Information Notice 1986-29, Effects of Changing Valve Moter-Operator Switch Settings

Effects of Changing Valve Moter-Operator Switch Settings

ML031220646
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, 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:	04/25/1986
From:	Jordan E NRC/IE
To:
References
IN-86-029, NUDOCS 8604240022
Download: ML031220646 (4)

SSINS No.: 6835 IN 86-29 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF INSPECTION AND ENFORCEMENT

WASHINGTON, D.C. 20555 April 25, 1986 IE INFORMATION NOTICE NO. 86-29: EFFECTS OF CHANGING VALVE MOTOR-OPERATOR

SWITCH SETTINGS

Addressees

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

construction permit (CP).

Purpose

This notice is provided-to alert recipients to potential significant safety

effects of-changing valve motor-operator switch settings as part of a program

to meet the requirements of Inspection and Enforcement Bulletin (IEB) 85-03,

"Motor-Operated Valve Common Mode Failures During Plant Transients Due to

Improper Switch Settings." Changes to switch settings can effect valve posi- tion indication and signals such as "permissives" to other equipment. It is

expected that recipients will review the information for applicability to their

facilities. However, suggestions contained in this notice do not constitute

NRC requirements; therefore, no specific action or written response is

required.

The information herein is being provided as an early notification of a possibly

significant matter that is still under consideration by-the NRC staff. If NRC

evaluation so indicates, licensees will be kept informed of further

developments.

Description of Circumstances

On January 23, 1986 the Southern California Edison Company notified NRC

[licensee event report (LER) 85-036] that-it had exceeded the cooldown rate

limitation of its Technical Specifications at Unit 3 of the San Onofre Nuclear

Generating Station on December 24, 1985. The licensee failed to fully followup

on the effect of changing-the valve motor-operator torque bypass switch setting

as a part of the program to meet the-requirements of IEB 85-03.

The plant had entered Mode 3 on December 18, 1985 following their first refuel- ing outage. The plant entered Mode-4 on December 22, 1985 to perform mainte- nance on a reactor coolant pump. Cooldown continued, and on December 24,-1985 the shutdown cooling system (SDCS) was aligned for warmup. At the time of

alignment, the SDCS heat exchangers were thought to be bypassed and isolated, as indicated by observation of the isolation valve position in the control

K> room. When SDCS flow was aligned, an initial increase in the reactor coolant

8604240022

IN 86-29 April 25, 1986 system (RCS) cooldown rate was expected; however, RCS temperature was found to

decrease at a rate which was considerably greater than expected and which

exceeded the technical specification limitations. When the plant operators

recognized the excessive cooldown rate, they attempted to reduce the rate of

RCS temperature decrease by throttling the SDCS loop injection valves to reduce

the SDCS flow rate. As part of this process, the control room switches for the

SDCS heat exchanger isolation valves were depressed and held in the closed

position to confirm the existing control room indication that these valves were

indeed in the closed position. The RCS cooldown rate was immediately noted to

decrease, thereby indicating SDCS flow had, until then, been permitted to pass

through the SDCS heat exchangers, contrary to the control room indication.

With the SDCS heat exchanger isolation valves truly closed, the RCS cooldown

rate was adjusted and maintained within the limitations of the Technical

Specifications.

Another limiting condition of the plant's Technical Specifications requires

that two independent emergency core cooling system (ECCS) subsystems be opera- ble in Modes 1, 2, and 3 (with the pressurizer pressure greater than or equal

to 400 psia). The valve alignment to assure this condition is verified twice a

day by observation of the control room position indications. Subsequent

investigation indicated that both of the SOCS heat exchanger isolation valves

could have been as much as 16 percent open while the control room indication of

their position showed closed.

The valve motor-operator torque bypass switches on the SDCS heat exchanger

isolation valves had been adjusted because of concerns raised in IEB 85-03.

The motor operators on these valves are protected from overload by torque

switches. It was determined that the torque bypass switch had to be precisely

set such that the increased torque required to initially open valves against -

high differential pressure would not result in deenergizing the motor operator.

