Resolution of Generic Safety Issues: Issue 60: Lamellar Tearing of Reactor Systems Structural Supports ( NUREG-0933, Main Report with Supplements 1–35 )

DESCRIPTION

The issue of lamellar tearing was originally addressed in NUREG-0410³⁸⁷ in connection with Technical Activity No. A-12, "Fracture Toughness of Steam Generator and Reactor Coolant Pump Supports." The significance of this issue as a potential safety issue was raised again by MTEB on November 16, 1981. The lamellar tearing issue was incorporated into USI A-12 which has been resolved, as documented in Revision 1 to NUREG-0577.³⁸⁸

Lamellar tearing is a sub-surface flaw condition which is virtually impossible to detect by visual means. Because of this sub-surface nature, the tears do not represent a fracture of the structural joint but rather a potential reduction in the maximum load that the joint could withstand, particularly under emergency conditions such as in the event of a seismic occurrence.

CONCLUSION

The safety issue concerning lamellar tearing of reactor systems structural supports is a sub-task of USI A-12.

REFERENCES

0387. NUREG-0410, "NRC Program for the Resolution of Generic Issues Related to Nuclear Power Plants," U.S. Nuclear Regulatory Commission, January 1978. 0388. NUREG-0577, "Potential for Low Fracture Toughness and Lamellar Tearing in PWR Steam Generator and Reactor Coolant Pump Supports," U.S. Nuclear Regulatory Commission, (Rev. 1) October 1983.