United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 86-53: Improper Installation of Heat Shrinkable Tubing

                                                          SSINS No.: 6835  
                                                          IN 86-53         

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555

                                June 26, 1986

Information Notice No. 86-53:   IMPROPER INSTALLATION OF HEAT SHRINKABLE 
                                   TUBING 

Addressees: 

All nuclear power reactor facilities holding an operating license or a 
construction permit. 

Purpose: 

This notice is to alert licensees to a potentially generic safety problem 
involving improper installation of heat shrinkable tubing over electrical 
splices and terminations. 

It is expected that recipients will review this information for 
applicability to their facilities and consider actions, if applicable, to 
prevent or identify this and similar problems at their facilities. 
Suggestions contained in this notice do not constitute NRC requirements; 
therefore, no specific action or written response is required. The NRC staff 
is continuing to evaluate this matter. If specific action is determined to 
be necessary, a separate notification will be issued. 

Description of Circumstances: 

Problems involving improper installation of heat shrinkable tubing 
manufactured by Raychem have been identified at a number of plants as 
described below. 

Davis-Besse 

On May 14, 1986, the licensee for the Davis-Besse plant reported pursuant to
10 CFR 50.72 that it had been discovered that over the past several years 
terminations and splices may have been incorrectly installed. Plant 
operation in this configuration constituted an unanalyzed condition outside 
the licensing basis (i.e., potential common-mode failures). The licensee had
recently contracted with Raychem to present training sessions to their 
electricians and I&C technicians. During the training, the licensee realized
that heat shrinkable tubing used to cover electrical terminations and 
splices had not been installed according to the manufacturer's instructions 
and acceptance criteria. A sample of 71 wire splices was subsequently 
inspected; 67 were found to be nonconforming in one or more of the following 
ways: 

1.   improper diameters 
2.   improper overlap onto wire insulation (i.e., length) 
3.   use of tubing directly over fabric cover of wire 
4.   improper bending of tubing/wires inside junction boxes  


8606240506  
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                                                            IN 86-53
                                                            June 26, 1986
                                                            Page 2 of 4

The licensee has stated that the potential problem involves wiring, ranging 
from small I&C signal wire up through large 4160-volt power cables and 
probably includes all plant systems, safety related and not safety related. 
One estimate suggests that 1500 cables with 2-4 splices each (total of 
3000-6000 splices) may be involved, of which 1000-2000 splices may be 
safety-related. 

The licensee plans to locate and rework or requalify all suspect uses of the
heat shrinkable tubing before restarting the plant. 

Dresden 

During a Safety System Outage Modification Inspection by the NRC at Dresden 
Unit 3, deficiencies on Raychem heat shrinkable tubing involving valve 
solenoids, valve motor operators, pressure transmitters, and HVAC fan motors
were found to be of the following types: 

1.   Insulation damage on several in-line splices apparently caused by 
     manipulation before the heat shrinkable tubing had cooled completely 
     and set. The degree of damage varied from minor abrasion to exposure of 
     bare conductors. 

2.   Severe bends apparently to fit into small compartments, but tight bends
     also were found inside larger valve operator compartments. 

3.   Less than the minimum total tubing length (6 inches) and absence of 
     inner tubing; in some cases the tubing did not extend over the cable 
     jacket and in one case the bare conductor was exposed. 

4.   Heat shrinkable tubing directly over braided cable jackets. 

The licensee is evaluating corrective actions. 

Comanche Peak 

Certain Bunker Ramo Corporation electrical containment penetrations were 
found to have improper pigtail splices. The Raychem heat shrinkable tubing 
over the splices did not have the sufficient length and, in some cases, bare
conductors were exposed. Numerous instances were found where the heat 
shrinkable tubing was not adhering to the cable jacket. In addition, the 
splices were not staggered. As a result of these and other penetration 
related deficiencies, the affected electrical penetrations are being 
replaced. 

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                                                            IN 86-53
                                                            June 26, 1986
                                                            Page 3 of 4

Watts Bar 

On April 2, 1986, the applicant for the Watts Bar plant provided an initial 
notification of several problems with Raychem heat shrinkable tubing 
associated with Conax electrical penetrations including: 

1.   heat shrinkable tubing not heat shrunk properly 
2.   heat shrinkable tubing sleeves taped improperly 
3.   incorrect heat shrinkable materials used on cable splices 
4.   bare conductors exposed 

The applicant characterized the situation as a potential that circuit 
malfunctions (shorts, grounds, or opens) could occur and cause associated 
equipment or instrumentation failure and adversely affect safe operations of
the plant. The applicant is evaluating alternate corrective actions. 

In addition, installation discrepancies with Raychem heat shrinkable tubing 
have been reported at Surry, Bellefonte, and Shearon Harris plants. 

Discussion: 

The fundamental purpose of applying heat shrinkable tubing over electrical 
terminations and splices is to provide electrical insulation. If the tubing 
has not been installed according to the manufacturer's instructions, 
electrical failures may occur during a range of conditions including 
off-normal non-accident conditions, mild-environment accident conditions, 
and harsh-environment accident conditions. 

The problems described above appear to arise in a wide variety of 
situations. The degree that Bechtel installers or Bechtel installation 
instructions have contributed to the problem is unknown. In some cases, the 
manufacturer's installation instructions were apparently used directly and 
problems arose. 

The existence of improperly installed heat shrinkable tubing could result in
multiple equipment failures in safety-related systems. Potential common-mode
failure of safety-related systems which could prevent the fulfillment of a 
safety function is an unanalyzed condition outside the licensing basis of 
the plant. 

The degree to which this potential problem will manifest itself in actual 
equipment or system failures is not well known. Our review of operating 
experience revealed that there were no reported failures during normal plant
operation that were attributed to improper installation of heat shrinkable 
tubing. Operating experience does provide at least one data point regarding 
harsh environments. The Davis-Besse plant experienced a blowdown inside 
containment in 1977; no failures attributed to heat shrinkable tubing were 
identified. 

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                                                            IN 86-53
                                                            June 26, 1986
                                                            Page 4 of 4

The Raychem heat shrinkable tubing was tested in certain configurations for 
equipment qualification for postulated harsh-environment accident 
conditions. These configurations are included in the manufacturer's 
installation instructions and identified as "LOCA/HELB accident" or simply 
"Accident" specifications. For example, the minimum total length of the 
tubing for a 0.7-1.2 inch connection length is specified as 6 inches minimum 
for the LOCA/HELB accident case and as 4 inches minimum for the non-accident 
case. If actual installation configurations are not those specified as 
having been qualified by type testing, the status of the equipment 
qualification is indeterminate. 

10 CFR 50.49 requires that safety-related electrical equipment that may be 
exposed to a harsh environment during an accident, be qualified to be able 
to perform the safety functions. If a licensee finds that the qualification 
may not be valid because heat shrinkable tubing was improperly installed, 
action would become necessary to establish compliance regarding system 
operability and reporting. 

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:  J. T. Beard, NRR 
                    (301) 492-4415 

Attachment:    List of Recently Issued IE Information Notices 

Page Last Reviewed/Updated Tuesday, November 12, 2013