05000298/LER-2018-001, Inadequate Packing on Motor Operated Valve Results in Unplanned High Pressure Coolant Injection Inoperability and a Loss of Safety Function
| ML18136A539 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/08/2018 |
| From: | Dent J Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2018030 LER 2018-001-00 | |
| Download: ML18136A539 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982018001R00 - NRC Website | |
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Nebraska Public Power District Always there when you need us NLS2018030 May 8, 2018 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2018-001-00 Cooper Nuclear Station, Docket No. 50-298, DPR-46
Dear Sir or Madam:
The purpose of this correspondence is to forward Licensee Event Report 2018-001-00.
There are* no new commitments contained in this letter.
Sincerely, ohn Dent, Jr.
Vice President Nuclear-
. Chief Nuclear Officer
/jo Attachment: Licensee Event Report 2018-001-00 cc:
Regionai Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Plant Licensing Branch IV Senior Resident Inspector w/attachment USNRC-CNS SRAB Administrator w/attachment NPG Distribution w/attachment INPO Records Center w/attachment via ICES entry SORC Chairman w/attachment CNS Records w/attachment COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com
NRG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2018) i
, the NRC may not conduct or sponsor, and a person is not required to respond to the information collection.
- 13. Page Cooper Nuclear Station 05000298 1 OF 3
- 4. Title Inadequate Packing on Motor Operated Valve Results in Unplanned High Pressure Coolant Injection lnoperability and a Loss of Safety Function
- 5. Event Date
- 6. LER Number
- 7. Report Date
- 8. Other Facilities Involved Sequential Rev Facility Name Docket Number Month Day Year Year Month Day Year Number No.
05000 03 10 18 2018
- - 001
- - 00 05 08 18 Facility Name Docket Number 05000
- 9. Operating Mode Abstract (Limit to 1400 spaces, i.e., approximately 14 single-spaced typewritten lines)
On March 10, 2018, while returning High Pressure Coolant Injection (HPCI) and Augmented Off-Gas to service following planned maintenance, Cooper Nuclear Station (CNS) Operations personnel observed rising pressure in the drywell.
During the HPCI restoration, HPCI-MOV-M015 was cycled and left open as part of the return to service process. Shortly thereafter, drywell temperature and pressure started to slowly rise. It was determined the most likely cause of the change in drywell parameters was due to the stroking of HPCI-MOV-M015. A decision was made to close the valve to stop the leak, resulting in an unplanned entry into Technical Specification Limiting Condition for Operation 3.5.1, due to HPCI inoperability. Following valve closure, drywell temperature and pressure, along with the unidentified leakage rate, decreased. A decision was made to perform a normal plant shutdown to make repairs.
CNS entered Mode 3, Hot Shutdown, on March 11, 2018. New packing was installed on HPCI-MOV-M015 and CNS returned to Mode 1, Power Operation, on March 17, 2018.
The cause of the packing leak was determined to be that in effort to preserve and maximize the margin for the stroking function, packing consolidation and torquing methods were altered which impacted packing sealing performance.
No safety consequences were associated with this condition.
NRC FORM 366 (04-2018)
PLANT STATUS SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 Cooper Nuclear Station (CNS) was in Mode 1, Power Operations, 100 percent power, at the time of discovery.
BACKGROUND The High Pressure Coolant Injection (HPCI) System [EIIS:BJ] provides protection to the core for the case of a small break in the reactor coolant pressure boundary which does not result in a rapid depressurization of the reactor vessel. The HPCI System permits the nuclear plant to be shutdown while maintaining sufficient reactor vessel water inventory until the reactor vessel is depressurized. The HPCI System continues to operate until reactor vessel pressure is below the pressure at which Low Pressure Coolant Injection [EIIS:BO] operation or Core Spray System [EIIS:BM] operation can be used to maintain core cooling.
HPCI consists of a steam turbine assembly [EIIS:TRB] driving a multi-stage booster and main pump assembly [EIIS:P] and system piping, valves, controls and instrumentation. The HPCI turbine is driven by steam from the reactor which is generated by decay and residual heat.
There are two normally open containment isolation valves in the main steam supply line to the turbine. One of these valves, HPCI-MOV-M015 is located in the drywell. These containment isolation valves [EIIS:ISV]
automatically close upon receipt of a HPCI turbine steam line high flow signal, or a HPCI turbine steam supply low pressure signal, or high steam line space temperature.
EVENT DESCRIPTION
On March 10, 2018, while returning HPCI and Augmented Off-Gas to service following planned maintenance to repair a steam leak on an associated drain line, CNS entered abnormal procedure 2.4PC, "Primary Containment Control" due to rising pressure in the drywell.
During the HPCI restoration, HPCI-MOV-M015 steam supply inboard isolation valve was cycled and left open as part of the return to service process. Shortly thereafter, drywell temperature and pressure started to slowly rise, causing entry into the abnormal procedure. Operations and Engineering personnel determined the most likely cause of the change in drywell parameters was due to the stroking of HPCI-MOV-M015. A decision was made to close the valve to stop the leak, causing HPCI to be inoperable resulting in an unplanned entry into Technical Specification Limiting Condition for Operation 3.5.1 due to isolating the steam supply to HPCI.
Following valve closure, drywell area temperatures and pressure, along with the unidentified leakage rate, decreased. A decision was made to perform a normal plant shutdown to make repairs.
CNS entered Mode 3, Hot Shutdown, on March 11, 2018. New packing was installed on HPCI-MOV-M015 on March 15, 2018, and CNS returned to Mode 1, Power Operation, on March 17, 2018.
NRC FORM 366 (04-2018)
Page 2 of 3 (04-2018)
U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 3/31/2020
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LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readinq-rm/doc-collections/nureqs/staff/sr1022/r3[)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITYNAME
- 2. DOCKET NUMBER
- 3. LER NUMBER YEAR Cooper Nuclear Station 05000-298 2018 BASIS FOR REPORT SEQUENTIAL NUMBER
- - 001 REV NO.
- - 00 This event is being reported per 1 O CFR 50. 73(a)(2)(v) as "any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to..... (D) Mitigate the consequences of an accident."
Event Notification 53253 was made at 13:54, March 10, 2018.
SAFETY SIGNIFICANCE
This is a safety system functional failure. There were no safety consequences of this failure since the plant shutdown to repair the problem long before any technical specification limits were exceeded. All plant systems responded as expectep.
CAUSE
In effort to preserve and maximize the margin for the MOV stroking function, packing consolidation and torquing methods were altered which impacted packing sealing performance.
CORRECTIVE ACTIONS
Verified Reactor Core Isolation Cooling [EIIS:BN] was operable by administrative means concurrent with declaration of HPCI inoperable.
HPCI-MOV-M0-15 was repacked.
To prevent recurrence, station procedures, where the margin to packing performance has been allowed to decline, will be corrected.
PREVIOUS EVENTS There have been no events reported in the last three years related to valve packing.
NRC FORM 366 (04-2018)