Information Notice No. 82-10: Following up Symptomatic Repairs to Assure Resolution of the Problem
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 31, 1982
Information Notice No. 82-10: FOLLOWING UP SYMPTOMATIC REPAIRS TO ASSURE
RESOLUTION OF THE PROBLEM
There have been a number of instances in which licensees have attempted to
correct valve problems by treating the symptoms rather than the underlying
cause. This failure to distinguish between the problem and its symptoms has
resulted in recurrence of the problem and further damage to or destruction
of the valve or operator. Symptomatic repairs provide for a return to
operability without addressing the underlying problem, earning the label
"quick and dirty fixes." The industry jargon recognizes not only that the
immediate needs are met, but also that the underlying problem remains to be
corrected. It is this second point which is emphasized: the underlying
problem remains to be corrected.
Specifically, valves that leak beyond Technical Specification limits have
been restored to operability by allowing additional stem travel. The direct
result of this symptomatic solution has been damage to or destruction of the
valve or operator.
One licensee has routinely backseated valves with Limitorque operators using
the full motor torque in order to stop stem packing leakage, resulting in
damage to the valve backseat. Bypassing the open limit switch allowed over-
travel in the open direction resulting in binding of the stem in the stem
nut. Because the unthreaded portion of the stem galled in the threads of the
stem nut, the threads deformed and the nut cracked. The valves involved
were 600 psi class, Anchor 10-inch integral backseat gate valves with
pressure seal bonnets. Stem and body were type 316 stainless steel.
On a larger scale, in a survey of Licensee Event Reports (LER) for 1978
through 1980, 444 valve operator events were identified for 66 plants. Of
these, 193 were identified as motor operator events. Corrective actions
which involved torque switches comprised the largest single corrective
action group. The principal means of corrective action identified was the
adjustment of torque switch setting. This solution was applied to valves in
similar service and, repetitively, to the same valve at several plants.
This indicates that the problem was not being corrected.
March 31, 1982
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The second major corrective action group was limit switch adjustments. This
was a common solution to problems involving valve operation within a time
limit. The cause for the problem is repeatedly given as instrument drift
which is undoubtedly true as far as it goes; however, repetition of the
events points to the need for a wider ranging solution which will prevent
recurrences and improve system reliability.
During the survey period, there were 16 reported instances of motors
replaced in motor operators in the high-pressure coolant injection (HPCI),
reactor core isolation cooling and residual heat removal systems of boiling
water reactors. This was the third largest corrective action group. The
damage that required replacement of some of the 16 motors resulted from
thermal overload protection being bypassed and may be another indication
that the underlying valve problem was not corrected.
The common thread in the events as reported by LERs surveyed is the
repetition of the problem or the solution, either of which can indicate that
a symptomatic repair has been made. Symptomatic repairs become of concern
to the NRC where they impact upon the reliability of the system and where
they may adversely affect the health and safety of the public.
When considering the solution to a valve problem, it must be recognized that
a symptomatic repair may cause damage to the vale or operator which could
impair the safety function of the system to which it is applied.
Consideration should be given to the kind of damage that can occur as a
result of the repair and the consequences should a valve fail in a
nonconservative direction. A mechanism should exist to identify and resolve
the underlying problem when symptomatic repairs are applied.
When the possibility exists for degradation of a safety system as a result
of a temporary symptomatic repair to restore operability, prudence dictates
a closer surveillance of the system so affected.
This information notice is provided as notification of a potentially
significant matter. It is expected that recipients will review the
information for applicability to their facilities. No specific action or
response is required at this time. If you have any questions regarding this
matter, please contact this Regional Administrator of the appropriate NRC
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