The Simulation Of ?-radioactive Surface Contamination Based On Magnetic Particles And Its Detection Technology

The ?-radioactive surface contamination detection and decontamination is an important part in the training for nuclear emergency medical rescue.However,it is usually difficult to use real radioactive sources in training,because radioactive substances is potentially harmful to people and to the environment,and the use of radioactive sources must undergo strict examination and approval.This may lead the difficulty in achieving the effect of the training.The simulation method of the ?-radioactive surface contamination and its detection technology is attractive practise to solve the existing safety hazards,which could improve the training effect of the nuclear emergency medical rescue team.This study faces the actual needs in the training of nuclear emergency medical rescue teams.This work aims to develop a kind of safe and reliable method and equipment to simulate the real a-radioactive surface contamination and its detection,and to solve the potential health hazards in the using of real radioactive sources,and finally to improve the training effect of the nuclear emergency medical rescue team.The main contents and results of this study are as following:1.Study on the simulation method of ?-radioactive surface contamination based on magnetic particles.Based on the analysis of the training requirements and the main factors,a simulation method using magnetic particles and its magnetic field to simulate alpha-radioactive surface contamination is proposed.The magnetic particles is used to simulate the surface contamination,and the magnetic field is used to simulate the a-activity.By analyzing the main factors affecting the performance of the magnetic particles,we formulate the preparation scheme and preparation process of the magnetic particles.The simulating a-active source has a similar appearance with the ?-activie surface pollutants,and can generate a stable magnetic field signal to simulate ?-radioactive surface contamination.2.Study on detection technology of magnetic particles simulating ?-radioactive surface contamination.We designed the magnetic field measurement method and used an anisotropic magnetoresistive sensor as the detecting sensor.The transformation formulas of magnetic particles simulation source and ?-radioactive surface contamination measurement value with measurement distance and erasure ratio are given respectively by theoretical research and actual measurement methods.As the result,the magnetic flux density of the magnetic particles is inversely proportional to the cube of the distance and linearly to the erasure ratio.By calculation,we find that the counting rate are negative linearly relative with the measurement distance of the big ?-radioactive surface source within the detection range.Finally,the conversion formula between the measurement value of the simulation source and the count rate is given according to the rule of the measured value of the magnetic powder simulation source and the conversion relationship of the count rate with the activity of the ?-radioactive surface source.3.Design of hardware for magnetic particles simulating ?-radioactive surface contamination.The sensor array and set / reset circuit was designed based on HMC1021 Z single-axis anisotropic magnetoresistive sensor.Based on C8051F120 single-chip microcomputer,the analog switch switching circuit,programmable amplifier filter circuit,zero-adjusting circuit and single-chip control circuit was designed.Finallt the functions of magnetic field signal detection,data conversion and display,alarm and so on was realized.4.Design of a software program for simulation equipment.The usually used Como170 portable ?-acvitity surface contamination detector was used as the simulation object.The control software was programmed according to the requirements of hardware circuit control and the operation method and control flow of the surface contamination detector.The software program realized the functions such as simulation signal detection and hardware circuit control,and fully emulated the Como170 operation interface and operation flow.5.Test of simulation equipment.The test results showed that: the software and hardware design of the simulation equipment was reasonable and could realize the designed functions;the use of the simulating radioactive source and the simulation detection equipment could realize the training purpose of ? radioactive surface contamination detection and decontamination.The measurement results of the simulating magnetic field are consistent with the regularity of the measurement results of the actual ?-radioactive surface contamination.The research on the simulation method of alpha-radioactive surface contamination based on magnetic particles and its detection technology provides a new method for the training of alpha radioactive surface contamination detection.The simulation source is close to the real alpha radioactive surface contaminants in appearance,provides a stable simulation signal,is less disturbed by external environment,and can be applied to the detection and decontamination training of alpha surface radioactive contamination.The simulation equipment simulates the interface,operation flow and operation method of Como170 portable ?-acvitity surface contamination detector.The change of the simulated magnetic field signal can simulate the change of ?-radioactive surface contamination signal under certain conditions,so that the training environment is close to that using a real radioactive source.After the system is further improved,it can be used for surface radioactive contamination simulation detection and decontamination training of the nuclear emergency medical rescue team to improve the training effect.