The origins and use of the equivalent temperature concept

In some graphite research fields, it is accepted practice to apply an equivalent temperature correction when using graphite data from facilities with differing fast neutron fluxes. The origins of the equivalent temperature hypothesis are described, including the data and theory originally used to justify the approach, and some reservations that have been expressed by various authors are discussed. Relevant findings of recent statistically based work on Gilsocarbon materials irradiated in test reactors at differing flux are presented. The data originally used for justifying the approach and the more recent data analyses both suggest that the use of equivalent temperatures may be justified at low temperatures but not at temperatures above about 300–350 °C. Unfortunately the quantity and quality of the data does not allow for a more exact temperature to be defined.