ML23352A247
| ML23352A247 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/18/2023 |
| From: | Byrd T NRC/NRR/DORL/LPL4 |
| To: | Dewhirst L Nebraska Public Power District (NPPD) |
| Byrd T | |
| References | |
| L-2023-LLR-0035 | |
| Download: ML23352A247 (6) | |
Text
From: Thomas Byrd Sent: Monday, December 18, 2023 1:47 PM To: Dewhirst, Linda R.
Cc: Unruh, Mark E.; Van Der Kamp, David W.
Subject:
Cooper - RAI - Relief Request RC3-02 Drywell Head Inspections (EPID L-2023-LLR-0035)
Attachments: Cooper RAI RC3-02 Relief Request 12132023 EPID L-2023-LLR-0035.pdf On December 13, 2023, the U.S. Nuclear Regulatory Commission (NRC) Staff sent Nebraska Public Power District (the licensee) the draft Request for Additional Information (RAI) identified below. This RAI relates to the Relief Request RC3-02, dated June 27, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23178A273), seeking relief from certain containment inservice inspection (ISI) requirements concerning drywell head bolting in accordance with Title 10 of the Code of Federal Regulations (10 CFR) section 50.55a(g)(5) (iii). The relief request pertains to the visual inspection requirements of the American Society of Mechanical Engineers (ASME) Code Rules for ISI of Nuclear Power Plant components.
The licensee subsequently informed the NRC staff that the information requested was understood and that no additional clarification was necessary. A publicly available version of this final RAI (attached with Draft removed) will be placed in the NRCs ADAMS system. As agreed, please provide a response to this RAI within 38 days of this correspondence or by January 26, 2024.
Thomas Byrd Project Manager - Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Office: (301) 415-3719 From: Thomas Byrd Sent: Wednesday, December 13, 2023 10:48 AM To: Dewhirst, Linda R. <lrdewhi@nppd.com>
Cc: Unruh, Mark E. <m1unruh@nppd.com>; Van Der Kamp, David W. <dwvande@nppd.com>
Subject:
Cooper - Draft RAI - Relief Request RC3-02 Drywell Head Inspections By letter dated June 27, 2023 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML23178A273), Nebraska Public Power District (the licensee) submitted a relief request for Cooper Nuclear Station (Cooper), seeking relief from certain containment inservice inspection (ISI) requirements concerning drywell head bolting in accordance with Title 10 of the Code of Federal Regulations (10 CFR) section 50.55a(g)(5) (iii). The relief request pertains to the visual inspection requirements of the American Society of Mechanical Engineers (ASME) Code Rules for ISI of Nuclear Power Plant components.
The NRC staff reviewed the submittal and determined that additional information, as described in the attached request for additional information (RAI), is required for the staff to complete its review of the application. This RAI is identified as a draft at this time to confirm your understanding of the information that the Nuclear Regulatory (NRC) staff needs to complete the evaluation. Please let me know if you would like to have a call with the NRC staff to clarify this request. If the request for information is understood, please respond to this RAI within 30 days of the date of this request.
Thomas Byrd Project Manager - Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Office: (301) 415-3719
Hearing Identifier: NRR_DRMA Email Number: 2344 Mail Envelope Properties (BLAPR09MB63396465B19EF0BC52F96DC5FA90A)
Subject:
Cooper - RAI - Relief Request RC3-02 Drywell Head Inspections (EPID L-2023-LLR-0035)
Sent Date: 12/18/2023 1:47:19 PM Received Date: 12/18/2023 1:47:00 PM From: Thomas Byrd Created By: Thomas.Byrd@nrc.gov Recipients:
"Unruh, Mark E." <m1unruh@nppd.com>
Tracking Status: None "Van Der Kamp, David W." <dwvande@nppd.com>
Tracking Status: None "Dewhirst, Linda R." <lrdewhi@nppd.com>
Tracking Status: None Post Office: BLAPR09MB6339.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 2945 12/18/2023 1:47:00 PM Cooper RAI RC3-02 Relief Request 12132023 EPID L-2023-LLR-0035.pdf 125546 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
1 REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST RC3-02 ALTERNATIVE EXAMINATION OF BOLTED CONNECTIONS OF DRYWELL SHELL FLANGE NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. 50-298
1.0 INTRODUCTION
By letter dated June 27, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23178A273), Nebraska Public Power District (the licensee) submitted a relief request for Cooper Nuclear Station (Cooper), seeking relief from certain containment inservice inspection (ISI) requirements concerning drywell head bolting in accordance with Title 10 of the Code of Federal Regulations (10 CFR) section 50.55a(g)(5)
(iii). The relief request pertains to the visual inspection requirements of the American Society of Mechanical Engineers (ASME) Code Rules for ISI of Nuclear Power Plant components.
On September 5, 2023 (ML23233A188), the U.S. Nuclear Regulatory Commission (NRC) staff issued an audit plan that conveyed the intent to conduct a regulatory audit to support its review of the subject relief request.
The NRC staff requests the following additional information (RAI) to complete its review of the relief request.
