Information Notice 1988-24, Failures of Air-Operated Valves Affecting Safety-Related Systems

Failures of Air-Operated Valves Affecting Safety-Related Systems

ML031150195
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
Issue date:	05/13/1988
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-88-024, NUDOCS 8805090186
Download: ML031150195 (8)

NUCLA UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 May 13, 1988 NRC INFORMATION NOTICE NO. 88-24: FAILURES OF AIR-OPERATED VALVES

AFFECTING SAFETY-RELATED SYSTEMS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees to potential

problems with air-operated valves in safety-related systems. These problems

result from overpressurizatlon failures of solenoid valves caused by the in- stallation of solenoid valves that may not operate against the supplied air

pressure. It Is expected that recipients will review the Information for ap- plicability to their facilities and consider actions, as appropriate, to avoid

similar problems. However, suggestions contained in this information notice

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

response is required.

Description of Circumstances

Kewaunee: On February 8, 1988 the licensee, Wisconsin Public Service Corporation, notified the NRC in Licensee Event Report 50-305/87-12 of a potentially generic

problem. During a periodic inservice timing test required by technical speci- fications, the licensee observed that one of the redundant pressurizer relief

tank makeup isolation valves and one of the redundant reactor coolant drain

tank discharge header isolation valves failed to close on loss of electric

power to their respective 3-way solenoid valves. The isolation valves perform

a containment Isolation function and since their source of actuator power, the

instrument air system, is not a safety-related system, they are designed to

fail closed on loss of either air or electrical power.

For this application, when the solenoid valve is deenergized, its internal

spring moves the valve core so that the inlet port from the instrument air

system is blocked. This action simultaneously opens a flow path connecting

the solenoid valve outlet and exhaust ports, permitting the air pressure on

the actuator diaphragm to decrease, and causing the isolation valve to close.

C 8805090186 Z A4

TN 88-24 May 13, 1988 Investigation revealed that the regulated inlet air pressure of 80 psi was

forcing the solenoid valve core away from the inlet port seat; as a result

the flow path to the actuator diaphragm was being maintained. This happened

because the supply pressure exceeded the rating for the internal spring (70 psi).

This rating is called the design maximum operating pressure differential (MOPD).

After the internal spring and core assembly were replaced in the failed sole- noid valves and the supply air pressure was reduced to 60 psi, the solenoid

valves and hence the containment isolation valves worked satisfactorily. The- licensee inspected ratings for other solenoid valves and did find instances

where the solenoid valve had an MOPD less than the supplied air pressure.

In September 1987, the licensee had decided to replace a number of solenoid

valves to upgrade their level of environmental qualification. For both the

failed solenoid valves discussed above, the licensee found that whereas the

original valves had MOPD ratings greater than the supplied air pressure, the

replacement valves had MOPD ratings less than the supplied air pressure.

The licensee's investigation disclosed the following data:

Original solenoid valves ASCO Model No. LB83146- Catalog 26 (late 1960s vintage)

General-purpose enclosure

MOPD: 100 psi

Replacement solenoid valves ASCO Model No. NP8314C13E

Catalog 30A (1980s vintage)

Watertight and explosion-proof enclosure

MOPD: 70 psi'

According to the catalog, the letter "C" In the model number "indicates a maJor

design change affecting spare parts kits, rebuild kits and colls." 'Apparently, one of the changes made by ASCO (the vendor) to the original Model No. 831413 valve, currently listed as a Model No. 8314C13 valve, involved the internal- spring and core assembly and resulted in a reduced MOPD.

On seeing the difference in MOPD between the original and replacement solenoid

valves, the design engineer assigned the task of upgrading the environmental

qualification of these valves contacted the vendor for advice on which model

was a direct nuclear grade replacement for the LB83146 model. The vendor :

recommended that model number NP8314C13E be used. The design engineer ques- tioned the vendor on the significance of the MOPD difference. The vendor

responded in writing essentially that if the supply pressure exceeded the MOPD

rating, the solenoid valve would not operate correctly (in the way described

above).

IN 88-24 May 13, 1988 The design engineer and engineering supervisor discussed this letter and con- cluded that if the solenoid valve were exposed to 100 psi instrument air pressure

when deenergized, there would be some air leakage from the inlet to the outlet

ports, but some venting to atmosphere through the exhaust port would also occur.

This would pressurize the control valve diaphragm, but equilibrium would occur

at a pressure below that required for control valve actuation. Their conclusion

was heavily influenced by their belief that the original solenoid valves were

actually rated for 70 psi and had been operating successfully for approximately

13 years.

