The Development Of Portable Pipe Inner α Contamination Monitor

As the development of China’s nuclear technology and nuclear decommissioning work is unfolding, radioactivity measurement of a surface contamination for the irregular geometry which not easy to get close (such as small diameter and the inner surface of pipeline) is increasingly urgent demanded. This topic to nuclear decommissioning pipeline pollution monitoring facilities as the research background, based on the application of the LRAD technology and alpha pollution key technical features of a measuring instrument, developed a new type of portable alpha pipe pollution measuring instrument by using ARM processor STM32. This instrument can be used to detect the pipe inner surface alpha pollution which traditional pollution meter sensor can’t detect. When monitoring small diameter pipe surface alpha activity, it is not need to damage the test pipeline but would can monitoring on the real-time activity safely and efficient.The work of this thesis is mainly reflected in the following aspects:First, the study of the method of micro-current measurement and the way to improve the accuracy and stability, including measuring principle analysis and the selection of device, etc; Second, instruments processor selection:taking the Cortex-M3kernel STM32processor as the main controller to improve performance of data processing and control of the equipment; Third, Power Scheme is carried out by the studies of AC direct power and lithium battery-powered respectively. According to the system’s power requirements of each module, providing a suitable power supply design; Fourth, PC software for data storage and display on the interface in the form of graph and text display; Fifth, based on the theory of probability and statistics, the standard error of measurement data distribution for limited time to calculate and singular number discriminate out processing, and display the histogram statistical distribution, analysis of measurement data reliability and validation; And last, reliability design:through some anti-interference measures, overcome external factors affect the performance of instruments, in order to improve the stability of alpha contamination monitor detection limit and sensitivity.This article made a detailed introduction to the design of portable a pollution measuring instruments, including hardware circuit design and software program design and error analysis of the communication protocol and anti-jamming processing, etc. Finally, the performance of the equipment was tested, the sensitivity of measurement system is5×10-15A/Bq, micro-current measurement accuracy in10-15A level, relative error is within0.4%, the stability is better.