CNL-19-068, Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for
| ML19203A314 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar, Sequoyah  |
| Issue date: | 07/22/2019 |
| From: | Polickoski J Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CNL-19-068, EPID L-2018-LLR-0005 | |
| Download: ML19203A314 (7) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-19-068 July 22, 2019 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328 Watts Bar Nuclear Plant, Units 1 and 2 Facility Operating License Nos. NPF-90 and NPF-96 NRC Docket Nos. 50-390 and 50-391
Subject:
Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN)
Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternatives RP-09 (SQN) and IST-RR-7 (WBN) (EPID L-2018-LLR-0005)
References:
- 1.
TVA letter to NRC, CNL-18-137, Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternatives RP 09 (SQN) and IST-RR-6 (WBN), dated January 18, 2019 (ML19018A118)
- 2.
NRC Electronic Mail to TVA, Sequoyah Nuclear Plant and Watts Bar Nuclear Plant - Final Request for Additional Information Related to Request for Alternative to OM Code Requirements (EPID L-2019-LLR-0005), dated May 28, 2019 (ML19148A791)
In Reference 1, Tennessee Valley Authority (TVA) requested an alternative to the inservice testing requirements of the American Society of Mechanical Engineers (ASME) Operation and Maintenance (OM) Code, Section ISTB-3310, Effect of Pump Replacement, Repair, and Maintenance on Reference Values. This alternative request applies to testing of the turbine driven auxiliary feedwater pumps (TDAFWP) for the Sequoyah Nuclear Plant (SQN)
Units 1 and 2 (alternative request RP-09) and the Watts Bar Nuclear Plant (WBN) Units 1 and 2 (alternative request IST-RR-7).1 1 Reference 1 incorrectly identified the WBN alternative request as IST-RR-6, the correct reference is IST-RR-7.
U.S. Nuclear Regulatory Commission CNL-19-068 Page 2 July 22, 2019 In Reference 2, the Nuclear Regulatory Commission (NRC) issued a Request for Additional Information (RAI) and requested that TVA provide a response by July 22, 2019. Enclosure 1 to this letter provides the TVA response to the RAI. As noted in Enclosure 1, Enclosure 2 to this letter provides revised alternative request RP-09 (SQN) and IST-RR-7 (WBN) that supersedes the alternative request provided in Reference 1.
As noted in Reference 1, TVA requests approval of this alternative request by October 1, 2019, in the event this alternative request is needed to support the SON Unit 1 refueling outage in Fall 2019.
There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Kimberly D. Hulvey at (423) 751-3275.
Respectfully, c?__:-.2~~~-
~i-. Polickoski Interim Director, Nuclear Regulatory Affairs
Enclosures:
- 1. Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SON) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternatives RP-09 (SON) and IST-RR-7 (WBN) (EPID L-2018-LLR-0005)
- 2. Revised American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-09 (SON) and IST-RR-7 (WBN) cc (w/Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant NRC Project Manager - Sequoyah Nuclear Plant NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant CNL-19-068 E1-1 of 2 Response to Request for Additional Information Regarding the Sequoyah Nuclear Plant (SQN)
Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternatives RP-09 (SQN) and IST-RR-7 (WBN) (EPID L-2018-LLR-0005)
NRC Introduction By letter dated January 19, 2019 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML19018A118), Tennessee Valley Authority (TVA, the licensee) requested to use alternatives to specified requirements of the American Society of Mechanical Engineers (ASME) Operations and Maintenance (OM) Code for the Sequoyah Nuclear Plant (SQN), Units 1 and 2, and the Watts Bar Nuclear Plant (WBN), Units 1 and 2. The NRC staff has determined that the following additional information is needed to complete its review of TVAs ASME OM Code alternative request.
RAI EMIB-1 Regulatory Basis If repair, replacement, or routine servicing that could affect reference values of a turbine driven auxiliary feedwater (TDAFWP) is performed during an outage, ASME OM Code ISTB-3310 requires a Group A, comprehensive, or preservice test to be performed to confirm existing reference values or establish new reference values before declaring the pump operable. These tests require vibration monitoring during the test.
Issue Description Section V of the licensees request states that if repair, replacement, or routine servicing that could affect reference values of a TDAFW pump is performed during an outage, then initial pump operability for compliance with Technical Specification (TS) Limiting Condition for Operation 3.7.5 will be established by performance of the required TS Surveillance Requirement (SR) 3.7.5.2 pump test in Mode 3 with the required steam pressure test conditions. The SR 3.7.5.2 required test will be performed using the fixed resistance pump minimum flow recirculation path, in which pump speed is set, then flow and differential pressure are measured and compared to acceptance criteria established in accordance with OM Code provisions ISTB-3300, ISTB-5122, and Table ISTB-5121-1. This acceptance criteria is truncated if necessary to ensure the pump minimum design limits are met.
