²⁴Na Activity Neutron Dose MC Simulation Technique And Mathematical Model Analysis

In recent years, measurement of neutron dose for the nuclear accident has beendone extensive research, but it has not been found an ideal way.In the laboratory andspecial places, a variety of neutron dosimeters were used to assess neutron dose，forexample: Fast neutron dosimeter, fluorescent glass neutron dose meter as well as solidstate nuclear track dosimeters, etc. But in a nuclear accident, we usually do not havethese conditions, so scientists proposed the use of human biological reflex to assess theneutron dose. Neutron irradiation can cause the body to some elements （such as sodiumelements） activation. Neutron dose was able to be assessed by measurement of sodiumactivity.The difficulty of the activation method is how to determine the mathematicalrelationship between the activity of sodium and the neutron dose. Under idealcondition, theory formula of conversion between sodium activity of human body andneutron dose was deduced, based on based on the literature available. Using theMonte Carlo simulation program MCNP, active blood detection efficiency of thewell-shaped NaI detector and conventional cylindrical NaI detector were calculated,and influence of detector shape to detection efficiency of²⁴Na was studied，then，wecome to the conclusion that the well-shaped detector can effectively improve thedetection efficiency of²⁴Na. At the same time, using MCNP5, model of the humanbody was built, neutron accident in the Los Alamos science laboratory was simulated,the equivalent dose and effective dose were calculated, and the relationship between²⁴Na activity and dose was established.