United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-13: Standby Liquid Control System Squib Valves Failure to Fire

                                                            SSINS No: 6835 
                                                            IN 86-13       

                                UNITED STATES
                           WASHINGTON, DC 20555

                              February 21, 1986

                                   VALVES FAILURE TO FIRE 


All boiling water reactor facilities holding an operating license (OL) or a 
construction permit (CP) 


This notice is to alert addressees to a potentially generic problem with 
explosive squib valves used in the standby liquid control system Recipients
are expected to review the information for applicability to their facilities
and consider actions, if appropriate, to preclude similar problems occurring
at their facilities However, suggestions contained in this information 
notice do not constitute NRC requirements; therefore, no specific action or 
written response is required 

Description of Circumstances: 

During a recent routine surveillance, Vermont Yankee found that squib valves
used in both pathways of the standby liquid control system (SLCS) failed to 
fire The failure of the squibs to fire was caused by two problems One 
problem was that the plant had changed the wiring in the terminal box to the
squib valves firing circuit and the other problem was incorrect wiring of 
the connector that is supplied with the squib valve primer charge 

The explosive primer charge assembly for the SLCS at Vermont Yankee was 
supplied by Conax Corporation The explosive primer charge assembly has two 
sets of resistance wires, ie, bridgewires, internal to the charge either 
of which will fire the explosive However, some of the charges were 
manufactured with incorrect pin-to-bridgewire groupings so that when 
connected at Vermont Yankee, two high-side leads were connected to one 
bridgewire set and two neutral leads were connected to the other bridgewire 
set internal to the explosive primer Examination of spare squibs at Vermont
Yankee identified four others with incorrect pin--to-bridgewire groupings 

The squibs are connected to the plant's wiring via four pin connectors 
Incorrect wiring at the Vermont Yankee local terminal box resulted in the 
sequence around the connector being high, high, neutral, neutral If the 
wiring in the terminal box had been according to the design drawing and had 
been high, neutral, high, neutral, the squib charge would have fired even 


                                                          IN 86-13         
                                                          February 21, 1986 
                                                          Page 2 of 3      

though the pin-to-bridgewire connection was incorrect (See Attachment 1) 
In addition, at Vermont Yankee the control room indication of SLCS circuit 
status indicated circuit continuity due to the presence of a sneak circuit 

At this time, it is not clear whether other primer assemblies, ie , those 
manufactured at a facility in Florida rather than New York, have the 
incorrect pin-to-bridgewire groupings However, some potentially suspect 
primer assemblies are: 

Primer Part Assembly     Plant          of Pieces      Serial Numbers

1617-139-01              Vt Yankee     6 (defective)  552-557 

1617-139-01              Dresden        6              546-551 

1621-240-01              Shoreham       7              635-640, 668 

1621-240-01              Duane Arnold   6              669-674 

1621-240-01              Susquehanna    19             675-681, 686-697 

1621-240-01              Limerick       10             699-708 

1621-240-01              Pilgrim        3              659-661

NRC Regional representatives have contacted the above facilities by 

In addition, some of the explosive primer charge assemblies were provided to
the NORCA Machinery Company, Great Neck, New York for distribution outside 
of the United States 

The explosive primer charge assembly may be tested for correct 
pin-to-bridgewire grouping with an ohmmeter that is current limited to no 
more than 10 milliamperes Larger currents will cause the charge to explode

Inquiries concerning this problem may be addressed to: 

          Conax Corporation 
          2300 Walden Avenue
          Buffalo, New York 14225
          Mr Art Haefner
          phone: (716) 684-4500 extension 233

                                                          IN 86-13         
                                                          February 21, 1986 
                                                          Page 3 of 3      

No specific action or written, response is required by this information 
notice If you have questions about this matter, please contact the Regional
Administrator of the appropriate NRC regional office or this office 

                                   Edward L Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  Eric Weiss, IE 
                    (301) 492-9005

1   Squib Schematic
2   List of Recently Issued IE Information Notices

Page Last Reviewed/Updated Friday, May 22, 2015