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.: 6835IN 86-57UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555July 11, 1986IE INFORMATION NOTICE NO. 86-57: OPERATING PROBLEMS WITH SOLENOID OPERATEDVALVES AT NUCLEAR POWER PLANTS

Addressees

All nuclear power reactor facilities holding an operating license or aconstruction permit.

Purpose

This notice is to advise recipients of a series of valve failures that haveoccurred 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 failuresoccurring at their facilities. However, suggestions contained in this noticedo not constitute NRC requirements; therefore, no specific action or writtenresponse is required.

Description of Circumstances

The NRC has received reports from licensees of operating nuclear power plantsinvolving failures of certain valves that are actuated by solenoid operatedvalves (SOVs) to operate properly. These failures have adversely affected theintended functions of the main steam isolation system, pressure relief andfluid control systems. Attachment 1 to this information notice describes thefailure events and the corrective actions taken.Discussion:In most of the cases described in Attachment 1, the cause for triggering theevent was attributed to a malfunctioning SOV that served as a pilot valve. Thisin turn resulted in the malfunction of the associated main valve. The failuresof the SOVs can be traced to the following different causes: (1) potentiallyhigh-temperature ambient conditions are not being continuously monitored in areaswhere SOVs are installed and operating in an energized state, (2) hydrocarboncontaminants, probably because backup air systems (e.g., plant service or shopair systems) are being used periodically and are not designed to "oil-free"specifications as required for Class IE service, (3) chloride contaminantscausing open circuits in coils of the SOVs, possibly as a result of questionablehandling, packaging, and storage procedures, (4) an active replacement partsprogram associated with the elastomers and other short-lived subcomponents usedin SOVs has not been adequately maintained, and (5) lubricants have been usedexcessively during maintenance. ASCO provides installation and maintenance8607090425 Attachment 1IN 86-57July 11, 1986 b. Viton has superior high-temperature performance when compared to EPand is impervious to hydrocarbons. Its major disadvantage is that itis less resistant to radiation than EP by a factor of ten. ASCOrecommends Viton for applications that are not oil-free and whereradiation levels do not exceed 20 megarads.On the basis of a licensee review of the Brunswick Station maintenancehistory, which showed the performance of Viton to be satisfactory in ASCOvalves, and the available literature and industry experience, the licenseereplaced all Unit 2 dual solenoid valves with valves having Viton seatsand seals. Because Viton has a 20-megarad limit, the licensee plans toreplace 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 sealmaterial, the licensee experienced several SOV failures resulting fromopen circuits of the dc coils on Unit 2. (Brunswick Station employs ASCONP8323A36V valves that use one ac coil and one dc coil in applicationsusing 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 thefailures indicated an open circuit in the dc coils. The coils werereplaced and the valves subsequently retested satisfactorily.On October 15, 1985, an unplanned closure of an MSIV occurred while Unit 2was operating at 99 percent full power. Closure of the MSIV occurred whenthe ac solenoid coil portion of the MSIV associated SOV was de-energizedin accordance with a periodic test procedure. It was not known then thatthere was an open circuit in the associated dc solenoid coil portion ofthe dual SOV. Consequently, when the ac coil was de-energized, closure ofthe MSIV resulted. The failed dc coil was replaced and then retestedsatisfactorily.Investigation into the failures of the dc coil by the licensee determinedthat the failures appeared to be separation of the very fine coil wire atthe junction point where it connects to the much larger field lead. Thisconnection point is a soldered connection that is then taped andlacquered.Further analysis of the coils (two failed dc coils plus five spares fromstorage) by the CP&L Research Center indicated the separation might becorrosion induced by chloride contaminants. To date, the licensee andASCO are unable to determine the source of the chloride. However,followup investigation by the NRC revealed that ASCO had previouslyexperienced similar dc coil open circuit anomalies after a surface ship-ment of SOVs overseas to Japan. At that time, ASCO believed that the saltwater ambient conditions during shipping may have been the source of thechlorine-induced failures. ASCO recommends specific handling, packaging,and storage conditions for spare parts and valves at facilitie Attachment 1IN 86-57July 11, 1986 The licensee initiated a temporary surveillance program to monitor opera-bility of the solenoid coils on October 16, 1985. A modification wasperformed to install a voltage dropping resistor in the individual coilcircuits so that they can be monitored directly from cabinets in thecontrol room. This allows continuity of the coil circuitry to be verifiedby measuring a voltage drop across the resistor. According to thelicensee, until the cause for failure can be determined, plans are tocheck the coil circuitry for continuity on a daily basis.2. Scram Discharge Solenoid Valve FailureIn November 1985, Carolina Power and Light's Brunswick facility experi-enced problems with several scram discharge SOVs. The problems wereidentified during periodic surveillance testing to determine the singlerod insertion times and resulted in several rods with slow insertiontimes. Initial troubleshooting isolated the problem to the SOVs in thescram discharge line for two of the control rods, which were subsequentlyreplaced 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 beenapplied by the licensee to all gaskets, seals, and diaphragms internal tothe valves during previous routine maintenance.. The licensee believesthat the excessive amount of lubricant may have blocked some of thevalves' internal passages or caused sticking of the diaphragms, therebycontributing to the slow insertion times. The technical manual for thesubject valves states that body passage gaskets should be lubricated withmoderate amounts of Dow Corning's Valve Seal Silicone Lubricant or anequivalent high-grade silicone grease.The licensee conducted successful scram tests on all other rods. Aperiodic retest of 10 percent of the control rods every 120 days asrequired by the Technical Specifications provides sufficient assurancethat this problem does not exist in other SOVs. In addition, the licenseestated that maintenance procedures and practices would be reviewed andmodified, as required, to prevent the application of excessive amounts oflubricant during repair or overhaul of components.Haddam Neck Nuclear Power PlantOn September 10, 1985, the Haddam Neck Nuclear Power Plant was operating at 100percent 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 theperformance of a preventive maintenance procedure developed to periodicallycycle 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, twofeedwater 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 thelicensee has been unable to determine the cause of the malfunction. The Attachment 2IN 86-57July 11, 1986LIST OF RECENTLY ISSUEDIE INFORMATION NOTICESInformation Date ofNotice No. Subject Issue Issued to86-56Reliability Of Main SteamSafety Valves7/10/86All PWR facilitiesholding an OL or CP86-5586-54Delayed Access To Safety-Related Areas And EquipmentDuring Plant EmergenciesCriminal Prosecution Of AFormer Radiation SafetyOfficer Who WillfullyDirected An UnqualifiedIndividual To PerformRadiographyImproper Use Of Heat Shrink-able Tubing7/10/866/27/866/26/8686-5386-52Conductor Insulation Degrada- 6/26/86tion On Foxboro Model EControllersExcessive Pneumatic Leakage 6/18/86In The Automatic Depressuriza-tion SystemAll power reactorfacilities holdingan OL or CPAll holders of by-product, source, orspecial nuclearmaterialAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll BWR facilitiesholding an OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll BWR facilitiesholding an OL or CP86-5186-5086-49Inadequate Testing To DetectFailures Of Safety-RelatedPneumatic Components OrSystemsAge/Environment InducedElectrical Cable FailuesInadequate Testing Of BoronSolution Concentration In TheStandby Liquid Control System6/18/866/16/866/13/8686-48OL = Operating LicenseCP = Construction Permit