1987 Fiscal Year Final Research Report Summary
Development of negative-ion mass spectrometry for monitoring trace amounts of radioactive iodine molecules included in off-gasses of a nuclear fuel reprocessing plant
| Project/Area Number |
60880026
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| Research Category |
Grant-in-Aid for Developmental Scientific Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Nuclear engineering
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| Research Institution | Ehime University |
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Principal Investigator |
KAWANO Hiroyuki Faculty of Science, Ehime University, Professor, 理学部, 教授 (50006144)
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| Co-Investigator(Kenkyū-buntansha) |
KISHI Hiroshi Oyama Technical College, Assist.Professor, 工業化学科, 助教授 (60042529)
麓 弘道 (財)工業開発研究所, 主任研究員
TSUCHIYA Masahiko Faculty of Engineering, Univ. of Tokyo, Assist.Professor, 工学部, 助教授 (40010756)
FUJII Toshihiro Natl. Inst. Environ. Studies, Researcher, 計測技術部, 主任研究員 (60109907)
MATSUOKA Shingo Faculty of Engineering, University of Tokyo. Researcher, 工学部, 助手 (30092331)
FUMOTO Hiromichi Industrial Research Institute, Japan, Researcher
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| Project Period (FY) |
1985 – 1987
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| Keywords | Atmospheric radioactive iodine / Thermal negative lonization mass spectrometry / Lanthanum hexaboride / Work function / 仕事関数 / 付着率 |
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| Research Abstract |
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.
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