Information Notice 1989-63, Possible Submergence of Electrical Circuits Located Above the Flood Level Because of Water Intrusion and Lack of Drainage

Possible Submergence of Electrical Circuits Located Above the Flood Level Because of Water Intrusion and Lack of Drainage

ML031180733
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, 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, Crane
Issue date:	09/05/1989
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-89-063, NUDOCS 8908290014
Download: ML031180733 (4)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555September 5, 1989NRC INFORMATION NOTICE NO. 89-63: POSSIBLE SUBMERGENCE OF ELECTRICALCIRCUITS LOCATED ABOVE THE FLOOD LEVELBECAUSE OF WATER INTRUSION AND LACK OFDRAINAGE

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

This information notice is being provided to alert addressees that electricalcircuits located above the plant flood level within electrical enclosures maybecome submerged in water because appropriate drainage has not been provided.Failure of electrical circuits during service conditions, including postulatedaccidents, can occur due to submergence if water enters these enclosures andthere is no provision for drainage. The electrical enclosures addressed by thisnotice include terminal boxes, junction boxes, pull boxes, conduits, condulets,and other enclosures for end-use equipment (such as limit switches, motor oper-ators, and electrical penetrations), the contents of which may include cables,terminal blocks, electrical splices and connectors. It is expected that reci-pients will review this information for applicability to their facilities andconsider actions, as appropriate, to avoid similar problems. However, sugges-tions contained in this information notice do not constitute NRC requirements;therefore, no specific action or written response is required.

Description of Circumstances

On March 20, 1989, the Clinton Power Station experienced an unexpected ingressof water into the drywell. About 10 feet of water from the dryer pool drainedinto the reactor cavity pool causing about 4 inches of standing water in thedrywell. Following the event, the licensee found evidence of water intrusionin several electrical enclosures located above the flood level. These enclosuresdid not have drain holes. The licensee corrected the problem by drilling holesin all appropriate Junction boxes, terminal boxes, pull boxes, condulets, andend-use equipment enclosures inside the drywell and the containment.The Monticello plant found that a junction box for RHR pump motor leads con-tained several inches of water (NRC Inspection Report 50-263/87-013-DRS). Thebox did not have a drain hole. The licensee initially determined that the as-sociated conduits were routed through humid areas, which could have resulted8908290014

