A Simple Rn-220 Chamber for the Calibration of Passive and Integrated Rn-220 Dosimeter

Abstract

用有機玻璃板制作了一 3 5 0mm× 2 5 0mm× 1 80mm的2 2 0 Rn積累箱 ,用特制的閃爍室測量2 2 0 Rn室內2 2 0 Rn水平 ,閃爍室測量2 2 0 Rn的刻度因子是用標準氡源刻度其對氡及其子體釋放α粒子的探測效率 ,并經能量修正后得到。2 2 0 Rn源和循環氣流混合后以約 1 3L·min-1充進積累箱 ,其2 2 0 Rn水平通過充源回路添加不同體積的延遲箱和氣體流量的控制加以調節。在充源和循環氣流條件不變時 ,測量充源孔和循環孔所在兩個側面上不同位置采樣孔的2 2 0 Rn水平 ,測量結果的相對標準偏差為 0 3 % ;每 1h測量一次 ,連續 1 0h在同一采樣孔采樣 ,測量結果的相對標準偏差為 1 0 %。系統總不確定度小于 5 6%。 Abstract: A 220 Rn accumulation box w ith the size of 350 mm ×250 mm ×180 mm is made of perspex plate .220Rn level in the chamber is moni tored by a special scintillation cell.The calibration facto r for 220 Rn concent ration measurement is determined by the detection eff iciency of αparticles emit ting f rom radon and its progenies .220Rn g as and circulation air are mixed together before entering the accumulation box with a flow rate of about 13 L min .220 Rn concentration can be changed by adding different volumes of delay boxes o r by controlling gas flow rate in the 220Rn input circuit .The simple 220 Rn chamber has a good stabili ty of concentration w ith deviations of 1 .0 %during 10 h continuous measurement , and a good unifo rmity w ith deviations of only 0 .3 %.The uncertainty of the system is less than 5 .6 %.