United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-05: Pipe Whip Restraints

                                                            SSINS No.: 6835 
                                                            IN 85-05       

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

                              January 23, 1985

Information Notice No. 85-05: PIPE WHIP RESTRAINTS 

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 energy absorbing material used in pipe
whip restraints. 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: 

The Byron Nuclear Generating Station retested the energy absorbing material 
used in the pipe whip restraints and on October 31, 1984, reported that the 
dynamic crush strength of some samples was considerably lower than the 
values used in the design. The "6 KSI" material supplied by HEXCEL/MCI 
Division should have a strength between 5,400 and 7,000 psi. The 
manufacturer's test results were between 5,800 and 6,200 psi, but 40% of the 
material from Byron had a strength between 3,800 and 4,500 psi. In one 
instance, the dynamic crush strength was only 2,700 psi. 

The function of the material is to slow the motion of major piping, such as 
the main steam line, in the event of a double-ended guillotine pipe break. 
The material is contained within the pipe whip restraint. This structure is 
not intended to serve as a restraint in normal operation or seismic loading.

The material consists of stainless steel sheets formed into a honeycomb 
shape and joined by a nickel brazing alloy. The product is in the form of 
rectangular plates up to 36 in. in length, width, or depth. 

HEXCEL manufactured the material for the Byron Nuclear Generating Station in
1978 and 1979. A recent audit by the Office of Inspection and Enforcement 
found that an acceptable quality assurance program was not in effect during 
the period from 1978 to 1982. This material has been supplied by HEXCEL to 
other nuclear generating stations. It is not known if the material supplied 
by other vendors was made by HEXCEL. 


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                                                          IN 85-05        
                                                          January 23, 1985 
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The licensee is conducting a further investigation and assessing the impact 
on the unit. HEXCEL is continuing their internal investigation. It should be
noted that separate from this specific problem the NRC is presently 
reviewing, the pipe break criteria to determine if some whip restraints may 
be eliminated. 

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 NRC regional office or this 
office. 


                                   Edward L. Jordan Director 
                                   Division of Emergency Preparedness 
                                     and Engineering Response 
                                   Office of Inspection and Enforcement 

Technical Contact:  P. Cortland, IE 
                    (301) 492-4175

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