2.0 REGULATORY BASIS In accordance with 10 CFR 50.55a(g)(4), components that are classified as Class MC [metal containment] pressure retaining components and their integral attachments, and components that are classified as Class CC [concrete containment] pressure retaining components and their integral attachments, must meet the requirements set forth in Section XI of the ASME Code, Rules for lnservice Inspection of Nuclear Power Plant Components. The regulations require that all inservice inspection conducted during the first 10-year interval, and subsequent intervals, comply with the requirements in the latest edition and addenda of Section XI of the ASME Code, incorporated by reference into 10 CFR 50.55a(b), on the date 18 months prior to the start of the 10-year interval, subject to the conditions in 10 CFR 50.55a to the extent practical within the limitation of design, geometry, and materials of construction of the components.
3.0 REQUEST FOR ADDITIONAL INFORMATION
RAI-1
Issue Relief Request RC3-02 does not make clear whether the fully examined bolt connections (e.g.,
bolts, washers, and nuts) on the drywell head flange would maintain the leak-tightness and structural integrity if the bolt connections that are not able to be fully visually examined are degraded.
Request Discuss the design analysis or qualitative factors of the containment drywell head bolted connection demonstrating that structural integrity and leak tightness of the drywell is maintained,
2 assuming the bolt connections that could not be examined are degraded (e.g., bolts could not be tightened).
RAI-2
Issue Page 4 of Relief Request RC3-02 states that the drywell head to drywell shell flange joint is tested for leakage at the end of each refueling outage as required by 10 CFR 50, Appendix J.
During a regulatory audit, the licensee discussed the local leak rate test and how the two O-rings at the flange are being pressurized to determine potential leakage.
Request (a) Discuss the test pressure when performing the leak rate test per 10 CFR 50, Appendix J.
(b) Discuss the hold time to determine potential leakage at the drywell closure head flange.
(c) Discuss how the O-rings are being pressurized to determine the leakage of the drywell closure head flange per 10 CFR 50, Appendix J.
(d) If leakage does occur during the leak rate test, discuss the corrective action.
RAI-3
Issue The licensee stated in the submittal that 6 lower spherical washers and 33 nuts were able to be removed, and therefore accessible, for direct VT-1 visual examination. The following requests have to do with ensuring that these 6 lower spherical washers and 33 nuts would provide a reasonable sample that would detect degradation in these components if degradation occurred.
Request (a) Discuss how the six lower spherical washers and 33 nuts that were able to be removed and examined by VT-1 visual examination represent a reasonable sample that would detect degradation in these components if degradation occurred.
(b) Are there any asymmetric load conditions with respect to azimuthal bolting location that could cause certain bolting locations to be at higher stress conditions?
(c) Are there any unique environmental conditions around the drywell closure circumference in the subject bolting regions that could cause general corrosion of the nuts and lower spherical washers?
RAI-4
Issue Relief Request RC3-02 states that best effort remote VT-1 visual examinations were attempted on the remaining nuts and washers that are tack welded in place to the lower side of the drywell shell flange. During a regulatory audit, the licensee stated that underwater cameras were used to examine these remaining tack-welded nuts and washers. Relief Request RC3-02 does not make clear how remote VT-1 visual examinations were performed using underwater cameras and what the bolting reassembly process and requirements are.
Request
3 (a) Describe best effort remote VT-1 visual examinations on these remaining tack-welded nuts and washers using underwater cameras in addition to the 63 percent direct VT-1 visual examinations mentioned in the submittal.
(b) Describe the bolting reassembly process and requirements.
RAI-5
Issue During a regulatory audit, the NRC staff noted that light to heavy rust, flaking, blistering, and peeling with some signs of under-deposit corrosion on the lower spherical tack-welded washers and nuts were identified during the RE32 outage remote VT-1 examinations. In addition, Relief Request RC3-02 does not describe the examination results from direct (although the aggregate percent coverage is summarized in a table) and remote VT-1 examination results, such as cracking, discoloration, wear, pitting, corrosion, gouges, surface discontinuities, dents, and other signs of surface irregularities.
Request (a) Summarize examination results, conclusions, and disposition of non-conformances for direct and remote VT-1 examinations.
(b) Evaluate whether these lower spherical tack-welded and corroded washers and nuts are acceptable.
(c) Evaluate whether these lower spherical tack-welded and corroded washers and nuts will result in loose nuts or bolts that may affect the intended function of the pressure retaining bolting.
RAI-6
Issue Relief Request RC3-02 states that VT-3 examinations of the bolting were conducted on the accessible portions after disassembly as required per the 2001 Edition/2003 Addenda during the previous 2nd ten-year containment inservice inspection interval. During a regulatory audit, the licensee discussed that remote VT-3 examination by using a handheld video exam was also conducted of the nuts and washers that could not be disassembled. In addition, Relief Request RC3-02 does not describe the examination results from direct and remote VT-3 examinations.
Request (a) Summarize examination results, including remote VT-3 inspections on nuts and washers that could not be disassembled, conclusions, and disposition of non-conformances for direct and remote VT-3 examinations.
(b) Describe the bolting reassembly process and requirements.