Information Notice No. 85-90: Use of Sealing Compounds in an Operating System
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C., 20555
November 19, 1985
Information Notice No. 85-90: USE OF SEALING COMPOUNDS IN AN OPERATING
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
This information notice is provided to alert recipients of a potentially
significant problem pertaining to the injection of a sealing compound into
an operating system. It is expected that recipients will review the
information for applicability to their facilities and consider actions, if
appropriate, to preclude a similar problem 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:
Catawba Nuclear Station Unit 1 has a closed-loop component cooling water
system (CCWS) with equipment receiving cooling flow arranged in two parallel
circuits (trains). Each train provides cooling water to one train of
redundant engineered safety equipment (essential header). In addition,
cooling water for the nonessential header can be provided by branches from
either train of the CCWS. The nonessential header is isolated from both
essential headers by a 20-inch, butterfly-type, motor-operated valve in the
branch for each train (See Figure 1).
In May 1985, operations personnel identified that there was excessive
leakage past the seats of both of the 20-inch butterfly valves. An attempt
was made to shut down train B and the nonessential header to allow for work
on the butterfly valve in train B. However, because of the excessive valve
seat leakage from train A, train B could not be depressurized. A decision
was made to inject a sealing compound into the branch piping of the
operating train (train A) immediately upstream of the butterfly valve.
Because the valve was located in a section of branch piping just downstream
from a dead leg (approximately a 5-foot drop in piping), the conjecture was
that the sealing compound would migrate to the leaking valve seat area, thus
stopping the leak without being carried to any component being cooled by the
main run of train A.
November 19, 1985
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To inject the sealing compound, holes were drilled in the valve body at an
angle so that the injection would be on the upstream side of the valve and
below the dead leg. Sealing compound of various consistencies was then
injected into this area. A total of 146 boxes (2 pounds per box) was
injected into this area without stopping the leakage.
Following this unsuccessful effort, a mechanical plugging technique was used
to successfully plug the A train branch line downstream of the valve. The
leaking butterfly valves were then removed and replaced sequentially. Also
replaced during this time was a 1-inch drain line and valve located between
the two 20-inch butterfly valves. The 1-inch line and valve had become
plugged with sealing compound that had passed the seat of the butterfly
valve. In the course of replacing the valves, it was found that most of the
sealing compound settled as a large plug just upstream of the 20-inch A
train valve, but this plug had not sealed the leak in the valve.
Subsequent to replacement of the two 20-inch butterfly valves and the
smaller piping, the CCWS was returned to service. With the system operating,
higher than normal differential pressures were identified on some train A
components. Further, the required cooling water flow could not be achieved.
As a result of these findings, various heat exchangers were inspected and
cleaned. It was found that a small amount of sealing compound had gone back
up the dead leg of the branch and into the main run piping. Sealing compound
was found in varying amounts in these heat exchangers. The train A coolant
charging pump motor cooler had approximately 2 pounds of sealing compound
(maximum amount identified) and some coolers had none.
Other problems associated with the use of sealing compounds have occurred in
the past. Information Notice No. 82-06, "Failure of Steam Generator
Primary Side Manway Closure Studs," was issued March 12, 1982 and addressed
another situation where the use of sealants to stop a leak may have
contributed to other unforeseen problems. In that situation, the sealing
compound was injected using a procedure which essentially created an
enclosure around the bolt circle between the flanges. This resulted in an
autoclave type of atmosphere where corrodents from the coolant could
concentrate and contribute to degradation of the flange bolting.
The results of tests sponsored by the Electric Power Research Institute
(EPRI) on sealants and on line sealing procedures also show additional
problems that may develop with the use of sealants. These results are
published in EPRI NP-3111, "Testing and Evaluation of On-Line Leak Sealing
Licensees are reminded that ANSI/ANS-3.2-1982, "Administrative Controls and
Quality Assurance for the Operational Phase of Nuclear Power Plants," part
5.2.71, Maintenance Programs, requires that "planning for maintenance shall
include evaluation of the use of special processes, equipment and materials
in performance of the task, including assessment of potential hazards to
personnel and equipment."
November 19, 1985
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No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the
Regional Administrator of the appropriate regional office or this office.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: William F. Anderson, IE
1. Figure 1, "Component Cooling Water Header Interconnection"
2. List of Recently Issued IE Information Notices
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