ML18282A030
| ML18282A030 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 10/18/2018 |
| From: | Robert Pascarelli Plant Licensing Branch IV |
| To: | Entergy Operations |
| Pulvirenti A, 415-1390 | |
| References | |
| EPID L-2018-LLR-0025, W3-ISl-030 | |
| Download: ML18282A030 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 18, 2018 Site Vice President Entergy Operations, Inc.
Waterford Steam Electric Station, Unit 3 17265 River Road Killona, LA 70057-3093
SUBJECT:
WATERFORD STEAM ELECTRIC STATION, UNIT 3-PROPOSED ALTERNATIVE TO ASME CODE, SECTION XI, REGARDING CHARGING PIPE VISUAL INSPECTION (EPID L-2018-LLR-0025)
Dear Sir or Madam:
By letter dated February 20, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18051B559), as supplemented by letter dated May 31, 2018 (ADAMS Accession No. ML18151B063), Entergy Operations, Inc. (Entergy or the licensee) requested approval for an alternative to the VT-2 visual examination requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI, for the fourth inservice inspection (ISi) interval at Waterford Steam Electric Station, Unit 3 (Waterford 3).
Specifically, pursuant to Title 1 O of the Code of Federal Regulations (10 CFR) 50.55a(z)(2), the licensee requested to use an alternative for VT-2 visual examination of certain portions of letdown and charging piping enclosed in a vertical pipe chase on the basis that complying with the specified requirement would result in hardship or unusual difficulty, without a compensating increase in the level of quality and safety. A similar request for the subject piping was approved for the third ISi interval by the U.S. Nuclear Regulatory Commission (NRC) staff, as documented in the safety evaluation dated January 13, 2011 (ADAMS Accession No. ML103570392).
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that Entergy has adequately addressed all of the regulatory requirements set forth in 1 O CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the use of the proposed alternative in W3-ISl-030 at Waterford 3 for the fourth 10-year ISi interval that began on December 1, 2017, and is scheduled to end on November 30, 2027.
All other ASME Code,Section XI requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the authorized nuclear inservice inspector.
If you have any questions, please contact the Project Manager, April Pulvirenti, at 301-415-1390 or via e-mail at april.pulvirenti@nrc.gov.
Docket No. 50-382
Enclosure:
Safety Evaluation cc: Listserv Sincerely, Robert J. Pascarelli, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION PROPOSED ALTERNATIVE W3-ISl-030 REGARDING CHARGING PIPE VISUAL INSPECTION ENTERGY OPERATIONS INC.
WATERFORD STEAM ELECTRIC STATION, UNIT 3 DOCKET NO. 50-382
1.0 INTRODUCTION
By letter dated February 20, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18051B559), as supplemented by letter dated May 31, 2018 (ADAMS Accession No. ML18151B063), Entergy Operations, Inc. (Entergy or the licensee) requested approval for an alternative (W3-ISl-030) to the VT-2 visual examination requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI, for the fourth inservice inspection (ISi) interval at Waterford Steam Electric Station, Unit 3 (Waterford 3).
Specifically, pursuant to Title 1 O of the Code of Federal Regulations ( 10 CFR) 50.55a(z)(2), the licensee requested to use an alternative for VT-2 visual examination of certain portions of letdown and charging piping enclosed in a vertical pipe chase on the basis that complying with the specified requirement would result in hardship or unusual difficulty, without a compensating increase in the level of quality and safety. A similar request for the subject piping was approved for the third ISi interval by the U.S. Nuclear Regulatory Commission (NRC) staff, as documented in the safety evaluation dated January 13, 2011 (ADAMS Accession No. ML103570392).
2.0 REGULATORY EVALUATION
The regulations in 10 CFR 50.55a(g) require that the ISi of ASME Code Class 1, 2, and 3 components be performed in accordance with Section XI of the ASME Code and applicable addenda (as incorporated by reference in 10 CFR 50.55a). Paragraph (z)(2) of 10 CFR 50.55a states, in part, that alternatives to the requirements of 10 CFR 50.55a(g) may be used when authorized by the NRC if the licensee demonstrates that compliance with the specified requirements would result in hardship or unusual difficulty, without a compensating increase in the level of quality and safety.
Enclosure Based on the foregoing discussion 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 ASME Code Components Affected
The subject components are letdown line 2CH2-60 A/B and charging line 2CH2-53 A/B located in a vertical pipe chase that is part of a controlled ventilation area system (CVAS) boundary.
The piping lines are ASME Code Class 2 components in the chemical and volume control system.
