Information Notice 1988-24, Failures of Air-Operated Valves Affecting Safety-Related Systems
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
May 13, 1988 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
I
Information
Date of
Notice No.
Subject
Issuance
Issued to
88-23
88-22
88-21
88-20
88-19
Potential for Gas Binding
of High-Pressure Safety
Injection Pumps During a
Loss-of-Coolant Accident.
Disposal of Sludge from
Onsite Sewage Treatment
Facilities at Nuclear
Power Stations
Inadvertent Criticality
Events at Oskarshamn
and at U.S. Nuclear
Power Plants
Unauthorized Individuals
Manipulating Controls and
Performing Control Room
Actilvi ties
Questionable Certification
of Class 1E Components
5/12/88
.5/12/88
5/9/88
5/5/88
4/26/88
All holders of OLs
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power, test and
research reactors, and all licensed
operators.
All holders of OLs
or CPs for nuclear
power reactors.
88-18 Malfunction
Radiography
of. Lockbox on
Device
4/25/88
All NRC licensees
authorized to
manufacture, distribute, and/or operate radio- graphic exposure
devices.
88-17
Summary of Responses to NRC
Bulletin 87-01, "Thinning of
Pipe Walls in Nuclear Power
Plants"
4/22/88
All holders of OLs
or CPs for nuclear
power reactors.
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
- D/DSP:AEOD
- EAB:DOEA:NRR
TNovak
RKarsch
04/22/88
4/27/88
- OGCB:DOEA:NRR
CVHodge
04/04/88
- RIII
RNelson
03/28/88 LCShao
04/14/88
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
E. G. Greenman, Region III,
notice was sent
to C. E. Rossi, by memo dated March
DOEA.
17, 1988 from
A-
- SEE PREVIOUS CONCURRENCES
D/DOEA:NRR
CERossi
05/ /88
- D/DEST:NRR
LCShao
04/14/88 C/OGCB: DOEA:NRR*PPMB:ARM
CHBerlinger
TechEd
05/Do/88
04/18/88
- D/DSP:AEOD
- EAB:DOEA:NRR
TNovak
RKarsch
04/22/88
4/27/88
- OGCB:DOEA:NRR
CVHodge
04/04/88
- RIII
RNelson
03/28/88
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 RIM I
Sw<
D/DEST:NIT 0 o
D/DSP:AEOD
,
phme
DOEA:EAB
CVHodge
RNelson
6,k
LCShao
1A
TNovak
RKarsch
04/oq/88
03/7g/88
04/1l /88
04/72-/88
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