05000333/LER-2016-002

LER-2016-002, Sticking DC Pilot in Solenoid Valve Cluster Assembly Results in Slow MSIV Closures

James A. Fitzpatrick Nuclear Power Plant
Event date:	2-25-2016
Report date:	4-25-2016
Reporting criterion:	10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
3332016002R00 - NRC Website

LER 16-002-00 for James A. Fitzpatrick Nuclear Power Plant, Regarding Sticking DC Pilot in Solenoid Valve Cluster Assembly Results in Slowly MSIV Closure

ML16116A245
Person / Time
Site:	FitzPatrick
Issue date:	04/25/2016
From:	Brian Sullivan Entergy Nuclear Northeast, Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
JAFP-16-0066 LER 16-002-00
Download: ML16116A245 (5)

used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

James A. FitzPatrick Nuclear Power Plant 05000 — 333

3. LER NUMBER

— 002 — 00 2016

Background

James A. FitzPatrick Nuclear Power Plant (JAF) has four main steam lines [El IS identifier: SB] between the reactor and the main turbine [TA]. These lines are designed to isolate in the event of design basis accidents. In the event of a main steam line break, the isolation prevents further radiological release. In the event of a loss of coolant (LOCA) accident, they isolate to maintain coolant inside of containment.

Two isolation valves are provided in series in a horizontal run of each main steam line, as close as practical to the primary containment. One inside (inboard) and the other outside (outboard) together form part of the primary containment barrier for Reactor Coolant System breaks inside the containment and part of the Reactor Coolant Pressure Boundary for main steam line breaks outside the primary containment.

The closure time of the main steam isolation valves (MSIVs) is a significant variable from a radiological standpoint. The MSIVs are required to close within 3 to 5 seconds after signal generation. The closure speed is designed to be slower than 3 seconds in order to lessen the pressure transient caused by an inadvertent simultaneous closure of all steam lines. The closure speed is designed to be faster than 5 second to minimize the release of fission products to the environment and retain reactor coolant.

Each MSIV is controlled by a solenoid I SUPPLY I valve cluster assembly (SVCA). There are three solenoid valves within the AC PILOT 2 WAY SVCA; AC Pilot solenoid valve, AC Test solenoid valve and a DC pilot solenoid valve. These three solenoids port air to and from other control TEST 3 WAY valves. The normally energized AC pilot valve and DC pilot valve must move to the de-energized position to change the DC PILOT 4 WAY position of the 2 and 4 way valves MSIV ACTUATOR which closes the MSIV. When both solenoids are de-energized, the below ♦ NORMAL CLOSED piston operator space is vented.

Simultaneously, the above piston operator space is pressurized, thus assisting the spring in closing the MSIV.

This licensee event report (LER) addresses a slow closure response for outboard MSIV 29A0V-86B and 29A0V-86C due to their DC pilot solenoid valves 2950V-86B3 and 2950V-86C3.

Event Description

On January 23, 2016, control room Operators inserted a manual Scram due to lowering intake levels resulting from frazil ice conditions in Lake Ontario. As part of the plant shutdown the MSIVs were closed. The closing time for the "B" outboard MSIV 29A0V-86B, was slow by as much as 9 seconds after the other valves indicated closed. The SVCA and 4-way valve were replaced and 29A0V-86B then stroked satisfactorily.

On January 27, 2016, the MSIV fast closure test ST-1B was performed on all MSIVs. MSIV 29A0V-86C closed in 6.9 seconds and all other MSIVs tested satisfactorily. The SVCA and 4-way valve were replaced and 29A0V-86C then stroked satisfactorily.

CLOSED

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James A. FitzPatrick Nuclear Power Plant 05000 — 333

3. LER NUMBER

— 002 — 00 2016

Event Analysis

On January 27, 2016, 29A0V-86C was taken closed using the slow close push button; the manual control switch was then taken from "Auto-open" to "closed". At this point, Operators released the slow close push button and the expected response was that the valve would remain closed. It temporarily drifted open and then reclosed. This can occur because both the AC and DC solenoids need to deenergize in order to close the MSIVs. If either the AC or DC solenoids stick in their seats the 2-way and 4-way valves would be positioned to port instrument air to the underside of the MSIV actuator piston causing the valve to open.

