New code for analysis of nonlinear effects of radiation exposure to materials :: SPE RESST

New code for analysis of nonlinear effects of radiation exposure to materials

The development of methods and tools for computer-aided mathematical modeling of radiation effects in materials subjected to reactor irradiation and accelerators' driven irradiation with charged particles is an important factor in increasing the efficiency of applied studies of radiation resistance of advanced materials for alternative nuclear power systems of the new Generation IV and the development and implementation of promising sources of radiation for socially significant sustainable industrial irradiation technologies and nuclear medicine.

Changes in the state of a substance under the impact of high-dose irradiation affect the transport of radiation in it. These changes are expressed in the nonlinear dependence of the yield of radiation effects on the fluence and dose of irradiation, but are not taken into account in the linear theory of radiation transport.

The SPE RESST developed novel modification of the multi-purpose 4D-code RaT 3.1 implements advanced algorithms for Monte Carlo modeling of non-linear dose dependent effects. It allows efficient solution of diverse nonlinear problems of radiation transfer in heterogeneous media, calculation the irradiation-induced evolution of their parameters over time and its self-consistent effect on radiation transport.

The new code has been validated on model exactly solvable problems of formation and propagation of nonlinear density waves in the material (see Figure 1). With its help, nonlinear phenomena under the conditions of a supercritical transition in water irradiated by electrons at the LUE-10 accelerator of the NSC KIPT were considered for the first time. It was shown that the transition of the water to the supercritical state can obey the dynamics of a self-similar nonlinear waves of density and temperature (see Fig. 2).

Fig. 1 – Results of analytical calculations of the dynamics of a nonlinear wave of the density change rate R of a water-like medium under irradiation with 100 keV energy primary photons (on the left) in comparison with the results of Monte Carlo simulation using the RaT 3.1 code (on the right) for different values of the nonlinearity parameter ? of the model equation of state of the medium

Spatio-temporal dependences of temperature

Fig. 2 – Spatio-temporal dependences of the density (a) and temperature (b) of water in the vicinity of the supercritical transition caused by the electron beam of the accelerator. Monte Carlo simulation

The developed code can be efficiently applied in solving many topical problems of radiation material science of nuclear power systems of a new generation and in optimization of nuclear and irradiation technologies. For example, they are:

calculations of burnup profiles of promising neutron-absorbing materials, including randomly dispersed ones;

modeling of secondary effects of radiation damage and helium production in nickel-containing structural reactor materials;

simulation of a nonlinear wave of nuclear combustion in the Feoktistov-Teller prospective reactor (TWR);

process optimization of production of gamma-radiation sources for ecological technologies and of medical isotopes on various types of charged particles accelerators and in subcritical systems;

simulation of the processes of ion implantation of metals, alloys, semiconductors and nanostructures to high doses.