ML19093B274
| ML19093B274 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/15/2019 |
| From: | Markley M Plant Licensing Branch II |
| To: | Heacock D Virginia Electric & Power Co (VEPCO) |
| Hall J 415-4032 | |
| References | |
| EPID L-2018-LLR-0115 | |
| Download: ML19093B274 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION Mr. Daniel G. Stoddard Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, VA 23060-6711 WASHINGTON, 0.C. 20555-0001 April 15, 2019
SUBJECT:
NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 - INSERVICE INSPECTION ALTERNATIVE REQUESTS N1-15-SPT-001 AND N2-15-SPT-001 (EPID L-2018-LLR-0115)
Dear Mr. Stoddard:
By letter dated August 17, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18235A317), Virginia Electric and Power Company (the licensee) submitted a request for a proposed alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, to the U.S. Nuclear Regulatory Commission (NRC) for the North Anna Power Station (North Anna),
Unit Nos. 1 ahd 2. Pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR), Part 50, Paragraph 55a(z)(2), the licensee requested the NRC to authorize the use of an alternative for the examination of the reactor pressure vessel (RPV) bottom heads. Specifically, the licensee proposed to perform visual examinations of the bottom heads of the reactor vessels with the containment at atmospheric pressure in lieu of the sub-atmospheric pressure required by the ASME Code, on the basis that compliance with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that complying with the ASME Code requirements for performing a visual examination (VT-2) of the bottom of the reactor vessels during the system leakage testing when the containments are at sub-atmospheric conditions would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Additionally, the NRC staff finds that there is reasonable assurance that the proposed alternative will provide effective methods for identifying leakage or degradation at the bottom of the reactor vessels. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the use of alternatives N1-15-SPT-001 and N2-15-SPT-001 at the North Anna Power Station for the fifth 10-year ISi interval for each unit; from May 1, 2019, through April 30, 2029, for Unit No. 1, and from December 14, 2020, through December 13, 2030, for Unit No. 2.
All other requirements of Section XI of the ASME Code for which an alternative was not specifically requested and approved remain applicable, including third party review by the Authorized Nuclear lnservice Inspector.
If you have any questions, please contact the Project Manager, Randy Hall, at 301-415-4032 or via e-mail at Randy.Hall@nrc.gov.
Docket Nos. 50-338 50-339
Enclosure:
Safety Evaluation cc: Listserv Sincerely,
~~fofl Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
1.0 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR ALTERNATIVE NOS. N1-15-SPT-001 AND N2-15-SPT-001 PROPOSED ALTERNATIVE TO REACTOR PRESSURE VESSEL BOTIOM HEAD EXAMINATION REQUIREMENTS VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-338 AND 50-339 INTRODUCTION By letter dated August 17, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18235A317), Virginia Electric and Power Company (Dominion Energy Virginia, the licensee), submitted to the U.S. Nuclear Regulatory Commission (NRC), a proposed alternative to the inservice inspection (ISi} requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) for the examination of the reactor pressure vessel (RPV) bottom heads for the North Anna Power Station (North Anna), Unit Nos. 1 and 2. The licensee proposed to perform visual examinations of the RPV bottom heads with the containment at atmospheric pressure, in lieu of the ASME Code-required sub-atmospheric test pressure, due to the hostile environmental conditions.
Specifically, pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR),
Section 50.55a(z)(2), the licensee requested to use the proposed alternative on the basis that complying with the specified ASME Code requirements would result in hardship and/or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
Adherence to Section XI of the ASME Code is mandated by 10 CFR 50.55a(g)(4), 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 the ASME Code,Section XI.
Paragraph 1 O CFR 50.55a(z) states 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 licensee must demonstrate that: (1) The proposed alternative Enclosure would provide an acceptable level of quality and safety; or (2) Compliance with the specified requirements of this section 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 the use of an alternative and for the NRC to authorize the proposed alternative.
