Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS No.: 6835
IN 86-78
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
September 2, 1986
Information Notice No. 86-78: SCRAM SOLENOID PILOT VALVE (SSSPV)
REBUILD KIT PROBLEMS
Addressees:
All boiling water reactor facilities holding an operating license or a
construction permit.
Purpose:
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
required.
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.
8608270353
.
IN 86-78
August , 1986
Page 2 of 2
Discussion:
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
44-869-23).
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
