In this paper the results of the practical definition of the braking parameter of uranium coating fission fragment in the active laser element of nuclear-pumped laser in a gaseous environment are presented. A description of the experimental method for removing the fission spectra of a NPL uranium coating is given. This method is based on measuring the fission fragments energy spectra emitted from the coating to a gas mixture with the help of a semiconductor detector. To calibrate the fission fragment sensors a californium source the fragments of which have a characteristic spectrum is used. The results of the analysis of the sections of the experimental spectra are presented. On the basis of the findings the theoretical model of the fission energy transfer process in a gaseous environment were checked. As the determining parameters in the modeling of this process, the pressure of the gas mixture in the cuvette with the source and the distance from the fission fragment source to the semiconductor sensors are chosen. The functional dependences of the obtained amplitude spectra on these parameters are determined. A mathematical description of the disperse energy fragment process is presented. The basis of this description is a two-parameter dependence.