WEKO3
アイテム
Transfer factor of radium-226 from soil to rice
https://repo.qst.go.jp/records/68485
https://repo.qst.go.jp/records/684855a41cff5-473b-4daf-9fd7-a6faf3efc264
| アイテムタイプ | 会議発表用資料 / Presentation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2006-06-19 | |||||
| タイトル | ||||||
| タイトル | Transfer factor of radium-226 from soil to rice | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_c94f | |||||
| 資源タイプ | conference output | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
Uchida, Shigeo
× Uchida, Shigeo× Tagami, Keiko× Tabei, Ken× et.al× 内田 滋夫× 田上 恵子× 田部井 健 |
|||||
| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Transfer factor of radium-226 from soil to rice \nS. Uchida1, K. Tagami1, K. Tabei2 and T. Fujikawa3 1 Office of Biospheric Assessment for Waste Disposal, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba-shi, 263-8555, Japan 2 Tokyo Nuclear Services Co., Ltd., SA-Building 2F, Ueno 7-2-7, Taitou-ku, Tokyo, 110-0005 Japan 3 Kansai Environmental Engineering Center Co., Ltd., Azuchi-machi 1-3-5, Chu-o-ku, Osaka, 541-0052, Japan \nAbstract Radium-226 (Ra-226), an alpha emitter with a half-life of about 1600 y, is one of the important radionuclides for the assessment of radioactive waste disposal, because it is found in the uranium-238 decay series. Therefore it requires long-term management and understanding of Ra-226 behavior in the environment is of interest. Measurement of Ra-226 concentration in compartments of the environment gives us useful information for this purpose. In the environment, radium occurs naturally and distributed widely in environmental materials, such as rock, soil, water and plants, however, usually Ra-226 concentration is very low. It is difficult to measure Ra-226 without chemical separation and concentration from sample matrices, especially for plant samples. Thus, soil-to plant transfer factor (TF) data are limited for mathematical models for a precise long-term radiological assessment. In this study, we determine the concentrations of Ra-226 in rice grains and associated paddy soils using radiation counting methods. We focused on rice and wheat, because the consumption of cereals is very high in Japan and other Asian countries. The rice samples and the paddy soils were collected from 11 locations throughout Japan. For soil samples, they were air-dried and sieved with a 2-mm sieve. About 60-g of each pretreated soil sample was charged and sealed into a plastic vessel. The sample was kept in a room temperature for more than 30 days to reach an equilibrium condition with its progeny nuclides. Then, the concentration of Pb-214 was determined by a Ge detector system. For the rice samples, they were incinerated at 450?C for 24 h after they husked. Then, a chemical separation was carried out using about 15 g of the incinerated sample. It was recommended to use about 5 g of incinerated rice in a standard method, however, to obtain lower level of detection limit (D.L.), the sample amount was increased by three times in the present study. After the chemical separation, Ra-226 concentration was determined by a liquid scintillation counter system. The chemical yield of Ra was obtained directly but barium (Ba) was used as a yield tracer in the samples because they have similar chemical behaviors. To check the accuracy of the method, we used IAEA-315 (marine sediment) and IAEA-368 (Pacific ocean sediment); no standard reference material is available for plant samples. The recoveries of Ba for Ra were more than 97% for all the samples. Detection limit was lowered since a 15-g of sample was applied; that is, the D.L. was about 0.7 Bq/kg-dry, while it was about 2 Bq/kg when a 5-g of soil sample, a typical weight for the standard method, was used. The concentrations of Ra-226 in paddy soil samples ranged from 20 to 65 Bq/kg-dry soil, and those in the brown rice samples ranged from 8 to 65 mBq/kg-dry except for two samples (<D.L.). Using the data, TFs were calculated and the average TF of Ra-226 from the paddy soil to the rice (brown rice) was 6.8E-04. The value was close to TFs for maize reported in technical report series No. 364, IAEA. In the presentation, we will report the details of the chemical separation conditions and radiation measurement conditions as well as Ra-226 values in soil and rice samples determined by the developed method. |
|||||
| 会議概要（会議名, 開催地, 会期, 主催者等） | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Waste Management 2005 | |||||
| 発表年月日 | ||||||
| 日付 | 2005-03-03 | |||||
| 日付タイプ | Issued | |||||
