ML24256A232
| ML24256A232 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 10/22/2024 |
| From: | Markley M Plant Licensing Branch II |
| To: | Carr E South Carolina Electric & Gas Co |
| Miller, GE | |
| References | |
| EPID L-2023-LLR-0069 | |
| Download: ML24256A232 (1) | |
Text
October 22, 2024 Eric S. Carr Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, VA 23060-6711
SUBJECT:
VIRGIL C. SUMMER NUCLEAR STATION, UNIT NO. 1 - RE: RELIEF REQUEST RR-5-P1 CHARGING/SAFETY INJECTION PUMPS (EPID L-2023-LLR-0069)
Dear Eric Carr:
By letter dated December 21, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML23361A104) Dominion Energy South Carolina (Dominion, the licensee), submitted a request for the Virgil C. Summer Nuclear Station, Unit No. 1 (Summer, VCSNS), to the U.S. Nuclear Regulatory Commission (NRC or Commission) for a proposed alternative to certain American Society of Mechanical Engineers (ASME) Operations and Maintenance (OM) Code inservice testing (IST) requirements.
Specifically, Dominion requested approval of a proposed alternative from ASME OM Code Subsection ISTB-3000, General Testing Requirements, Subsection ISTB-3000-1, Inservice Test Parameters, Subsection ISTB-3000(e)(2), Reference Values, Subsection ISTB-3400, Frequency of Inservice Tests, Subsection ISTB-3400-1, Inservice Test Frequency, Subsection ISTB-3510(a), Accuracy, Subsection ISTB-3510-1, Required Instrument Accuracy, Subsection ISTB-3550, Flow Rate, Subsection ISTB-5100(a)(1), Duration of Tests, Subsection ISTB-5100(b)(1), Bypass Loops, and Subsection ISTB-5121, Group A Test Procedure, on the basis that the proposed alternative provides an acceptable level of quality and safety.
The NRC staff has reviewed the alternative request and concludes, as set forth in the enclosed safety evaluation, that Dominion has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Therefore, the NRC authorizes the proposed alternative for the Fifth IST Interval that begins January 1, 2025. All other ASME Code requirements for which relief was not specifically requested and approved remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
If you have any questions, please contact the Project Manager, Ed Miller at 301-415-2481 or via e-mail at Ed.Miller@nrc.gov.
Sincerely, Michael Markley, Chief Plant Licensing Branch 2-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-395
Enclosure:
Safety Evaluation cc: Listserv MICHAEL MARKLEY Digitally signed by MICHAEL MARKLEY Date: 2024.10.22 12:44:27 -04'00'
Enclosure SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CHARGING/SAFETY INJECTION PUMPS RR-5-P1 DOMINION ENERGY SOUTH CAROLINA VIRGIL C. SUMMER NUCLEAR STATION, UNIT 1 DOCKET NO. 50-395
1.0 INTRODUCTION
By letter dated December 21, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML23361A104), Dominion Energy South Carolina (Dominion, the licensee), submitted a request for the Virgil C. Summer Nuclear Station, Unit No. 1 (Summer), to the U.S. Nuclear Regulatory Commission (NRC or Commission) for a proposed alternative to certain American Society of Mechanical Engineers (ASME) Operations and Maintenance (OM)
Code inservice testing (IST) requirements.
Specifically, Dominion requested approval of a proposed alternative from ASME OM Code Subsection ISTB-3000, General Testing Requirements, Subsection ISTB-3000-1, Inservice Test Parameters, Subsection ISTB-3000(e)(2), Reference Values, Subsection ISTB-3400, Frequency of Inservice Tests, Subsection ISTB-3400-1, Inservice Test Frequency, Subsection ISTB-3510(a), Accuracy, Subsection ISTB-3510-1, Required Instrument Accuracy, Subsection ISTB-3550, Flow Rate, Subsection ISTB-5100(a)(1), Duration of Tests, Subsection ISTB-5100(b)(1), Bypass Loops, and Subsection ISTB-5121, Group A Test Procedure, on the basis that the proposed alternative provides an acceptable level of quality and safety.
