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, 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:	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

C. V. Hodge, IE

301-492-7275 Attachments:

1. Figure 1

2. List of Recently Issued IE Information Notices

TEST SOLENOID II

I..

V--qI

SPRING ASSIST

TO CLOSE MSIV

(NOT ACTUAL

ARRANGEMENT)

-

INSTRUMENT

AIR

CLOSING SOLENOID

CLOSING SOLENOID

OPENING SOLENOID

OPENING SOLENOID

V - VENT TO ATMOSPHERE

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

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r4+

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coPa

= cn 0

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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

Due To Hammering Effect

85-19

85-10

Sup. 1

84-18

83-70

Sup. 1

85-17

85-16

Alleged Falsification Of

Certifications And Alteration

Of Markings On Piping, Valves

And-Fittings

Posstensioned Containment

Tendon Anchor Head Failure

Failures Of Undervoltage

Output Circuit Boards In The

Westinghouse-Designed Solid

State Protection System

Vibration-Induced Valve

Failures

Possible Sticking Of ASCO

Solenoid Valves

Time/Current Trip Curve

Discrepancy Of ITE/Siemens-

Allis Molded Case Circuit

Breaker

Nonconforming Structural

Steel For Safety-Related

Use

Failure Of A Heavy Control

Rod (B4C) Drive Assembly

To Insert On A Trip Signal

Consequences Of Using

Soluble Dams

3/11/85

3/8/85

3/7/85

3/4/85

3/1/85

2/27/85

2/22/85

2/22/85

2/21/85

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All Westinghouse

PWR facilities

holding an OL or CP

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All power reactor

facilities holding

an OL or CP

All BWR and PWR

facilities holding

an OL or CP

t

85-15

85-14

~1

85-13 OL = Operating License

CP = Construction Permit