ML20121A193
| ML20121A193 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 05/06/2020 |
| From: | Siva Lingam NRC/NRR/DORL/LPL4 |
| To: | Entergy Operations |
| Lingam S - NRR/DORL/ 301-415-1564 | |
| References | |
| EPID L-2019 LLR-0088, EPID L-2019-LLR-0085 | |
| Download: ML20121A193 (13) | |
Text
May 6, 2020 ANO Site Vice President Arkansas Nuclear One Entergy Operations, Inc.
N-TSB-58 1448 S.R. 333 Russellville, AR 72802
SUBJECT:
ARKANSAS NUCLEAR ONE, UNIT 2 - ALTERNATIVE REQUESTS FOR THE FIFTH 10-YEAR INTERVAL INSERVICE TESTING OF LOW-PRESSURE SAFETY INJECTION PUMPS AND SERVICE WATER VALVES (EPID L-2019-LLR-0085 AND EPID L-2019-LLR-0088)
Dear Sir or Madam:
By letter dated September 3, 2019, as supplemented by letter dated February 11, 2020, Entergy Operations, Inc. (Entergy, the licensee) submitted Alternative Requests PRR-ANO2-2019-1, PRR-ANO2-2019-2, SRR-ANO2-2019-1, and VRR-ANO2-2019-1 for alternatives to the requirements of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a, Codes and standards, and the 2012 Edition of the American Society of Mechanical Engineers (ASME)
Code for Operation and Maintenance of Nuclear Power Plants (OM Code) for Arkansas Nuclear One, Unit 2 (ANO-2) for the fifth 10-year interval of the inservice testing (IST) program.
By letter dated April 9, 2020 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML20100F427), Entergy requested to withdraw the applications for Alternative Requests PRR-ANO2-2019-2 regarding IST of service water (SW) pumps, and SRR-ANO2-2019-1 related to visual examination of the snubbers. By letter dated April 29, 2020 (ADAMS Accession No. ML20119A073), the U.S. Nuclear Regulatory Commission (NRC) acknowledged Entergys request to withdraw the applications. As a result, the NRC staffs reviews of the applications for Alternative Requests PRR-ANO2-2019-2 and SRR-ANO2-2019-1 were ceased and the corresponding Enterprise Project Identifiers (EPIDs) L-2019-LLR-0086 and L-2019-LLR-0087 were closed.
The enclosed safety evaluations address the NRC staffs review of the remaining two alternative requests: PRR-ANO2-2019-1 associated with IST of low-pressure safety injection (LPSI) pumps (EPID L-2019-LLR-0085), and VRR-ANO2-2019-1 concerning the IST of SW valves (EPID L-2019-LLR-0088).
Alternative Request PRR-ANO2-2019-1 proposes an alternative to the requirements of the ASME OM Code, Subsection ISTB, Inservice Testing of Pumps in Light-Water Reactor Nuclear Power Plants - Pre-2000 Plants. The licensee requested authorization to categorize the ANO-2 LPSI pumps as Group B during Modes 1, 2, 3, and 4, and Group A during Modes 5 and 6. The licensee submitted proposed Alternative Request PRR-ANO2-2019-1 pursuant to 10 CFR 50.55a(z)(1), Acceptable level of quality and safety, on the basis that complying with
the specified ASME OM Code requirements would provide an acceptable level of quality and safety.
Alternative request VRR-ANO2-2019-1 proposes an alternative when using the requirements of the ASME OM Code, Subsection ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, paragraph (a), Frequency, pertaining to the frequency of the leak-rate testing for SW Valves 2CV-1541-1 and 2CV-1560-2. Specifically, Entergy proposes to test one valve each refueling outage with the individual valve test frequency of once every two refueling outages. Refueling outages at ANO-2 occur on an 18-month cycle. Further, Entergys proposal is based on the leak testing of the affected SW valves on a rotating basis combined with good history of previous test results, which provides reasonable assurance of the operational readiness of these SW valves to perform their safety functions. The licensee submitted proposed Alternative Request VRR-ANO2-2019-1 pursuant to 10 CFR 50.55a(z)(2), Hardship without a compensating increase in quality and safety, on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
As set forth in the enclosed safety evaluations, the NRC staff has determined for Alternative Request PRR-ANO2-2019-1 that the licensee has demonstrated that the proposed alternative testing of the LPSI pumps as Group B during Modes 1 through 4, and as Group A during Modes 5 and 6, provides reasonable assurance of operational readiness. Therefore, the NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety.