2.0 REGULATORY EVALUATION
The NRC regulations in 10 CFR 50.55a(z), Alternatives to codes and standards requirements, state that alternatives to the requirements of 10 CFR 50.55a(b) through (h) 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 of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
3.0 TECHNICAL EVALUATION
The IST Code of Record for the Fifth Interval IST Program at VCSNS, Unit 1, is the 2020 Edition of the ASME OM Code, as incorporated by reference in 10 CFR 50.55a. The applicable ASME OM Code edition for the NRC staff technical evaluation of Request RR-5-P1 is the 2020 Edition of the ASME OM Code as incorporated by reference in 10 CFR 50.55a.
The licensee proposes the duration of RR-5-P1 as the VCSNS Unit 1 Fifth Interval IST Program, which begins on January 1, 2025.
ASME OM Code Components Affected The following plant equipment within the scope of this request are:
Table 2 Component ID Component Description Code Class Valve Category XPP0043A Charging/Safety Injection (SI) Pump A 2
A XPP0043B Charging/SI Pump B 2
A XPP0043C Charging/SI Pump C 2
A Applicable ASME OM Code Requirements In its letter dated December 21, 2023, the licensee specified the following IST requirements of the ASME OM Code as incorporated by reference in 10 CFR 50.55a as related to this request:
ASME OM Code Subsection ISTB-3000, General Testing Requirements, states in part, that The parameters to be measured during preservice and inservice testing are specified in Table ISTB-3000-1.
ASME OM Code Table ISTB-3000-1, lnservice Test Parameters, specifies in part that, Flow Rate (Q) is required to be measured during Group A pump tests.
ASME OM Code Subsection ISTB-3300(e)(2), Reference Values, states that Reference values shall be established at the comprehensive pump test flow rate for the Group A and Group B tests, if practicable. If not practicable, the reference point flow rate shall be established at the highest practical flow rate.
ASME OM Code Subsection ISTB-3400, Frequency of lnservice Tests, states in part that, An inservice test shall be run on each pump as specified in Table ISTB-3400-1.
ASME OM Code Table ISTB-3400-1, lnservice Test Frequency, specifies in part that Group A pumps are to be tested quarterly.
ASME OM Code Subsection ISTB-3510(a), Accuracy, states in part that, Instrument accuracy shall be within the limits of Table ISTB-3510-1. If a parameter is determined by analytical methods instead of measurement, then the determination shall meet the parameter accuracy requirement of Table ISTB-3510-1 (e.g., flow rate determination shall be accurate to within
+/-2% of actual).
ASME OM Code Table ISTB-3510-1, Required Instrument Accuracy, specifies in part that when measuring Flow Rate, the required instrument accuracy is +/-2% for Group A Tests.
ASME OM Code Subsection ISTB-3550, Flow Rate, states in part, When measuring flow rate, a rate or quantity meter shall be installed in the pump test circuit. If a meter does not indicate the flow rate directly, the record shall include the method used to reduce the data. Internal recirculated flow is not required to be measured.
ASME OM Code Subsection ISTB-5100(a)(1), Duration of Tests, states that, For the Group A test and the comprehensive test, after pump conditions are as stable as the system permits, each pump shall be run at least 2 min. At the end of this time at least one measurement or determination of each of the quantities required by Table ISTB-3000-1 shall be made and recorded.
ASME OM Code Subsection ISTB-5100(b)(1), Bypass Loops, states that A bypass test loop may be used for a Group A test or comprehensive test, provided the flow rate through the loop meets the requirements as specified in ISTB-3300.
ASME OM Code Subsection ISTB-5121, Group A Test Procedure, details requirements for the conduct of pump inservice testing and evaluation/analysis of test results. ISTB-5121(c) states that, Where it is not practical to vary system resistance, flow rate and pressure shall be determined and compared to their respective reference values." ISTB-5121(e) states in part that, "All deviations from the reference values shall be compared with the ranges of Table ISTB-5121-1 and corrective action taken as specified in ISTB-6200.
