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 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 OF RECENTLY ISSUED NRC !IIFORMATION

NCTICES Information

Notice No. Subject Issuance Issued to es.62 89-61 88-468 Supp. 2 89-6C 89-59 89-5S 89-57 89-56 89-45, Supp. 1 89-55 Malfunction

of Borg-Warner

8/31/89 Pressure Seal Bonnet Check Valves Caused By Vertical Misalignment

of Disk Failure of Borg-Warner

Gate 8/30/89 Valves to Close Against Differential

Pressure Licensee Report of Defective

8/22/89 Refurbished

Valves Maintenance

of Teletherapy

8/18/PS Units Suppliers

of Potentially

8/16/89 Misrepresented

Fasteners Disablement

of Turbine-Driven

8/3/89 Auxiliary

Feedwater

Pump Due to Closure of One of the Parallel Steam Supply Valves Unqualified

Electrical

7/26/89 Splices in Vendor-Supplied

Environmentally

Qualified Equipment Questionable

Certification

7/20/89 of material Supplied to the Defense Department

by Nuclear Suppliers Metalclad, Low-Voltage

7/6/89 Power Circuit Breakers-RefawblisheWthl

Substamlard- Parts Degradation

of Containment

6/30/69 Isolation

Capability

by a High-Energy

Line Break All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All NRC Medical Teletherapy

Licensect.

All holders of OLs or CPs for nuclear power reactors.All holoers of OLs or CPs for PWRs.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactbirs All holders of OLs or CPs for nuclear powrer reactors.OL

• Operating

License CP

• Construction

Permit UNITED STATES NUCLEAR REGULATORY

COMMISSION

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