3.2 Applicable ASME Code Edition and Addenda The current Code of record for the Waterford 3 fourth ISi interval is the 2007 Edition through the 2008 Addenda of ASME Code,Section XI.
3.3 Applicable Code Requirements Examination Category C-H, Item No. C7.10 of ASME Section XI, Table IWC-2500-1, requires the subject lines to be visually examined (VT-2) during a system leakage test each inspection period. IWA-5211 requires that the visual examination be performed while the components that are being tested are at normal operating pressure.
3.4
Reason for Request
The licensee's reason for the request is summarized as follows. The subject letdown lines are located in a pipe chase that is part of a CVAS boundary. Waterford 3 utilizes the CVAS to provide high efficiency particulate filtration and iodine adsorption in the controlled ventilation area. The system must exhaust air from the controlled ventilation area at a rate required to create and maintain a negative pressure below 0.25-inch water gage relative to the surrounding areas. CVAS is composed of two independent trains, as discussed in the Waterford 3 Updated Final Safety Analysis Report, Section 6.5.1.
Waterford 3 Technical Specification (TS} 3/4.7.7 provides the OPERABILITY requirements for CVAS. Specifically, TS Section 4.7.7.d.2 requires that each CVAS train be capable of maintaining a negative pressure of 0.25-inch water gage. In the event this condition cannot be met, the TS requires the associated train to be declared INOPERABLE and restored to OPERABLE status within 7 days, or the plant must be placed in HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. With both trains INOPERABLE, entry into TS Limiting Condition for Operation (LCO) 3.0.3 is required.
LCO 3.0.3 requires the appropriate LCO to be met within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, or the plant must be in HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, HOT SHUTDOWN with the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and COLD SHUTDOWN with the subsequent 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Temporary access to the inside of the pipe chase is provided through special block-out sections consisting of multiple layers of solid concrete blocks. Except for such temporary access block-outs, the pipe chase is totally enclosed by reinforced concrete walls, and the blocks are mortared in place. The block-out sections penetrate into the CVAS boundary; therefore, removing the block wall during normal operation (Modes 1, 2, 3, or 4) violates the CVAS boundary, placing both CVAS trains in INOPERABLE status in accordance with the TS. The time required to perform the subject VT-2 examination on the CVAS train is estimated to be a minimum of 6 days, which significantly exceeds the allowed 1-hour LCO. This estimate accounts for removing the concrete blocks to access the pipe chase, performance of the examination, restoration of the pipe chase, and performance of the necessary surveillances to demonstrate operability.
In addition, the subject piping is inaccessible during normal operation without deliberate entry into a TS action statement requiring plant shutdown. When the pipe is accessible during plant shutdown (Modes 5 and 6), the system cannot be operated to obtain the Code-required test conditions.
3.5 Proposed Alternative and Its Basis The licensee requested authorization to perform VT-2 visual examination of the subject lines and the surrounding areas once each period during a refueling outage with no pressure/temperature requirements. This examination would be performed in lieu of the requirements of ASME Code,Section XI, IWA-5211, and prior to any maintenance being performed inside the pipe chase or on the subject lines. The licensee also stated that the proposed alternative provides an acceptable level of quality and safety. The licensee's basis for the alternative is summarized below.
IWA-5213(a) of ASME Code,Section XI requires that a non-insulated component be at system operating pressure for 10 minutes and VT-2 visual examination be performed while at pressure.
IWA-5241(b) allows examination of the surrounding area (including floor areas or equipment surfaces located underneath the components) for evidence of leakage for non-insulated components that are inaccessible for direct VT-2 visual examination. IWA-5245 also allows the pressure to be lowered to a level corresponding to a temperature of 200 °F after the required hold time but prior to the VT-2 visual examination for systems that operate above 200 °F.
Therefore, the ASME Code allows a non-insulated, non-borated standby system to be VT-2 examined by inspecting surfaces below the piping after being at test pressure for 1 O minutes. In addition, the Code allows owners to perform this VT-2 examination after the pressure has been reduced to a pressure corresponding to a temperature of 200 °F.
These two non-insulated sections of piping experience significant pressure while at normal plant conditions during plant operation. If leakage were to occur from the subject sections of charging and letdown piping, it would show up as unidentified leakage in the reactor coolant system inventory balance. Waterford 3 operations personnel confirms this balance at least once every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in accordance with TS 4.4.5.2.1 in Modes 1, 2, 3, and 4.
