Information Notice 1989-66, Qualification Life of Solenoid Valves
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
September 11, 1989 NRC INFORMATION NOTICE NO. 89-66: QUALIFICATION LIFE OF SOLENOID VALVES
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
This information notice is being provided to alert addressees to a potential
problem, resulting from a common-mode failure, that may affect the operability
of main steam line isolation valves or similarly designed components. The
problem relates to control solenoid valves whose elastomer discs (seats) are
exposed to temperatures higher than originally assumed in calculating their
qualified life and which may be presently in service beyond their actual
qualified service life. It is expected that recipients will review the
information for applicability 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
Following a reactor trip in August 1989, the operators of Grand Gulf Unit 1 closed the main steam line isolation valves (MSIVs) manually. However, they
observed that one outboard MSIV did not close until more than 15 minutes after
a subsequent automatic closure set point (low vacuum) was reached. Upon
investigating the event, the licensee found a piece of the elastomer seat
from the solenoid valve used for control of that MSIV on an outlet screen.
The licensee concluded that the piece had been lodged in the solenoid valve
internals, thereby keeping the solenoid valve from venting control air and
hence keeping the MSIV from closing.
It is believed that after the piece of
elastomer became dislodged from the internals, the MSIV closed.
Subsequent inspections by the licensee of all eight dual-coil solenoid valves
piloting the MSIVs disclosed that all eight solenoid valves had degraded seats.
Initial visual inspection did not reveal the degradations. However, the degra- dations became apparent under microscopic examination.
The EPDM (ethylene
propylene dimer) seats of all eight solenoid operated valves had cracking.
However, on six of them, the raised portion of the seat formed by the annular
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IN 89-66 September 11,
1989 impression made in the seat by the exhaust port was missing.
Thus, it appears
as if six of the eight solenoid valves had experienced similar sloughing of
material from the seat.
This had been sufficient to prevent one of the solenoid
valves from operating properly, thereby preventing the MSIV from operating
properly.
The solenoid valves in question are dual-coil solenoid valves manufactured by
Automatic Switch Co. (ASCO Model NP8323).
In 1985, the Grand Gulf licensee
calculated the qualified life of these valves with EPDM seats using single-coil
heatup data.
The resultant qualified life was calculated at 5.9 years on
inboard MSIVs. After the recent event, the licensee repeated the qualification
calculations using heatup data for dual-coil solenoids (which became available
in 1987) and estimated the life to be about 2.9 years.
These solenoid valves
had been in service for about 4.5 years.
Recent qualification calculations by the Perry licensee for their solenoid
valves, which have operating conditions similar to those at Grand Gulf, found
that NP8323 solenoid valves with Viton seats on the inboard MSIVs have an
estimated service life of about two years. These solenoid operated valves
are routinely changed every refueling outage at Perry.
Discussion:
A number-of operab1+-ty-problems-have-been-associated-with-the-dual-coi- solenoid- valve Model NP8323 manufactured by ASCO.
Information Notice No. 88-43, "Solenoid
Valve Problems," dated June 23, 1988, identifies older generic communications and
describes potential common-mode failure mechanisms, for example, contamination, thermal degradation of the elastomer, sticky material, and deficient maintenance.
ASCO issued a service bulletin dated May 23, 1989, which stated that rebuilding
kits for the NNPN series valves were being discontinued. ASCO has also recently
indicated that it plans to phase out the NP8323 solenoid valve and that two NP8320
nuclear qualified single-coil solenoid operated valves connected in series may be
an acceptable substitute.
Since better and more recent temperature information is now available, it is
important to note that the calculated maximum service period data supplied with
solenoid valves used at both boiling water reactors and pressurized water reactors
may be based on temperatures at the elastomer seat that are too low.
Therefore, the calculated service life may be in error. Temperatures in the vicinity of
the elastomer seat are dependent upon the plant-specific ambient temperatures, localized hot spot heat sources, and heat input from the solenoid coils during
the time the solenoids are energized. A temperature rise of about 1000F above
ambient temperature could be expected in the vicinity of the seat with the dual
solenoid coils energized. ASCO has temperature profile data available for various
solenoid valve designs. The temperature profile data vary for different solenoid
valves under different operating conditions.
IN 89-66 September 11, 1989 In a service bulletin dated April 12, 1988, ASCO stated that it had no evidence
of elastomer degradation when Viton was used. General Electric Company issued
SIL No. 481, dated February 14, 1989, which recommended that the elastomer be
changed from EPDM to Viton.
Regardless of the material used, the qualified
life will be adversely affected by higher temperatures and may be significantly
less than the initially determined qualified life and possibly even less than
the actual operating time.
MSIVs are subject to different testing and surveillance requirements. Some
licensees test MSIYs for operability once each quarter and others may use special
slow-closing testing techniques such as that described in IN 88-43. Regardless
of the testing or frequency, the MSIVs may be susceptible to a common mode of
failure which could disable both MSIVs in a steam line. This failure, in itself, would not cause a significant accident; however, should the MSIV failures occur
in conjunction with a steam line break, radioactivity released to the public
could result in doses in excess of the guidelines of 10 CFR Part 100.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact one
of the technical contacts listed below or the appropriate NRR project manager.
