This paper describes recent work on irradiation embrittlement of pressurized water reactor (PWR) pressure vessel (PV) steels in the United Kingdom (U.K.). It also describes current relevant developments, namely, the Sizewell ‘B’ PWR, the recent Light Water Reactor Study Group (LWRSG) report on PWR PV integrity, and the presentation of a design for a 300-MW(e) PWR by Rolls-Royce.

The paper goes on to describe the U.K. involvement in two major international programs on irradiation embrittlement, the International Atomic Energy Agency (IAEA), Coordinated Research Programme and the Nuclear Regulatory Commission (NRC) Surveillance Dosimetry Improvement Programme, and stresses the significance of including standard, known-response materials in irradiation programs. U.K. involvement in other international programs is also described.

U.K. national program results on strain aging, dynamic strain aging, background underlying small angle nuclear scattering (SANS), and microstructural and positron annihilation studies are reported. The role of phosphorus in the neutron irradiation embrittlement of lowcopper steels is described. Recent results from modelling studies are noted and the results from a recent irradiation program mentioned.