Information Notice 1985-85, Systems Interaction Event Resulting in Reactor System Safety Relief Valve Opening Following a Fire-Protection Deluge System Malfunction

Systems Interaction Event Resulting in Reactor System Safety Relief Valve Opening Following a Fire-Protection Deluge System Malfunction

ML031180210
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, Skagit, Marble Hill, Crane
Issue date:	10/31/1985
From:	Jordan E NRC/IE
To:
References
IN-85-085, NUDOCS 8510290039
Download: ML031180210 (4)

SSINS No.: 6835 IN 85-85 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 October 31, 1985 IE INFORMATION NOTICE 85-85: SYSTEMS INTERACTION EVENT RESULTING IN REACTOR

SYSTEM SAFETY RELIEF VALVE OPENING FOLLOWING

A FIRE-PROTECTION DELUGE SYSTEM MALFUNCTION

Addressees

All nuclear power reactor facilities holding an operating license (OL) or a

construction permit (CP).

Purpose

This notice is provided to alert licensees of a serious systems interaction

event involving the fire-protection deluge system located in the control room

ventilation charcoal filter housing. Following inadvertent actuation of this

system, an analog transient trip system (ATTS) panel was sprayed with water

causing malfunctions in certain safety system components.

It is expected that recipients will review this notice for applicability to

their facilities and consider actions, if appropriate, to preclude a similar

problem occurring at their facilities. However, suggestions contained in this

notice do not constitute requirements; therefore, no specific action or written

response is required.

Description of Circumstances

On May 15, 1985, at Georgia Power Company's Hatch Unit 1, personnel manually

scrammed the reactor from 75% power because of a stuck open low-low-set safety

relief valve (LLS-SRV). Shorting of one of the two redundant power supplies

and/or possibly intermittent shorting of logic system contacts in the ATTS

panel is believed to have caused the stuck open LLS-SRV. The panel is one of

two redundant panels located in the control room. The cause of the electrical

shorts in the affected panel was water intrusion into the panel.

The event began about 8:35 p.m. when an instrument water supply vent valve was

damaged, apparently by dragging of a crane hook along the line. The instru- ment water supply line eventually depressurized causing a portion of the fire- protection deluge system to actuate. The water supply line is located above

the control building and the deluge system is located in the control room

charcoal filter housing.

Following actuation of the deluge system, approximately 15 to 25 gal of water

backed up into the ventilation header before the system could be secured. The

8510290039

IN 85-85 October 31, 1985 backup was caused by plugged drains in the charcoal filter housing. Water

eventually leaked through a hole in the ventilation piping that was located

above the ATTS panel in the control room. Whenthe water sprayed onto the panel, one of two redundant panel power supplies apparently shorted because of water

intrusion into the panel. As a result, a LLS-SRV valve began to cycle open and

closed. The SRV cycled three times and then opened and remained open. The

operator manually scrammed the reactor from 75% power. A false turbine high

exhaust pressure trip signal also was generated, temporarily disabling the high

pressure core injection (HPCI) system. The reactor core isolation cooling

(RCIC) system was inoperable at the time, so neither HPCI nor RCIC was imme- diately available for use. Fortunately, neither system was needed during the

event. This is because the water level was restored and maintained by the

reactor feedwater system until the MSIVs were shut. Subsequent to MSIV closure, water level was maintained by the control rod drive (CRD) system with the

excess water being dumped to the condenser via the reactor-water cleanup-system.

The LLS-SRV closed without operator action at 9:52 pm.

Discussion:

The event is of considerable concern because of the potential for multiple

safety system failures through unanalyzed systems interactions. In this event, the water from the fire-suppression deluge system in the control room caused

opening of a safety relief valve and loss of primary system inventory. The

event could have been seriously aggravated by the spurious HPCI turbine high

exhaust pressure-trip-that-wasreceived-also apparently as a result of the

water intrusion. Because the RCIC system was inoperable at-the time of the

event, no safety-related high pressure injection system'would have been imme- diately available to restore water level should that have been necessary.

The HPCI turbine trip signal was reset shortly after it occurred, however, and

the system was returned to operability.

Perhaps more serious is the potential effect the water could have had on

numerous other safety systems. The ATTS panels have permissive and arming

logic and trip, logic for various safety systems, as well as water level inputs

to the HPCI, RCIC, core spray (CS)., automatic depressurization system (ADS),

residual heat removal (RHR) system, and diesel activation logic. It is hard to

predict the anomalous behavior that could occur if both power supplies had been

lost, or if other portions of the logic had been shorted; but quite possibly, several safety systems could have malfunctioned, seriously handicapping the

operators during their efforts to stabilize the unit.

Prior to this event, no procedures were in place at Hatch Unit 1 for adequately

cleaning the ventilation plenums or drains in the charcoal filter units. Had

these procedures been prepared and implemented, the drain's would have functioned

as designed with no serious adverse effects. In response to this event, the

licensee cleaned and inspected drains in the remaining filter units and is

preparing cleanout and inspection procedures to be added to the maintenance

schedules.

IN 85-85 October 31, 1985 Another example of a design feature which could cause potential adverse system

interactions was recently found at Unit 1 of the South Texas Project. A non- seismic, non-category I potable water line> was found to pass through the control

room envelope via a relay room next to the> control room. This could subject the

solid-state protection system cabinets ancI the Westinghouse 7300 process control

system located nearby to water damage foll owing a seismic event. Although this

unit is under construction, it does point out that these problems can occur.

Also, IE Information Notice 83-41, "Actuation of Fire Suppression System

Causing Inoperability of Safety Related Equipment," was issued on June 22, 1983.

That notice identified a number of instances in which automatic actuation of

fire suppression systems degraded or jeopardized the operability of safety- related equipment.

No specific action or written response is required by this information notice.

If you have any questions regarding this matter, please contact the Regional

Administrator of the appropriate NRC regional office or the technical contact

listed below.

w4ar . Jordan, Director

Divis n of Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

David R. Powell, IE

(301) 492-8373 Attachment: List of Recently Issued IE Information Notices

Attachment 1 IN 85-85 October 31, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-84 Inadequate Inservice Testing 10/30/85 All power reactor

Of Main Steam Isolation Valves facilities holding

an OL or CP

85-83 Potential Failures Of General 10/30/85 All power reactor

Electric PK-2 Test Blocks facilities holding

an OL or CP

85-82 Diesel Generator Differen- 10/18/85 All power reactor

tial Protection Relay Not facilities holding

Seismically Qualified an OL or CP

85-81 Problems Resulting In 10/17/85 All power reactor

Erroneously High Reading facilities holding

With Panasonic 800 Series an OL or CP and

Thermoluminescent Dosimeters certain material

and fuel cycle

licensees

85-80 Timely Declaration Of An 10/15/85 All power reactor

Emergency Class Implemienta- facilities holding

tion Of An Emergency Plan, an OL or CP

And Emergency Notifications

85-17 Possible Sticking Of ASCO 10/1/85 All power reactor

Sup. 1 Solenoid Valves facilities holding

an OL or CP

85-79 Inadequate Communications 9/30/85 All power reactor

Between Maintenance, facilities holding

Operations, And Security an OL or CP; research

Personnel and nonpower reactor

facilities; fuel

fabrication and

processing facilities

85-78 Event Notification 9/23/85 All power reactor

facilities holding

an OL or CP

OL = Operating License

CP = Construction Permit