A TTT-diagram for alpha - > beta transformation of unalloyed plutonium

摘要

The paper offers a variant of the generalized TTT-diagram (temperature-time-transition) for the alpha - > beta transformation of unalloyed plutonium under isothermal conditions. The authors constructed it using published information on plutonium phase transformation kinetics under isothermal conditions and alpha - > beta transformation parameters under the conditions of pulsed electric heating. The authors also present their results-parameters of the beginning of the alpha - > beta transformation in isothermal conditions and in linear-through-volume heating by neutrons from pulsed nuclear reactors exploited at RFNC-VNIITF. Using a number of typical TTT-diagrams as examples, the authors demonstrate characteristic features in the dependence of the phase transformation incubation time on plutonium temperature in isothermal conditions (for example, in samples hold in oil) and in electric heating conditions. They identify segments where, in the authors' view, phase transformation conditions were not isothermal and justify the use of the most authentic experimental data including those obtained by the authors for isothermal conditions for the construction of the generalized TTT-diagram. To justify the use of their own results obtained for the uniform-through-volume heating of samples by neutrons, the authors used known theoretical results for non-isothermal first-kind transition kinetics. Theoretical results suggest that for certain conditions of the first-kind transition, it is possible to relate the temperature dependences of the incubation time for non-isothermal and isothermal transformations. So, the authors propose a generalized TTT-diagram for a range of plutonium temperatures corresponding to the incubation times of unalloyed plutonium phase transformation between 10~(-5) and 10~5 s.