3.0 TECHNICAL EVALUATION
3.1 Components Affected Code Class:
Examination Category:
Item Number:
Component Numbers:
ASME Code,Section XI, Class 1 8-P, "All Pressure Retaining Components" 815.10 Reactor Vessels 1-RC-R-1 and 2-RC-R-1 3.2 Applicable ASME Code Edition The ASME Code of record for North Anna, Unit Nos. 1 and 2, for the fifth ten-year ISi interval is the 2013 Edition of the ASME Code,Section XI.
3.3 ASME Code Requirements The 2013 Edition of the ASME Code,Section XI, Table IWB-2500-1, Examination Category 8-P, Item Number B 15.1 O requires that a visual (VT-2) examination of the bottom of the reactor vessel be performed during the system leakage test in accordance with IWB-5220.
3.4 Reason for Proposed Alternative The licensee provided the following reason for the proposed alternative:
In order to meet the Section XI pressure and temperature requirements for the system leakage test of the reactor vessel, the reactor containment at North Anna Unit 1 is required to be at a sub-atmospheric pressure. Station administrative procedures require that self-contained breathing apparatus be worn for containment entries under these conditions. This requirement significantly complicates the visual (VT-2) examination of the bottom of the reactor vessel during testing. Access to the bottom of the reactor vessel requires that the examiner descend several levels by ladder and navigate a small entrance leading to the reactor vessel. In addition to these physical constraints, the examiner must contend with extreme environmental conditions: elevated air temperatures due to reactor coolant at temperatures above ;:: 350 degrees F and limited air circulation in the vessel cubicle. In addition, the examiner is limited to the approximate 30 minute capacity of the breathing apparatus to accomplish containment entry, the VT-2 examination, and containment exit.
The hardship arises less from the time constraint created by the use of bottled air or the involved radiation levels, but rather more from the environmental conditions that exist during the test. During the test, the reactor coolant system is at the operational temperature of;:: 350 degrees F, and the containment is sub-
3.5 atmospheric. Performing the examination in these conditions is complicated by the following factors:
The need to use a self-contained breathing apparatus (SCBA) with a full-face respirator. The weight of the air bottle is approximately 25 pounds.
Access to the bottom of the reactor vessel under sub-atmospheric conditions requires the examiner to descend several levels by ladders and to navigate a small, 2'-7.25" by 2'-0" hatch wearing the SCBA.
The physical environment that results due to the heat generated by a reactor vessel elevated to a temperature of 2: 350 degrees F coupled with a lack of ventilation.
These factors increase the safety hazard associated with the examination. To
. place the examiner under this increased risk and burden is not justified. This combination of conditions does not exist during refueling outages when the proposed alternative examination would take place. The proposed alternate examination would be performed under conditions that are safer and would allow for a more thorough examination.
Proposed Alternative and Basis for Use The licensee stated the following regarding the proposed alternative and basis for use:
Dominion will continue to monitor leakage on the bottom of the reactor vessel with other surveillance requirements and alarms. The Improved Technical Specifications (ITS) establishes limits on RCS [reactor coolant system] leakage of one gallon per minute of unidentified leakage and no identified leakage in the pressure boundary. To monitor for leakage, the ITS requires that; a) one containment sump (level or discharge flow) monitor, and; b) one containment atmosphere radioactivity monitor (gaseous or particulate) be operable during Modes 1, 2, 3, and 4. In addition, the plant must verify RCS operational leakage is within limits by performance of a RCS inventory balance at a frequency not exceeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The ITS also requires a containment atmosphere radioactivity monitor channel check be performed at a frequency not exceeding 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The incore sump room has a level alarm in the control room requiring operator action. Additionally, a VT-2 examination will be conducted when containment is at atmospheric conditions during each refueling for evidence of boric acid leakage. The proposed alternative will ensure that the overall level of plant quality and safety will not be compromised and eliminates the burden and hardship in performing the Code requirements.