Based on this interpretation, the design review package made available to the

second level reviewer did not include a reference to this correspondence with

the vendor. Thus, an independent assessment of the interpretation was not

performed.

To see if other safety-related control valves and damper actuators could be

vulnerable to the same failure, the licensee inspected all the containment

Isolation solenoid valves and those solenoid valves included in the list of

systems and components that prevent or mitigate the consequences of postulated

accidents. The licensee recorded the solenoid valve and air regulator name- plate data and the air regulator settings. For those valves with insufficient

MOPD, the licensee determined the reason for the purchase and installation of

incorrect solenoid valves. They also reviewed the functional operability of

the instrument air regulators to provide assurance they will not fail high and

thus overpressurize the solenoid valves.

Calvert Cliffs Unit 2: On April 14, 1988, the licensee, Baltimore Gas and

Electric Company, notified the NRC in a 10 CFR 50.72 report that several safety

systems were vulnerable to a single failure of the air supply pressure regu- lating system: the auxiliary feedwater system, the safety injection fill and

vent system, the containment isolation system, and the steam generator blowdown

isolation system. Investigation had shown that those air regulators located in

a harsh environment after a postulated accident can fail in a way that applies

high pressure to solenoid valves. If such solenoid valves are not rated for

sufficient MOPD, then the solenoid valves will affect the correct post accident

alignment of the system valves they control. To correct this problem, the

licensee will expand emergency procedures to Include local operation of af- fected valves and will replace the affected solenoid valves with valves rated

for higher MOPD.

Discussion:

In many plants, the air supply systems for safety-related components are not

designed as safety-related systems. Hence, safety-related components that

depend on the air system are designed to assume a fail safe condition on loss

of air; however, the converse condition of air overpressurization may not always

be considered. Such a condition could render the affected safety-related com- ponents inoperable.

IN 88-24 May 13, 1988 Quality assurance requirements include procurement of materials, equipment, and

services (10 CFR 50.34 and Appendix B). The similarity of part numbers for

components with different operating characteristics illustrates how a qualified

component or system can be degraded if controls over the design and procurement

of replacement parts are not adequate.

Other events in which air system failures have affected safety-related systems

are discussed in Information Notice 87-28, "Air System Problems at U.S. Light

Water Reactors," and Information Notice 87-28, Supplement 1, of the same title.

The supplement notice transmitted copies of NUREG-1275, Vol. 2, "Operating

Experience Feedback Report - Air Systems Problems."'

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

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge, NRR

(301) 492-1169 I. Villalva, Region III

(312) 790-5763 R. Nelson, Region III

(414) 388-3156 Attachment: List of Recently Issued -NRC Information Notices e

Attachment

IN 88-24 May 13, 1988 LIST OF RECENTLY ISSUED I

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

88-23 Potential for Gas Binding 5/12/88 All holders of OLs

of High-Pressure Safety or CPs for PWRs.

Injection Pumps During a

Loss-of-Coolant Accident.

88-22 Disposal of Sludge from .5/12/88 All holders of OLs

Onsite Sewage Treatment or CPs for nuclear

Facilities at Nuclear power reactors.

Power Stations

88-21 Inadvertent Criticality 5/9/88 All holders of OLs

Events at Oskarshamn or CPs for nuclear

and at U.S. Nuclear power reactors.

Power Plants

88-20 Unauthorized Individuals 5/5/88 All holders of OLs

Manipulating Controls and or CPs for nuclear

Performing Control Room power, test and

Actilvi ties research reactors, and all licensed

operators.

88-19 Questionable Certification 4/26/88 All holders of OLs

of Class 1E Components or CPs for nuclear

power reactors.

88-18 Malfunction of. Lockbox on 4/25/88 All NRC licensees

Radiography Device authorized to

manufacture, distribute, and/or operate radio- graphic exposure

devices.

88-17 Summary of Responses to NRC 4/22/88 All holders of OLs

Bulletin 87-01, "Thinning of or CPs for nuclear

Pipe Walls in Nuclear Power power reactors.

Plants"

OL = Operating License

CP = Construction Permit

A.

IN 88-24 May 13, 1988 Quality assurance requirements include procurement of materials, equipment, and

services (10 CFR 50.34 and Appendix B). The similarity of part numbers for

components with different operating characteristics illustrates how a qualified

component or system can be degraded if controls over the design and procurement

of replacement parts are not adequate.