The licensee has demonstrated that the proposed alternative for VRR-ANO2-2019-1 to change the frequency of leak testing of the SW valves on a rotating basis combined with good history of previous test results provides reasonable assurance of the operational readiness of these SW valves to perform their safety functions. The licensee justified that compliance with the leak testing requirements in the ASME OM Code for these SW valves would result in hardship without a compensating increase in the 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) and (2) for PRR-ANO2-2019-1 and VRR ANO2-2019-1, respectively. Therefore, the NRC staff authorizes the use of the proposed alternatives in Alternative Requests PRR-ANO2-2019-1 and VRR ANO2-2019-1 for the duration of the fifth 10-year IST interval.
All other ASME OM Code requirements for which relief or an alternative was not specifically requested and approved as part of this request remain applicable.
If you have any questions, please contact the ANO Project Manager, Thomas J. Wengert, at 301-415-4037 or by e-mail to Thomas.Wengert@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. 50-368
Enclosures:
- 1. Safety Evaluation for PRR-ANO2-2019-1
- 2. Safety Evaluation for VRR-ANO2-2019-1 cc: Listserv
SAFETY EVALUATION BY THE OFFICE NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST PRR-ANO2-2019-1 RELATED TO THE INSERVICE TESTING PROGRAM FOR THE FIFTH 10-YEAR INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated September 3, 2019 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML19246B361), Entergy Operations, Inc., (Entergy, the licensee),
submitted alternative requests to the U.S. Nuclear Regulatory Commission (NRC). Specifically, the licensee requested an alternative to certain Inservice Testing (IST) requirements of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), Division 1, for the IST program at Arkansas Nuclear One, Unit 2 (ANO-2) during the fifth 10-year IST program interval.
For Alternative Request PRR-ANO2-2019-1, related to the test frequency of low-pressure safety injection (LPSI) pumps 2P-60A and 2P-60B, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(z)(1), Acceptable level of quality and safety, the licensee requested to implement the proposed alternative on the basis that it will provide an acceptable level of quality and safety.
2.0 REGULATORY EVALUATION
Paragraph 50.55a(f)(4) of 10 CFR, Inservice testing standards requirement for operating plants, states, in part, that:
Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in paragraphs (f)(2) and (3) of [10 CFR 50.55a]
and that are incorporated by reference in paragraph (a)(1)(iv) of
[10 CFR 50.55a], to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Pursuant to 10 CFR 50.55a(z), Alternatives to codes and standards requirements, alternatives to the requirements of paragraph (g) of 10 CFR 50.55a 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 (1) the proposed alternative 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.
The ANO-2 fifth 10-year IST program interval is scheduled to begin on September 26, 2020, and end on March 25, 2030. The applicable ASME OM Code edition for the ANO-2 fifth 10-year IST program interval is the 2012 Edition, which is incorporated by reference in 10 CFR 50.55a with conditions.
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 the NRC to authorize the alternatives requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request PRR-ANO2-2019-1 Applicable ASME OM Code The following request is an alternative test plan in lieu of certain IST requirements of the 2012 Edition of the ASME OM Code for the IST program at ANO-2 for the fifth IST program interval, which is currently scheduled to begin on September 26, 2020, and end on March 25, 2030.
ASME OM Code Requirements Alternative testing is requested for the following pumps:
Table 1 LPSI Pump ID Function ASME Class Code Group 2P-60A Core cooling during loss-of-coolant accident and shutdown II B
2P-60B Core cooling during loss-of-coolant accident and shutdown II B
The licensee requested an alternative to the pump testing requirements of the ASME OM Code, Subsection ISTB, Inservice Testing of Pumps in Light-Water Reactor Nuclear Power Plants -
Pre-2000 Plants.