The NRC staff evaluated RR-5-P1 with respect to these IST requirements in the ASME OM Code as incorporated by reference in 10 CFR 50.55a Proposed Alternative for Request RR-5-P1 In its letter dated December 21, 2023, the licensee specified the following as the proposed alternative in RR-5-P1:
VCSNS proposes to continue use of the method identified in GL [Generic Letter]
89-04 [ML031150259] that was approved for the fourth (4th) interval as an alternative method for meeting the surveillance requirement for the fifth (5th)
VCSNS IST interval, thereby maintaining an acceptable level of quality and
safety. Performing inservice testing using a non-instrumented recirculation line was also previously found acceptable by NRC in GL 89-04, Position 9, Pump Testing using Minimum-flow Return Line With or Without Flow Measuring Devices.
Under the alternative approach, pump flow is measured during a comprehensive test each refueling outage with the minimum-flow line isolated. Pump performance is then compared to Design Basis Accident (DBA) analysis requirements.
The Group A pump quarterly test of the Charging/SI Pumps will be performed in accordance with GL 89-04, Position 9, by measuring pump differential pressure and vibration. The Charging/SI Pump orifices are large differential pressure orifices, with backpressure having minimal effect on orifice performance.
=
Reason for Request===
In its letter dated December 21, 2023, the licensee specified the following as the reason for RR-5-P1:
The test circuit used during the quarterly Group A Charging/SI Pump inservice test is described in VCSNS Updated Final Safety Analysis Report (UFSAR)
Section 6.3.2.2.4.2, Centrifugal Charging Pumps, and states, in part that, A minimum flow bypass line is provided on each pump discharge to recirculate flow to the volume control tank after cooling via the seal water heat exchanger during normal plant operation, and, during normal plant operation, at least one charging pump is continuously in service. The second pump is a non-running pump on the inactive loop and the third, if available, is designated as a spare and its breaker(s) are racked out. The other charging pumps may be tested during power operation via the minimum flow bypass lines.
The VCSNS Charging/SI system was constructed without installed flow measurement instrumentation in the Charging/SI minimum flow recirculation lines. During the second and third intervals, Charging/SI pump inservice testing was conducted in accordance with Generic Letter (GL) 89-04, Guidance on Developing Acceptable lnservice Testing Programs, Position 9.
Prior to the start of the fourth interval, efforts were made to measure flow through the recirculation lines using ultrasonic flow meters. During the first 12-months of the fourth interval, strap-on ultrasonic flow meters were used to measure recirculation flow during Charging/SI Pump quarterly Group A testing. The required instrument repeatability established in ASME OM Code Table ISTB-3510-1 could not be achieved. During field use, flow rate variations of up to 6 percent and higher from average were noted. Inaccuracies associated with clamp-on ultrasonic flow measurement devices were the subject of NRC Information Notice (IN) 95-08, Inaccurate Data Obtained with Clamp-on Ultrasonic Flow Measurement Instruments.
As such, based on the lack of consistency in data measurement using the ultrasonic meters and lack of installed instrumentation to measure recirculation line flow during Charging/SI Pump Group A testing, pursuant to 10 CFR 50.55a,
Codes and standards, paragraph (z)(1), an alternative to the surveillance testing methodology of the ASME OM Code is requested.
Licensees Assessment In its letter dated December 21, 2023, the licensee provided the following assessment of Request RR-5-P1:
Based on recirculation flow measurement data repeatability issues, an alternative to the requirement of the ASME OM Code to measure Charging/SI Pump recirculation line flow during quarterly Group A testing is requested. This test alternate is endorsed in Position 9 of GL 89-04. The test methodology using Position 9 was used during previous test intervals at VCSNS. The Alternative was not requested prior to the 4th interval, as NUREG-1482, Revision 0 was used during the third (3rd) ten-year interval update and did not require licensees to submit relief requests prior to utilizing GL 89-04, Position 9.
