CNL-18-104, Submittal of Revised Response to Request for Additional Information Regarding Application to Modify Plant Technical Specifications to Extend Surveillance Requirements 3.3.1.5, 3.3.2.2 and 3.3.6.2 Specified Intervals
| ML18215A055 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 07/30/2018 |
| From: | Henderson E Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 390-WBN-TS-2018-14, CNL-18-104, EPID L-2018-LLA-0187 | |
| Download: ML18215A055 (4) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-18-104 July 30, 2018 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390
Subject:
Revised Response to Request for Additional Information Regarding Application to Modify Watts Bar Nuclear Plant Unit 1 Technical Specifications to Extend Surveillance Requirement 3.3.1.5, 3.3.2.2, and 3.3.6.2 Specified Intervals (390-WBN-TS-2018-14)
References:
- 1. TVA Letter to NRC, CNL-18-090, Application to Modify Watts Bar Nuclear Plant Unit 1 Technical Specifications to Extend Surveillance Requirement 3.3.1.5, 3.3.2.2, and 3.3.6.2 Specified Intervals (390-WBN-TS-2018-14),
dated July 8, 2018 (ML18189A001)
- 2. NRC Electronic Mail to TVA, Request for Additional Information Regarding Watts Bar Unit 1 Extension of Surveillance Requirement Intervals (EPID L-2018-LLA-0187), dated July 18, 2018 (ML18199A182)
- 3. TVA Letter to NRC, CNL-18-102, Response to Request for Additional Information Regarding Application to Modify Watts Bar Nuclear Plant Unit 1 Technical Specifications to Extend Surveillance Requirement 3.3.1.5, 3.3.2.2, and 3.3.6.2 Specified Intervals (390-WBN-TS-2018-14)
(EPID L-2018-LLA-0187), dated July 24, 2018 (ML18206A416)
In Reference 1, Tennessee Valley Authority (TVA) submitted an expedited request for an amendment to Facility Operating License No. NPF-90 for Watts Bar Nuclear Plant (WBN)
Unit 1. This expedited license amendment request (LAR) requested Nuclear Regulatory Commission (NRC) approval of a modification to WBN Unit 1 Technical Specification (TS)
Surveillance Requirement (SR) 3.0.2 and Table SR 3.0.2-1 to permit the extension of certain functions associated with SRs 3.3.1.5, 3.3.2.2, and 3.3.6.2 to no later than October 1, 2018, in order that these SRs can be performed during the WBN U1R15 outage, scheduled to commence in September 2018. The SRs for which an extension is requested are currently due to be completed no later than August 17, 2018. The reason for this SR extension request was due to an anomaly in the solid state protection system (SSPS) Train B test circuitry.
U.S. Nuclear Regulatory Commission CNL-18-104 Page 2 July 30, 2018 In Reference 2, the NRC transmitted a request for additional information (RAI). In Reference 3, TVA provided a response to the RAI. The enclosure to this letter provides a revised response to NRC RAl-1 that supersedes in its entirety the response to NRC RAl-1 provided in Reference 3.
As noted in Reference 1, TVA requests approval of the expedited LAR by August 16, 2018, and that the implementation of the revised TS be effective immediately to avoid an unnecessary operational transient to initiate a plant shutdown.
Consistent with the standards set forth in 10 CFR 50.92(c), TVA has determined that the additional information, as provided in this letter, does not affect the no significant hazards determination associated with the request provided in Reference 2.
There are no new regulatory commitments associated with this submittal. Please address any questions regarding this request to Ed Schrull at 423-751-3850.
I declare under penalty of perjury that the foregoing is true and correct. Executed on this 30th day of July 2018.
