Information Notice 1986-57, Operating Problems with Solenoid Operated Valves at Nuclear Power Plants

Operating Problems with Solenoid Operated Valves at Nuclear Power Plants

ML031220718
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	07/11/1986
From:	NRC/IE
To:
References
IN-86-057, NUDOCS 8607090425
Download: ML031220718 (4)

11$S ORIGINAL SSINS No.:

IN 86-57 6835 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 July 11, 1986 IE INFORMATION NOTICE NO. 86-57: OPERATING PROBLEMS WITH SOLENOID OPERATED

VALVES AT NUCLEAR POWER PLANTS

Addressees

All nuclear power reactor facilities holding an operating license or a

construction permit.

Purpose

This notice is to advise recipients of a series of valve failures that have

occurred recently at several nuclear power plants. It is expected that recipi- ents will review the events discussed below for applicability to their facili- ties and consider actions, if appropriate, to preclude similar valve failures

occurring at their facilities. However, suggestions contained in this notice

do not constitute NRC requirements; therefore, no specific action or written

response is required.

Description of Circumstances

The NRC has received reports from licensees of operating nuclear power plants

involving failures of certain valves that are actuated by solenoid operated

valves (SOVs) to operate properly. These failures have adversely affected the

intended functions of the main steam isolation system, pressure relief and

fluid control systems. Attachment 1 to this information notice describes the

failure events and the corrective actions taken.

Discussion:

In most of the cases described in Attachment 1, the cause for triggering the

event was attributed to a malfunctioning SOV that served as a pilot valve. This

in turn resulted in the malfunction of the associated main valve. The failures

of the SOVs can be traced to the following different causes: (1) potentially

high-temperature ambient conditions are not being continuously monitored in areas

where SOVs are installed and operating in an energized state, (2) hydrocarbon

contaminants, probably because backup air systems (e.g., plant service or shop

air systems) are being used periodically and are not designed to "oil-free"

specifications as required for Class IE service, (3) chloride contaminants

causing open circuits in coils of the SOVs, possibly as a result of questionable

handling, packaging, and storage procedures, (4) an active replacement parts

program associated with the elastomers and other short-lived subcomponents used

in SOVs has not been adequately maintained, and (5) lubricants have been used

excessively during maintenance. ASCO provides installation and maintenance

8607090425

Attachment 1 IN 86-57 July 11, 1986 b. Viton has superior high-temperature performance when compared to EP

and is impervious to hydrocarbons. Its major disadvantage is that it

is less resistant to radiation than EP by a factor of ten. ASCO

recommends Viton for applications that are not oil-free and where

radiation levels do not exceed 20 megarads.

On the basis of a licensee review of the Brunswick Station maintenance

history, which showed the performance of Viton to be satisfactory in ASCO

valves, and the available literature and industry experience, the licensee

replaced all Unit 2 dual solenoid valves with valves having Viton seats

and seals. Because Viton has a 20-megarad limit, the licensee plans to

replace these elastomers every 3.3 years to meet environmental qualifica- tion requirements for the MSIV application.

After replacing the faulty valves with valves having Viton disc and seal

material, the licensee experienced several SOV failures resulting from

open circuits of the dc coils on Unit 2. (Brunswick Station employs ASCO

NP8323A36V valves that use one ac coil and one dc coil in applications

using the subject dual solenoid valve.)

On October 5, 1985, the dc coils of two MSIVs failed during the perfor- mance of post-maintenance testing of the MSIVs. Investigation into the

failures indicated an open circuit in the dc coils. The coils were

replaced and the valves subsequently retested satisfactorily.

On October 15, 1985, an unplanned closure of an MSIV occurred while Unit 2 was operating at 99 percent full power. Closure of the MSIV occurred when

the ac solenoid coil portion of the MSIV associated SOV was de-energized

in accordance with a periodic test procedure. It was not known then that

there was an open circuit in the associated dc solenoid coil portion of

the dual SOV. Consequently, when the ac coil was de-energized, closure of

the MSIV resulted. The failed dc coil was replaced and then retested

satisfactorily.

Investigation into the failures of the dc coil by the licensee determined

that the failures appeared to be separation of the very fine coil wire at

the junction point where it connects to the much larger field lead. This

connection point is a soldered connection that is then taped and

lacquered.

