Resolution of Generic Safety Issues: Item A-11: Reactor Vessel Materials Toughness (Rev. 2) ( NUREG-0933, Main Report with Supplements 1–35 )

DESCRIPTION

Because of the remote possibility of failure of nuclear reactor pressure vessels designed to the ASME Boiler and Pressure Vessel Code, the design of nuclear facilities does not provide protection against reactor vessel failure. Prevention of reactor vessel failure depends primarily on maintaining the reactor vessel material fracture toughness at levels that will resist brittle fracture during plant operation. At service times and operating conditions typical of existing operating plants, reactor vessel fracture toughness properties provide adequate margins of safety against vessel failure; however, as plants accumulate more and more service time, neutron irradiation reduces the material fracture toughness and initial safety margins. 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 issuance of NUREG-0744, ⁷⁴³ Revision 1, which was later transmitted to all licensees with Generic Letter 82-26. ⁷⁴⁴

REFERENCES

0002. NUREG-0371, "Task Action Plans for Generic Activities (Category A)," U.S. Nuclear Regulatory Commission, November 1978. 0186. NUREG-0510, "Identification of Unresolved Safety Issues Relating to Nuclear Power Plants," U.S. Nuclear Regulatory Commission, January 1979. 0743. NUREG-0744, "Resolution of the Task A-11 Reactor Vessel Materials Toughness Safety Issue," U.S. Nuclear Regulatory Commission, (Rev. 1) October 1982. 0744. Letter to All Power Reactor Licensees (Except Ft. St. Vrain) from U.S. Nuclear Regulatory Commission, "NUREG-0744 Rev. 1; Generic Letter No. 82-26—Pressure Vessel Material Fracture Toughness," November 12, 1982. [ML031080494]