Information Notice No. 87-26: Cracks in Stiffening Rings on 48-Inch-Diameter UF6 Cylinders

                                                 SSINS No.:  6835 
                                                        IN 87-26 

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             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
                                                                 Page 2 of 2

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 
identified cylinders.  

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 
                                     and Safeguards

DOT Technical Contact on
transportation questions:
Michael E. Wangler
Telephone:  (202)366-4498

NRC Technical Contact on
all other questions:
Leland C. Rouse
Telephone:  (301)427-4309

Attachment:  List of Recently Issued NRC Information Notices

Page Last Reviewed/Updated Friday, May 22, 2015