Paragraph ISTB-1300, Pump Categories, states, that All pumps within the scope of paras.
[paragraphs] ISTA-1100 and ISTB-1100 shall be categorized as either a Group A or Group B pump.
Paragraph ISTB-1400, Owners Responsibility, paragraph (b) states, in part, that A pump that meets both Group A and Group B pump definitions shall be categorized as a Group A pump.
Paragraph ISTB-2000, Supplemental Definitions, states, in part, Group A Pumps: pumps that are operated continuously or routinely during normal operation, cold shutdown, or refueling
operations. Group B pumps: pumps in standby systems that are not operated routinely except for testing.
The licensee requested to use proposed Alternative Request PRR-ANO2-2019-1 for LPSI Pumps 2P-60A and 2P-60B at ANO-2. The LPSI pumps are ASME Boiler and Pressure Vessel Code,Section III, Class 2 pumps.
=
Reason for Request===
The ANO-2 LPSI pumps meet the categorization requirements of Group A pumps according to the definitions of pump groups in the ASME OM Code during Modes 5 and 6, because they are routinely operated for shutdown cooling. These pumps also meet the requirements of Group B pumps in Modes 1, 2, and 3 because they remain in standby and are only operated for IST activities. The pumps are also considered standby pumps in Mode 4, although a pump may be operated to support the decay heat removal transition from the steam generators to the shutdown cooling mode of operation.
The licensee tests the LPSI pumps quarterly using a minimum flow recirculation path. The flow resistance is fixed because there is an orifice in the system pipeline. Although there is no installed flow instrumentation in the recirculation line, the licensee has determined that the flow is approximately 100 gallons per minute (gpm). This low flow point occurs on the pump hydraulic curve in a flat area where degradation is difficult to detect. The quarterly test also satisfies ANO-2 Technical Specification (TS) Surveillance Requirement (SR) 4.5.2.f to verify that the LPSI pumps develop the indicated differential pressure for recirculation flow when tested pursuant to the IST program. In accordance with the ASME OM Code, the licensee performs a biennial comprehensive pump test (CPT) of the LPSI pumps during plant shutdown at the CPT flow rate, which is 4250 to 4350 gpm. The CPT flow rate point is located on the sloped portion of the pump hydraulic curve where gradual pump degradation can be detected. Therefore, the licensee considers that the CPTs provide monitoring of operational time-based pump degradation, and the quarterly pump tests assess the operational readiness of the pumps.
The Group A test requires both flow rate and differential pressure to be measured. Because the minimum flow path does not have flow instrumentation installed in the pipeline, either portable flow instrumentation would have to be installed or a plant modification would be required to install permanent flow instrumentation. The licensee does not consider the cost of these options to be commensurate with the minimal benefit of additional pump performance data.
The licensee summarized data from the previous vibration measurements during the quarterly Group A tests and CPTs in the third 10-year IST program interval. The licensee stated that at the Group A test low flow rate, there was significant recirculation flow noise, which caused a high vibration spectral noise floor, and overall vibration values that were as much as five times the values observed during the CPT for certain vibration points.
The licensee evaluated the vibration readings by spectral analyses under the ANO Predictive Maintenance Vibration Analysis Program. These analyses confirmed that recirculation flow noise is the major contributor to the high overall vibration readings. Therefore, the licensee considers that vibration readings during the quarterly tests are of minimum value due to the effects of low flow operation.
Proposed Alternative In Alternative Request PRR-ANO2-2019-1, the licensee proposes to test LPSI Pumps 2P-60A and 2P-60B as Group B pumps during Modes 1, 2, 3, and 4, and as Group A pumps during Modes 5 and 6. The licensee will measure the differential pressure provided by these pumps during the quarterly Group B test.
Quarterly Group B tests require the measurement of either flow or the differential pressure, not both as required by a Group A test. Also, vibration measurements are not required during Group B tests. This will reduce the time required to perform the test, which will reduce pump wear and maintain radiation dose exposure to plant personnel as low as reasonably achievable.
