Test reactor irradiation

Abstract This chapter discusses the role of simulation irradiation techniques in studies of radiation embrittlement mechanisms. The chapter first reviews characteristics and examples of test reactor irradiation, ion irradiation and electron irradiation. The chapter then discusses advantages and limitations of these techniques from the viewpoint of damage rate, sample volume and damage characteristics. 

It is widely known that radiation embrittlement behaviour of reactor pressure vessel (RPV) steels depends on various parameters such as material composition, neutron flux and irradiation temperature. Sound understanding and modelling of embrittlement mechanisms require systematic knowledge of effects of individual parameters and their synthesis on microstructural development and then mechanical properties. Most such knowledge has been obtained from single-parameter experiments using test reactor irradiation. This is because test reactor irradiation allows researchers to obtain mechanical property data together with microstructural data on materials with well-controlled chemical compositions under well-controlled irradiation conditions such as flux and temperature. Surveillance data in commercial power reactors are non-systematic in this context and relevant microstructural data are very scarce. 

One of the merits of test reactor irradiation is the higher dose irradiation at higher flux compared to irradiation at vessels or surveillance capsules in commercial power reactors. As of the end of 2013, the maximum fast neutron fluence of surveillance data was around 9 x lO n/cm E> MeV) while the maximum fluence at the inner surface of a RPV may exceed 1 x 10 °n/cm E > IMeV) for a 60-year operation in a pressurized water reactor (PWR). Test reactor irradiation is the only way to obtain experimental data for embrittlement behaviour at fluences relevant to 60 years or longer operation, together with an understanding of neutron flux effects on embrittlement behaviour. 

Test reactor irradiation has been widely used for studies of radiation embrittlement in RPV steels and huge amounts of data and reports are... 

Irradiation in test reactors with mixed neutron energy spectrum produces basically the same damage morphology as in commercial reactors. Available size and volume of specimens are similar to or larger than those in surveillance of commercial reactors. These are great advantages of test reactor irradiation, although influences of differences in flux and neutron... 

In the development of a new correlation method, microstructural characterization of the surveillance materials of some PWR plants was also performed in order to understand the embrittlement mechanism of RPV steels with different Cu contents. At the same time, another test reactor irradiation project, the PLIM project, was also conducted by Japan Nuclear Energy Safety (JNES), where extensive microstructural characterization of base metals and weld metals with a wide range of chemical compositions in terms of Cu and Ni was performed using APT, transmission electron microscopy and positron annihilation to obtain new insights with the embrittlement mechanism at high fluences.The mechanism of embrittlement identified or confirmed in these projects was summarized as follows ... 

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