A failure analysis on the SVCA for MSIVs 29A0V-86B and 29A0V-86C was conducted by Exelon PowerLabs and the results were delivered to JAF on February 25, 2016, in report ENT-40072. The only anomaly discovered was that both DC pilots in the SVCAs exhibited slow average vent times of 4.94-seconds for 29S0V-86B3 and 1.95-seconds for 29S0V-86C3 instead of an instantaneous actuation. A momentarily 'stuck' AC or DC solenoid could explain an increase in MSIV stroke time. However, the Exelon PowerLabs tests confirm that the AC solenoid consistently stroked to relieve air pressure instantaneously while the DC solenoid exhibited a delay.

The slow DC pilot valve responses affected the required closing time in two MSIVs. This condition caused two independent channels of a system used to control the release of radioactive material to become inoperable; reportable per 10 CFR 50.73(a)(2)(vii).

Cause

The common cause of the delayed closure of MSIVs 29A0V-86B and 29A0V-86C was "sticking" of DC solenoid valves 29S0V-86B3 and 29S0V-86C3.

Similar Events Internal The ST-1B MSIV fast closure testing and results are trended by the 1ST Program. Prior to this event there were two recent instances where MSIV closing time was greater than 5 seconds at JAF.

CR-JAF-2014-04335 - Close time on 29A0V-86B was 5.5 seconds during ST-1B testing. The apparent cause was high resistance in an electrical contact for the MSIV pilot closure logic.

CR-JAF-2008-01147 - Close time on 29A0V-86C was 43.12 seconds during ST-1B testing. The apparent cause was attributed to contamination introduced through the instrument air system into the 4-way valve.

External Limerick Generating Station, Unit 1, LER-2012-001 — Three MSIVs failed hot closing stroke time due to issues with testing accuracy.

Quad Cities Nuclear Power Station, Unit 1, LER-2013-002 — Four outboard MSIVs failed to close within 5 seconds because the actuator seals had degraded due to age and wear.

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James A. FitzPatrick Nuclear Power Plant 05000 — 333

3. LER NUMBER

— 002 — 00 2016 Manufacturer:

Manufacturer Model Number:

NPRDS Manufacturer Code:

NPRDS Component Code:

FitzPatrick Component ID:

Automatic Valve Corp AV 6910-075 A613

FSV

29S0V-86B3 and 29S0V-86C3

Corrective Actions

Completed Actions

• SVCAs were replaced and both MSIVs were tested successfully.

Future Actions

• MSIV SVCA Preventative Maintenance (PM) frequency change from 8 years to 6 years

• Vendor is investigating the DC pilot solenoid failures and additional corrective actions will be based on the results.

Safety Significance

There was no actual radiological or nuclear safety consequence during this event.

Two isolation valves in each main steam line close automatically to prevent fuel damage by limiting the loss of reactor coolant in the case of a major steam system leak, and to limit the release of radioactive materials by isolating the primary containment. Valve stroke time is required to be short enough to limit the release of radioactive material in accordance with accident analyses. A maximum MSIV closure time of 10.5 seconds would limit the total amount of liquid and steam lost from the primary system to prevent core damage, and this closure time will ensure that any radiological doses are well below the guidelines set forth in 10 CFR 100.

This deficiency only affected two outboard MSIVs. In both cases, the inboard MSIVs performed satisfactorily.

Therefore, all main steam lines were able to perform their intended safety function to isolate.

References

• Condition Report: CR-JAF-2016-00263, 29A0V-86B Slow Closure

• Condition Report: CR-JAF-2016-00324, 29A0V-86C Slow Closure

• Exelon PowerLabs Report: ENT-40072, Failure Analysis on MSIV Solenoid Valve Cluster Assemblies 29A0V-86B and 29A0V-86C

• FSAR-JAF-4.6, Main Steam Line Isolation Valves