The Development Of Pipe Inner Surface α Activity Monitoring System

With the nuclear science and technology is widely used in the field ofmedicine,medical radiation measuring instruments has become one of the keydeveloping direction in medical equipment.Ionization chamber is important one ofalpha radiation detectors, it quantitatively measure ionizing radiation. through thecollection of electronic generated in gases or telecommunications which produced byion movement.But, when element strength very low, ionization current of ionizationchamber produced i rather weak, in10-15A (fA) orders of magnitude. The currentdomestic measuring such weak current technology is not mature. The purpose of thispaper is to develop a set of signal acquisition, data processing technique in a body,especially for pipe α activity monitoring of surface stability, low detectable limit, highprecision, the operation is convenient and flexible, intelligent applicable gammaradiation monitoring system.α rays is composed of the rapid movement of helium nuclei, usually also calledalpha particle, and alpha particles decay at most energy in4to9MeV range. Alphaparticle produce the coulomb’s role with target material when it through targetmaterial, and make the target material atomic ionization or excited, forming a freeelectrons and positive ions composition of ions. These ions are aligned to bottom driftin the action of ionization chamber’s voltage, induced current, the current strength isdirectly proportional to produce ions alpha activity. This design through optimizingcircuit design, overcome temperature effect, and to increase the multilayer shieldingand other measures to improve the stability of α activity monitor, detectable limit andsensitivity, and developed a series of remote control, intelligent PC software system ofmeasurement data effective treatment. This paper mainly introduces the pipe inner surface for α activity monitoringsystem of the hardware and software of the realization of the function of and relatedtechnical key points. This thesis of the work and the achievements of the following:(1) Developing a set of pipe inner surface α activity monitor. α pollutionmonitoring system hardware circuit mainly composed by the nuclear radiationdetector-ionization chamber, ionization chamber power supply high voltage powersupply, weak current measurement circuit, measurement of the front of the host.Ionization chamber convert α ion to weak ionization current; The ionization currentby ionization lead I-V switching circuit, fight aliasing filter circuit, A/D conversioncircuit, converted into digital signals. Measuring unit is responsible for receiving thedigital signal sent by ADC, and through to the inverse calculation to restore ADCreflect the true signal into the digital quantity; At the same time is responsible forreceiving the control signal from the upper machine, the relevant operation andprocessing.(2) Developing a set of the PC software data processing. PC software systemmainly includes six function module: data transceiver module, system setting module,the data display module, document management module, data query model and dataanalysis module. Data transceiver module sent control command through a serial port,received the measurement data sent by α activity monitor; Through the data real-timedisplay module to display the measurement data, through data analysis for α activity.After completing the pipe inner surface α activity monitoring system hardwareand software development, we test the on the system’s performance. Preliminary testinvolves ionization chamber linearity test and measurement stability testing ofionization current. System after the installation of four different activity of239Pu αsource in different experimental conditions continuous measurement, themeasurement result is good, which verify the sensitivity of the monitor and thestability of system.The design of the monitoring technology and α activity measurement system canreal-time, high efficiency, continuous, safe and reliable monitor the pipe inside surfaceof α activity. Therefore, the technology is very suitable for mass long pipe insidesurface of α activity nondestructive monitoring, has a good application prospect indecommissioning nuclear facilities and radiation detection field.