United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 79-01A: Environmental Qualification of Class IE Equipment (Deficiencies in The Environmental Qualification of ASCO Solenoid Valves)

                               UNITED STATES 
                           WASHINGTON, D.C. 20555
                                June 6, 1979

                                                     IE Bulletin No. 79-01A 


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 

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

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 

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 

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 

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 
                               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
Page Last Reviewed/Updated Friday, May 22, 2015