Information Notice No. 87-26: Cracks in Stiffening Rings on 48-Inch-Diameter UF6 Cylinders
SSINS No.: 6835
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, D. C. 20555
June 11, 1987
Information Notice No. 87-26: CRACKS IN STIFFENING RINGS ON
48-INCH-DIAMETER UF6 CYLINDERS
All uranium fuel fabrication and conversion facilities.
This notice is being issued to alert recipients to a possible safety problem
related to UF6 cylinders. It is suggested that recipients review the informa-
tion and consider actions, if appropriate, to preclude possible safety
problems 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 NRC has received information from the manufacturer that some
48-inch-diameter UF6 cylinders manufactured by the W. H. Stewart Company of
Oklahoma City, Oklahoma, have stiffening rings fabricated from a material
(ASTM A306, Grade 75 steel) which is not specified in ANSI Standard
N14.1-1982, or in a previous edition thereof and which is not an equivalent
approved material under the ASME Boiler and Pressure Vessel Code, Section
VIII, Division 1. The cylinders in question are identified by the following
manufacturer's serial numbers:
2309 through 2333
2442 through 2617
2782 through 2828
However, because W. H. Stewart Company records are incomplete, other
48-inch-diameter cylinders manufactured after May 1975 may be affected.
Therefore, this Information Notice is also applicable to any other UF6
cylinder you have cause to believe contains stiffening rings made of ASTM
A306, Grade 75 steel.
The Department of Transportation (DOT) has published a rule (see 51 Fed. Reg.
46675, December 24, 1986) that after June 30, 1987, will require UF6 shipping
containers to meet the provisions of ANSI Standard N14.1-1982, or a previous
edition thereof [49 CFR Part 173.420(a)(2)]. The ANSI Standard specifies the
design of UF6 cylinders, including materials of construction for stiffening
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June 11, 1987
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rings. The ANSI Standard also permits substitute materials to be used for
stiffening rings provided they are equivalent approved materials under the
ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, which are
compatible with fabrication of the cylinders involved. Shipment of cylinders
that do not meet the ANSI Standard is not authorized under the new DOT rule
scheduled to become effective on June 30, 1987.
Wedge-shaped cracks have been detected on some of the stiffening rings on
The cause and safety significance of the cracks have not been determined. The
stiffening rings may serve multiple safety and functional purposes; they are
welded to the lifting lugs and may contribute to the strength of those lugs.
Therefore, licensees may want to consider inspecting the cylinders in question
for cracks in the stiffening rings, lifting lugs, and associated weldments,
including those weldments that join the stiffening rings to the cylindrical
shell and to the lifting lugs. Extra care and caution should be used when
lifting or handling any cylinder that has cracked stiffening rings, lifting
lugs, or weldments.
DOT regulates the transport of UF6 cylinders. Shipment of UF6 cylinders that
do not meet the ANSI Standard is not authorized under the new DOT rule
scheduled to become effective on June 30, 1987. DOT should be consulted
before you ship any of the identified cylinders off site.
No specific action or written response is required by this Information Notice.
If you have questions about this matter, please contact those listed below.
Richard E. Cunningham, Director
Division of Fuel Cycle, Medical,
Academic, and Commercial Use Safety
Office of Nuclear Material Safety
DOT Technical Contact on
Michael E. Wangler
NRC Technical Contact on
all other questions:
Leland C. Rouse
Attachment: List of Recently Issued NRC Information Notices
Page Last Reviewed/Updated Friday, May 22, 2015