The subject charging and letdown lines are part of the chemical and volume control system, which is borated for the purpose of controlling reactivity. The boric acid provides a chemical marker that leaves behind a white stain when very small amounts of leakage occur. As this leakage occurs over a period of time, the boric acid residue builds up, thereby allowing discovery of very small leaks. In addition, the subject piping lines are pressurized during normal operations. Since they are borated and non-insulated, sufficient time is available for boric acid to build up on the piping or adjacent surfaces. Subsequent VT-2 visual examination, after the block wall has been removed and prior to any maintenance activities, is adequate to discover any leakage.
3.6 Duration of the Proposed Alternative The duration of the proposed alternative is for the fourth 10-year ISi interval, which is from December 1, 2017 through November 30, 2027.
3.7
NRC Staff Evaluation
Examination Category C-H specified in the ASME Code of record requires VT-2 visual examination for the subject piping during a system leakage test each inspection period. During normal operation, the VT-2 examination of the subject piping in the vertical pipe chase would cause entry into a TS action statement requiring plant shutdown. During plant shutdown (Modes 5 and 6), the subject piping in the vertical pipe chase can be accessed through block-out sections for VT-2 visual examination. However, the system cannot be operated to meet the leakage test conditions, as required by ASME Code,Section XI, IWA-5211.
Therefore, the NRC staff finds that the licensee appropriately identified the hardship and unusual difficulty of the system leakage test for the subject piping based on the LCO action statements for pipe chase operability as a CVAS boundary.
In lieu of the requirements of IWA-5211 for the subject piping, the licensee proposed to perform VT-2 visual examination of the piping and surrounding areas during a refueling outage once each period with no pressure or temperature requirements applied. This visual examination will be performed prior to any maintenance being performed inside the pipe chase or on the subject piping. Since the charging and letdown lines are borated as part of the chemical and volume control system for the purpose of controlling reactivity, the NRC staff notes that the visual examination during an outage will allow the licensee to detect even minor leakage by the presence of boric acid residue or corrosion product.
In addition to the system being borated, the operating time at pressure for the subject piping since the latest VT-2 visual examination is in excess of 20,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br />, which is significantly greater than the Code-required 10-minute hold time. The NRC staff finds that the period of operation before the next system leakage test and VT-2 visual examination provide reasonable assurance thal leakage from the subject piping can be detected regardless of the system pressure applied during the leakage test.
The licensee indicated that the susceptibility of the subject piping to known degradation mechanisms was performed as part of the aging management review for the chemical and volume control system. Based on those evaluations, the licensee confirmed that the aging mechanisms of stress corrosion cracking and thermal fatigue do not apply to the subject piping.
In its supplement dated May 31, 2018, the licensee confirmed that a search of operating experience for past inspection results was performed in order to identify a potential indication of past degradation, including a review of work order history. The licensee clarified that leakage due to degradation could have been identified by an increase in the makeup rate of the charging system when analyzing the water inventory balance of the reactor coolant system. Based on these reviews, the licensee confirmed that (a) the operating experience review revealed no indications of previous occurrences of degradation in the subject piping, and (b) all previous inspections were performed with satisfactory results, as documented in the visual inspection reports for the leakage tests.
As discussed above, the NRC staff finds that (a) the results of the degradation susceptibility evaluation for the piping are consistent with the operating experience review, indicating the absence of degradation in the subject piping, and (b) the previous visual inspections conducted during system leakage tests have been effective to maintain the integrity of the subject piping.
In addition, the staff finds that the licensee appropriately identified the hardship and unusual difficulty of the system leakage test.
4.0 CONCLUSION
The NRC staff determines that the proposed alternative provides reasonable assurance of structural integrity of the subject components and that complying with the requirement would result in hardship or unusual difficulty, without a compensating increase in the level of quality and safety. In addition, the staff determines that the licensee appropriately identified the hardship and unusual difficulty associated with meeting the requirements of ASME Code Section XI. Accordingly, the NRC staff concludes that Entergy 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 the proposed alternative in W3-ISl-030 at Waterford 3 for the fourth 10-year ISi interval that began on December 1, 2017, and is scheduled to end on November 30, 2027.
All other ASME Code,Section XI requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the Authorized Nuclear lnservice Inspector.
Principal Contributor: S. Min Da~: October 18, 2018
ML18282A030 OFFICE NRR/D0RULPL4/PM NRR/D0RULPL4/LA NAME APulvirenti PBlechman (LRonewicz for)
DATE 10/15/18 10/11/2018 NRR/DMLR/MPHB/BC*
SRuffin 9/6/18