Development of FT-II Code for Dynamic Analysis of Thermal Energy Transfer Caused by Fission Fragments

Fission track method for strengthening the safeguards system is expected to be very useful to detect undeclared nuclear activities. An increased number of environmental swipe samples taken from or around the nuclear facilities require developing more quick and effective technique for isotopic analysis. But there exists a technical problem that too many fission tracks will cause dropping the sample particle from a film material during etching process. Such problem attracts us from the microscopic point of view of how much fission fragment will affect the characteristics of the sample particle. Fission fragment loses its energy in collisions with electrons of an absorbing material. As a result, a great many atoms or molecules are ionized or excited by fission fragment along its path. In an ionization or excitation processes, the sample particle will take some kinetic energy in the form of a linear heat source through collision relaxation processes. We have been developing a computer code FT-II on the base of several simplifications, and simple physical model. Two types of particles composed of the quasi-particles are chosen as the basic model of our study, and the characteristic difference in thermal energy transfer and in structural defect is to be clarified for both model particles. At the present time, we would like to show a brief outline of FT-II code and to discuss what subjects we should be solved in the future.