Theoretical Study Of Tailings Exemption Standards-setting And Optimization Design Of Radiation Shielding Materials

Tailing is one of the naturally occurring radioactive material(NORM), mostly following with the emission of ? rays, It must be supervised and managed. This study disscuss the talllings discharge exemption standard in Chian; Then ? radiation protection and more complex n-? radiation protection problems are studied from the aspect of radiation protection, the reason that cause shielding effect difference between various materials were analyzed seriously. The results are conluded as below:(1) The research beginning with an ideal infinity volumetric source of smooth and uniform, the conservation relationship between radioactivity concentration and absorb dose rate is found through Beck formula and Monte Carlor calculation, correcting the conservation cosfficient after considering the factors of model dimension and water content; reference relative document of IAEA and ICRP, the talllings discharge exemption standard in our nation have been given, In-suit experiments is taken at the same time sampling and laboratory analysis. The result show that two dates coincide well.(2) The radiation protection performance of functional particles against ?-rays is simulated with WinXCom software. The relationship between mass attenuation coefficient and material absorption edge effect have been discussed in detail. The results shows that simulated materials have weak absorption area and strong absorption area to the incidend low energy gamma rays, weak absorption area could be improved throught the principle of absorption edge complementment. In addition, the complement effect more obvious when the material's absorption edge more close to each other.(3) The shielding performance with the range of element weigth percentage to the several materials have bene calculated by MCNP code, the results showed that the simutated material have a better shielding effect compare to pure lead with some thickness. The best shielding performance could be get throught change the element mass ratio to the special material.(4) MCNP code was selected to simulate the reactor fission radiation source 235 U, shielding effects of differet materials to neutron with different energy were calculated. Several materials were selected to search the optimized design of compounds through MCNP code combine with Genetic Alogrithm(GA). The research show that to the neutron that energy more than 3MeV heavy metal materials have a better slowing effect than light hydrogen materials, however, the situation is contray to the neutron that energy distribute from 0.5eV to 1MeV. Heavy metal material has a little slowing ability to the thermal neutron; GA is an effective method to solve the problem of shielding material's optimize design.