Information Notice 1990-02, Potential Degradation of Secondary Containment: Difference between revisions

Potential Degradation of Secondary Containment
	ML031130355
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
Issue date:	01/22/1990
From:	Rossi C; Office of Nuclear Reactor Regulation
To:	;
References
	IN-90-002, NUDOCS 9001160420
	Download: ML031130355 (9)
	v • d • e

Latest revision as of 04:02, 24 November 2019

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UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 January 22, 1990

NRC INFORMATION NOTICE NO. 90-02: POTENTIAL DEGRADATION OF SECONDARY

CONTAINMENT

Addressees

All holders of operating licenses or construction permits for boiling water

reactors (BWRs).

Purpose

This information notice is intended to alert addressees to potential problems

involving degradation of secondary containment as a result of unforeseen inter- actions with various normal plant ventilation systems and inadequate surveillance

testing of secondary containment integrity. It is expected that recipients will

review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in

this information notice do not constitute NRC requirements; therefore, no specific

action or written response is required.

Detcription of Circumstances:

Duane Arnold Energy Center

During a reactor building exhaust ventilation inspection, an Iowa Electric

system engineer discovered a large hole in the duct work (see Figure 1).

This hole allowed the main plant ventilation system to communicate directly

with the reactor building ventilation system, thus bypassing the standby gas

treatment system (SGTS) and providing a direct path for an untreated release

of radioactive effluents to the environment. This pathway would have existed

even with an automatic Engineered Safety Feature (ESF) isolation of the reactor

building ventilation system and an autostart of the SGTS. The licensee dis- covered that .its normal secondary containment integrity surveillance test

(which requires a measurement of 0.25 inch water vacuum with one train of

SGTS operating) was still apparently satisfied with the main plant ventilation

fans running. This has been the test configuration used at the plant since

initial startup in 1974. However, upon conducting the test with the SGTS

operating as designed and the main plant ventilation secured, the 0.25-inch

vacuum could not be achieved because of numerous secondary containment leaks.

A 10 CFR 50.72 4-hour notification was made to the NRC upon this discovery.

The licensee determined that during the performance of the secondary contain- ment integrity surveillance as it was previously conducted, the main plant

9001160420 Zjl

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IN 90-02 January 22, 1990 ventilation, turbine building ventilation, and the radwaste building ventila- tion exhaust fans had aided the SGTS in drawing the required vacuum. Because

surveillance tests performed since initial unit startup usually indicated that

the required negative pressure had been obtained, numerous secondary contain- ment integrity deficiencies went undetected and uncorrected. The maintenance

to correct this overall degradation of the secondary containment required more

than 3 weeks of effort to locate and repair numerous door seals, electrical

penetrations, steam tunnel boot seals, dampers, building seals, and duct systems.

These repairs resulted in an improvement in the measured secondary containment

vacuum from less than 0.08 inch of water to greater than 0.25 inch of water, as

determined by retesting with a new surveillance test procedure. This test now

requires all major plant exhaust ventilation fans that potentially communicate

with secondary containment to be secured.

Continued testing after repairs has shown that one main plant exhaust ventilation

fan can still draw an approximate 500 to 1000 standard cubic feet-per-minute (SCFM)

volume' from the reactor building ventilation system (the secondary containment

boundary) when the ESF-required isolation is in effect. As this circumstance

could result in an untreated ground-level release under certain accident scenarios, the licensee developed alarm response procedures designed to secure the main

plant ventilation fans when secondary containment isolation is initiated and

main plant exhaust ventilation radiation monitors reach specified values. Iowa

Electric is also considering long-term corrective action involving hardware

modifications that would prevent main plant ventilation from drawing air out

of the reactor building under accident conditions.

Monticello

As a result of the secondary containment deficiencies identified at Duane Arnold, the NRC resident inspector contacted the licensee for the Monticello plant con- cerning the procedures and practices for testing the secondary containment system.

