4.05 - Radiation Damage of Reactor Pressure Vessel Steels

• Published in: Comprehensive Nuclear Materials pp. 151 - 180
• Main Authors: English, C., Hyde, J.
• Format: Book Chapter
• Language: English
• Published: Elsevier Ltd 2012
• Subjects: CMn steels; Cu cluster; Dose–damage relationships; Embrittlement; Hardening; Matrix damage; MnMoNi steels; Reactor pressure vessel; Thermal reactors; Hardening; MnMoNi steels; CMn steels; Thermal reactors; Embrittlement; Cu cluster; Dose–damage relationships; Matrix damage; Reactor pressure vessel
• ISBN: 0080560334; 008056027X; 9780080560335; 9780080560274
• DOI: 10.1016/B978-0-08-056033-5.00087-2

Radiation damage of reactor pressure vessel (RPV) ferritic steels has been the subject of intensive study since the 1950s. This is because it was found that neutron irradiation caused degradation in the mechanical properties of the steel, and knowledge of the resultant hardening and embrittlement was required to predict the in-service properties of RPVs. This chapter focuses on the progress made in understanding the underlying radiation damage mechanisms and applying such insight to develop mechanistically based dose–damage relationships (DDRs). These DDRs allow embrittlement of irradiated RPV steels to be assessed as a function of the important irradiation and material variables. It is to be noted that this chapter is concerned with the effects of neutron irradiation over quite a narrow set of irradiation conditions, that is, irradiation temperatures of ∼250–300°C (although there was interest in irradiation temperatures as low as 160°C) and irradiation doses typical of in-service exposures (<0.1dpa). It will be shown that although the level of embrittlement is sensitive to irradiation temperature, fluence, and flux, the greatest sensitivity was to steel composition, in particular the level of Cu. In early vessels, the base metal and welds contained significant levels of Cu, from either the scrap metal or the Cu coatings on weld wires. Levels as low as 0.1wt% Cu were found to cause significant embrittlement at the doses of interest. This chapter reviews the effect of composition on RPV embrittlement. The deleterious effect of Cu was identified in the late 1960s. It was not until the mid-1980s that equivalent progress was made in understanding the underlying radiation damage mechanisms. Extensive research has been undertaken, worldwide, over the last 20years covering the pressurized water reactor (PWR), boiling water reactor (BWR), and Magnox pressure vessel applications. The accepted mechanistic framework is presented. Studies on characterizing the radiation damage microstructure are reviewed and the detailed insight supporting the framework is assessed. Finally, mechanistically informed DDRs based on this framework are reviewed. Different DDRs have been developed in different countries to describe the hardening and embrittlement of the various RPV steels. The limitations in the form of the DDRs and the R&D into outstanding issues are also discussed.