GL 89-04, Position 9 acknowledged that earlier (and current) inservice test Codes required pump differential pressure and flow rate to be measured and then evaluated together to determine pump hydraulic performance during testing.
The GL states that Certain safety-related systems are designed such that the minimum-flow return lines are the only flow paths that can be utilized for quarterly pump testing. Furthermore, some of these systems do not have a flow path that can be utilized for pump testing during any plant operating mode except the minimum-flow return lines. In these cases, pumping through the path designed for fulfilling the intended system safety function could result in damage to plant equipment. Minimum-flow lines are not designed for pump testing purposes, and few have installed flow measuring devices.
The GL goes on to state 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 shutdowns or refueling outages to perform a test of the pump under full or substantial flow conditions, the staff has determined that the increased interval is an acceptable alternative to the Code requirements provided that pump differential pressure, flow rate, and bearing measurements are taken during this testing and that quarterly testing also measuring at least pump differential pressure and vibration is continued. Data from both testing frequencies should be trended as required by (the Code).
GL 89-04 also references NRC Bulletin 88-04 which advised licensees of the potential for pump damage while running pumps in the minimum-flow condition.
The GL states that, Licensees should ensure that if pumps are tested in the low flow condition, the flow is sufficient to prevent damage to the pump.
The acceptability of operation of VCSNS Charging/SI Pumps in the minimum-flow configuration has been evaluated. While on minimum-flow, each pump will run at greater than 60 gallons per minute, regardless of which combination of pumps are operating. This is because the individual pump minimum-flow orifices govern the operating point for each pump. A stronger pump will have negligible impact on the operating point of the weaker pump since a slight increase in orifice backpressure will have minimal effect on orifice performance. This is true
for the charging pump minimum flow orifices which are large differential pressure orifices. The required minimum-flow of 60 gallons per minute is sufficient to prevent pump damage.
The large differential pressure orifices establish a fixed operating point for each Charging/SI Pump which allows testing under repeatable conditions, without the need to measure flow, as endorsed in GL 89-04, Position 9. Pump condition will be evaluated by trending pump differential pressure and vibration. Flow rate will be assumed to be fixed and at its reference value similar to the previous inservice testing interval. The Charging/SI Pumps also undergo comprehensive inservice testing during refueling outages. The minimum-flow lines are isolated and total flow is measured at substantial flow conditions as required by the ASME OM Code.
NUREG-1482, Revision 3, Guidelines for lnservice Testing at Nuclear Power Plants [ML20202A473], Section 3.1, NRC Recommendations and Guidance, states, in part that, The recommendations herein replace the guidance and technical positions in GL 89-04. Note that specific relief is required to implement the guidance derived from GL 89-04. However, relief justification may refer to the positions in GL 89-04 with clarifying information to clearly show how it would apply to a licensee's situation.
The proposed alternative is consistent with the guidelines provided in NUREG-1482, Section 5.9 and GL 89-04, Position 9. Using the provisions of this request provides a reasonable alternative to the Code requirements based on the determination that the proposed alternative will provide adequate indication of pump performance, permit detection of component degradation, and continue to provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(z)(1), VCSNS requests approval of this alternative to the specific ISTB requirements identified in this request.
NRC Staff Evaluation of RR-5-P1 The ASME OM Code, Subsection ISTB, paragraph ISTB-5120, Inservice Testing, provides specific IST requirements for Group A pump tests, Group B pump tests, Comprehensive Pump Tests, and Periodic Verification Tests. Paragraph ISTB-5121, Group A Test Procedure, requires that Group A tests shall be conducted with the pump operating as close as practical to a specified reference point and within the variances from the reference point as described in this paragraph. Paragraph ISTB-5121 also requires that the test parameters shown in Table ISTB-3000-1 shall be determined and recorded as required by this paragraph.
Paragraph ISTB-5123, Comprehensive Test Procedure, requires that comprehensive tests shall be conducted with the pump operating as close as practical to a specified reference point and within the variances from the reference point as described in this paragraph.
