United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-90: Use of Sealing Compounds in an Operating System

                                                        SSINS No.: 6835 
                                                            IN 85-90       

                                UNITED STATES
                        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 
                                   SYSTEM 

Addressees: 

All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 

Purpose: 

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 
required. 

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. 

8511150120 
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                                                       IN 85-90         
                                                       November 19, 1985 
                                                       Page 2 of 3      

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 
Methods." 

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." 
.

                                                       IN 85-90         
                                                       November 19, 1985 
                                                       Page 3 of 3      

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
                    (301) 492-4819

Attachments:
1.   Figure 1, "Component Cooling Water Header Interconnection" 
2.   List of Recently Issued IE Information Notices 
Page Last Reviewed/Updated Tuesday, November 12, 2013