The effects of neutron radiation on nickel-based alloys

Abstract

The effects of neutron radiation on nickel-based alloys in thermal reactors are defying predictions that were made based upon accelerated testing in fast reactors. As nickel-based alloy components face significant doses in aging thermal reactors and their role in Gen-IV reactor designs becomes prominent, the literature on the effects of radiation on such alloys must be reviewed to enable better structural integrity assessments for relevant components and optimise alloys with respect to irradiation embrittlement resistance. This paper reviews the available data on the effects of radiation, notably neutron radiation, on nickel-based alloys and discusses the possible mitigation strategies and design opportunities for radiation embrittlement-resistant alloys based on recent developments in alloy computational design. This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.

Materials for Sustainable Nuclear Energy: A European Strategic Research and Innovation Agenda for All Reactor Generations

“…Exposure to irradiation is known to produce a number of detrimental consequences on materials. In structural materials these range from hardening and embrittlement with loss of elongation to changes of dimension and shape due to swelling and creep [76][77][78][79][80][81]. In addition, if the neutron spectrum leads to transmutation with production of helium (α particles) and hydrogen(protons), depending also on material composition, the mentioned effects may be significantly exacerbated and the temperature ranges of susceptibility increased on the high side, this problem being especially serious for fusion and Ni-containing materials [77][78][79][80][81].…”

“…In structural materials these range from hardening and embrittlement with loss of elongation to changes of dimension and shape due to swelling and creep [76][77][78][79][80][81]. In addition, if the neutron spectrum leads to transmutation with production of helium (α particles) and hydrogen(protons), depending also on material composition, the mentioned effects may be significantly exacerbated and the temperature ranges of susceptibility increased on the high side, this problem being especially serious for fusion and Ni-containing materials [77][78][79][80][81]. Radiation-induced hardening with subsequent loss of elongation and embrittlement typically occurs when irradiating at low temperature, where "low" depends on the material [77,79,82], for instance in steels the threshold is roughly below 400 • C, but in tungsten alloys it is below 800 • C [82].…”

“…Hardrning and subsequent embrittlement appear to some extent from the very beginning of the irradiation and increase with dose, but generally saturate at high enough dose [77,79]. In contrast, dimensional changes occur only at high enough dose, on the order of tens of dpa [77][78][79][80][81]: they do not necessarily saturate with increasing irradiation (only the rate does) and typically they only appear above a certain irradiation temperature (about 400 • C in steels) [77,83]. Clearly, these high temperature/high dose effects, which are hardly observed in current generation reactors, are expected to be significant in next generation ones.…”

Overview of the Mechanical Properties of Tungsten/Steel Brazed Joints for the DEMO Fusion Reactor

“…As discussed above, Ni-based brazing compositions are often used, but its applicability according to reduced activation requirement is of concern (see Figure 1). Furthermore, it is known that radiation embrittlement of Ni alloys occurs at high temperatures (>300 • C), and transmutation into helium has a huge impact on its properties [37].…”

Cavitation wear of Eurofer 97, Cr18Ni10Ti and 42HNM alloys

“…Nickel superalloys are selected for their usage in nuclear reactor core systems [12][13][14][15][16][17], in particular, nuclear power plants with a molten salt coolant [18][19][20] and Advanced Ultra Super Critical (AUSC) power plants [21,22]. It is due to their advantage over the austenitic steels in terms of radiation and corrosion resistance (including molten salts) [12,13] at relatively low neutron irradiation temperatures.…”