Software and Methods

In the Experimental Nuclear Physics Laboratory of CPST the MCNP6, MCNPX, SCALE 6.2, GEANT4 program packages are used for different applications solving tasks of particle interaction with material.

1. The deterministic methods (SCALE 6.2) are used for numerical modelling of criticality, radiation shielding safety, nuclide composition analysis in the licensed critical reactors (RBMK, PWR, VVER) and spent nuclear fuel casks.  Monte Carlo (MCNP6, MCNPX, GEANT4) are used for modelling of both critical and sub-critical systems (IV generation reactors (GT-MHR) (Fig. a), hybrid systems (fusion-fission hybrid system), accelerator driven systems (EURISOL) or conventional power rectors (VVER, RBMK).  The accuracy of Monte Carlo codes is limited by ÖN (number of traced particles), so despite wide application possibilities, sometimes advantage is on deterministic codes. The latest version of SCALE 6.2 can use MCNP neutron fluxes for material activation tasks in cases of distant neutron sources or shielded materials.  In practice, experiments are needed to validate the models in each analysed case. MCNP6 and GEANT4 codes are used modelling response of various types of detectors on radiation.

Codes of calculation of few body systems: parallel code for calculation of 3-5 particle harmonic oscillator brackets, which is used for description of few fermion systems; and code for parameter calculation of 3-6 nucleon systems. Intended for calculation of binding energies and other parameters of the lightest atomic nuclei.
Computer codes for the evaluation of the contamination levels of various radionuclides in the nuclear power plant equipment, buildings, waste and enironment:

1. Assessment of radioactive contamination of reactor primary circuit by the computer code OSCAR (CEA, France), taking into account the radiological characterisation important for the decommissioning of NPPs.
2. LIETDOS computer code package aimed to simulate radionuclides migration in the environment and to assess exposure doses to the humans and non-human biota.
3. THYROID computer code for the assessment of the inhabitants’ thyroid exposure doses after the accidents in the nuclear power plants. 

Methods

1. Determination of nuclide content in radioactive waste by scaling factor (nuclide vector) method. For radioactive waste characterization, techniques based on theoretical modelling have to be used. To this end, our laboratory is developing a semi-empirical nuclide vector, otherwise called scaling factors, method, which enables a reliable assessment of all radioactive waste by cheap measurement of easily measurable high-energy gamma emitters such as ⁶⁰Co and / or ¹³⁷Cs and use of the theoretical model of generation of radionuclides in a nuclear reactor and migration of radionuclides in NPP, i. e. to calculate specific activity of the difficult-to-measure radionuclides using ratios of their specific activity to specific activity of the easy-to-measure radionuclides, which (ratios) are determined from the theoretical modelling and measurements of specific activity of radionuclides in a small amount of specially selected samples (Fig. b).

1. The available laboratory equipment and methods for plutonium (238Pu, 239,240Pu), cesium (134Cs, 137Cs), americium (241Am, 243Am), strontium (89Sr, 90Sr), technetium (99Tc), iron (55Fe), nickel (63Ni) and lead (210Pb) isotope identification in different media.
2. Analytical model of air transport of pollutants, for the case of point source and decay of primary pollutant into the secondary one during the air transport (due to e.g. photo, chemical, radioactive decay and other reactions) and taking into account atmospheric stability classes and wind conditions with the use of widely acknowledged Gaussian dispersion parameters σx  and σy for disperssion specification. Dry deposition factor used for the settlement of the pollutants. Innovativity:  the model is unique and provides analytically precise solution of pollutant chain (primary and secondary pollutant) problem. It can be used as a callibration and validation tool of sophisticated numerical models or the modelling algorithm for the modeling of pollutants transport.
3. The model of radionuclide transport in the technological circuits of a nuclear reactor for the assessment of the activity of difficult to measure radionuclides (I-129, Cs-135) in the circuit or the generated radioactive waste.
4. The available laboratory equipment and methods for plutonium (²³⁸Pu, ^239,240Pu), cesium (¹³⁴Cs, ¹³⁷Cs), americium (²⁴¹Am, ²⁴³Am), strontium (⁸⁹Sr, ⁹⁰Sr), technetium (⁹⁹Tc), iron (⁵⁵Fe), nickel (⁶³Ni) and lead (²¹⁰Pb) isotope identification in different media.

Based on laboratory experiments, the fix-bed column of biosorbent was applied to pre-concentrate plutonium from fresh water basins. This approaching equipment allowed to determine plutonium with lower input of chemical reagents and was labour as well as time consuming.