< N 89-63dSeptember 5, 1989 in condensation from the conduits accumulating in the box. However, the licenseelater postulated that hosing down of equipment in that area may have caused waterto enter the box through unsealed openings. In this instance, the circuits werefound wet but not yet submerged in the accumulating water. The licensee drilledweep holes in all appropriate motor-lead junction boxes and other enclosures tocorrect the problem.During an inspection performed at Clinton Power Station from August 17 throughAugust 21, 1987, NRC inspectors identified a terminal box without drain holes.The box was required to be environmentally qualified in accordance with therequirements of 10 CFR 50.49. Although the box was located above the postulatedplant flood level, it was subject to possible water and moisture intrusion thatcould submerge the contents of the box in an accident. Subsequently, the licenseeidentified 156 terminal boxes without drain holes, which could affect multiplesafety systems. The licensee drilled drain holes in the affected terminal boxes.During a followup inspection performed from February 6 through February 24, 1989,the NRC identified six additional junction boxes requiring drain holes. Severalof these boxes contained taped electrical splices which the licensee's environ-mental qualification program had not demonstrated to be environmentally qualifiedto perform their required function for the required duration if they became sub-merged following a loss-of-coolant accident (LOCA). Following this finding, thelicensee identified numerous other enclosures with taped splices that requireddrain holes.Discussion:The NRC regulation pertaining to environmental qualification specificallyregarding submergence is addressed in 10 CFR 50.49(e)(6), which states thatthe electrical equipment qualification program must consider submergence (ifsubject to being submerged). The regulation also makes reference to twoguidance documents: "Guidelines for Evaluating Environmental Qualificationof Class lE Electrical Equipment in Operating Reactors," November 1979 (DORGuidelines), and NUREG-0588, "Interim Staff Position on Environmental Quali-fication of Safety-Related Electrical Equipment." NUREG-0588, Paragraph 2.2(5)states that where equipment could be submerged, it should be identified anddemonstrated to be qualified by test for the duration required. DOR Guide-lines, Section 6, state that particular emphasis should be placed on commonproblems, such as protective enclosures installed upside down with drain holesat the top and penetrations in equipment housings for electrical connectionsbeing left unsealed or susceptible to moisture intrusion through strandedconductors.Water can enter and accumulate in electrical enclosures located above theflood level through various unsealed openings, including enclosure covers,conduits, and conduit fittings. Water may enter an enclosure through a runof conduit from an upper elevation or by directly impinging on unsealedopenings. Steam and humidity also may enter an enclosure through conduitsand unsealed openings and then condense and accumulate at the bottom of theenclosure. The content of the enclosure may become submerged as a result.Proper drain holes will prevent thi V N 89-63September 5, 1989 Submergence could occur during service conditions, including accidents such asa LOCA or other high-energy line break. For clarity,'aicomponent is consideredsubmerged if it is partially or completely immersed in water. Submergence ofcomponents in electrical enclosures may occur even though the enclosures arelocated above the plant flood level because of inadequate drainage in theenclosure.Water intrusion also may occur from hosing down the equipment during house-keeping. It is important to note that extreme care needs to be taken duringsuch activities so that the water does not penetrate unsealed enclosure openingsand travel through conduits to enclosures at lower elevations.Information Notice 84-57, "Operating Experience Related to Moisture Intrusionon Safety-Related Electrical Equipment at Commercial Power Plants," addressedwatertight sealing of all electrical conduits to junction boxes and conduit-to-terminal box connection points for safety-related equipment located in areas ofthe reactor building as well as for areas that are potentially subject to hightemperature steam or water impingement. This notice further addressed theimportance of ensuring that box drain holes and equipment interfaces are inconformance with the test setup established during equipment qualificationtesting and with the vendor's recommendations.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate NRR project--manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: A. S. Gautam, NRR(301) 492-1376H. Walker, NRR(301) 492-0867

Attachment:

List of Recently Issued NRC Information Notices Attachment11 89-63September 5, 1999Page 1 of ILIST OF RECENTLY ISSUEDNRC !IIFORMATION NCTICESInformationNotice No. Subject Issuance Issued toes.6289-6188-468Supp. 289-6C89-5989-5S89-5789-5689-45,Supp. 189-55Malfunction of Borg-Warner 8/31/89Pressure Seal Bonnet CheckValves Caused By VerticalMisalignment of DiskFailure of Borg-Warner Gate 8/30/89Valves to Close AgainstDifferential PressureLicensee Report of Defective 8/22/89Refurbished ValvesMaintenance of Teletherapy 8/18/PSUnitsSuppliers of Potentially 8/16/89Misrepresented FastenersDisablement of Turbine-Driven 8/3/89Auxiliary Feedwater Pump Dueto Closure of One of theParallel Steam Supply ValvesUnqualified Electrical 7/26/89Splices in Vendor-SuppliedEnvironmentally QualifiedEquipmentQuestionable Certification 7/20/89of material Supplied to theDefense Department by NuclearSuppliersMetalclad, Low-Voltage 7/6/89Power Circuit Breakers-RefawblisheWthl Substamlard-PartsDegradation of Containment 6/30/69Isolation Capability by aHigh-Energy Line BreakAll holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All NRC MedicalTeletherapy Licensect.All holders of OLsor CPs for nuclearpower reactors.All holoers of OLsor CPs for PWRs.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactors.All holders of OLsor CPs for nuclearpower reactbirsAll holders of OLsor CPs for nuclearpowrer reactors.OL

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• Construction PermitUNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON, D.C. 20555OFFICIAL BUSINESSPENALTY FOR PRIVATE USE, $300FIRST CLASS MAILPOSTAGE b FEES PAIDUSNRCPERMIT Ne. G-E7120555003956 1 1CO1CV1CY1FB1US NRC-OIRMDIV OF INFO SUP SVCSCHIEFRECORDS & ARCHIVES SVCS SECTW/F PD-122WASHINGTON DC 20555