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radiocesium concentration measurements in bottom sediments of agricultural pondsKatengeza, E. W.*; Sanada, Yukihisa; Ochi, Kotaro; Iimoto, Takeshi*
Cogent Engineering (Internet), 11(1), p.2340203_1 - 2340203_9, 2024/04
The uncertainty of radioactivity measurements can be influenced by the vertical distribution of the target radionuclide in the sediments. This study used 2015-2019 field measurement data from 47 ponds to evaluate the depth dependence of calibration factors of plastic scintillation fiber (PSF) and its influence on measurement uncertainty. By changing the depth of focus from 10 cm to 15-20 cm when calculating the conversion factor, the normalized mean square error of the radiocesium concentration estimated by the PSF with respect to the radiocesium concentration in core sediments sampled at the same location was found to be smaller.
Sanada, Yukihisa; Urabe, Yoshimi; Orita, Tadashi; Takamura, Yoshihide; Torii, Tatsuo
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05
There are approximately 3,700 irrigation ponds in the Fukushima prefecture. Contamination by radiocesium at the bottom of these ponds has been a concern since the accident at the TEPCO's Fukushima Daiichi Nuclear Power Station (FDNPS). Among them, there are some reservoirs which contain radioactive materials in the bottom sediment. Three years have passed since the accident of the Fukushima Daiichi Nuclear Power Station. In relation to the restoration of agriculture in the disaster-stricken area, there are concerns over the migration of radioactive cesium in the environment. We developed 20 meter-length a plastic scintillation fiber (PSF) for measurement in water. We have conducted tests at dozens of irrigation ponds in Fukushima pref. using PSF to confirm the performance of the devices and to standardize measurement techniques and analytical procedures.
Sanada, Yukihisa; Torii, Tatsuo
Nihon Genshiryoku Gakkai-Shi ATOMO
, 57(2), p.94 - 98, 2015/02
In Fukushima, quick and direct technique to measure a wide area of bottom of water is needed. We developed the plastic scintillation fiber (PSF) since accident at 1F. Therefore, the PSF was applied to measurement of irrigation pond. Here, the measuring method and the monitoring result are reported.
Takamura, Yoshihide; Urabe, Yoshimi; Yamada, Tsutomu; Sanada, Yukihisa
no journal, ,
no abstracts in English
Katengeza, E.*; Ochi, Kotaro; Sanada, Yukihisa; Iimoto, Takeshi*
no journal, ,
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.
Katengeza, E.*; Sanada, Yukihisa; Ochi, Kotaro; Iimoto, Takeshi*
no journal, ,
This study aimed at evaluating the vertical distribution of radiocesium in bottom sediment core samples from 45 ponds sampled in 2015-2019 and clarifying the impact of the vertical distribution on the efficiency of decontamination by stripping the top 10 cm of bottom sediments. The relaxation mass depths and depth of sediment containing 90% of the inventory were larger than on land indicating faster downward migration of radiocesium in ponds. This may have been caused by accumulation from the ponds' catchments where radiocesium enrichment occurred. This indicates that local behavior of radiocesium in reservoirs are more important to decontamination outcomes.
Katengeza, E.*; Sanada, Yukihisa; Ochi, Kotaro; Iimoto, Takeshi*
no journal, ,
Since 2013, plastic scintillation fiber (PSF) is calibrated from counting rate to radiocesium concentration by comparing with the average concentration of the top 10 cm of sediment core sample. The purpose of this study is to clarify influence of radiocesium depth distribution on PSF calibration factor and measurement uncertainty. The radiocesium concentration was estimated by varying the calibration depth of PSF from 5 to 30 cm at 5 cm intervals. The estimated radiocesium concentration was compared with the radiocesium concentration in the bottom sediment collected at the PSF measurement point. The normalized mean squared error values were the smallest at the calibration depth of 15-20 cm, suggesting that the measurement can be optimized by changing the calibration depth.
