05000293/LER-2016-006, C Main Steam Isolation Valve Inoperable
| ML16298A390 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 10/13/2016 |
| From: | Perkins E Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2.16.063 LER 16-006-00 | |
| Download: ML16298A390 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) |
| 2932016006R00 - NRC Website | |
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~Entergx October 13, 2016 U.S. Nuclear Regulatory Commission Attn: qocument Control Desk Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.
Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth. MA 02360
SUBJECT:
Licensee Event Report 2016-006-00, "C" Inboard Main Steam Isolation Valve Inoperable Pilgrim Nuclear Power Station Docket No. 50-293 Renewed License No. DPR-35 LETTER NUMBER: 2.;16.063
Dear Sir or Madam:
The enclosed Licensee Event Report 2016-006-00, "C" Inboard Main Steam Isolation Valve Inoperable, is submitted in accordance with 1 O Code of Federal Regulations 50. 73.
If you have any questions or require additional information please contact me at (508) 830-8323.
There are no regulatory commitments contained in this letter.
Sincerely,
~P~,!,
Everett P. Perkins, Jr.
Manager, Regulatory Assurance EPP/sc Attachment: Licensee Event Report 2016-006-00, "C" Inboard Main Steam Isolation Valve Inoperable (4 pages)
Entergy Nuclear Operations, Inc.
Pilgrim Nuclear Power Station cc:
Mr. Daniel H. Dorman Regional Administrator, Region I U.S. Nuclear Regulatory Commission 2100 Renaissance Blvd., Suite 100 King of Prussia, PA 19406-2713 Ms. Booma Venkataraman, Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8C2A Washington, DC 20555 NRC Senior Resident Inspector Pilgrim Nuclear Power Station Letter No. 2.16.063 Page 2 of 2
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Attachment Letter Number 2.16.063 Licensee Event Report 2016-006-00 "C" Inboard Main Steam Isolation Valve Inoperable (4 Pages)
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:
(11-2015) 1013112018
),_
Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.
Reported lessons learned are incorporated into the licensing process and fed back to LICENSEE EVENT REPORT (LER) industry. Send comments regarding burden estimate to the FOIA, Privacy and Information
..... :!I<.
Collections Branch (T-5 F53),
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer,
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Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct nr """"""' """ ~ ""'""" ic nnt '""' "" tn '""""" tn lhP '"'"-"""" """°""""
- 3. PAGE Pilgrim Nuclear Power Station 05000293 1 OF 4
- 4. TITLE "C" Main Steam Isolation Valve Inoperable
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR NIA NIA FACILITY NAME DOCKET NUMBER 08 16 2016 2016 -
006 - 00 10 13 2016 NIA
- - NIA
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 6: fCheckallthatann/vJ D 20.2201 (b)
D 20.2203(a)(3)(i)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
N D 20.2201 (d)
D 20.2203(a)(J){ii)
D 50.73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(a)(1)
D 20.2203(a)(4)
D so.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2)(i)
D 50.36(c)(1 )(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(a)(2)(ii)
D 50.36(c)(1)(ii)(A)
D 50.73(a)(2)(v)(A)
D 13.11 (a)(4)
D 20.2203(a)(2)(iii)
D so.3s(c)(2)
D 50.73(a)(2)(v)(B)
D 13.71(a)(5)
D 20.2203(a)(2)(iv)
D so.4s(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 13.11<a><1>
100 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50. 73(a)(2)(v)(D)
D 13.77(a)(2)(i)
D 20.2203(a)(2)(vi)
Q9 50.73(a)(2)(i)(B)
D 50.73(a)(2)(vii)
D 13.11 (a)(2)(ii)
D 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER I
LICENSEE CONTACT TELEPHONE NUMBER (Include Area.
Mr. Everett P. Perkins, Jr. - Regulatory Assurance Manager Code) 508-830-8323 MANU-REPORTABLE i MANU-REPORTA
CAUSE
SYSTEM COMPONENT FACTURER TOEPIX
CAUSE
SYSTEM COMPONENT FACTURER BLE
- 14. SUPPLEMENTAL REPORT EXPECTED
- 15. EXPECTED MONTH I DAY I YEA D YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
JXl NO SUBMISSION DATE I
I ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On 811612016, during performance of Main Steam Isolation Valve (MSIV) stroke time testing, with the plant operating at approximately 60% power, "C" inboard MSIV closure time was 7.4 seconds, exceeding the maximum closure time of 5 seconds referenced in Final Safety Analysis Report (FSAR) Table 5.2-4. The MSIV was declared inoperable. In accordance with the plant Technical Specifications (TS) the "C" outboard MSIV was closed and isolated. A team was formed to perform troubleshooting and determine corrective actions. With one main steam line inoperable the plant was limited to less than 75% power. On 8121116 the plant was shut down and entered a forced outage to repair the "C" inboard MSIV. The air pack was replaced and post maintenance tests were satisfactorily performed to restore the valve to Operable status.
On 8130116 Pilgrim Nuclear Power Station conservatively concluded that, based on the historical issues with the "C" inboard MSIV, the valve had been inoperable since stroke time testing was performed on May 24, 2016.
I There was no impact to public health and safety from this condition.
Page 2 of 4 BACKGROUND The function of the MS IVs is to prevent coolant inventory loss and protect plant personnel in the event of a steam line break outside containment. Also MSIVs provide a primary containment boundary after a loss of coolant accident (LOCA). The MSIVs are 20-inch air/spring operated, balanced "Y"-type globe valves.