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Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: J. Carter, NRR
(301) 492-1194
H. Ornstein, AEOD
(301) 492-4439 Attachment:
List of Recently Issued NRC Information Notices
""Attschmsnt
September 11, 1989
Pago I of I
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
InTor05atlon
Notice No.
88-46.
Supp. 4
89-65
89-64
89-63
89-62
89-61
88-48, Supp. 2
89-60
89-59 Subject
Licensee Report of
Defective Refurbished
Circuit Breakers
Potential for Stress
Corrosion Cracking in
Steam Generator Tube
Plugs Supplied by
Babcock and Wilcox
Electrical Bus Bar Failures
Possible Submergence of
Electrical Circuits Located
Above the Flood Level Because
of Water Intrusion and Lack
of Drainage
Malfunction of Borg-Warner
Pressure Seal Bonnet Check
Valves Caused By Vertical
Misalignment of Disk
Failure of Borg-Warner Gate
Valves to Close Against
Differential Pressure
Licensee Report of Defective
Refurbished Valves
Maintenance of Teletherapy
Units
Suppliers of Potentially
Misrepresented Fasteners
uate oT
Issuance
9/11/89
9/8/89
9/7/89
9/5/89
8/31/89
8/30/89
8/22/89
8/18/89
8/16/89 Issued to
All holders of OLs
or CPs for nuclear
power reactors.
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 reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All holders of OLs
or CPs for nuclear
power reactors.
All NRC Medical
Teletherapy Licensees.
All holders of OLs
or CPs for nuclear
powerreiactors.
OL - Operating License
- Construction Permit
UNITED STATES
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
OFFICIAL BUSINESS
PENALTY FOR PRIVATE USE, $300
FIRST CLASS MAIL
POSTAGE & FEES PAID
USMNC
PERMIT No. con7
-
=
IN 89-66 September 11, 1989 In a service bulletin dated April 12, 1988, ASCO stated that it had no evidence
of elastomer degradation when Viton was used.
General Electric Company issued
SIL No. 481, dated February 14, 1989, which recommended that the elastomer be
changed from EPDM to Viton. Regardless of the material used, the qualified
life will be adversely affected by higher temperatures and may be significantly
less than the initially determined qualified life and possibly even less than
the actual operating time.
MSIVs are subject to different testing and surveillance requirements. Some
licensees test MSIVs for operability once each quarter and others may use special
slow-closing testing techniques such as that described in IN 88-43. Regardless
of the testing or frequency, the MSIVs may be susceptible to a common mode of
failure which could disable both MSIVs in a steam line.
This failure, in itself, would not cause a significant accident; however, should the MSIV failures occur
in conjunction with a steam line break, radioactivity released to the public
could result in doses in excess of the guidelines of 10 CFR Part 100.
This information notice requires
you have any questions about the
of the technical contacts listed
no specific action or written response. If
information in this notice, please contact one
below or the appropriate NRR project manager.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts:
J. Carter, NRR
(301) 492-1194
H. Ornstein, AEOD
(301) 492-4439 Attachment:
List of Recently Issued NRC Information Notices
- SEE PREVIOUS PAGE FOR CONCURRENCE
- Tech Ed
RSanders
8/30/89
- EAB:DOEA:NRR
TJCarter
9/5/89
- EAB:DOEA:NRR
PBaranowsky
9/5/89
- C:EAB:DOEA:NRR*C:OGCB:DOEA:NRR
CHaughney
CHBerlinger
9/6/89
9/6/89
- AEOD
HOrnstein
9/5/89 CERos
gss A,-
9/ 4 /89
IN 89-
September , 1989
Page 3 of
In a service bulletin dated April 12, 1988, ASCO stated that it had no evidence
of elastomer degradation when Viton was used.
General Electric Company issued
SIL No. 481, dated February 14, 1989, which recommended that the elastomer be
changed from EPDf4 to Viton. Regardless of the material used, the qualified
life will be adversely affected by higher temperatures and may be significantly
less than the initially determined qualified life and possibly even less than
the actual operating time.
MSIVs are subject to different testing and surveillance requirements. Some
licensees test MSIVs for operability once each quarter and others may use special
slow-closing testing techniques such as that described in IN 88-43.
Regardless
of the testing or frequency, the MSIVs may be susceptible to a common mode of
failure which could disable both MSIVs in a steam line. This failure, in itself, would not cause a significant accident; however, should the MSIV failures occur
in conjunction with a steam line break, radioactivity released to the public
could result in doses in excess of the guidelines of 10 CFR Part 100.
No specific action or written response is required by this information
If you have any questions about this matter, please contact one of the
contacts listed below or the Regional Administrator of the appropriate
office.
notice.
technical
regional
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
J. Carter, NRR
(301) 492-1194 Technical Contacts:
H. Ornstein, AEOD
(301) 492-4439 Attachment:
List of Recently Issued NRC Information Notices
EA:OEA:NRR
TJCa ter
9/7
/89 EAADOEA:NRR
PBaranowsky
9/ 1 /89 C:E
EAC: NRR
CHaughney
9/( /89 D:DOEA:NRR
CERossi
9/ /89