The licensee had normally tested the secondary containment integrity with the

main plant exhaust fans running and isolated both supply and exhaust fans in

the reactor building. However, on October 14, 1989, the licensee conducted

the secondary containment integrity test with the main plant exhaust fans

secured and was not able to maintain the 0.25-inch water vacuum required by

the technical specifications. The vacuum reached in the reactor building was

only 0.1 inch of water. Preliminary investigation revealed that failure of

the test was due to leaks in the reactor building supply and exhaust system

dampers and various other secondary containment leaks. The licensee also

believes that the operation of the main plant exhaust fans assisted the SGTS

in drawing the required vacuum on the secondary containment, thus establishing

a path that bypassed the SGTS. A 10 CFR 50.72 notification was made to the NRC.

Discussion of Safety Significance:

Plant heating, ventilation, and air conditioning (HVAC) systems are diverse

among boiling water reactors. Interactions between these systems and the

standby gas treatment system could mask degradation of the secondary contain- ment boundary during surveillance testing and could exacerbate such degradatiof+t'

by diverting flow from the SGTS following an accident. -

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IN 90-02 January 22, 1990 For those plants discussed above, a portion of the secondary containment

boundary is formed by the ductwork and isolation dampers of the reactor build- ing ventilation system. This system exhausts to a common plenum area within

the reactor building, but outside secondary containment, where ventilation

flows from other plant HVAC systems are also directed. The high-capacity main

plant ventilation exhaust fans take suction from the plenum area and discharge

the flow through the reactor building roof stacks. Because of the high capa- city of the main plant exhaust fans and their proximity to the reactor building

ventilation system components that form part of the secondary containment

boundary, the potential exists for air flow to bypass the SGTS even when the

secondary containment is isolated. Further, if the main plant ventilation fans

are operated during surveillance testing, degradation of secondary containment

could go undetected as the main plant fans and the SGTS fans could collectively

draw the required vacuum.

In view of the possibility of the main plant ventilation systems masking

deficiencies in SGTS and/or secondary containment integrity and of creating

possible untreated release paths under accident conditions, licensees for other

BWR plants may wish to review the design and operation of major plant ventila- tion systems and to review their secondary containment integrity surveillance

procedures.

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: William L. Axelson, Region III

(708) 790-5574 John A. Kudrick, NRR

(301) 492-0871 James R. Hall, NRR

(301) 492-1391 Attachments:

1. Figure 1 - Reactor Building Ventilation

2. List of Recently Issued NRC Information Notices

Attachment 1 IN 90-02 January 22, 1990 Failed DucUng

Isolatlon Dampers

Reactor Buiding

VentShaft

Fgure 1

Reactor Building Ventilation

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Attachment 2 IN 90-02

- . . .11- 1 January 22, 1990 ti e

. .,

-1-LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

Importance of Proper 1/12/90 All holders of NRC

90-01 Response to Self-Identified materials licenses.

Violations by Licensees

89-90 Pressurizer Safety Valve 12/28/89 All holders of OLs

Lift Setpoint Shift or CPs for PWRs.

89-89 Event Notification 12/26/89 All holders of OLs

Worksheets or CPs for nuclear

power reactors.

Recent NRC-Sponsored 12/26/89 All holders of OLs

89-88 Testing of Motor-Operated or CPs for nuclear

Valves power reactors.

89-87 Disabling of Emergency 12/19/89 All holders of OLs

Diesel Generators by or CPs for nuclear

Their Neutral Ground-Fault power reactors.

Protection Circuitry

89-45, Metalclad, Low-Voltage 12/15/89 All holders of OLs

Supp. 2 Power Circuit Breakers or CPs for nuclear

Refurbished with power reactors.

Substandard Parts

89-86 Type HK Circuit Breakers 12/15/89 All holders of OLs

Missing Close Latch Anti- or CPs for nuclear

Shock Springs. power reactors.

89-85 EPA's Interim Final Rule 12/15/89 All medical, academic, on Medical Waste Tracking industrial, waste

and Management broker, and waste

disposal site licensees.

89-84 Failure of Ingersoll Rand 12/12/89 All holders of OLs

Air Start Motors as a Result or CPs for nuclear

of Pinion Gear Assembly power reactors.

Fitting Problems

OL = Operating License

CP = Construction Permit