There are four main steam lines. Each steam line has two MSIVs; one inside primary containment and one outside of primary containment. The MSIV "C" inboard valve is located inside primary containment, within the drywell.
Pneumatic power to the MS IVs located inside primary containment is supplied by nitrogen when the drywell atmosphere is inerted and by instrument air when the drywell is de-inerted. An air pack consisting of two-way, three-way and four-way valves and Alternating Current/Direct Current (AC/DC) solenoid valves are used to control MSIV position (open/closed).
The air pack employs a two-stage control scheme whereby pilot air pressure controls the position of a dual-cylinder four-way valve; repositioning spools within the cylinders to apply pneumatic power above or below the MSIV air actuator piston. The air pack has one AC and one DC solenoid operated valve for controlling pilot air pressure within the air pack.
Energizing either the AC or the DC solenoid valve individually will cause the MSIV to open. Pilot air (nitrogen) passes through the energized solenoid valves to the four-way valve, repositioning its spools to port air (nitrogen) beneath the MSIV air actuator piston which drives the valve stem and main poppet open.
To close the MSIV, the AC and DC solenoids must both be de-energized to vent pilot air from the four-way valve, repositioning its spools to vent nitrogen pressure below the actuator piston and to port air (nitrogen) above the MSIV air actuator piston which drives the MSIV closed (fast closure mode). De-energizing either the AC or the DC solenoid valve individually will not close the MSIV.
The MSIV is opened and held in the open position by compressed gas (air or nitrogen). Pneumatic pressure
' is required to compress the springs and open the MSIV. The air actuator assists the springs during fast closure of the MSIV. The springs extend when the valve closes. If loss of air or nitrogen gas pressure to the MSIV actuator occurs then spring force exerted upon the bottom spring seat will close the MSIV (fail-safe closure). The actuator provides no air-assist during fail-safe valve closure. The valve's fail-safe closure time is slower than its air-assisted fast closure time.
During fast closure mode, the MSIV must close in the required three to five seconds elapsed time using closure force provided by both its actuator and stored energy in the compressed springs. The MSIV utilizes a dashpot to control the valve closing speed The actuator stem passes through the dashpot. A piston threaded onto the actuator stem strokes within the dashpot cylinder, displacing dashpot hydraulic fluid through a needle valve (speed control valve). MSIV closing time can be controlled between three and five seconds by adjusting the speed control valve opening (orifice).
EVENT DESCRIPTION
On 8/16/2016, with Pilgrim Nuclear Power Station operating at approximately 60% Power during performance of MSIV Operability testing, closure time for the "C" inboard MSIV was 7.4 seconds which exceeded the maximum closure time of five seconds referenced in FSAR Table 5.2-4. The "C" inboard MSIV was declared inoperable. In accordance with plant TS the "C" outboard MSIV was closed and deactivated. The plant was restricted to less than 75% power due to only having three operating main steam lines. A decision was made to shut down and replace the air pack four-way valve and solenoid valves. The drywell was entered and an as-found inspection of the MSIV air pack was completed while the
Page 3 of 4 MSIV was open. The air pack four-way valve and solenoid valves were replaced. The pilot air pneumatic line was cleaned and sampled for debris. The "C" inboard MSIV was tested satisfactorily and declared operable.
CAUSE OF THE EVENT
The Root Cause of this event is system debris (accumulated dust/wear and corrosion products) in the "C" inboard MSIV pilot air tubing which were disturbed during the August 2015 pipe failure and subsequently collected in the solenoid valve soft disc. The vibration and high flow through the airline resulted in accumulated system debris being agitated and released into the airline. Subsequent MSIV stroke time testing moved the debris through the air line into the newly overhauled air pack and deposited it in the solenoid valve seats, resulting in slow stoke time of the "C" inboard MSIV. The *solenoid valves had been replaced in 2015 during RFO 20. At the same time, a new four-way valve had also been installed. during preventive maintenance.
CORRECTIVE ACTIONS
The "C" Inboard MSIV failed its TS required stroke time test. Therefore, the plant was shut down and the air pack four-way valve and solenoid valves were replaced.
The corrective action to prevent recurrence is to replace the Instrument Air header in the drywell along with all of the pilot air lines to the inboard MSIVs. This is currently scheduled to be accomplished during RF021.
SAFETY CONSEQUENCES
There were no consequences to the safety of the public, nuclear safety, industrial safety or radiological safety due to this event.
There were no potential consequences because the "C" inboard MSIV closed as required. The delay in the timing of closure is not significant. The "C" inboard MSIV is a fail-safe design and will fail closed. In addition, if the "C" inboard MSIV failed to close, reactor isolation is available by the "C" outboard MSIV. That valve remained operable and could have performed its design function if isolation had been necessary.
Based on the defense in depth fail-safe design of inboard and outboard MSIVs, risk is considered to be Low.
No actions to reduce the frequency or consequence are necessary.
REPORT ABILITY This event is reportable under 10 CFR 50. 73(a)(2)(i)(B), Condition Prohibited By Technical Specifications.
PREVIOUS EVENTS A review of Pilgrim Nuclear Power Station Licensee Event Reports for the past three years did not identify any similar occurrences.
REFERENCES:
Condition Report CR-PNP-2016-05987 Condition Report CR-PNP-2016-02163 Page 4 of 4