RADIOISOTOPES
Online ISSN : 1884-4111
Print ISSN : 0033-8303
ISSN-L : 0033-8303
Characteristics of Sensitivity for In-line Detection Methods of α-Emitters in Solution
Shigekazu USUDASatoshi SAKURAI
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JOURNAL FREE ACCESS

1995 Volume 44 Issue 11 Pages 776-784

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Abstract

In order to directly detect low concentration of α-emitters in solution by in-line detection methods, characteristics of sensitivity for the following three methods are discussed by measuring natural and 20% enriched uranium solutions.
1. Liquid scintillation counting : Detection efficiency (ε) of the method was very high (42%) and background (BC) was lowered by α-β (γ) pulse shape discrimination. The detection limit (DL) was, therefore, good (0.05 Bq) . The method is effective for monitoring of low level radioactive solution and for identification of the α-emitters. However, the accuracy was not always good and some waste solvents were produced.
2. Liquid contact counting : Since the detector used for the method must be protected with thin films and the layer of solution in the flow-cell is extremely thick compared with the range of α-particles, its sensitivity was bad (ε: 0.4%, DL : 1.5 Bq/ml) in spite of lowered BC in the α-region by the discrimination. The sensitivities will be improved by widening the contacting area and thinning the solution layer of the flow-cell. This method is suitable for monitoring of every kind of solution with low and middle level radioactivity.
3. ICP-MS : This method is applicable to in-line detection of elemental and isotopic constituents of the α-emitters and the DL was 2pgU/ml. If the half-life of the α-emitting nuclide is longer than about 103y, the ICP-MS will be of greater advantage than the α-counting methods and capable of direct detecting the α-emitters in water at the boundary of radiation monitoring area.
Each method has very wide dynamic range and is to be expected to monitor low concentration of α-emitters in solution as an in-line sensitive detection technique.

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© Japan Radioisotope Association
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