Respectfully,
~~
Erin K. Henderson Director, Nuclear Regulatory Affairs
Enclosure:
Revised Response to NRC RAl-1 cc (Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant Director, Division of Radiological Health - Tennessee State Department of Environment and Conservation
Enclosure CNL-18-104 E1 of 2 Revised Response to NRC RAI-1 Nuclear Regulatory Commission (NRC) Request for Additional Information (RAI)-1 The licensee stated in its LAR that troubleshooting, post maintenance testing, an independent Westinghouse review, and engineering judgement were used to determine that the cause of the unexpected opening of reactor trip breaker (RTB) B was an anomaly associated with the solid state protection system (SSPS) Train B test circuitry when aligned to the intermediate range trip circuits of the universal logic board. However, no documentation of the specific results of these troubleshooting activities was provided, nor was there any technical description regarding how it was concluded that the problem has been isolated to within the test portion of the circuitry. The NRC staff requests the licensee submit additional information on the specific results of the aforementioned activities. This information will be used as a basis for the staff being able to have reasonable assurance that the operability determination was properly made.
TVA Response to RAI-1 Following the performance of Surveillance Instruction (SI) 1-SI-99-10-B on June 13, 2018, TVA performed an operability determination in accordance with TVA procedure NEDP-22, Operability Determinations and Functional Evaluations. The operability determination took into account the work order that performed the SI and the post maintenance testing (PMT) that was performed to verify logic operability.
Troubleshooting and testing revealed that RTB B trips when the following test switch configuration is established during the performance of SSPS Train B testing:
- 1. Logic B switch (S502) is in position 2 while in blocks inhibited. Normal operation is with the switch in position 24.
- 2. Permissive switch (S505) is in position 1 (Actually, when S505 is in any position other than "off"). Normal operation is with the switch in the "off" position.
- 3. Memory switch (S506) is in position 1. Normal operation is with the switch in the "off" position.
All three of the above switches are used for testing only. The RTB B trip is repeatable when the same test configuration as indicated above is established. The above test switch configuration is associated with testing the Intermediate Range logic function of SR 3.3.1.5.
The troubleshooting of the test circuitry resulted in the replacement of the two universal logic boards (A407 and A308) and reseating of the undervoltage driver board (A515).
After the universal logic board A308 was replaced and the undervoltage driver board A515 was reseated, the PMT performed via WO# 119644407 demonstrated that the logic functions of the A308 board and the A515 board tested satisfactorily.
The testing for the A407 card performed by work order (WO) # 119644407 demonstrated that the logic portion test for the universal logic card passed. However, the PMT was not completed satisfactorily due to anomalies noted with the RTB B opening when the Intermediate Range configuration was established for testing.
Enclosure CNL-18-104 E2 of 2 Further confirmation that the issue is with the Intermediate Range logic is provided in the following discussion. The P-10 permissive is 'set' when 2 out of 4 Power Range Nuclear Instrumentation channels sense neutron flux above 10% reactor power. After the P-10 permissive is 'set,' plant operators inhibit the Intermediate Range high neutron flux setpoint trips by momentarily placing the independent, trained "Intermediate Range Trip Block P-10" switches in the BLOCK position. When this action is complete, the trip due to high neutron flux from the Intermediate Range Instrumentation is disabled. The Intermediate Range high neutron flux trip is automatically enabled at any time 3 out of 4 Power Range Nuclear Instrumentation channels sense neutron flux below 10% reactor power.
When the SSPS rack is not in surveillance mode (i.e., during normal operation), there are positive indications of every power range instrumentation channel above P-10 available via Control Room Panel 1-XX-55-5 (i.e., by each channel's bistable lamp lit for NC41M,.NC42M, NC43M, and NC44M) as well as the alarm window on Control Room Panel 1-XA 4A/64E. With these conditions present and with the blocks restored by performance of the restoration section of 1-SI-99-10-B, it is known that the P-10 permissive is functional in each train of SSPS with the plant operating in Mode 1 above the P-10 setpoint. Thus, with plant operations above 10% power, any trips from the A407 universal logic board (which produce Intermediate Range trip signals) are disabled.
Considering the engineering judgement based on data review and input from Westinghouse, the most probable cause of the opening of RTB B is a degraded test circuit when the test switches are aligned to test the Intermediate Range trip circuit of universal logic board A407.
Based on the successful PMTs performed in WO# 119644407, which verified all logic functions worked as designed, TVA concluded that SSPS Train B can perform its safety function. Although the opening of RTB B when aligned in the test mode to the Intermediate Range channels is unacceptable, this deficiency does not invalidate the successfully performed logic tests that prove operability of the automatic actuation logic.