{"id":7915,"date":"2025-04-27T13:12:06","date_gmt":"2025-04-27T04:12:06","guid":{"rendered":"https:\/\/www.envraddb.go.jp\/entesttest\/?page_id=7915"},"modified":"2026-06-08T07:11:43","modified_gmt":"2026-06-07T22:11:43","slug":"iodine","status":"publish","type":"page","link":"https:\/\/www.envraddb.go.jp\/en\/special\/tec-info\/iodine\/","title":{"rendered":"Iodine-129\uff08129<\/span>I\uff09"},"content":{"rendered":"
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Overview<\/h2>\r\n <\/div>\r\n
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What is iodine-129?*1<\/span><\/h3>\r\n <\/div>\r\n
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Iodine-129 is a radioactive isotope of iodine with a half-life of about 15.7\r\n million years.
\r\n Iodine-129 emits primarily \u03b2 and \u03b3 rays and decays to Xenon-129.\r\n <\/p>\r\n <\/div>\r\n

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Source of iodine-129*2<\/span><\/h3>\r\n <\/div>\r\n
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Iodine-129 is produced from natural sources, such as radioactivation of\r\n material by cosmic ray reactions, and from human sources, such as nuclear tests, nuclear fuel reprocessing\r\n plants, and accidents at nuclear facilities.\r\n <\/p>\r\n <\/div>\r\n\r\n <\/div>\r\n

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What is the purpose of iodine-129 analysis and measurement?**2<\/span>\r\n <\/h3>\r\n <\/div>\r\n
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\r\n Iodine-129 has a long half-life and is known to not only persist in the environment for extended periods but\r\n also migrate through various environmental samples. Therefore, iodine-129 is considered to be an important\r\n nuclide in environmental impact assessments, and it is important to understand and evaluate its\r\n environmental radioactivity level.
The primary source of iodine-129 in the environment is emissions from nuclear fuel reprocessing facilities and other sources.\r\n\r\n <\/p>\r\n <\/div>\r\n

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\r\n In the \"Routine Monitoring (Supplementary Reference Material for the Guidelines for Nuclear Emergency\r\n Preparedness),\" iodine-129 is excluded from routine monitoring targets due to its relatively small\r\n contribution to the total dose from facility-related sources and the associated measurement challenges.\r\n However, in monitoring the vicinity of reprocessing facilities, it is essential to assess the long-term\r\n accumulation and variability trends of iodine-129, considering the operational status of the facility.\r\n <\/p>\r\n <\/div>\r\n

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\r\n Furthermore, the Comprehensive Monitoring Plan, developed to ensure reliable and systematic environmental\r\n radiation monitoring outside the Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power\r\n Station, emphasizes the importance of assessing long-term variability trends in seawater and marine organism\r\n monitoring.\r\n <\/p>\r\n <\/div>\r\n\r\n <\/div>\r\n\r\n

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How do we analyze and measure iodine-129?<\/h3>\r\n
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Iodine-129 is analyzed and measured in various ways depending on the purpose\r\n of the investigation and research.<\/p>\r\n <\/div>\r\n <\/div>\r\n

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(1) Radiochemical analysis<\/h4>\r\n <\/div>\r\n
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Radiochemical analysis is primarily conducted by local governments and\r\n industries for environmental radiation monitoring around reprocessing facilities.
\r\n The method involves preparing measurement samples through chemical analysis tailored to the sample,\r\n followed by measuring the \u03b2 or \u03b3 radiation of iodine-129. This approach is widely employed due to the\r\n availability of common equipment and instruments.
\r\n In the analytical process, iodine is purified by solvent extraction after pretreatment operations such\r\n as combustion and ion exchange, depending on the sample type. The purified iodine is then converted into\r\n palladium iodide precipitate for measurement.\r\n <\/p>\r\n <\/div>\r\n <\/div>\r\n

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(2) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) \/ ICP-MS\/MS\r\n (Triple Quadrupole ICP-MS)<\/h4>\r\n <\/div>\r\n
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This method is primarily employed in marine monitoring conducted under the\r\n Comprehensive Radiation Monitoring Plan.
\r\n It involves preparing measurement solutions through chemical treatment tailored to the specific sample,\r\n followed by analyzing the target isotopes. Compared with conventional radiochemical analysis, ICP-MS\r\n offers excellent sensitivity and rapid measurement, and despite the relatively high cost of the\r\n instrumentation, its use has become increasingly widespread in recent years.
\r\n Triple quadrupole ICP-MS, also referred to as ICP-MS\/MS, is an advanced instrument that features an\r\n additional quadrupole and a collision\/reaction cell configured in series with a conventional ICP-MS\r\n system. This setup effectively eliminates spectral interferences, enabling even more precise trace-level\r\n analysis.\r\n\r\n <\/p>\r\n <\/div>\r\n

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(3) Accelerator mass spectrometry (AMS)<\/h4>\r\n <\/div>\r\n
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Accelerator Mass Spectrometry (AMS) is primarily employed by research\r\n institutions for analyzing environmental samples within research contexts.\r\n This method involves preparing measurement samples through chemical treatment tailored to the specific\r\n sample, followed by the use of an accelerator to measure the target isotopes. At present, it offers the\r\n highest sensitivity available for the quantification of iodine-129. However, because the measurement\r\n system is extremely large and expensive, it has not achieved widespread general use, and the number of\r\n analytical institutions capable of performing such measurements remains limited.\r\n\r\n <\/p>\r\n <\/div>\r\n <\/div>\r\n\r\n\r\n\r\n <\/div>\r\n <\/div>\r\n\r\n <\/section>\r\n

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Analytical flow: Inductively Coupled Plasma Mass Spectrometry (ICP-MS\/MS (Triple\r\n Quadrupole ICP-MS))<\/h2>\r\n <\/div>\r\n
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Water<\/p>\r\n <\/div>\r\n

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Filtration<\/p>\r\n