Paragraph ISTB-5123 also requires that the test parameters shown in Table ISTB-3000-1 shall be determined and recorded as required by this paragraph. Paragraph ISTB-5124, Periodic Verification Test, requires that tests be performed for the applicable pumps identified with specific design-basis accident flow rates in the Owners credited safety analysis.
Paragraph ISTB-5124 requires that if the required flow and differential pressure cannot be achieved, then the pump is in the action range, and corrective actions shall be taken in accordance with the applicable ISTB-6200 requirements.
In RR-5-P1, the licensee proposes to continue its use of the method identified in GL 89-04 that the NRC staff previously authorized for the Fourth 10-Year Interval IST Program as an alternative method for meeting the surveillance requirement for the Fifth Interval IST Program at VCSNS, Unit 1, based on maintaining an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1). The licensee proposes to perform the Group A pump quarterly test of the Charging/SI Pumps in accordance with GL 89-04, Position 9, by measuring pump differential pressure and vibration. The licensee proposes to measure pump flow during a comprehensive test of each RFO with the minimum flow line isolated. Pump performance is then compared to design-basis accident analysis requirements.
The ASME OM Code, Subsection ISTB, specifies requirements to provide reasonable assurance that pump testing will assess the operational readiness of the applicable pumps to perform their safety functions. For example, paragraph ISTB-3000 states, in part, that the parameters to be measured during preservice and inservice testing are specified in Table ISTB-3000-1. Table ISTB-3000-1 requires, in part, that the flow rate shall be measured during Group A pump tests. Paragraph ISTB-3300(e)(2) requires that reference values shall be established at the comprehensive pump test flow rate for the Group A and Group B tests, if practicable. If not practicable, paragraph ISTB-3300(e)(2) requires that the reference point flow rate shall be established at the highest practical flow rate. Paragraph ISTB-3400 requires, in part, that an inservice test shall be conducted on each pump as specified in Table ISTB-3400-1.
Table ISTB-3400-1 requires, in part, that Group A pumps are to be tested quarterly.
Paragraph ISTB-3510(a) requires, in part, that instrument accuracy shall be within the limits of Table ISTB-3510-1. Paragraph ISTB-3510(a) also requires that if a parameter is determined by analytical methods instead of measurement, then the determination shall meet the parameter accuracy requirement of Table ISTB-3510-1 (e.g., flow rate determination shall be accurate to within +/-2 percent of actual).
The NRC staff has determined that using a comprehensive pump test, as described, during an outage in lieu of Group A inservice test is consistent with the guidance in NUREG-1482, Revision 3, Section 5.9, Pump Testing Using Minimum Flow Return Lines With or Without Flow Measuring Devices, and GL 89-04, Position 9. The NRC staff finds that the proposed alternative in Request RR-5-P1 for the applicable pumps at VCSNS Unit 1 with respect to the IST requirements in ASME OM Code, Subsection ISTB, paragraph ISTB-5121 for Group A tests and paragraph ISTB-5123 for comprehensive pump tests will provide an acceptable level of quality and safety in accordance with 10 CFR 50.55a(z)(1).
4.0 CONCLUSION
Based on the above, the NRC staff concludes that RR-5-P1 has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1). Further, the proposed alternative provides an acceptable level of quality and safety in lieu of the specified ASME OM Code requirements. Therefore, the NRC authorizes Relief Request RR-5-P1 for the Fifth Interval IST Program at VCSNS Unit 1, which will begin on January 1, 2025.
All other ASME Code requirements for which relief has not been specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributors: M. Breach, NRR T. Scarbrough, NRR Date: October 22, 2024
- Via SE Input OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DEX/EMIB/BC NRR/DORL/LPL2-1/BC NAME GEMiller KGoldstein SBailey* (TScarbrough for) MMarkley DATE 9/6/2024 09/13/2024 8/30/2024 10/22/2024 OFFICE NRR/DORL/LPL2-1/PM NAME GEMiller DATE 10/22/2024