Designing light elements analysis System with neutron activation analysis (NAA) by using MCNP code

Identification and analysis of light elements using atomic layers due to low energy X ray is not a suitable method and They have weak energy and absorbed locally. Gamma rays have enough energy for detection. Nuclear techniques usually are used to identi-fy and analyze of light elements such as hydrogen، oxygen and etc that the major components of Tissues and drug. Nuclear methods have expensive equipment and high risk factor. Before using this equipment، the level of efficiency and all aspects of radiation protection issues measured by using computer codes such as MCNP. In this paper، a system designed can be used qualitative and quantitative analysis of tissues with in vivo and in vitro to investigate the changes of the elements percent، Observed dose rate of drug body tissue (spot check) and etc.

MCNP code has ability to transport and particle analysis a system was Designing for the analysis of light elements. The most important parameters were deter-mined and with ability of code to change the geometry of components determined an optimal point for each parameter. Effective Parameters in analysis Including material Component Sys-tem، Component dimensions and their shaped and located by writing several programs with MCNP code their parameters were studied and selected as the most suitable of them for sys-tem.

All parameters were evaluated in this study include: 1. With Research different ma-terial، beryllium oxide - Bismuth was chosen for collimator material. 2. change rate of flux with thickness of collimator was investigated، Result، no significant increase in the flux for 5cm thickness. 3. Flux rate was checked by changing Opening angle of collimator، It was found، collimator opening angle should be proportional to the radiation field. If collimator opening angle increase، Neutron scattering is increase and decrease opening angle flux rate will de-crease. 4. Output flux rate was check with changes collimator Length and found maximum point in 22cm collimator length. 5. Flux rate was checked by changing the distance of sample from source، It was found that would be better if their position nearest distance. 6. System dose calculations were performed It is quite standard. Discussion and

System designed According to the results of effective parameter of light elements analysis that all the optimized parameters and system works with using MCNP code simulation software. The system in Compared to other devices are used in light elements analysis such as reactors have smaller volume، higher utilization rate، less pollution and Lower cost. System is used for light element analysis in local and extensive tissues، monitoring of drugs in tissues and etc. Analysis results is given in (6) image.