Research On Rapid Test Technique Of Radioactive Leaking Gas

As the widespread application of nuclear power and technologies,radioactive monitoring is taken seriously to ensure radioactive security of nuclear facilities.The rapid monitoring of radioactive gas is the one of the most direct and sensitive methods characterizing the leakage of nuclear apparatus.The key of this technique lies in improvements of the period and sensitivity of measuring.In this paper,the rapid monitoring technique for radioxenon gas was proposed,which could provide supports for the leaking monitoring of nuclear apparatuses and other nuclear safety monitoring.Radioxenon was separated by membrane and enriched in ultra-low temperature absorption condition.Moreover,rapid and sensitive measurement can be accomplished in field by in-situ HPGe spectrometry.Physicochemical properties of xenon and pore structure characterization of nine kinds of adsorbents are studied.And on the basis of these results,the principle of the dynamic adsorption of xenon at 77K and the factors influencing the adsorption performances for carbon molecular sieve in different conditions are discussed using experimental results obtained by the test platform for the xenon adsorption designed independently.And the TJ-CMS is chosen for the adsorbent of xenon.In order to select impurity removal material,the removal performances of CO2,H2O and CO of several kinds of molecular sieves were tested.Based on the theory of gas separation with hollow fiber membrane,the removal abilities of impurities with hollow fiber membrane were studied.With test platform designed independently,the polyimide hollow fiber membranes was chosen as separation components,and the optimal equipping way and working conditions of gas separation were obtained.The on-site measurement method of radioxenon was deeply researched.The theoretic formulae of radioactivity variance during processes of sampling and measurement for two modes were presented.The detection efficiency calibration method proposed in this paper is suitable for inhomogeneous adsorption column,in which the segment efficiencies modeled by Geant 4 are weighted according to the fraction distributions of the adsorbed xenon in column based on the equilibrium adsorption theory.And the efficiencies of HPGe detector of radioxenon of adsorption column with complicated structure in the sample container were calibrated by this method.Based on the proposed principle combined with these techniques including adsorption at ultra low temperature,impurity removal with hollow fiber membranes,and low background measurement in this paper,the rapid test system of radioxenon was developed,which could enrich and measure radioxenon rapidly and efficiently.The technical indicators of this system are as follows:the recovery of xenon is larger than70%;and the MDC of ¹³³Xe and ¹³⁵Xe is 5.1 Bq/m³ and 0.5 Bq/m³ for 30min of the cycle of sampling and test,respectively.The MDC of ¹³³Xe accounts for 1/18000 to1/800 of MDC of other rapid noble gas monitors,and the monitoring period of this system is one over thirty of noble gas equipments for on-site inpections,for example,XESPM-?etc.Additionally,the standard uncertainties are less than 16%.