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Home > NRC Library > Document Collections > NUREG-Series Publications > Staff Reports > NUREG-0933, Main Report with Supplements 1–34 > Section 2. Task Action Plan Items > Item A-12: Fracture Toughness of Steam Generator and Reactor Coolant Pump Supports (Rev. 2)

Resolution of Generic Safety Issues: Item A-12: Fracture Toughness of Steam Generator and Reactor Coolant Pump Supports (Rev. 2) ( NUREG-0933, Main Report with Supplements 1–34 )

DESCRIPTION

During the course of the licensing action for North Anna Units 1 and 2, a number of questions were raised as to the potential for lamellar tearing and low fracture toughness of the steam generator and RCP support materials for these facilities. Two different steel specifications (ASTM A36 and ASTM A572) covered most of the material used for these supports. Toughness tests, not originally specified and not in the relevant ASTM specifications, were made at various temperatures. The toughness of the A36 steel was found to be adequate, but the toughness of the A572 steel was relatively poor at a temperature of 80°F. In the case of North Anna Units 1 and 2, the applicant agreed to raise the temperature of the A572 beams in the steam generator supports to a minimum temperature of 225°F, prior to reactor coolant system pressurization to levels above 1,000 psig. Auxiliary electrical heat was supplied as necessary to supplement the heat derived from the reactor coolant loop to obtain the required operating temperature of the support materials. Concerns regarding the supports at North Anna were applicable to all PWRs. This item was originally identified in NUREG-03712 and was later declared a USI in NUREG-0510.186

CONCLUSION

This USI was RESOLVED with the publication of NUREG-0577, 388 Revision 1. The resolution contained no backfit requirements and applied only to new construction after issuance of SRP 11 Section 5.3.4.
Page Last Reviewed/Updated Thursday, March 29, 2012