Information Notice 1985-21, Main Steam Isolation Valve Closure Logic

Main Steam Isolation Valve Closure Logic

ML031180457
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:	03/18/1985
From:	Jordan E NRC/IE
To:
References
IN-85-021, NUDOCS 8503140033
Download: ML031180457 (4)

SSINS No.: 6835 IN 85-21 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D. C. 20555 March 18, 1985 IE INFORMATION NOTICE NO. 85-21: MAIN STEAM ISOLATION VALVE CLOSURE LOGIC

Addressees

All nuclear power pressurized water reactor (PWR) facilities holding an operat- ing license (OL) or construction permit (CP).

Purpose

This information notice is provided as a notification of a potentially signifi- cant problem pertaining to logic for closure of main steam isolation valves

(MSIVs). It is expected that recipients will review the information for

applicability to their facilities and consider actions, if appropriate, to

preclude a similar problem from occurring at their facilities. However, suggestions contained in this information notice do not constitute NRC require- ments; therefore, no specific action or written response is required.

Description of Circumstances

In early 1985 the licensee for Robinson 2 discovered and reported a logic fault

with respect to MSIV closure. The MSIVs at Robinson are operated by air

pressure admitted to the top or bottom area of a piston controlling the MSIV

clapper (see Figure 1). The air pressure is controlled by two parallel "clos- ing" solenoid valves on the top of the piston and two parallel "opening"

solenoid valves on the bottom of the piston. For each MSIV, a closure signal

from either of the redundant ESF logic trains (A or B) should be able to

pressurize the top of the piston and to depressurize the bottom of the piston

to provide positive and rapid closure of the MSIV.

At Robinson, which is a three loop plant, the "B" and "C" MSIVs had both

opening solenoid valves controlled by the B train. In the event of a single

failure of the B logic train, it is not clear what the response of the B and C

MSIVs would be. While one closing solenoid valve would open to admit air

pressure to the top of the piston, both the opening solenoid valves would

remain in position to pressurize the bottom of the piston. The test solenoid

valve connected to the space above the piston would remain in position to

continue slowly venting the top of the piston through an orifice. The result- ing difference in pressure above and below the piston is judged to be nearly

zero. The only closing force remaining would be provided by the spring, which

is designed to move the clapper only partly closed for testing purposes.

Although steam flow may close the MSIV under accident conditions, this is not

how the valves were designed or qualified to close and rapidly terminate the

blowdown.

8503140033

IN 85-21 March 21, 1985 The licensee is correcting this situation by modifying the control circuitry to

ensure that either a Train A or a Train B closure signal will cause positive'

closure of all three MSIVs.

Discussion:

In the event of a steamline break accident, rapid closure of the MSIVs protects

against positive reactivity excursions from rapid cooling and against loss of

heat sink. At most, the design basis contemplates that one MSIV might fail to

close due to failure of a single active component. In this instance, two MSIVs

might have failed to close due to a single failure of the B closure signal.

Licensees may wish to review their MSIV control logic in the light of this

discovery.

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

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

Administrator of the appropriate NRC regional office or this office.

1iard J ordan, Director

Divisi of Emergency Preparedness

and gineering Response

Office of Inspection and Enforcement

C. V. Hodge, IE

301-492-7275 Attachments:

1. Figure 1

2. List of Recently Issued IE Information Notices

- INSTRUMENT

AIR

TEST SOLENOID II CLOSING SOLENOID

I.. V--qI

CLOSING SOLENOID

SPRING ASSIST

TO CLOSE MSIV

(NOT ACTUAL

ARRANGEMENT) OPENING SOLENOID

V - VENT TO ATMOSPHERE OPENING SOLENOID

Figure 1 Schematic representation for the closure logic before modification for 8 or C MSIV

3I §-:

"I r4+

0 coPa

= cn 0

_, e

o

Ce,

Attachment 2 IN 85-21 -

March 18, 1985 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

85-20 Motor-Operated Valve Failures 3/12/85 All power reactor

Due To Hammering Effect facilities holding

an OL or CP

85-19 Alleged Falsification Of 3/11/85 All power reactor t

Certifications And Alteration facilities holding

Of Markings On Piping, Valves an OL or CP

And-Fittings

85-10 Posstensioned Containment 3/8/85 All power reactor

Sup. 1 Tendon Anchor Head Failure facilities holding

an OL or CP

84-18 Failures Of Undervoltage 3/7/85 All Westinghouse

Output Circuit Boards In The PWR facilities

Westinghouse-Designed Solid holding an OL or CP

State Protection System

83-70 Vibration-Induced Valve 3/4/85 All power reactor

Sup. 1 Failures facilities holding

an OL or CP

85-17 Possible Sticking Of ASCO 3/1/85 All power reactor

Solenoid Valves facilities holding

an OL or CP

85-16 Time/Current Trip Curve 2/27/85 All power reactor

Discrepancy Of ITE/Siemens- facilities holding

Allis Molded Case Circuit an OL or CP

Breaker

85-15 Nonconforming Structural 2/22/85 All power reactor

Steel For Safety-Related facilities holding

Use an OL or CP

85-14 Failure Of A Heavy Control 2/22/85 All power reactor

Rod (B4C) Drive Assembly facilities holding

To Insert On A Trip Signal an OL or CP ~1

85-13 Consequences Of Using 2/21/85 All BWR and PWR

Soluble Dams facilities holding

an OL or CP

OL = Operating License

CP = Construction Permit