Development Of Portable Detector Of Gamma Radioactive Internal Contamination In Lungs

After developing for more than a century, nuclear technology has been widely used in the fields of military, industry, agriculture, etc., and also has brought enormous benefits to mankind. But everything has its negative side which also brought huge harm. From development of nuclear technology development so far, proliferation of nuclear weapons, leakage of nuclear radiation in nuclear power plant and the loss of radioactive sources, unexpected nuclear accidents occurred frequently, which caused not only enormous casualties, heavy environmental pollution and economic losses, but also seriously affect the security and stability of society.In the event of a nuclear accident, if the radionuclides went into the interior of the human body will cause internal radiation, which can trigger fatigue, dizziness, hair loss, leukemia and other radiation sickness, and also will greatly increase the probability of the distortion, cancer and hereditary diseases. Therefore when the nuclear accident happened, the relief agency should immediately evacuate personnel, take timely nuclear emergency medical rescue to detect the internal contamination of personnel, and take specific diagnosis and treatment according to the number of doses detected in the human bodies. Currently, nuclear safety issues are highly concerned, researchers around the world continue to develop vivo measurement techniques of radioactive contamination, the internal contamination detectors are widely used over the world. The aspect of internal contamination detector in our country is still in the preliminary stage although some research results have been achieved. There is still a big gap between our country and these developed countries, therefore our country urgently need to research and develop internal contamination detector with our own independent intellectual property rights.This paper is based on existing researches and relying on the subtask of y radioactive contamination detection in lungs supported by Special Program of Major Instruments of China’s Minister of Technology. Focusing y radioactive contamination detection within lungs, the researches of y spectrum of lungs measurement and analysis were carried out as well as hardware and software developing work. And a portable detector detecting y radioactive contamination of lungs in field was developed, which is suitable for measurement of nuclear accident site. The main contents and results as following:1) Combined with the principle of pulmonary y spectroscopy measurement, in-depth study of key technologies of y-ray detection, nuclear signal acquisition, pulse shaping, spectroscopy forming, spectrum transmission, etc. The integrated design method is proposed to develop a mainframe of Portable Detector of Gamma Radioactive Internal Contamination in Lungs, which integrated the NaI(TI) detector, PCB circuit and power source and this absolutely reduced the volume of the instrument, improved the anti-jamming capability, stability and reliability.2) The y-ray spectrometry hardware circuit was designed that Nal(TI) detectors are responsible for detection of y-ray from contaminated lungs, low power consumption, high integration and high processing speed of the FPGA was chosen as the master chip, combined with high-speed pulse acquisition ADC circuit and USB communication circuit, the nuclear signal acquisition and analog-digital transformation were completed. Wherein the internal circuitry of the FPGA was developed, signal acquisition circuit, nuclear trapezoidal pulse shaping circuit, peak detection circuit, spectrum shaping circuit, pulse memory core circuit and data transfer circuit were designed, and the nuclear signal processing was achieved.3) By using C#language (based on VS2010development environment) to develop y radioactive contamination analysis software to lungs. A USB communication interface program was developed to create communication protocols, to communicate with mainframe and to achieve real-time spectral data acquisition. The ACCESS database was developed to inquire and call nuclides information, energy calibration information, efficiency calibration information, port information, the pulse width parameter information in database, preservation of spectrum and pulse information was achieved. This software has many properties including friendly-interface, high-interaction, spectrum-displaying, parameter-setting, database-operation, data-storage and other functions. Meanwhile the preliminary work for analyzing y spectrum was carried out and an algorithm of effective dose to human lungs was settled.4) System testing, by testing nuclear analog signal that came from different levels of preamplifier and main amplifier circuits to verify all levels of the analog circuits will be workable. By real-time displaying nuclear signal pulse from ADC with different thresholds on PC software to verify the effectiveness of ADC circuit to signal acquisition and by comparing spectrums from digital multi-channel and software to verify the effectiveness of digital multi-channel. These tests showed that the hardware circuit worked properly. And on this basis, experimental studies on60Co,137Cs and other radioactive sources for testing were carried to verify the effectiveness of trapezoidal shaping, the results showed that the system can be used to quickly detect the γ radioactive contamination in lungs.The developments of hardware and software working for detecting γ radioactive contamination in lungs were carried out, innovations were continued in the process of design and development, finally the Portable Detector of Gamma Radioactive Internal Contamination in Lungs was completed. And performance testing and preliminary tests showed that the various technical indicators of detector were achieved as expected.