3.2
NRC Staff Evaluation
ASME OM Code, paragraph ISTB-1400(b), requires that pumps be categorized as either Group A or Group B pumps with pumps meeting both definitions to be categorized as Group A.
In lieu of these requirements of paragraph ISTB-1400(b), the licensee has proposed that the LPSI pumps be tested as standby pumps (Group B) during Modes 1 through 4, and as continuously operating pumps (Group A) during Modes 5 and 6. In Modes 5 and 6, the licensee proposes that a Group A test or CPT will apply to quarterly testing. The licensee states that the biennial CPT will continue to be performed in accordance with the ASME OM Code.
ASME OM Code, paragraph ISTB-2000 defines Group A pumps as pumps that are operated continuously or routinely during normal operation, cold shutdown, or refueling operations, and Group B pumps as pumps in standby systems that are not operated routinely except for testing. Based on these definitions, the LPSI pumps meet the definition of Group B pumps during normal operation in Modes 1 through 4. In Modes 5 and 6, the LPSI pumps are used for shutdown cooling and meet the definition of Group A pumps. Paragraph ISTB-1400(b) states that a pump that meets both Group A and Group B pump definitions shall be categorized as a Group A pump. This would normally cause the LPSI pumps to be classified as Group A.
However, because of the inability to achieve a substantial flow rate in Modes 1 through 4, the licensee is unable to conduct a Group A test that would provide meaningful data to detect degradation due to the relatively flat profile of the pump hydraulic curve at the test flow rate, and the higher vibration levels due to flow recirculation at these near-shutoff head flow conditions.
Additionally, the LPSI pumps are standby pumps during Modes 1 through 4, and little degradation is expected with respect to hydraulic performance during the operational period when the pumps are idle.
In NRC Generic Letter 89-04, Guidance on Developing Acceptable Inservice Testing Programs, Position 9, the NRC provided guidance that, in cases where flow can only be established through a non-instrumented, minimum flow path during quarterly pump testing, and a path exists at cold shutdown or refueling outages to perform a test of the pump under full or substantial flow conditions, the increased test interval would be considered reasonable in demonstrating the pump capability. The quarterly Group B test will be performed using the minimum recirculation flow path under low-flow conditions and only differential pressure will be measured. Additionally, during Modes 5 and 6 (during refueling outages and cold shutdowns), a Group A test or CPT will be performed as the quarterly test. The quarterly test also performs the TS SR 4.5.2.f differential pressure test to assure that the required differential pressure is developed to demonstrate continued pump hydraulic performance to provide reasonable assurance of operational readiness.
The proposed alternative testing of the LPSI pumps as Group B during Modes 1 through 4, and as Group A during Modes 5 and 6, provides reasonable assurance of operational readiness of the LPSI pumps. Therefore, the NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety.
In its alternative request, the licensee referenced a paper titled Description of Comprehensive Pump Test Change to ASME OM Code, Subsection ISTB, which is included in NUREG/CP-0137, Volume 1, Proceedings of the Third NRC/ASME Symposium on Valve and Pump Testing. This NUREG is a compilation of papers presented at an NRC/ASME Pump and Valve Symposium. The NRC staff notes that statements and opinions advanced in the papers presented at the symposium are individual expressions of the authors and not those of either the ASME or the NRC.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that proposed Alternative Request PRR-ANO2-2019-1 provides an acceptable level of quality and safety for LPSI Pumps 2P-60A and 2P-60B at ANO-2. Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(1) for PRR-ANO2-2019-1.
Therefore, the NRC staff authorizes the use of Alternative Request PRR-ANO2-2019-1 for the fifth 10-year IST program interval at ANO-2, which is currently scheduled to begin on September 26, 2020, and end on March 25, 2030.
All other ASME OM Code requirements for which relief or an alternative was not specifically requested and approved as part of this request remain applicable.
Principal Contributor: R. Wolfgang, NRR Date: May 6, 2020
SAFETY EVALUATION BY THE OFFICE NUCLEAR REACTOR REGULATION ALTERNATIVE REQUEST VRR-ANO2-2019-1 RELATED TO THE INSERVICE TESTING PROGRAM FOR THE FIFTH 10-YEAR INTERVAL ENTERGY OPERATIONS, INC.
