| This paper designed a suit of radiation activity monitor which used for containment discharge gas pressure relief measuring.The monitor including measuring detector, leader shielding, collimator, pre-amplifier circuit, on-site display unit, cabint of information and so on. The measuring detector made of Φ50mmx50mmNaI (T1) scintilla and match with Hamamatsu high-temperature photomultiplier tubes. During the design process adopting the jar lead shielding to surround the measure detector which insert of collimator, and collimator are sodium iodide crystal. The thickness of lead shielding, length of collimator, aperture of collimator, compensation filter are be optimized calculate by Geant4 software. Take the minimum detectable and detector efficiency into account we analysis the calculate results, and obtained the optimal geometrical for the monitor designs. Inord to reduce the impurity gamma effects to the measure results, use the copper and stannum as the underlayer to liner the collimator wall. After obtaining the design parameter and based on Geant4 code study the monitor performance such as energy spectra, measure efficiency and energy response, and simulation the total energy spectrum for the containment discharge gas. Through experiment of 137Cs dot source, get the results that the calculate spectrum is well matched the experiment spectrum during the middle range energy and mighty peak. For the low energy(<200keV) the experiment value is high than the calculate value, those gamma particle (energy≤200keV)are considerate as noise, so set a threshold to filter those gamma particle on the multi-channel.In this paper, the design of the monitor is mainly used for extremity dicky environment of nuclear accident monitoring, the equipment must be able to endure irradiation, high temperature and can resist for long hours work. It has a high requirement for subsequent electronics, so we do a well design for amplifier and studied the signal remote transmission.Through the oscilloscope experiment testing, the result show that this amplifier circuit can well realized the long distance collection of singles. Finally, aim at the collection of pulse amplitude singles and mulity-channel energy spectrum, detector scaling, spectrum data analyzing and project alert sets, radionuclide activity measurements do a simply reassure.In a word, by comparing the calculate spectrum with the experimental spectrum, the single test of oscilloscope and the spectrum measure by spectrum analysis software, it verified the monitor is able to used for nuclied analysis measurement for the adverse environment.Solve the problem that the radioactive nuclied can’t be quantitative measurment during the environment of high-temperature and high radiation .At the same time make up a defect for the containment vessel radiation monitoring system during the serious nuclear accident and provided a reference for environmental impact of containment vessel aftes the nuclear accident. |