It appears that the test that TVA is proposing (the TS SR 3.7.5.2 pump test) is equivalent to a less rigorous Group B test and does not require vibration monitoring.Section VII of TVAs alternative request references a similar alternative request for the Virgil C. Summer Nuclear Station Unit 1 (Summer) as a precedent. The NRC staff notes that in the Summer alternative request, the licensee stated that vibration data would also be obtained in accordance with ISTB-3540 as part of SR 3.7.5.2 when it is conducted following repair, replacement, or routine servicing.
Information Needed Clarify and discuss whether vibration data will be obtained during the proposed TS SR 3.7.5.2 pump test following repair, replacement, or routine servicing to insure operational readiness of the TDAFW pump, consistent with the requirements of the OM Code.
CNL-19-068 E1-2 of 2 TVA Response to RAI EMIB-1 WBN currently performs a Group A Test, consistent with the requirements of the OM Code, during the quarterly pump testing of the WBN Unit 1 and Unit 2 TDAFW pumps, which obtains vibration data.
During the last quarterly pump testing of the SQN Unit 1 and Unit 2 TDAFW pumps (June 3, 2019 and June 18, 2019, respectively), SQN demonstrated the ability to obtain acceptable, stable vibration data when pump speed was reduced below full rated speed. With the ability to obtain acceptable vibration data at reduced speed, SQN is also able to perform a Group A pump test in accordance with ISTB-5121 in Mode 3 using the fixed resistance pump minimum flow recirculation path to establish initial pump operability. Therefore, Enclosure 2 contains a revised alternative request to state if repair, replacement, or routine servicing that could affect reference values of a TDAFWP is performed during an outage, then initial pump operability for compliance with TS LCO 3.7.5 and SR 3.7.5.2 will be established by performance of a Group A pump test in Mode 3 with the required steam pressure test conditions. The revised alternative request provided in Enclosure 2 supersedes the one provided in the referenced letter.
Reference TVA letter to NRC, CNL-18-137, Sequoyah Nuclear Plant (SQN) Units 1 and 2 and Watts Bar Nuclear Plant (WBN) Units 1 and 2, American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternatives RP 09 (SQN) and IST-RR-6 (WBN), dated January 18, 2019 (ML19018A118)
CNL-19-068 E2-1 of 3 Revised American Society of Mechanical Engineers Operation and Maintenance Code, Request for Alternative RP-09 (SQN) and IST-RR-7 (WBN)
Turbine Driven Auxiliary Feedwater Pump Testing Following Maintenance During an Outage I.
ASME Operation and Maintenance (OM) Code Components Affected Site/Unit Pump ID Pump Description Pump Type Code Class OM Group SQN Unit 1 SQN-1-PMP-003-0142 Turbine Driven Auxiliary Feedwater (TDAFW) Pump 1A-S Centrifugal 3
B SQN Unit 2 SQN-2-PMP-003-0142 TDAFW Pump 2A-S Centrifugal 3
B WBN Unit 1 WBN-1-PMP-003-0001A-S TDAFW Pump 1A-S Centrifugal 3
B WBN Unit 2 WBN-2-PMP-003-0002A-S TDAFW Pump 2A-S Centrifugal 3
B II.
ASME Code Edition and Addenda SQN Unit 1 & 2 Fourth ten-year interval - September 1, 2016 to June 30, 2026 ASME OM Code 2004 Edition through 2006 Addenda WBN Unit 1 Third ten-year interval - October 19, 2016 to October 18, 2026 ASME OM Code 2004 Edition through 2006 Addenda WBN Unit 2 First ten-year interval - October 19, 2016 to October 18, 2026 ASME OM Code 2004 Edition through 2006 Addenda III.
Applicable Code Requirement
ISTB-3310, Effect of Pump Replacement, Repair, and Maintenance on Reference Values, states:
When a reference value or set of values may have been affected by repair, replacement, or routine servicing of a pump, a new reference value or set of values shall be determined in accordance with ISTB-3300, or the previous value reconfirmed by a comprehensive or Group A test run before declaring the pump operable. The Owner shall determine whether the requirements of ISTB-3100, to reestablish reference values, apply. Deviations between the previous and new set of reference values shall be evaluated, and verification that the new values represent acceptable pump operation shall be placed in the record of tests (see ISTB-9000).
CNL-19-068 E2-2 of 3 IV.
Reason for Request
If repair, replacement, or routine servicing that could affect reference values of a TDAFWP is performed during an outage, then ISTB-3310 requires a Group A, comprehensive, or preservice test to be performed to confirm existing reference values or establish new reference values before declaring the pump operable. SQN and WBN Technical Specifications (TS) Limiting Condition of Operation (LCO) 3.7.5, Auxiliary Feedwater (AFW) System, requires the TDAFWP to be operable in Modes 1, 2, and 3. Previous efforts to perform the periodic TDAFW comprehensive test in Mode 3 during start-up from a refueling outage have experienced difficulty in maintaining consistent and stable test conditions (e.g., speed, flow) long enough to complete the test due to decreasing steam pressure as result of the high flow rate of relatively cold AFW injection into the steam generators. Performance of a Group A test with a flow rate high enough to fully assess the mechanical and hydraulic performance or a preservice test both require flow to the steam generators and are expected to have the same issues in Mode 3 as the comprehensive test.
