Development of negative-ion mass spectrometry for monitoring trace amounts of radioactive iodine molecules included in off-gasses of a nuclear fuel reprocessing plant

开发用于监测核燃料后处理厂废气中微量放射性碘分子的负离子质谱仪

• 批准号: 60880026
• 负责人: KAWANO Hiroyuki
• 金额: $ 2.88万
• 依托单位: Ehime University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Developmental Scientific Research
• 财政年份: 1985
• 资助国家: 日本
• 起止时间: 1985 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-60880026/
• 关键词: Atmospheric radioactive iodine; Thermal negative lonization mass spectrometry; Lanthanum hexaboride; Work function; 仕事関数; 付着率; オキサイドカソード; 電子捕獲; 負イオン; 表面電離; 質量分析; ヨウ素; 排ガス

In order to detect the trace amount of iodine molecules included in air, a negative surface ionization type ion source employing an LaB_6ds -coated rhenium wire as an ion emitter was connected to a commercial mass spectrometer with an electron multiplier. Under the experimental condition that the surface temperature and the sample gas pres- sure around the ion source were about 1400 K and 3 x 10^<-5> Torr, respectively, the work function of the ionizing surface was about 2.7 eV, and the ionization efficiency of the iodine molecule was governed practically by its sticking probability to the surface because the degrees of dissociation of I_2 and of ionization of I were essentially unity, just as prodicted by our theory on negative surface ionization. After a sample gas inlet system readily controllable of iodine concentration in air was improved many times in order to decrease iodine contamination inside the system and also after the best condition for operating the system was found by preliminary experiments, the negative iodide ion current was measured as a function of the iodine concentration, theraby yielding such a calibration plot that the current was proportional to the concentration in the range between 50 and 0.1 ppm. This result suggests that the present method may be employed to monitor radioactive iodine molecules included in the off-gases of nuclear fuel reprocessing facilities.

为了检测空气中痕量的碘分子，采用LaB6DS涂层的Re丝作为离子发射体，将负表面电离型离子源连接到带有电子倍增器的商用质谱仪上。在离子源表面温度和样品气压分别约为1400K和3×10~(-5)Torr的实验条件下，电离面的功函数约为2.7 eV，碘分子的电离效率实际上由其附着在表面的几率决定，因为I_2的离解程度和I的电离程度基本上是统一的，正如我们的表面负电离理论所预言的那样。为了减少系统内的碘污染，多次改进了易于控制空气中碘浓度的进样系统，并通过初步实验找到了操作该系统的最佳条件后，测量了负离子电流与碘浓度的函数关系，从而得到了电流与浓度在50-0.1ppm范围内成正比的校准曲线。这一结果表明，本方法可用于监测核燃料后处理设施尾气中的放射性碘分子。

项目成果

河野博之,重松聖二,乗松美鈴: 日本化学会中国四国支部大会講演要旨集. 188 (1987)

Hiroyuki Kono、Seiji Shigematsu、Misuzu Norimatsu：日本化学会中国-四国分会会议记录 188 (1987)。

Int.J.Mass Spectrom.Ion Processes. (1986)

国际质谱离子过程杂志。

H.Kishi and H.Kawano: Int. J. Mass Spectrom. Ion Processes.

H.Kishi 和 H.Kawano：Int。

岸浩: 日本化学会第54春季年会講演予稿集. (1987)

Hiroshi Kishi：日本化学会第 54 届春季年会论文集（1987 年）。

Theoratgical study of the long-pending problem of how to select the best: "condition for operating a surface-ionization-type negative-ion source to detect gaseous sample molecules" International Journal of Mass Spectrometry and Ion Processes. 69. 97-108 (

如何选择最佳的长期悬而未决的问题的理论研究：“操作表面电离型负离子源检测气态样品分子的条件”国际质谱和离子过程杂志。