United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-78: Scram Solenoid Pilot Valve (SSSPV) Rebuild Kit Problems

                                                            SSINS No.: 6835 
                                                            IN 86-78       

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                              September 2, 1986

Information Notice No. 86-78:   SCRAM SOLENOID PILOT VALVE (SSSPV) 
                                   REBUILD KIT PROBLEMS 


All boiling water reactor facilities holding an operating license or a 
construction permit. 


This notice is to alert recipients of a potential problem with kits used to 
refurbish the scram solenoid pilot valves. 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 

Description of Circumstances: 

On June 14, 1986, Vermont Yankee nuclear power plant reported that one 
control rod failed to scram and five others hesitated a few seconds before 
scramming during a single-rod scram time test. During the outage that 
preceded the scram time test, all of the scram solenoid pilot valves had 
been rebuilt with replacement kits supplied by General Electric Company 
(GE). The reactor had been taken critical to perform shutdown margin tests 
using the in-sequence critical method before the testing that identified the 
problem with the scram solenoid pilot valves. 

Three types of problems were identified in the scram solenoid valves (SSPVs)
which operated six control rods. In the one SSPV associated with the failure
to scram, the core spring of the SSPV was separated from the core assembly. 
On another SSPV, the diaphragm was installed backwards on the exhaust side 
of the solenoid valve. On the remaining four SSPVs, an incorrect core 
assembly, provided with the kits, was installed in the valve. The latter two
types of problems were associated with delayed scram initiation. Subsequent 
inspection of the remaining SSPVs revealed two other types of discrepancies.
These were (1) out-of-round inside diameter of the solenoid base subassembly
and (2) a deformed spring. Although these two discrepancies did not cause 
abnormal scram performance in this case, they could have had an adverse 
effect on scram performance. 


                                                             IN 86-78     
                                                             August , 1986 
                                                             Page 2 of 2  


These problems would likely delay but not prevent rod insertion during 
normal operation because backup scram valves would depressurize the air 
header and cause the control rods to insert. 

The defective rebuild kits are used at BWR-2s, 3s, and most 4s and 5s. 
Vermont Yankee used replacement kits (ASCO type 204-139) to refurbish the 
scram solenoids in the Hydraulic Control Units (HCU). GE purchased 3000 of 
these replacement kits from Automatic Switch Company (ASCO), the 
manufacturer of the solenoid valves. GE purchased these kits as 
non-safety-related items and sold them as nuclear grade. Each kit contains 
11 components, of which two are assemblies. The two assemblies are the core 
assembly (ASCO part 65-716-2A) and the solenoid base sub-assembly (ASCO part 

On June 26, 1986, subsequent to the event at Vermont Yankee, GE returned to 
ASCO 200 replacement kits (ASCO type 204-139) from their stock and requested
ASCO to perform critical inspections. ASCO inspected the two assemblies in 
each kit and rejected 127 core assemblies and two solenoid base assemblies 
for out of tolerance conditions. The rejected parts were replaced with 
acceptable assemblies. 

Although the extent of the distribution of the parts kits used to rebuild 
the scram solenoid valves is not known at this time, preliminary information
suggests that these kits may be in wide distribution. GE issued Rapid 
Information Communication Services Information Letter (RICSIL) No. 008 on 
June 27, 1986 and SIL No. 441 on July 17, 1986 regarding these problems with
the rebuild kits. GE has advised all affected utilities to return spare 
rebuild kits for reinspection. 

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

                    K. R. Naidu, IE
                    (301) 492-4179

Attachment: List of Recently Issued IE Information Notices
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