5588

5222

كارشناسي ارشد

فيزيك هسته اي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1389

دوازده،102ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

محمد حسن علامت ساز

احمد شيراني

7/10/89

اكبر پروازيان، ظفرالله كلانتري

فيزيك

ID5222

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

The calculation of gamma ray exposure buildup factors for plane source in two layer shields with MCNP code including the effects of bremsstrahlung Sajjad Marri sajadmarri@yahoo com November 3 2010 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Dr Mohamad Hassan Alamatsaz Mail alamatsa@cc iut ac ir Abstract In this thesis by means of MCNP code Monte Carlo N Particle that is based on monte carlo method we are going to study the dependence of exposure buildup factors EBFs on depth of penetration for plane normal source in two layer shields of Pb Fe concrete and water The dependence of EBFs on atomic number and energy in monolayer shields is also studied So at first we studied the effect of atomic number on EBFs at 5 and 10 mean free path mfp in energy 0 5 and 10 MeV In the next step we studied the effect of energy on EBFs at depth 1 6 and 10mfp In last step we obtained the EBFs in energy range of 0 5 10 MeV in three stages First we obtained these EBFs without the effect of coherent scattering and bremsstrahlung and then by considering the effect of coherent scattering and at last we obtained them by considering the effect of both coherent scattering and bremsstrahlung radiation According to the MCNP results coherent scattering is important only in lower energies and high atomic number materials and we can ignore the effect of this interaction for low z material and energies higher than 3MeV because the cross section of this interaction at low energies is high Also from the studying the effect of bremsstrahlung we can find that this interaction is important for high atomic number and in high energies and we can ignore the effect of this interaction for low z material in energies lower than 3MeV For example coherent scattering at 4mfp for energy range of 0 5MeV 10MeV in Pb changes EBFs from 28 29 in 0 5MeV to 0 in 10 MeV These changes in Fe are from 8 47 in 0 5MeV to 0 in 10 MeV in concrete from 2 43 in 0 5MeV to 0 in 10 MeV and in water from 1 11 in 0 5MeV to 0 in 10MeV The bremsstrahlung in previous energy range and depth of penetration in Pb changes EBFs from 0 43 in 0 5MeV to 95 27 in 10 MeV These changes in Fe are from 0 18 in 0 5MeV to 24 42 in 10 MeV in concrete from 0 14 in 0 5MeV to 7 62 in 10 MeV and in water from 0 in 0 5MeV to 4 5 in 10 MeV Therefor when we plot the EBFs by diagram we can see that the coherent scattering is important just for energy 0 5 1MeV and in this energy range bremsstrahlung is negligible and by increasing the energy to 3MeV the effects of both are similar to each other and when we increase energy further bremsstrahlung will become more important and coherent scattering negligible Keyword MCNP monte carlo exposure buildup factor coherent scattering bremsstrahlung gamma ray mean free path

محمد حسن علامت ساز

احمد شيراني

اكبر پروازيان، ظفرالله كلانتري