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Emoto, Takehiko; ; Ando, Hideki
PNC TN9410 93-186, 65 Pages, 1993/09
From the viewpoint of radiation protection and radiation shielding evaluation, the needs to know the positions that are irradiated by radiation are increasing, because measuring irradiated positions is useful for detecting local streaming at working areas in nuclear facilities and evaluating beam-loss from accelerators. We have investigated and experimented the characteristics of plastic scintillating fiber(PSF), that has been recently developed one of most popular position sensitive particle detectors in high energy physics, for purpose of that we can apply them to the radiation measurements as a position sensitive radiation detector. First, we referred to the results of the committed research performed in last year and to relative works. And, to aim for improvement of efficiency of gamma-ray and for stretch of the detector, we investigated efficiency and resolution of the detectors giving priorities to (a) variation of length and bundle of PSFs hamess, and (b) variation of the irradiated positions. As the results of referring to the works and the experiments on the detectors, we got the followings, (1)The method using the difference of reaching time between the scintillation photons from both ends of PSF is hopeful as position sensitive radiation detecting, because PSF has good time resolution and the time measurements have been recently developed to be rather easy and accurate methods. (2)Position resolution is 20cm to 30cm for collimated gamma-ray of 
Cs. And, the detectors bundled of ten PSFs have better characteristics of both efficiency and resolution. (3)When the detector is irradiated at near one of the ends, the efficiency and resolution will be 10% to 30% worse than irradiated at middle of it.
; Kanamori, Masashi; Takeishi, Minoru*
PNC TN841 80-70, 101 Pages, 1980/10
no abstracts in English
Katengeza, E.*; Sanada, Yukihisa; Yoshimura, Kazuya; Ochi, Kotaro; Iimoto, Takeshi*
no journal, ,
The rate of temporal change of radiocesium concentration in bottom sediments is governed not only by its physical decay but also by various ecological processes. In this study, the decreasing trend of radiocesium concentration over wide pond areas of surface sediments (up to 10 cm depth), due to ecological processes, was investigated using plastic scintillation fibers (PSF) and was quantified by the ecological half life. PSF measurements were conducted between 2013 and 2019. Their conversion factors ((Bq/kg)/cps) were obtained by comparison between detected radiation counting rate obtained by PSF and the concentration of radiocesium in sediment cores collected from coinciding positions within the same ponds. A forest catchment pond exhibited the longest ecological half life and may indicate catchment derived radiocesium input as was partly evident in the spatial temporal patterns of radiocesium concentration at this pond's inlet.
Katengeza, E.*; Sanada, Yukihisa; Ochi, Kotaro; Iimoto, Takeshi*
no journal, ,
The calibration factor (CF) was determined by comparing the counting rate obtained by plastic scintillation fibers (PSF) with the average radiocesium (RCs) concentration in the top 10 cm of sediment core samples in previous study. The systematic biases and measurement uncertainty of estimated RCs concentration were evaluated by comparing against the RCs concentration in sampled sediment cores averaged over depths, ranging from 5 cm to 30 cm in 5 cm increments. When the calibration depth is 10 and 15 cm, the normalized mean square and relative deviation of PSF-derived RCs concentration against RCs concentration in sampled sediment were comparable. Thus, it may be necessary to revise calibration depth in order to sustainably optimize radiocesium concentration measurements by the PSF technique.
