Environmental radioactivity monitoring via newly developed optical fiber based thermoluminesence dosimeter / Siti Rozaila Zahariman

Siti Rozaila , Zahariman (2016) Environmental radioactivity monitoring via newly developed optical fiber based thermoluminesence dosimeter / Siti Rozaila Zahariman. Masters thesis, University of Malaya.

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Abstract

Thermoluminesence dosimeters (TLD) are increasingly being used in a variety of fields, including in support of medical irradiations, environmental radioactivity monitoring, food sterilization, the radiation processing industry and in other such involvements. The conventional phosphor based TLDs suffer in performance, due in part to their manifestly hygroscopic nature and poor resolution. In their use as TLDs, the optical fibers do not suffer from these drawbacks and in addition are seen to offer a number of other potential advantages, including sensitivity, stability and reliability. These factors help to introduce the fibers as a potential alternative to the phosphor-based TLDs. Recent studies have highlighted the use of optical fibers in radiation dosimetry applications for a wide range of electron and photon beam irradiations. Nevertheless, they have yet to be investigated at the very much lower environmental doses, with practically no very low doses studies. Realizing the importance of low dose environmental radioactivity monitoring, highly sensitive optical fiber based TLD materials in the form of collapsed Photonic Crystal Fiber (PCFc) has been developed here. In this study, the newly developed collapsed PCFs (with different dopant concentrations of Ge and B) together with phosphor based TLDs (TLD-200 and TLD-100) have been buried in eight selected areas within Gebeng, Pahang (off-site of the Lynas Advanced Materials Plant) to obtain exposure records for two, four, six, and eight months. The TLD readout doses (via a TLD reader) are compared with the bulk radioactivity in the associated soils obtained via HPGe gamma-ray spectrometry. Parameters concerning thermoluminesence (TL) for the samples induced by x-ray and gamma-ray irradiation have been investigated, including the linearity of dose response, energy response, fading, effective atomic number and glow curve. Present study indicates that the developed PCFs could be advantageously utilized in very low dose radiation dosimetry applications.

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