However, due to the design of the valve control circuitry, the torque bypass

switch and the valve position indicating limit switch are on the same position

indicating rotor. Therefore, when the position of the rotor was changed to

extend the range of the torque bypass switch, it also affected the closed

position indication.

The valves involved are throttle, or "jog", valves and are operated by holding

the control switch in the direction of valve travel until the desired position

is reached. Both maintenance and operations personnel were aware of the

premature fully closed indication which resulted from the recent adjustment to

the torque bypass switches on the valve motor operators. They planned on

compensating for this condition by holding the valve control switch in the

close position for a brief period of time after the "closed" indication was

observed. However, the exact time to hold the switch was not specified in the

procedures, and apparently, when the valves were operated on December 18, 1985, for the surveillance test, they were not fully closed. Subsequent observation

of the valve operation by operations personnel determined that it was necessary

to hold the valve switch in the closed position for at least 15 seconds after

the "closed" indication was observed in the control room. This information is

being incorporated into the appropriate operating procedures.

I-- -1, . - , _, L

IN 86-29 April 25, 1986 Discussion:

This LER points up the importance of fully understanding the effects of chang- ing any of the valve motor-operator switch settings. Even though the plant

operations personnel were aware of the premature valve "closed" signal, they

did not fully appreciate how early this signal was being produced; hence the

operator did not hold the close switch for a long enough time when they per- formed the initial valve verification as they entered Mode 3.

This problem occurred on a throttle valve that did not have a "seal-in" fea- ture. Valves that do have the "seal-in" feature should continue to torque

closed regardless of the setting of the close position limit switch, and thus

should not experience this particular problem.

However, whether or not the valve has the "seal-in" feature, the changing of

the valve motor-operator switch settings could have effects on other aspects of

plant operation, because of the limited number of position rotors available in

the typical valve motor operator. For instance, frequently the valve closed

signal is used as a "permissive" signal to other pieces of equipment. Thus, increasing the torque bypass switch setting could result in the premature

starting of some other plant operation--an action which may not have been fully

analyzed with respect to its safety implications.

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 regional office or this office.

ard L. Jorda , Director

Division of Em rgency Preparedness

and Engineering Response

Office of Inspection and Enforcement

Richard J. Kiessel, IE

(301)492-8119 Attachment:

List of Recently Issued IE Information Notices

If '

i

Attachment 1 IN 86-29 April 25, 1986 LIST OF RECENTLY ISSUED

IE INFORMATION NOTICES

Information Date of

Notice No. Subject Issue Issued to

86-27 Access Control at Nuclear 4/21/86 All power reactor

Facilities facilities holding

an OL or CP, research

and nonpower reactor

facilities, and fuel

fabrication & pro- cessing facilities

86-26 Potential Problems In 4/17/86 All power reactor

Generators Manufactured By facilities holding

Electrical Products an OL or CP

Incorporated

86-25 Traceability And Material 4/11/86 All power reactor

Control Of Material And facilities holding

Equipment, Particularly an OL or CP

Fasteners

86-24 Respirator Users Notice: 4/11/86 All power reactor

Increased Inspection Frequency - I/

facilities holding

For Certain Self-Contained an OL or CP; research

Breathing Apparatus Air and test reactor

Cylinders facilities; fuel

cycle licensees and

Priority 1 material

licensees

86-23 Excessive Skin Exposures Due 4/9/86 All power reactor

To Contamination With Hot facilities holding

Particles an OL or CP

86-22 Underresponse Of Radition 3/31/86 All power reactor

Survey Instrument To High facilities holding

Radiation Fields an OL or CP and

research and test

reactors

86-21 Recognition Of American 3/31/86 All power reactor

Society Of Mechanical facilities holding

Engineers Accreditation an OL or CP and all

Program For N Stamp Holders recipients of NUREG-

0040 (white book)

86-20 Low-Level Radioactive Waste 3/28/86 All power reactor

Scaling Factors, 10 CFR facilities holding

Part 61 an OL or CP

OL = Operating License

CP = Construction Permit