Study Of Aerosol Monitoring Of Nuclear Facilities And Nuclear Critical Security

Ionizing radiation from nuclear facilities has been widely concerned,due to the special use of plutonium and highly toxic radioactive hazard,in the national defense industries and other non-reactor type nuclear facilities.More attention has been paid to the study of ionizing radiation protection from plutonium.As the standardization of internal radiation protection technology of plutonium is relatively weak,the emphasis of radiation protection work is protection and monitoring of internal radiation hazards.Plutonium is fissile material,in the case of nuclear criticality accident,radiation damage to the staff and the public is very serious,so the nuclear criticality safety is an important work for safe operation of nuclear facilities.In this work,a set of plutonium aerosol measurement device was developed by double compensation technology.When the concentration of radon between 15.4 Bq/m3 and 43.1 Bq/m3(thoron concentration between 1.54 Bq/m3 and 4.31 Bq/m3),and the confidence level is 95%,the detection limit is 0.072 Bq/m3.It satisfies the rapid detection of plutonium aerosol index(DAC-h)requirements,which can estimate whether plutonium aerosol concentrations exceed the standard level and actualized fast detection under accident condition,achieved the purpose of radiation protection.In this work,we selected uranium and plutonium nuclear criticality system as benchmark experiment,the reliability of CHMCK program and program are verified.The nuclear reactivity of spherical plutonium samples,cylindrical plutonium samples and graphite radiation cylindrical plutonium samples were measured,and then compared with theoretical results.The theoretical results and the experimental measurements are consistent in the state of deep sub criticality nuclear system,both of them can be used for analysis and evaluation of the nuclear criticality safety.With increase of the criticality reactivity of plutonium monomer nuclear system,the agreement of experimental results and the theoretical calculation results are improved,and the safety of theoretical calculation gets better,which can satisfy with nuclear criticality safety assessment requirements.In the study of the criticality safety control technology of nuclear system,the effects of plutonium neutron energy spectrum and absorption rate by common neutron shielding material were calculated by MCNP program.The effects of boron containing polyethylene and polyethylene with cadmium protective layer shielding MCNP of neutron and gamma ray have been measured.When the thickness of polyethylene is greater than 6cm,nuclear system will achieve full water reflectance state,protective container can eliminate neutron influence between multi bodies.Synthesized factors such as neutron absorption property,process-ability of material,and product retirement processing,choose polyethylene and cadmium as protective container filling material,can absorb the neutrons of plutonium materials effectively,and eliminate the mutual influence between nuclear multi body array systems,then accomplish gapless store of fissile materials.Experiments proved that choose cadmium as inner layer of the container,and stainless steel as outer layer of the container,it not only can shielding gamma ray from plutonium,but also absorb characteristic x ray produced by cadmium in outer stainless steel layer,which benefits of the products and personnel protection.