Therefore, Dominion requests approval of this alternative pursuant to the provisions of 10 CFR 50.55a(z)(2).
3.6 Duration of Alternative.
The licensee is proposing to apply the alternatives during the fifth ten-year ISi intervals for North Anna; from May 1, 2019 through April 30, 2029 for Unit No.1 and from December 14, 2020 through December 13, 2030 for Unit No. 2.
- 3. 7
NRC Staff Evaluation
The NRC staff has reviewed the information submitted in alternative requests N1-15-SPT-001 and N2-15-SPT-001, for the fifth 10-year ISi intervals for North Anna Unit Nos. 1 and 2, respectively, pertaining to VT-2 visual examination of the bottom head of the reactor vessel.
The Code of Record requires a VT-2 visual examination be conducted during each system leakage test of the reactor coolant system while containment is at sub-atmospheric pressure. At sub-atmospheric conditions, the reactor coolant is at temperatures exceeding 350°F, which introduces elevated air temperatures in the containment building. The NRC staff finds that the raised temperature, in conjunction with the lack of ventilation for air circulation, constitutes an extreme environment for personnel performing the required examinations. Furthermore, due to the 25-pound breathing apparatus that the examiner is required to wear during these conditions, the NRC staff finds that navigating down several levels by ladders and through a narrow hatch to get to the bottom of the reactor vessel would impose further burden on the examiner.
Therefore, the NRC staff finds that performing the examinations in compliance with the ASME Code requirements would impose a significant burden on the licensee.
The licensee proposed, as an alternative, to perform a VT-2 visual examination for evidence of boric acid leakage and corrosion when the containments are at atmospheric conditions during each refueling outage. In addition, the licensee noted that the ITS (and the North Anna TS) require monitoring of reactor coolant leak rate, atmospheric particulate radioactivity, and containment sump level. The NRC staff finds the boric acid corrosion inspections performed at the end of each operating cycle to be a reliable inspection method for reactor coolant leakage, and that the VT-2 visual examination for evidence of boric acid corrosion conducted during each refueling outage would, therefore, provide reasonable assurance of leak-tight integrity of the RCS pressure boundary. The NRC staff has determined that the licensee's proposed alternative will provide reasonable assurance that inservice leakage greater than allowable limits that could develop at the bottom of the reactor vessel will be detected by at least one of the described monitoring methods in a timely manner and will allow for appropriate corrective action prior to returning the reactors back to service.
Therefore, the NRC staff has determined that the ASME Code-required examinations of the reactor pressure vessel bottom head during system leakage testing at sub-atmospheric containment pressure would result in hardship without a compensating increase in the level of quality and safety.
4.0 CONCLUSION
As set forth above, the NRC staff determines that complying with the ASME Code requirements for performing a VT-2 visual examination of the bottom of the reactor vessels during the system leakage testing when the containments are at sub-atmospheric conditions would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Additionally, the NRC staff finds that there is reasonable assurance that the proposed alternative will provide effective methods for identifying leakage or degradation at the bottom of the reactor vessels. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the use of alternatives N1-15-SPT-001 and N2-15-SPT-001 at the North Anna Power Station for the fifth 10-year ISi interval for each unit; from May 1, 2019, through April 30, 2029, for Unit No. 1, and from December 14, 2020, through December 13, 2030, for Unit No. 2.
All other requirements of Section XI of the ASME Code for which an alternative was not specifically requested and approved remain applicable, including third party review by the Authorized Nuclear lnservice Inspector.
Principal Contributor: A. Young, NRR Date:
~pril 1 5, 2019
ML190936274 OFFICE DORL/LPLll-1 /PM DORL/LPLll-1/LA NAME JRHall KGoldstein DATE 04/10/19 04/04/19 OFFICE DORL/LPL! 1-1 /PM NAME JRHall DATE 04/15/19 DMLR/MPHB/BC(A)*
SCumblidge 03/12/2019