Information Notice No. 85-05: Pipe Whip Restraints
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
January 23, 1985
Information Notice No. 85-05: PIPE WHIP RESTRAINTS
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 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.
January 23, 1985
Page 2 of 2
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
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
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: P. Cortland, IE
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