness requirements in 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities.
The licensee stated in its submittal that it conducts other visual and volumetric examinations in and on the reactor vessel that provide opportunity for detecting any adverse conditions at vulnerable regions of cladding. These include other ASME Section XI examinations for each ISI interval, such as Examination Category B-A, B-D, and B-N-2 examinations. The licensee also conducts boiling water reactor vessel and internals project (BWRVIP) examinations, which include reactor pressure vessel attachment welds, core spray piping, jet pumps, shroud support welds, and low pressure coolant injection couplings. The licensee stated that these examinations have found no recordable indications. The licensee further stated that volumetric examinations of the reactor pressure vessel to nozzle welds and nozzle inner radii are conducted in accordance with ASME Section XI, Category B-D requirements, as modified by Columbias Relief Request 4ISI-04, and have found no recordable indications.
Alternative Guidance and Practices Are in Place to Address Foreign Material and Debris in the Reactor Vessel The licensee stated in its submittal that foreign material exclusion guidance and work practices have been implemented throughout the industry to help reduce the amount of foreign objects or debris that may be introduced into the reactor coolant system as a result of human error. The licensee stated, in industry-wide practice, examinations for foreign material in the reactor vessel are carried out through foreign object search and retrieval and core verification maintenance activities performed during every refueling outage. The licensee stated foreign objects and debris are most often identified during routine activities, such as fuel receipt inspection and remote inspection of fuel assemblies as they are offloaded and prior to being reloaded, which makes such examinations under Examination Category B-N-1 redundant.
The licensee stated in its submittal that for Columbia several activities are performed in accordance with industry guidance during each refueling outage prior to fuel movement (reload),
during visual examinations, and during core verification (after reload) that provide the opportunity to detect and remove debris and foreign material that may threaten the fuel. This includes a foreign object search and retrieval activity that is performed prior to vessel closure, a core verification activity that is performed after reload, and vessel internals inspections that are performed each outage in accordance with BWRVIP and ASME inspection requirements.
3.1.6 Duration of Proposed Alternative This request is for the remainder of the fourth ISI interval for Columbia, scheduled to end December 12, 2025.
3.2
NRC Staff Evaluation
The licensee proposed an alternative to implement ASME Code Case N-885 in lieu of ASME Section XI, 2007 Edition with 2008 Addenda, Table IWB-2500, Category B-N-1 and B-N-2 examinations, for the remainder of the fourth 10-year ISI interval.
For Examination Category B-N-1, Examination Item No. B13.10, Code Case N-885 eliminates the visual examination of accessible areas of the vessel interior. The licensee stated in its submittal that this VT-3 visual examination is not needed to ensure the integrity of the vessel and is redundant to other foreign material examinations performed during an outage. The NRC staff agrees that Examination Category B-N-1 is limited to examination for loose or missing parts and debris above and below the reactor core. In its submittal, the licensee discussed the foreign material exclusion guidance and work practices that it implements every refueling outage. The NRC staff finds that these activities will observe the top of the fuel where loose or missing parts and debris accumulate and accomplish the purpose of Examination Category B-N-1 examinations.
The licensee also stated in its submittal that these Examination Category B-N-1 visual inspections are not necessary to detect corrosion or cracking of the reactor vessel cladding.
The licensee discussed the various mitigation activities, reactor vessel integrity assessments, and visual and volumetric examinations that provide opportunities to detect adverse conditions at vulnerable regions of cladding. The licensee stated that these examinations have found no recordable indications. The NRC staff notes that, since the purpose of Examination Category B-N-1 visual inspections are to detect foreign material and debris, expansion of the scope to include accessible regions of the vessel cladding is conservative. With the implementation of its various mitigation activities, reactor vessel integrity assessments, and visual and volumetric examinations, the NRC staff finds that Examination Category B-N-1 visual inspections are not needed to ensure the integrity of the vessel cladding Based on these reasons, the NRC staff finds that the proposed alternative to eliminate the Examination Category B-N-1, Item No. B13.10 examinations provides an acceptable level of quality and safety.
In regard to Examination Category B-N-2, Item Nos B13.20, B13.30, and B13.40, Code Case N-885 redefines the ASME item numbers but, with the exception of the vessel interior, it does not alter the components required to be examined, the examination method, or the examination frequency. However, the licensee stated that it will still retain the current ASME category and item number information in its ISI program plan. There is no change to the scope or frequency of these inspections, and therefore, the staff finds that there is no change to the level of quality and safety regarding these examinations.
The NRC intends to include Code Case N-855 in the proposed Revision 20 of Regulatory Guide 1.147, Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1, as noted in a letter dated January 31, 2020 (ADAMS Accession No. ML20013F353).
4.0 CONCLUSION
As set forth above, the NRC staff determines that the licensee has demonstrated that the proposed alternative provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC staff authorizes the use of proposed alternative 4ISI-08 at Columbia for the remainder of the fourth ISI interval for ASME Section XI, Examination Category B-N-1, Item No. B13.10 and Examination Category B-N-2, Item Nos. B13.20, B13.30, B13.40.
All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Mark Yoo Date: October 27, 2020
- via e-mail OFFICE NRR/DORL/LPL4/PM* NRR/DORL/LPL4/LA*
NRR/DNRL/NVIB/BC*
NRR/DORL/LPL4/BC*
NAME MChawla PBlechman HGonzales JDixon-Herrity DATE 10/27/2020 10/23/2020 09/28/2020 10/27/2020