超大面积屏栅电离室的研制

核设施退役过程中，需对超过1 000 cm²以上的大面积超铀核素平面板放射性进行准确定量，常用无损测量方法有效测量面积均较小，且探测限较高，不能满足快速分析大面积低活度样品的需求。屏栅电离室是一种用于低水平α放射性能谱测量的仪器，可满足以上分析需求，但受制于电极加工工艺，可测样品一般小于500 cm²。为解决以上问题，研制了灵敏面积接近2 000 cm²的超大面积屏栅电离室，通过对工作气压和电压的调试优化，该电离室对²⁴¹Am电沉积源的能量分辨率为1.8%，最小可探测活度为10^-2 Bq，对直径≤460 mm的平面样品2π角探测效率为97.7%。

Development of Ultra-large Area Grid Ionization Chamber

During the decommissioning of nuclear facility, it is necessary to accurately quantify the radioactivity of large-area transuranic nuclide planes over 1 000 cm². Common non-destructive measurement methods have small effective measurement area and high detection limit, which cannot meet the requirement of rapid analysis of large-area low-activity sample demand. The grid ionization chamber is an instrument used for low-level alpha radioactivity spectrum measurement, which can meet the analysis requirement of low-level sample. However, due to the electrode processing technology, the measurable sample is generally less than 500 cm². To solve this problem, an ultra-large area grid ionization chamber with a sensitive area close to 2 000 cm2 was developed. Through the adjustment and optimization of the pressure and voltage, the ultra-large area grid ionization chamber has a 1.8% energy resolution for the ²⁴¹Am electrode position source, a minimum detectable activity of 10^-2 Bq, and a 2π angle detection efficiency of 97.7% for a flat sample with a diameter less than 460 mm.