ARKANSAS NUCLEAR ONE, UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
By letter dated September 3, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19246B361), as supplemented by letter dated February 11, 2020 (ADAMS Accession No. ML20042E776), Entergy Operations Inc. (Entergy, the licensee),
submitted alternative requests to the U.S. Nuclear Regulatory Commission (NRC). Specifically, the licensee requested an alternative test plan in lieu of certain inservice testing (IST) requirements of the American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants, Division 1, for the IST program at Arkansas Nuclear One, Unit 2 (ANO-2) during the fifth 10-year IST program interval.
For Alternative Request VRR-ANO2-2019-1, related to the test frequency of service water (SW) valves 2CV-1541-1 and 2CV-1560-2, pursuant to Title 10 of the Code of Federal Regulations paragraph 50.55a(z)(2), Alternatives to codes and standards requirements, the licensee requested to implement the proposed alternative on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
2.0 REGULATORY EVALUATION
Paragraph 50.55a(f)(4) of 10 CFR, Inservice testing standards requirement for operating plants, states, in part, that:
Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, pumps and valves that are within the scope of the ASME OM Code must meet the inservice test requirements (except design and access provisions) set forth in the ASME OM Code and addenda that become effective subsequent to editions and addenda specified in paragraphs (f)(2) and (3) of [10 CFR 50.55a]
and that are incorporated by reference in paragraph (a)(1)(iv) of
[10 CFR 50.55a], to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Pursuant to 10 CFR 50.55a(z), Alternatives to codes and standards requirements, alternatives to the requirements of paragraph (g) of 10 CFR 50.55a 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 (1) the proposed alternative 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.
The ANO-2 fifth 10-year IST program interval is scheduled to begin on September 26, 2020, and end on March 25, 2030. The applicable ASME OM Code edition for the ANO-2 fifth 10-year IST program interval is the 2012 Edition, which is incorporated by reference in 10 CFR 50.55a with conditions.
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 the NRC to authorize the alternatives requested by the licensee.
3.0 TECHNICAL EVALUATION
3.1 Licensees Alternative Request VRR-ANO2-2019-1 Applicable ASME OM Code The following request is an alternative test plan in lieu of certain IST requirements of the 2012 Edition of the ASME OM Code for the IST program at ANO-2 for the fifth IST program interval, which is currently scheduled to begin on September 26, 2020, and end on March 25, 2030.
ASME OM Code Requirements ASME OM Code, paragraph ISTC-3630, Leakage Rate for Other Than Containment Isolation Valves, subparagraph (a), Frequency, states that Tests shall be conducted at least once every 2 yr [years].
Alternative testing is requested for the following valves:
Table 1 Valve ID Function Class Category 2CV-1541-1 Service Water Boundary Isolation Valve 3
A 2CV-1560-2 Service Water Boundary Isolation Valve 3
A
=
Reason for Request===
SW Valves 2CV-1541-1 and 2CV-1560-2 are normally closed motor-operated, 18 Tricentric stainless steel butterfly stop valves that have a primary active open safety function to direct the SW return flow to the emergency cooling pond and a secondary active close function to isolate a ruptured SW header to ensure long-term cooling capability is maintained and to serve as SW boundary isolation valves. These valves are leak tested to verify seat leakage does not exceed
the leakage allowed based on maintaining the minimum volume of water in the emergency cooling pond to meet design-basis accident requirements. As required by the ASME OM Code, the licensee has set valve leakage acceptance criteria for the close safety function as follows:
- 1. Inventory analysis for the emergency cooling pond assumes a total loss of 30 gallons per minute (gpm) from the SW boundary valves of both units combined. Currently, the analysis assumes the allowable leakage to be evenly distributed among the valves or 2.5 gpm per valve.
- 2. A maintenance limit intended to initiate corrective maintenance has been established to be less than or equal to 1.5 gpm.
- 3. Valve operability threshold is greater than or equal to 9.0 gpm.
