Clarification of measurement uncertainty of a plastic scintillation fiber (PSF) for in-situ monitoring of the distribution of radiocesium in bottom sediments of agricultural ponds

Katengeza, E.*; Sanada, Yukihisa   ; Ochi, Kotaro   ; Iimoto, Takeshi*

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.