Information Notice 1985-89, Potential Loss of Solid-State Instrumentation Following Failure of Control Room Cooling

Potential Loss of Solid-State Instrumentation Following Failure of Control Room Cooling

ML031180185
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, Skagit, Marble Hill
Issue date:	11/19/1985
From:	Jordan E NRC/IE
To:
References
IN-85-089, NUDOCS 8511150114
Download: ML031180185 (4)

SSINS No.: 6835 IN 85-89 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 November 19, 1985 IE INFORMATION NOTICE NO. 85-89: POTENTIAL LOSS OF SOLID-STATE INSTRUMENTATION

FOLLOWING FAILURE OF CONTROL ROOM COOLING

Addressees

or a

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

construction permit (CP).

Purpose

This information notice is to alert recipients of a potentially significant failure

problem involving the loss of solid-state instrumentation following the event

mitigate the

of control room cooling. Actions taken by the licensee to

also are discussed. It is expected that recipients will review this informa- tion for applicability to their facilities and consider actions, if appropri- ate, to preclude a similar problem occurring at their facilities. However, require- suggestions contained in this information notice do not constitute NRC

ments; therefore, no specific action or written response is required.

Description of Circumstances

at

On June 4, 1984, both units of the McGuire Nuclear Station were operating of

100% power with one of the two main control room ventilation units out

low

service for maintenance. At 8:02 p.m., the remaining chiller tripped on approxi- oil level resulting in a total loss of main control room cooling. At

on

mately 8:45 p.m., as the control room temperature increased, numerous alarms on

Unit 1 high reactor coolant loop C Tave were received, as well as alarms

Unit 1 pressurizer level. Attempts to restore the air conditioning were At

unsuccessful and at 9:00 p.m. the air conditioning was declared inoperable. the

10:00 p.m., the operators opened the doors between the control room and

the

computer room, which still had cooling available. Operators also opened

doors of the Westinghouse PCS 7300 cabinets, which contain the solid-state

with

circuit cards generating the alarms. The licensee then used portable fans

ducting to provide cooling from the computer room to the PCS 7300 cabinets.

p.m.

The required technical specification power reduction was started at 10:05re- and terminated at 10:55 p.m. when one of the air conditioning units was

follow- turned to service. The solid-state instrumentation returned to normal

ing restoration of the air conditioning.

8511150114

IN 85-89 November 19, 1985 Discussion:

Before June 4, 1984, the McGuire Nuclear Station had experienced numerous

printed solid-state circuit card failures with the Westinghouse PCS 7300

cabinets and associated solid-state protection system (SSPS). The card fail- ures, which involved reactor trips and spurious instrument indications, were

attributed, by the licensee, to overheating in the PCS 7300 cabinets. In some

cases, the spurious instrumentation indications disappeared when adequate

ventilation was provided to the cabinets; however, in other cases, continued

erratic instrumentation indicated that the overheating had significantly

shortened the life expectancy of the solid state components. The licensee also

had previously reported that the air chillers develop oil level problems when

loaded at less than full capacity. The beat load calculated during plant

design was too large compared to the actual heat load resulting in oversized

chillers.

Following the event, the licensee took temperature measurements inside the PCS

7300 cabinets and determined that with an ambient temperature of about 720 F the

cabinets had internal temperatures of up to 1250 F on the top rack. The McGuire

operators estimate that the ambient temperature, during the event, reached 900 F

before alternate cooling was provided. The licensee has rebalanced the airflow

in the control area ventilation system to provide additional cooling to the PCS

cabinets. Though the licensee's remedial actions to provide better normal

--cooling appear to have increased the reliabiility-of the solid-state cabinets

under design operating conditions, the safety concern following loss of all

control room HVAC units remains.

The McGuire operators, alerted by prior experience, took prompt action to

provide alternate cooling to the solid-state equipment during the event.

Without such action, the possible loss of some instrumentation and erratic

instrument readings may have made it difficult to bring the plant to a safe

condition, such as hot shutdown. If no control room cooling is available to

the solid-state cabinets, it may not be prudent to delay in going to a hot

shutdown condition even though the plant technical specifications may allow

appreciable time to achieve the shutdown. The failure rate of the instrumenta- tion can be expected to increase as the control room temperature increases and

the erratic instrumentation may cause a reactor trip at the same time that the

instrumentation is unreliable or unavailable to assist the operators.

Loss of all control room cooling may be more likely than previously thought.

In addition to the McGuire event, there has been recent identification of other

reported possible common-mode HVAC failures at Browns Ferry and Limerick.

Therefore, licensees should be alert for the possibility of the loss of control

room cooling and the impact this may have on their solid-state instrumentation.

IN 85-89 November 19, 1985 this information notice.

No specific action or written response is required bycontact the Regional

If you have any questions about this matter, please this office.

Administrator of the appropriate regional office or

ef brdan, Director

Division f Emergency Preparedness

and Engineering Response

Office of Inspection and Enforcement

James Stewart, IE

(301)492-9061 Attachment: List of Recently Issued IE Information Notices

Attachment 1 IN 85-89 November 19, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-88 Licensee Control Of 11/18/85 All power reactor

Contracted Services Providing facilities holding

Training an OL or CP

85-87 Haiards Of Inerting '11/18/85 All power reactor

Atmospheres facilities holding

. an OL or CP; and

fuel facilities

85-86 Lightning Strikes At Nuclear 11/5/85 All power reactor

Power Generating Stations facilities holding

an OL or CP

85-85 Systems Interaction Event 10/31/85 All power reactor

Resulting In Reactor System facilities holding

Safety Relief Valve Opening an OL or CP

Following-A Fire-Protection

Deluge System Malfunction

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

OL = Operating License

CP = Construction Permit