ML20027C017
| ML20027C017 | |
| Person / Time | |
|---|---|
| Site: | Zion, Kewaunee File:ZionSolutions icon.png |
| Issue date: | 08/22/1980 |
| From: | Lanning W NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| References | |
| TASK-AE, TASK-E009, TASK-E9 AEOD-E009, AEOD-E9, NUDOCS 8210120182 | |
| Download: ML20027C017 (2) | |
Text
---
o
- glW a'4
/-
g4 UAITED STATES E
NUCLEAR REGULATORY COMMISSION AE00/E009 o
I This is an internal, pre-i AUG 2 21980 decisional document not
- /
necessarily representing a NOTE TO:
Files
' FROM:
-Wayne D. Lanning, Office for Analysis and Evaluation pp g j
of Operational Data
SUBJECT:
FAILURE OF CONTAINMENT ISOLATION VALVES AT ZION NUCLEAR POWER STATION
}
Zion Units 1 and 2 have reported 15 events since 1977 which involve failure of containment isolation valves. Because of the large number of failures for a station in a high density population area, an exploratory study was initiated.
l The following findings have been made:
+
l.
All the failures to effect containment isolation have resulted from inoperable ASCO series 8320 solenoid valves. These solenoi.d valves provide j
the control function for the air-operated isolation valves. Most of the failures have occurred in the Containment Air Sample System and in the Liquid Waste Disposal-System (specifically from the containment sump).
(
I 2.
The majority of the solenoid valve failures has been attributed to oil in the air supply. Heat from the solenoid coil bakes the oil into a i
varnish causing the plunger to adhere to the plunger seat.
Consequently, the plunger cannot move in order to vent the air from the diaphragm of the isolation valve enabling it to close. The failure rate does not appear to j
depend on the frequency of valve operation. Each of the four lines contains two isolation valves. One of the valves is open continuously and the other is cycled every five minutes. The number of failures is about equal for the two valves.
3.
The most recent failures of solenoid valves (FCV-PR20A, 208, 248) have been the control valves for the isolation valves in the Containment l
Air Sample System. The piping where these valves are located originate from each quadrant of the reactor vessel head and is used to monitor radia-l tion leaks. Of interest is the fact that all the failed solenoid valves are located in the containment penetration room approximately 10 feet from contain-ment at different locations. The implication is that the environment may be contributing to the failure mode of the solenoid valves.
In a telephone discussion with the representatives of the licensee, they indicated that they had not considered this potential common mode failure contributor. Although they did not know to what environmental qualifications the solenoid valves were designed, they did indicate that these were the standard valves and not the nuclear grade.
8210120182 800822 PDR ADOCK 05000295 S
- - ~
4.
Prior to 1978, the service air system would be connected to the instrument air system whenever the instrument air compressor was out of service. Since t
the service air compressors are oil lubricated, it is believed that these compressors provided the source of the oil which has contaminated the instrument air system.
In 1978 a second non-lubricated compressor was installed in the instrument air system. Both the instrument and service air systems are common to both Zion units.
5.
As a result of IE Bulletin 79-01 A, all the solenoid valves in both Zion units are bei;g rebuilt.
The coils and the valve seats are being replaced.
As of July 15,1980, Unit 1 maintenance of the 79 solenoid valve was 60%
complete and the remainder will be rebuilt during the next refueling outage.
The licensee believed that changing the seat material from a plastic (Buna "N" elastomer) to a non-plastic (viton elastomer) material would also reduce the effects of oil on valve operation.
6.
The Instrument Air System, which is not safety related, contains filters and dryers for the air. Although the licensee representatives indicated that these components were not effective for oil removal, they indicated that the maintenance for the dryers and filters had not received as much attention as they could have.
For example, the filters are changed and the dryers are serviced only one time per year during the refueling outage. In addition no efforts have been made to remove oil from the instrument air lines. The failed solenoid valves have been replaced without correcting the root cause of the failure.
I have discussed the environmental qualification of.the solenoid valves located in the penetration room with Jim Lombardo. Equipment Qualification Branch, NRR.
He indicated that a contractor was evaluating the qualification of equipment, for the Zion plant. It was determined that the valves are included in the study and will be required to be environmentally qualified for a hostile environment (LOCA or SLB).
The failure of these valves will continue to be on my watch list for future consid-eration.
) haw
- /
Wayne D. Lanning Office for Analys nd Evaluation of Operational Da a cc:
C. Michelson J. Heltemes 2
J