Compliance with ISTB-3310 under the circumstances described above represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, this request for alternative is being submitted in accordance with 10 CFR 50.55a(z)(2).
V.
Proposed Alternative and Basis for Use Proposed Alternative If repair, replacement, or routine servicing that could affect reference values of a TDAFWP is performed during an outage, then initial pump operability for compliance with TS LCO 3.7.5 and Surveillance Requirement (SR) 3.7.5.2 will be established by performance of a Group A pump test in Mode 3 with the required steam pressure test conditions. The Group A pump test will be performed using the fixed resistance pump minimum flow recirculation path in which pump speed is set, then flow, differential pressure, and vibration are measured and compared to acceptance criteria established in accordance with ISTB-3300, ISTB-5121, and Table ISTB-5121-1. This acceptance criteria is truncated if necessary to ensure the pump minimum design limits are met.
If repair, replacement, or routine servicing that could affect reference values of a TDAFWP is performed during an outage, the ISTB-3310 required comprehensive or preservice test will be performed in Mode 1 during power ascension at approximately 30 to 50% power level, but no later than ten days from entering Mode 3. Testing will be performed in accordance with ISTB-3100, ISTB-3300, ISTB-5123, and Table ISTB-5121-1, as applicable. If the required comprehensive or preservice test is not performed within these timeframes, the unit will enter the required Action Statement of TS 3.7.5. If for some unforeseen reason, the unit needs to shutdown and cooldown below Mode 3 before completing the Group A, comprehensive, or preservice test, the ten-day period will restart upon re-entering Mode 3 ascension.
Basis for Use SQN Unit 1 and Unit 2 TS Bases for SR 3.7.5.2 state:
Verifying that each AFW pump's developed head at the flow test point is greater than or equal to the required developed head ensures that AFW pump performance has not degraded during the cycle. Flow and differential head are normal tests of centrifugal pump performance required by the ASME Code (Ref 2). Because it is undesirable to introduce cold AFW into the steam generators while they are CNL-19-068 E2-3 of 3 operating, this testing is performed on recirculation flow. This test confirms one point on the pump design curve and is indicative of overall performance. Such inservice tests confirm component OPERABILITY, trend performance, and detect incipient failures by indicating abnormal performance. Performance of inservice testing discussed in the ASME Code (Ref. 2) (only required at 3 month intervals) satisfies this requirement.
This SR is modified by a Note indicating that the SR should be deferred until suitable test conditions are established. This deferral is required because there is insufficient steam pressure to perform the test.
WBN Unit 1 and Unit 2 TS Bases for SR 3.7.5.2 states:
Verifying that each AFW pump's developed head at the flow test point is greater than or equal to the required developed head ensures that AFW pump performance has not degraded during the cycle. Flow and differential head are normal tests of centrifugal pump performance required by the American Society of Mechanical Engineers (ASME) OM Code (Ref. 2). Because it is undesirable to introduce cold AFW into the steam generators while they are operating, this testing is performed on recirculation flow. This test confirms one point on the pump design curve and is indicative of overall performance. Such inservice tests confirm component OPERABILITY, trend performance, and detect incipient failures by indicating abnormal performance. Performance of inservice testing discussed in the ASME OM Code (Ref. 2) (only required at 3 month intervals) satisfies this requirement.
The 31 day Frequency on a STAGGERED TEST BASIS results in testing each pump once every 3 months, as required by Reference 2.
This SR is modified by a Note indicating that the SR should be deferred until suitable test conditions are established. This deferral is required because there may be insufficient steam pressure to perform the test.
The TS Bases provided above demonstrate the inservice test performed at the recirculation flow point on the pump design curve is adequate to confirm component operability. The TS SR and Bases do not place additional requirements on AFW pumps that have undergone repair, replacement, or routine servicing.
The performance of a Group A pump test is adequate to identify any significant issues resulting from a repair, replacement, or routine servicing and provide reasonable assurance the TDAFWP is capable of performing its safety-related function until plant conditions are stable enough to complete the ISTB-3310 required comprehensive or preservice test.
VI.
Duration of Proposed Alternative This alternative request is for the duration of SQN Units 1 and 2 fourth IST ten-year interval and the WBN Unit 1 third IST ten-year interval and the WBN Unit 2 first IST ten-year interval.
VII.
Precedents A similar alternative (RR-4-12) was approved by the NRC for Virgil C. Summer Nuclear Station, Unit 1 on April 28, 2017 (ML17088A256 and ML17103A533).