Further analysis of the coils (two failed dc coils plus five spares from

storage) by the CP&L Research Center indicated the separation might be

corrosion induced by chloride contaminants. To date, the licensee and

ASCO are unable to determine the source of the chloride. However, followup investigation by the NRC revealed that ASCO had previously

experienced similar dc coil open circuit anomalies after a surface ship- ment of SOVs overseas to Japan. At that time, ASCO believed that the salt

water ambient conditions during shipping may have been the source of the

chlorine-induced failures. ASCO recommends specific handling, packaging, and storage conditions for spare parts and valves at facilities.

Attachment 1 IN 86-57 July 11, 1986 The licensee initiated a temporary surveillance program to monitor opera- bility of the solenoid coils on October 16, 1985. A modification was

performed to install a voltage dropping resistor in the individual coil

circuits so that they can be monitored directly from cabinets in the

control room. This allows continuity of the coil circuitry to be verified

by measuring a voltage drop across the resistor. According to the

licensee, until the cause for failure can be determined, plans are to

check the coil circuitry for continuity on a daily basis.

2. Scram Discharge Solenoid Valve Failure

In November 1985, Carolina Power and Light's Brunswick facility experi- enced problems with several scram discharge SOVs. The problems were

identified during periodic surveillance testing to determine the single

rod insertion times and resulted in several rods with slow insertion

times. Initial troubleshooting isolated the problem to the SOVs in the

scram discharge line for two of the control rods, which were subsequently

replaced and tested satisfactorily.

The licensee disassembled the failed SOVs, which were manufactured by ASCO

(Model HV-90-405-2A), for failure analysis. When the valves were disas- sembled, it was noted that copious amounts of silicone lubricant had been

applied by the licensee to all gaskets, seals, and diaphragms internal to

the valves during previous routine maintenance.. The licensee believes

that the excessive amount of lubricant may have blocked some of the

valves' internal passages or caused sticking of the diaphragms, thereby

contributing to the slow insertion times. The technical manual for the

subject valves states that body passage gaskets should be lubricated with

moderate amounts of Dow Corning's Valve Seal Silicone Lubricant or an

equivalent high-grade silicone grease.

The licensee conducted successful scram tests on all other rods. A

periodic retest of 10 percent of the control rods every 120 days as

required by the Technical Specifications provides sufficient assurance

that this problem does not exist in other SOVs. In addition, the licensee

stated that maintenance procedures and practices would be reviewed and

modified, as required, to prevent the application of excessive amounts of

lubricant during repair or overhaul of components.

Haddam Neck Nuclear Power Plant

On September 10, 1985, the Haddam Neck Nuclear Power Plant was operating at 100

percent power when one of the six SOVs in the auxiliary feedwater system (AFW)

failed to change state when de-energized. This failure was detected during the

performance of a preventive maintenance procedure developed to periodically

cycle each of the six SOVs to prevent a sticking problem similar to SOV fail- ures previously experienced on November 2, 1984. In that earlier event, two

feedwater bypass valves failed to open automatically and the cause was deter- mined to be sticking SOVs. The faulty SOV was ASCO Model NP8320A-185E and the

licensee has been unable to determine the cause of the malfunction. The

Attachment 2 IN 86-57 July 11, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-56 Reliability Of Main Steam 7/10/86 All PWR facilities

Safety Valves holding an OL or CP

86-55 Delayed Access To Safety- 7/10/86 All power reactor

Related Areas And Equipment facilities holding

During Plant Emergencies an OL or CP

86-54 Criminal Prosecution Of A 6/27/86 All holders of by- Former Radiation Safety product, source, or

Officer Who Willfully special nuclear

Directed An Unqualified material

Individual To Perform

Radiography

86-53 Improper Use Of Heat Shrink- 6/26/86 All power reactor

able Tubing facilities holding

an OL or CP

86-52 Conductor Insulation Degrada- 6/26/86 All power reactor

tion On Foxboro Model E facilities holding

Controllers an OL or CP

86-51 Excessive Pneumatic Leakage 6/18/86 All BWR facilities

In The Automatic Depressuriza- holding an OL or CP

tion System

86-50 Inadequate Testing To Detect 6/18/86 All power reactor

Failures Of Safety-Related facilities holding

Pneumatic Components Or an OL or CP

Systems

86-49 Age/Environment Induced 6/16/86 All power reactor

Electrical Cable Failues facilities holding

an OL or CP

86-48 Inadequate Testing Of Boron 6/13/86 All BWR facilities

Solution Concentration In The holding an OL or CP

Standby Liquid Control System

OL = Operating License

CP = Construction Permit