United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 76-04: Cracks in Cold Worked Piping at BWR's

                          WASHINGTON D. C. 20555  

                                                       IE Bulletin No. 76-04 
                                                       DATE:  March 30, 1976
                                                       Page 1 of 2 



On March 22, 1976, at the Nine Mile Point 1 facility, a leak was found in a 
reactor water clean-up system six-inch stainless steel pipe located outside 
of the drywell. The leak resulted from a throughwall crack in the base 
material at a pipe bend. Similar leaks had been experienced in this system 
on November 28, 1975 and March 19, 1976. The cracks do not appear to have 
any preferred orientation. The facility was shutdown on March 22 to permit 
nondestructive examination of the base material at similar pipe bends. 

The piping involved is schedule 80, ASTM A-376, Type 304 stainless steel 
which had undergone cold bending during k fabrication without subsequent 
solution annealing. Examination of the pipe section which leaked on November
28, revealed that the crack initiated in the transgranular mode at the 
inside surface and changed to the intergranular mode after it had propagated 
through the cold worked surface. Significant carbide precipitation around 
grain boundaries was observed although the reason for this precipitation is 
not known at this time. The cracking mechanism was categorized as stress 
corrosion. The stress field is believed to be caused by cold forming. 


All licensees of BWR power reactor facilities are to take the following 

1.   Develop the following information for those systems located within, or 
     connected to, the reactor coolant pressure boundary and which are 
     exposed to reactor coolant system pressure during operation: 

                                                       IE Bulletin No. 76-04 
                                                       DATE:  March 30, 1976
                                                       Page 2 of 2 

Action To Be Taken By Licensee (Continued) 

     a.   A specific listing of installed austenitic stainless steel piping 
          or fittings made from pipe, greater than two inches nominal size, 
          which may have been cold worked without solution annealing 
          following forming. (Verification that cold worked material 
          received full solution annealing following the forming operation 
          must be based on acceptable time-temperature heat treating 
          records, Metallurgical analyses, or equivalent and may be on a 
          sampling basis for each lot number.) 

     b.   A description of the program and procedures, including inspection 
          criteria and schedules, for the nondestructive volumetric 
          examination of the items identified in (a) above. 

2.   A report of the above applications, descriptions, plans and schedules 
     should be submitted within 60 days after receipt of this Bulletin. 

3.   The NRC Regional Office should be promptly informed, within 24 hours, 
     of any adverse findings resulting during nondestructive evaluation of 
     identified piping or fittings. 

4.   A report of the performance, the results, and the evaluation of any 
     nondestructive evaluation conducted on cold worked stainless steel 
     piping or fittings should be submitted within 60 days following 
     completion of the examination. 

Reports should be submitted to the Director of the NRC Regional Office and a 
copy should be forwarded to the NRC Office of Inspection and Enforcement, 
Division of Reactor Inspection Programs, Washington, D. C. 20555. 

Approval of NRC requirements for reports concerning possible generic 
problems has been obtained under 44 U.S.C. 3152 from the U. S. General 
Accounting Office.
(GAO Approval B-180255(R0072), expires 7/31/77).
Page Last Reviewed/Updated Thursday, July 09, 2020