Bulletin 76-04: Cracks in Cold Worked Piping at BWR's
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON D. C. 20555
IE Bulletin No. 76-04
DATE: March 30, 1976
Page 1 of 2
CRACKS IN COLD WORKED PIPING AT BWR's
DESCRIPTION OF CIRCUMSTANCES:
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.
ACTION TO BE TAKEN BY LICENSEES:
All licensees of BWR power reactor facilities are to take the following
action:
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 Tuesday, March 09, 2021