The two valves can only be tested when the unit is shutdown in Modes 5 or 6, and the associated SW loop is out of service. The leak test is normally performed during refueling outages and requires the system to be drained. In doing so, all loads on the affected SW loop are declared inoperable. The removal of an SW loop from operation reduces the defense-in-depth with respect to loss of decay heat removal events because only one SW cooling loop will remain available. This unnecessarily increases the risk and vulnerability of ANO-2 during a refueling outage. The estimated time to complete the leak test is approximately 125 man-hours over a 2-day period for each valve. The licensee stated that, due to the potential for increased plant risk, compliance with the specified requirements would result in a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Proposed Alternative Entergy proposes to test one valve each refueling outage with the individual valve test frequency of once every two refueling outages. Refueling outages at ANO-2 occur on an 18-month cycle. This would alter the frequency to leak test approximately 3 years, depending on outage durations and/or unscheduled outages. Entergy programs would ensure that the 3-year frequency is not exceeded by more than 6 months. This is consistent with the guidance of ASME OM Code Case OMN-20, Inservice Test Frequency. If problems are found with the valves tested (2CV-1541-1 or 2CV-1560-2) that results in leakage in excess of the limiting value for operability described in the test procedure, both valves will be tested during the same outage to verify operability.
The proposed alternative identified in this request, upon approval, shall be utilized during the entire fifth 10-Year IST program interval, beginning September 26, 2020, and ending March 25, 2030.
3.2
NRC Staff Evaluation
Safety-related valves that have specific leakage criteria other than containment isolation valves are required to be leak-rate tested at least once every 2 years per ASME OM Code, paragraph ISTC-3630. In lieu of meeting this requirement for SW Valves 2CV-1541-1 and 2CV-1560-2, the licensee has proposed leak testing each valve on a refuel outage rotating basis, which would alter their leak test frequency interval to approximately once every 3 years.
If the tested valve has leakage in excess of the limiting value for operability, both valves will be tested during the same outage.
As noted in the licensees alternative request, leak testing of these valves must be completed in Modes 5 or 6 with the associated SW loop isolated, drained, and vented. Historical performance to test one valve requires the SW system to be out of service for about 2 days and requires a significant number of man-hours to complete. This represents an undue risk and vulnerability in defense-in-depth of decay heat removal events because only one train of the SW system would be available during leak testing of one of these SW valves. These vulnerabilities are repeated when the other SW valve is tested during the same outage.
As stated in the licensees alternative request, a similar request was made and authorized by NRC staff for use during the fourth 10-year IST program interval (ADAMS Accession No. ML093370316). A review of the safety evaluation completed for the previous alternative request along with the review of the updated valve leak test history results over a period of 9 years (2009 through 2018) for each of these valves yields no significant valve performance issues. Consequently, there are no changes to the NRC staff analysis performed on the previous safety evaluation completed for the alternative request for the fourth 10-year IST program interval. The NRC staff finds that the licensees proposal for leak testing the affected SW valves on a rotating basis combined with a good history of previous test results provides reasonable assurance of the operational readiness of these SW valves to perform their safety functions.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that the proposed alternative request VRR-ANO2-2019-1 provides reasonable assurance that the specific SW valves are operationally ready. The NRC staff also has determined that the licensee has justified that compliance with the leak testing requirements in the ASME OM Code for these SW valves would result in hardship without a compensating increase in the level of quality and safety.
Accordingly, the NRC staff concludes that the licensee has adequately addressed the regulatory requirements set forth in 10 CFR 50.55a(z)(2). Therefore, the NRC staff authorizes the proposed Alternative Request VRR-ANO2-2019-1 for the fifth 10-Year IST program interval at ANO-2, which is currently scheduled to begin on September 26, 2020, and end on March 25, 2030.
All other ASME OM Code requirements for which relief or an alternative was not specifically requested and approved in the subject request remain applicable.
Principal Contributor: M. Farnan, NRR Date: May 6, 2020
- by e-mail concurrence OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/LA*
NRR/DEX/EMIB/BC (A)*
NRR/DORL/LPL4/BC*
NAME TWengert (SLingam for)
PBlechman TScarbrough JDixon-Herrity DATE 5/6/2020 5/6/2020 4/20/20 5/6/2020