A prompt gamma neutron activation analysis system with a 252Cf neutron source for on-line cement analysis has been simulated with the MCNP code.The results indicate that the optimum arrangement is a Bi shield of 20-mm...A prompt gamma neutron activation analysis system with a 252Cf neutron source for on-line cement analysis has been simulated with the MCNP code.The results indicate that the optimum arrangement is a Bi shield of 20-mm thickness,a polyethylene moderator of 50-mm thickness,a source-to-sample distance of 70 mm,and cement samples of 1200 mm×600 mm×170 mm.To absorb thermal neutrons and suppress low-energy γ-rays,the optimum-sized sheets are 150 mm×7 mm Cd,and 150 mm×15 mm Pb.展开更多
The distribution characteristics of the neutron field in cement was simulated using the MCNP code to comply with the requirements of an online Prompt Gamma Neutron Activation Analysis system.Simulation results showed ...The distribution characteristics of the neutron field in cement was simulated using the MCNP code to comply with the requirements of an online Prompt Gamma Neutron Activation Analysis system.Simulation results showed that the neutron relative flux proportion reduced with increasing cement thickness.When the cement thickness remains unchanged,the reduced proportion of thermal neutrons increases to a small extent,but the epithermal, intermediate,and fast neutrons will decrease according to the geometric progression.H element in the cement mainly affects the reduction of fast neutrons and other single-substance elements,e.g.,O,Ca,56Fe,Si,and Al.It also slows down the reduction of the fast neutrons via inelastic scattering.O contributes more than other elements in the reduction of fast neutrons.Changing the H content affects the thermal,epithermal,intermediate,and fast neutrons, while changing the Ca,Fe,and Si contents only influences the thermal,epithermal,and intermediate neutrons;hence, there is little effect on the reduction of fast neutrons.展开更多
基金Supported by NSFC(40974065)National Innovation Method(2008IM021500)+1 种基金National Key Technology R & D Program(2008BAC44B04)Province Key Technology R & D Program(2008SZ0148,2008GZ0197,2008GZ0040)
文摘A prompt gamma neutron activation analysis system with a 252Cf neutron source for on-line cement analysis has been simulated with the MCNP code.The results indicate that the optimum arrangement is a Bi shield of 20-mm thickness,a polyethylene moderator of 50-mm thickness,a source-to-sample distance of 70 mm,and cement samples of 1200 mm×600 mm×170 mm.To absorb thermal neutrons and suppress low-energy γ-rays,the optimum-sized sheets are 150 mm×7 mm Cd,and 150 mm×15 mm Pb.
基金Supported by National Natural Science Foundation for Distinguished Young Scholar(41025015)NSFC(40974065,11105132)+3 种基金Province Key Technology R&D Program(2011FZ0055)National High Technology Research and Development Program of China(2012AA063501)the Basic Research for Application of Sichuan Province(2012JY0109)China Postdoctoral Science Foundation(2012M520245)
文摘The distribution characteristics of the neutron field in cement was simulated using the MCNP code to comply with the requirements of an online Prompt Gamma Neutron Activation Analysis system.Simulation results showed that the neutron relative flux proportion reduced with increasing cement thickness.When the cement thickness remains unchanged,the reduced proportion of thermal neutrons increases to a small extent,but the epithermal, intermediate,and fast neutrons will decrease according to the geometric progression.H element in the cement mainly affects the reduction of fast neutrons and other single-substance elements,e.g.,O,Ca,56Fe,Si,and Al.It also slows down the reduction of the fast neutrons via inelastic scattering.O contributes more than other elements in the reduction of fast neutrons.Changing the H content affects the thermal,epithermal,intermediate,and fast neutrons, while changing the Ca,Fe,and Si contents only influences the thermal,epithermal,and intermediate neutrons;hence, there is little effect on the reduction of fast neutrons.
