Bulletin 79-01A: Environmental Qualification of Class IE Equipment (Deficiencies in The Environmental Qualification of ASCO Solenoid Valves)
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
June 6, 1979
IE Bulletin No. 79-01A
SUPPLEMENT NO. 79-01A TO IE BULLETIN 79-01 - ENVIRONMENTAL QUALIFICATION OF
CLASS IE EQUIPMENT (DEFICIENCIES IN THE ENVIRONMENTAL QUALIFICATION OF ASCO
SOLENOID VALVES)
Description of Circumstances:
Recently, a noncompliance report under 10 CFR Part 21 was received by the
NRC from the Henry Pratt Company, manufacturer of butterfly valves which are
installed in the primary containment at the Three Mile Island Unit 2 Nuclear
Station. These butterfly valves are used for purge and exhaust purposes and
are required to operate during accident conditions. The report discusses the
use of an unqualified solenoid valve for a safety-related valve function
which requires operation under accident conditions. The solenoid valve in
question is Catalogue No. HT-8331A45, manufactured by the Automatic Switch
Company (ASCO) of Florham Park, New Jersey. This pilot valve is used to
pilot control the pneumatic valve actuators which are installed on the
containment ventilation butterfly valves at this facility.
The deficiency in these solenoid valves identified in the Part 21 Report
concerns the parts made of acetal plastic material. The acetal disc holder
assembly and bottom plug in the pilot valve assembly are stated by ASCO to
have a maximum service limit of 400,000 Rad integrated dosage and 200
degrees F temperature. According to ASCO, exposure of these acetal plastic
parts to specified maximum environmental conditions may render the solenoid
pilot valve inoperable which would cause the associated butterfly valve to
malfunction.
Further investigation at ASCO by the NRC staff has revealed that the valve
seals in most ASCO solenoid valves contain Buna "N" elastomer material,
which reportedly has a maximum service limit of 7,000,000 Rad integrated
dosage and 180 degrees F temperature. The investigation further revealed
that ASCO has available a line of qualified solenoid operated pilot valves
(ASCO Catalogue No. NP-1) which have no plastic parts, utilize ethylene
propylene or viton elastomers and have a continuously energized operating
life of four years, under normal embient conditions up to 140 degrees F.
According to the manufacturer, at the end of this period, the coil, manual
operator (optional feature) and all resilient parts must be replaced. These
preventive maintenance instructions are specified in the installation and
instruction bulletins which are provided to the purchaser with each shipment
of solenoid valves.
The final items of concern identified during this investigation deals with
the application of Class "A", "B", or "F", solenoid coils which are exposed
to an accident environment. In this regard, ASCO representatives stated that
the
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IE Bulletin No. 79-01A June 6, 1979
Page 2 of 3
high temperature coils identified as Class "HT" or "HB" are the only coils
considered suitable for service under accident conditions; whereas, Class
"A", "B", and "F" coils are not.
With respect to the corrective measures to be taken to resolve the above
concerns, ASCO recommends the following:
1. The parts of the solenoid valve made of acetal plastic material should
be replaced with similar parts made of metal which can be provided by
ASCO.
2. The valve seals and gaskets which are made of Buna "N" material should
be replaced with either ethylene propylene or viton elastomers,
considered by ASCO as suitable for the service intended.
3. Review and determine that the coils of the solenoid valves installed
inside containment are Class "HT" or "HB" as required for high
temperature environmental conditions.
4. Review and determine that the solenoid enclosures installed inside
containment have at least a NEMA 4 enclosure rating.
5. Establish a preventive maintenance program to assure replacement of
those valve parts identified above in the time period recommended in
the appropriate ASCO valve bulletin.
6. ASCO also stated that all unqualified solenoid valves inside
containment be retrofitted to qualified ASCO No. NP-l valves in lieu of
the above.
7. Questions from licensees to ASCO concerning corrective measures should
reference both catalogue and serial numbers of each valve in question.
These numbers are stamped on the metal nameplate on each solenoid
valve.
Action to be Taken by Licensees of all Power Reactor Facilities (except
those 11 SEP Plants listed on Enclosure 3) with an Operating License:
1. Determine whether or not ASCO solenoid valves are used or planned for
use in safety-related systems at your facility(ies).
2. If such valves are used or planned for use, identify the safety system
involved and determine that: (a) valves which could be subjected to a
LOCA environment are qualified to that environment. Specifically that
no parts made of acetal plastic or Buna "N" materials or Class "A",
"B", or "F" solenoid coils are used in such valves; (b) a preventive
maintenance program is being conducted such that the solenoid coil, the
manual operator (if applicable), and the resilient parts of the valve
are being replaced in accordance with the time period established by
the manufacturer and documented as the qualified life of the assembled
component.
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IE Bulletin No. 79-01A June 6, 1979
Page 3 of 3
3. All holders of operating licenses of power reactor facilities are
obligated to meet the review and reporting requirements established in
previously issued IE Bulletin 79-01, regarding environmental
qualification of electrical equipment installed in their plants.
No additional written response to this Supplement IE Bulletin is required
other than those responses described above. NRC inspectors will continue to
monitor the licensees' progress in completing the requested action described
above. If additional information is required, contact the Director of the
appropriate NRC Regional Office.
Approved by GAO, 8180225 (ROO72); clearance expires 7/31/80. Approval was
given under a blanket clearance specifically for identified generic
problems.
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SEP Plants
Plant Region
Dresden 1 III
Yankee Rowe I
Big Rock Point III
San Onofre 1 V
Haddam Neck I
LaCrosse III
Oyster Creek I
R. E. Ginna I
Dresden 2 III
Millstone I
Palisades III
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