Other events in which air system failures have affected safety-related systems

are discussed in Information Notice 87-28, "Air System Problems at U.S. Light

Water Reactors," and Information Notice 87-28, Supplement 1, of the same title.

The supplement notice transmitted copies of NUREG-1275, Vol. 2, "Operating

Experience Feedback Report - Air Systems Problems."

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

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge, NRR

(301) 492-1169 I. Villalva, Region III

(312) 790-5763 R. Nelson, Region III

(414) 388-3156 Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCES /

• C/OGCB:DOEA:NRR*PPMB:ARM

CHBerl inger TechEd

05/06/88 04/18/88

• OGCB:DOEA:NRR *RIII *D/DSP:AEOD *EAB:DOEA:NRR

CVHodge RNelson LCShao TNovak RKarsch

04/04/88 03/28/88 04/14/88 04/22/88 4/27/88

IN 88-XX

May xx, 1988 Quality assurance requirements include procurement of materials, equipment, and

services (10 CFR 50.34 and Appendix B). The similarity of part numbers for

components with different operating characteristics illustrates how a qualified

component or system can be degraded if controls over the design and procurement

of replacement parts are not adequate.

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

If you have any questions about this matter, please contact one of the techni- cal contacts listed below or the Regional Administrator of the appropriate

regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge, NRR

(301) 492-1169 I. Villalva, Region III

(312) 790-5763 R. Nelson, Region III

(414) 388-3156 Attachment: List of Recently Issued Information Notices

A draft of this information notice was sent by memo dated March 17, 1988 from

E. G. Greenman, Region III, to C. E. Rossi, DOEA. A-

• SEE PREVIOUS CONCURRENCES

D/DOEA:NRR C/OGCB: DOEA:NRR*PPMB:ARM

CERossi CHBerlinger TechEd

05/ /88 05/Do/88 04/18/88

• OGCB:DOEA:NRR *RIII *D/DEST:NRR *D/DSP:AEOD *EAB:DOEA:NRR

CVHodge RNelson LCShao TNovak RKarsch

04/04/88 03/28/88 04/14/88 04/22/88 4/27/88

IN 88-XX

April xx, 1988 of the instrument air regulators to document that they will not fail high and

detrimentally affect the performance of the solenoid valves. Future corrective

actions include the replacement of 27 of 130 solenoid valves inspected and the

establishment of a program for instrument air regulator settings.

Calvert Cliffs Unit 2:

On April 14, 1988, the licensee notified the NRC that several safety systems were

vulnerable to a single failure of the air supply pressure regulation systems:

the auxiliary feedwater system, the safety injection fill and vent system, the

containment isolation system, and the steam generator blowdown isolation system.

Investigation had shown that those air regulators located in a harsh environment

after a postulated accident can fail in a way that applies high pressure to

solenoid control valves. If such control valves are not rated for sufficient

MOPD, then the control valves will affect the correct post accident alignment of

the system valves they control. To correct this problem, the licensee will

expand emergency procedures to include local operation of affected valves and

will replace the affected solenoid control valves with valves rated for higher MOPD.

Discussion:

In many plants, the air supply systems for safety-related components are not

designed as safety-related systems. Hence, safety-related components that depend

on the air system are designed to assume a fail safe condition on loss of air;

however, the converse condition of air overpressurization may not always be

considered. Such a condition could render the affected safety-related components

inoperable. The similarity of part numbers for components with different operating

characteristics illustrates how a qualified component or system can be degraded

if controls over the design and procurement of replacement parts are not adequate.

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

If you have any questions about this matter, please contact a technical contact

listed below or the Regional Administrator of the appropriate regional office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge, NRR

(301) 492-1169 I. Villalva, Region III

(312) 790-5763 R. Nelson, Region III

(414) 388-3156 Attachment: List of Recently Issued Information Notices

• SEE PREVIOUS PAGE FOR CONCURRENCE

D/DOEA:NRR C/OGCB:DOEA:NRR PPMB:ARM

CERossi CHBerlinger TechEd

04/ /88 04/ /88 04/11/881 OGCB:DOEA:NRR RIMI

CVHodge RNelson 6,k

Sw< D/DEST:NIT

LCShao

0o

1A TNovak

,

D/DSP:AEOD phme DOEA:EAB

RKarsch

04/oq/88 03/ 7g/88 04/1l /88 04/72-/88 4/tf /88'Zo'I