核電廠放射性廢棄物中Tc-99、I-129核種分析技術之精進

The enhancement of analytical technology for Tc-99、I-129 in the nuclear power plant radwastes

簡立維(Li-Wei Jian)

指導教授 ： 王竹方

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2011年)

https://doi.org/10.6843/NTHU.2011.00281

摘要

為了針對放射性廢料工程障壁的設計，放射性強度的測量是非常重要的。長半衰期元素例如Tc-99(半衰期為21.3萬年)其具有非常液溶於水的特性及I-129(半衰期為1600萬年)其具有非常易揮發的特性，上述兩者對於環境及人體均扮演著非常重要的角色。一般而言再測量放性活度的方法有：測量核種衰變所釋放出來的能量或者是經由美國電力研究所所開發出來的比例因數的方法來進行量測。然而，上述的兩種方法均不適用於長半衰期核種的量測當中。在本研究當中，鹼消化法被選用為針對碘的樣品前處理步驟，而TEVA管柱則被選用為針對鎝的樣品前處理步驟，並將上述的兩種樣品前處理步驟搭配ICP-MS的偵測來克服這些問題。
整體的流程來說，碘及鎝的樣品前處理步驟均擁有良好的精密度及準確度，且ICP-MS的方法偵測極限(碘的為3 ng/L、鎝的為0.02 ng/L)均優於傳統的液態閃爍偵檢器(碘的為700 ng/L、鎝的為10 ng/L)。在本研究當中實際樣品所偵測到的放射性強度值也均小於利用比例因數所得到的值，也證明了本方法可以有效改善利用傳統方法測量所產生的問題。

關鍵字

比例因數

並列摘要

For the design of radwaste disposal repository, the measurement of radioactivity in it is very important. Long half-life nuclides such as Tc-99 (t1/2=2.13x105y) which is very soluble and I-129 (t1/2=1.6x107y) which is easy to volatile play important roles for the environment and human. In general, the radioactivity is obtained from the energy of radiation emitted from the nuclides or from the “Scaling factor” method developed by Electric Power Research Institute (EPRI) of America. However, both of the methods are difficult to measure the radioactivity for long half-life nuclides. In this study, alkaline digestion used as the method of sample pretreatment for iodine and the TEVA extraction chromatographic resin for technetium are combined with ICP-MS to overcome these difficulties. The overall sample pre-treatment steps of both iodine and technetium have good precision and accuracy and the method detection limits of iodine and technetium by ICP-MS are 3 ng/L and 0.02 ng/L that are extremely lower than that by the traditional liquid scintillation counter (10 ng/L for 99Tc and 700 ng/L for 129I). The radioactivity of the real samples obtained by this method are all greatly lower than that obtained by the scaling factor. It proves that this method can improve the disadvantages of traditional methods.

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