05000254/LER-2020-002, Main Steam Line Drain Valve Declared Inoperable Due to Improper Torque Switch Setting
| ML20315A447 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 11/10/2020 |
| From: | Ohr K Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVP-20-080 LER 2020-002-00 | |
| Download: ML20315A447 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| 2542020002R00 - NRC Website | |
text
=~Exelon Generation SVP-20-080 November 10, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Unit 1 Renewed Facility Operating License No. DPR-28 and DPR-29 NRC Docket No. 50-254 and 50-265 10 CFR 50.73
Subject:
Licensee Event Report 254/2020-002-00 "Main Steam Line Drain Valve Declared Inoperable Due to Improper Torque Switch Setting" Enclosed is Licensee Event Report 254/2020-002-00 "Main Steam Line Drain Valve Declared Inoperable Due to Improper Torque Switch Setting," for Quad Cities Nuclear Power Station, Unit 1 and 2.
This report is submitted in accordance with 1 O CFR 50. 73(a)(2)(i)(B), for any operation or condition which was prohibited by the plant's Technical Specifications.
There are no regulatory commitments contained in this letter.
Should you have any questions concerning this report, please contact Sherrie Grant at (309) 227-2800.
'1. ~ \\c.."'
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Kenneth S. Ohr Site Vice President Quad Cities Nuclear Power Station cc:
Regional Administrator - NRC Region Ill NRC Senior Resident Inspector - Quad Cities Nuclear Power Station
Abstract
On July 1, 2020 and July 23, 2020, engineering identified the torque switch setting on the Unit 2 and Unit 1 Main Steam Line (MSL) outboard drain (1(2)-0220-2) motor operated valves (MOV) were found to be nonconservative with respect to the valve's design function under the expected worst-case operating conditions. Both valves were initially evaluated and declared operable because the valve was closed (safety function position) and was not required to be opened during the normal two-year operating cycle. On September 11, 2020 at 1100 CDT, Operations determined that although the valves were performing their isolation function, operability was no longer supported and the MSL outboard drain valves were declared inoperable.
This issue is being reported under 10CFRSO.73(a)(2)(i)(B) for any operation or condition which was prohibited by the plant's Technical Specifications (TS) because TS 3.6.1.3 Action Statement A.1 was not completed within the required time in July 2020 during the initial discovery of the torque switch setting issue.
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EllS) codes are identified in the text as [XX].
EVENT IDENTIFICATION Main Steam Drain Valve Declared Inoperable Due to Improper Torque Switch Setting
A. CONDITION PRIOR TO EVENT
Unit: 1&2 Event Date: September 11, 2020 Event Time: 1100 Reactor Mode: 1 Mode Name: Power Operations Power Level: 100%
SEQUENTIAL NUMBER 002 REV NO.
00 There were no other structures, systems or components (SSC) inoperable during this event time period that could have contributed to this event.
B. DESCRIPTION OF EVENT
On July 1, 2020, following review of an industry operating experience report, engineering identified the torque switch setting on the Unit 2 Main Steam [SB] Line outboard drain valve [ISV] (2-0220-2) motor operated valve (MOV) was nonconservative with respect to its design function under the expected worst-case operating conditions. The cause of as-left torque switch setting being lower than the required value was determined to be a latent error in the calculation used for these valves. The valve was initially called operable with a request for a formal Operability Evaluation (Op Eval), because the valve was closed (safety function position) and was not required to be opened during the normal two-year operating cycle.
Revision 00 of the Op Eval, completed on July 7, 2020, provided compensatory actions for the degraded automatic isolation function by revising procedures to have a dedicated operator ready to enter the Main Steam Isolation Valve (MSIV) room to manually ensure full closure of the valve should the valve need to be opened.
On July 23,2020, following an extent of condition review, engineering identified that the Unit 1 Main Steam Line outboard drain valve (1-0220-2) MOV torque switch setting was also incorrect. The Op Eval that was written to cover the previously identified Unit 2 valve was revised on August 5, 2020 to include the Unit 1 valve and requested similar compensatory actions. The basis for the Unit 2 valve operability was also applied to the Unit 1 valve.
On September 11, 2020 at 1100 CDT, Operations determined that the Op Eval no longer supported operability of the Unit 1 and Unit 2 Main Steam Line outboard drain valves because of an inability to meet Primary Containment Isolation Valve (PCIV) TS surveillance requirements (SR). The affected valves were declared inoperable and Technical Specification 3.6.1.3 Condition A was entered at that time. On SEQUENTIAL NUMBER 002 REV NO.
00 September 11, 2020 at 1339 CDT, the affected penetration flow path was isolated in accordance with TS 3.6.1.3 Action Statement A.1.
It was determined the valves had been inoperable since the initial discovery of the torque switch trip setting issue in July 2020. Thus, this issue is being reported under 10 CFR 50. 73(a)(2)(i)(B) for any operation or condition which was prohibited by the plant's Technical Specifications.
C. CAUSE OF EVENT
The cause of the Main Steam Line Drain MOVs inoperability was an incorrect torque switch setting due to historical non-conservatisms in the governing calculation. The condition prohibited by TS was caused by an operability determination that was not in alignment with the TS SRs regarding PCIV operability.
D. SAFETY ANALYSIS
System Design
The Main Steam Line Drain Valves are considered automatic PCIVs. The function of the PC IVs, in combination with other accident mitigation systems, is to limit fission product release during and following postulated Design Basis Accidents (DBAs). Primary Containment isolation within the time limits specified for those isolation valves designed to close automatically ensures that the release of radioactive material to the environment will be consistent with the assumptions using the safety analyses for a DBA. The MSL drain valves are normally closed and not required to be opened during the normal operating cycle.
Safety Impact Both Unit 1 and Unit 2 Main Steam Line Drain Valves have been fully closed, which is their safety function position, since Unit 1 and Unit 2 have been at power operation following their respective refueling outages. Since the valves are not opened during normal unit operation, the safety consequences of the degraded condition which only affects the valves ability to re-close after opening is minimal.
E. CORRECTIVE ACTIONS
YEAR 2020 SEQUENTIAL NUMBER 002 The Main Steam Line drain valves will be repaired to correct the torque switch setting issue in the next refuel outage on each unit.
Follow-up corrective actions include additional training for both Operations and Engineering on the Operability Evaluation process and an extent of condition review on all open Operability Evaluations to ensure conclusions support continued operability.
F. PREVIOUS OCCURRENCES
REV NO.
00 The station events database, LERs and IRIS were reviewed for similar events at Quad Cities Nuclear Power Station, with one event being identified. This event was a Safe Shutdown Makeup Pump (SSMP) discharge pressure calculation error. This event is similar in that it resulted in a condition outside of Technical Specification that was related to an engineering error in a calculation.
LER (254/2008-001-00) Past Operation of Safe Shutdown Makeup Pump Outside Technical Specifications Surveillance Requirements, 09/04/2008. An error in a calculation found that SSMP discharge pressure necessary to meet the TS surveillance requirement (SR) had increased. This calculation error resulted in historical TS SR testing failures of the corrected required SSMP discharge pressure. The cause was determined to be lack of procedural guidance in the performance and review of calculations.
G. COMPONENT FAILURE DATA
Failed Equipment: Unit 1 and Unit 2 Main Steam Line outboard drain valve MOV Component Manufacturer: Crane Component Model Number: 783-U Component Part Number: NIA This event has been reported to IRIS. Page _4_ of _4_