Information Notice No. 86-13: Standby Liquid Control System Squib Valves Failure to Fire
SSINS No: 6835
IN 86-13
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, DC 20555
February 21, 1986
Information Notice No. NO 86-13: STANDBY LIQUID CONTROL SYSTEM SQUIB
VALVES FAILURE TO FIRE
Addressees:
All boiling water reactor facilities holding an operating license (OL) or a
construction permit (CP)
Purpose:
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
8602210291
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:
Number
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
telephone
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
Attachments:
1 Squib Schematic
2 List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Tuesday, March 09, 2021