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 Office of Nuclear Reactor Regulation
To:
References
IN-89-063, NUDOCS 8908290014
Download: ML031180733 (4)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 September 5, 1989 NRC INFORMATION NOTICE NO. 89-63: POSSIBLE SUBMERGENCE OF ELECTRICAL

CIRCUITS LOCATED ABOVE THE FLOOD LEVEL

BECAUSE OF WATER INTRUSION AND LACK OF

DRAINAGE

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees that electrical

circuits located above the plant flood level within electrical enclosures may

become submerged in water because appropriate drainage has not been provided.

Failure of electrical circuits during service conditions, including postulated

accidents, can occur due to submergence if water enters these enclosures and

there is no provision for drainage. The electrical enclosures addressed by this

notice 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 and

consider 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 ingress

of water into the drywell. About 10 feet of water from the dryer pool drained

into the reactor cavity pool causing about 4 inches of standing water in the

drywell. Following the event, the licensee found evidence of water intrusion

in several electrical enclosures located above the flood level. These enclosures

did not have drain holes. The licensee corrected the problem by drilling holes

in all appropriate Junction boxes, terminal boxes, pull boxes, condulets, and

end-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). The

box did not have a drain hole. The licensee initially determined that the as- sociated conduits were routed through humid areas, which could have resulted

8908290014

< N 89-63 dSeptember 5, 1989 in condensation from the conduits accumulating in the box. However, the licensee

later postulated that hosing down of equipment in that area may have caused water

to enter the box through unsealed openings. In this instance, the circuits were

found wet but not yet submerged in the accumulating water. The licensee drilled

weep holes in all appropriate motor-lead junction boxes and other enclosures to

correct the problem.

During an inspection performed at Clinton Power Station from August 17 through

August 21, 1987, NRC inspectors identified a terminal box without drain holes.

The box was required to be environmentally qualified in accordance with the

requirements of 10 CFR 50.49. Although the box was located above the postulated

plant flood level, it was subject to possible water and moisture intrusion that

could submerge the contents of the box in an accident. Subsequently, the licensee

identified 156 terminal boxes without drain holes, which could affect multiple

safety 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. Several

of these boxes contained taped electrical splices which the licensee's environ- mental qualification program had not demonstrated to be environmentally qualified

to perform their required function for the required duration if they became sub- merged following a loss-of-coolant accident (LOCA). Following this finding, the

licensee identified numerous other enclosures with taped splices that required

drain holes.

Discussion:

The NRC regulation pertaining to environmental qualification specifically

regarding submergence is addressed in 10 CFR 50.49(e)(6), which states that

the electrical equipment qualification program must consider submergence (if

subject to being submerged). The regulation also makes reference to two

guidance documents: "Guidelines for Evaluating Environmental Qualification

of Class lE Electrical Equipment in Operating Reactors," November 1979 (DOR

Guidelines), 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 and

demonstrated to be qualified by test for the duration required. DOR Guide- lines, Section 6, state that particular emphasis should be placed on common

problems, such as protective enclosures installed upside down with drain holes

at the top and penetrations in equipment housings for electrical connections

being left unsealed or susceptible to moisture intrusion through stranded

conductors.

Water can enter and accumulate in electrical enclosures located above the

flood level through various unsealed openings, including enclosure covers, conduits, and conduit fittings. Water may enter an enclosure through a run

of conduit from an upper elevation or by directly impinging on unsealed

openings. Steam and humidity also may enter an enclosure through conduits

and unsealed openings and then condense and accumulate at the bottom of the

enclosure. The content of the enclosure may become submerged as a result.

Proper drain holes will prevent this.

V N 89-63 September 5, 1989 Submergence could occur during service conditions, including accidents such as

a LOCA or other high-energy line break. For clarity,'aicomponent is considered

submerged if it is partially or completely immersed in water. Submergence of

components in electrical enclosures may occur even though the enclosures are

located above the plant flood level because of inadequate drainage in the

enclosure.

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 during

such activities so that the water does not penetrate unsealed enclosure openings

and travel through conduits to enclosures at lower elevations.

Information Notice 84-57, "Operating Experience Related to Moisture Intrusion

on Safety-Related Electrical Equipment at Commercial Power Plants," addressed

watertight sealing of all electrical conduits to junction boxes and conduit-to- terminal box connection points for safety-related equipment located in areas of

the reactor building as well as for areas that are potentially subject to high

temperature steam or water impingement. This notice further addressed the

importance of ensuring that box drain holes and equipment interfaces are in

conformance with the test setup established during equipment qualification

testing and with the vendor's recommendations.

This information notice requires no specific action or written response. If

you have any questions about the information in this notice, please contact

one of the technical contacts listed below or the appropriate NRR project

--manager.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: A. S. Gautam, NRR

(301) 492-1376 H. Walker, NRR

(301) 492-0867 Attachment: List of Recently Issued NRC Information Notices

Attachment

11 89-63 September 5, 1999 Page 1 of I

LIST OFRECENTLY ISSUED

NRC!IIFORMATION NCTICES

Information

Notice No. Subject Issuance Issued to

es.62 Malfunction of Borg-Warner 8/31/89 Pressure Seal Bonnet Check All holders of OLs

Valves Caused By Vertical or CPs for nuclear

Misalignment of Disk power reactors.

89-61 Failure of Borg-Warner Gate 8/30/89 Valves to Close Against All holders of OLs

Differential Pressure or CPs for nuclear

power reactors.88-468 Licensee Report of Defective

Supp. 2 Refurbished Valves 8/22/89 All holders of OLs

or CPs for nuclear

power reactors.

89-6C Maintenance of Teletherapy 8/18/PS All NRCMedical

Units Teletherapy Licensect.

89-59 Suppliers of Potentially

Misrepresented Fasteners 8/16/89 All holders of OLs

or CPs for nuclear

power reactors.

89-5S Disablement of Turbine-Driven

Auxiliary Feedwater Pump Due 8/3/89 All holoers of OLs

to Closure of One of the or CPs for PWRs.

Parallel Steam Supply Valves

89-57 Unqualified Electrical 7/26/89 Splices in Vendor-Supplied All holders of OLs

Environmentally Qualified or CPs for nuclear

Equipment power reactors.

89-56 Questionable Certification 7/20/89 of material Supplied to the All holders of OLs

Defense Department by Nuclear or CPs for nuclear

Suppliers

power reactors.

89-45, Metalclad, Low-Voltage 7/6/89 Supp. 1 Power Circuit Breakers All holders of OLs

- RefawblisheWthl Substamlard- or CPs for nuclear

Parts power reactbirs

89-55 Degradation of Containment 6/30/69 All holders of OLs

Isolation Capability by a or CPs for nuclear

High-Energy Line Break powrer reactors.

OL

• Operating License

CP* Construction Permit

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