Nükleer Maddelerin İzotopik İçeriğinin Monte Carlo Yöntemi ile Belirlenmesi

Abstract

Uranium needs to be enriched in order to be used in Light Water Reactors (LWR) as fuel cells. This process can be accomplished in enrichment facilities by increasing U-235 isotope mass content in the uranium element. Monitoring the enrichment process and checking the enrichment level of uranium are crucial in the terms of fuel cell convenience and nuclear safeguard. Enrichment determination could be achieved by examining gamma spectrometry of radioactive uranium element. Gamma spectrum of isotopes of radioactive elements carry information of enrichment level of material. In this way, detection of enrichment could be performed without using any reference material. Specific regions on gamma spectrum or full energy peaks of specific gamma rays were used in order to determine the enrichment level in the studies until now. However, in this work whole spectrum information was taken into account, thanks to that all gamma ray peaks information can be used in determination process. In this thesis, different types of detectors were examined by their performance during enrichment determination. Gamma spectrums were created via using MCNP program. Based on Monte Carlo Technique, result of MCNP program were developed to simulate real life gamma spectrums. This process achieved by determining of energy resolution of detectors and time information for the system via Python programming language. Results show that detector volume and resolution is important for both whole spectrum and peak ratio techniques. In second step, enrichment, density and production time information were defined for the system and Levenberg-Marquardt Method was used over whole spectrum. In this method, separate isotope spectrums were not used as it was used in previous step. Only desired spectrum itself was used in determination process. In this way, dependency of seperate isotope gamma spectrums was eliminated. Usage of enrichment and production time information detection together has failed since both affect the spectrum in similar way. For this reason, only enrichment and density variables were set for the process and results show that system converges the desired variable values.