[1D09-14] Environmental Radioacitivty and Monitoring 2

[1D13] Investigation on distribution of radioactive substances in Fukushima

(9)Analysis of temporal changes in ambient dose equivalent rates in forests over 6 years

*Alex Malins¹, Naohiro Imamura², Tadafumi Niizato¹, Minsik Kim¹, Kazuyuki Sakuma¹, Yoshiki Shinomiya², Satoru Miura², Masahiko Machida¹ (1. JAEA, 2. FFPRI)

Keywords:forest, environment, ambient dose equivalent, radiocesium, 134Cs, 137Cs, FDNPP accident, PHITS, Monte Carlo, Simulation

We analyzed changes in ambient dose equivalent rates (H*(10)) between 2011 and 2017 in forests in Fukushima Prefecture. PHITS was used to calculate the effect of re-distribution of ¹³⁴Cs and ¹³⁷Cs over time within forests on H*(10). Transfer of radiocesium from the crowns of evergreen coniferous trees to the forest floor appeared to cause slower declines in H*(10) at 1 m height initially after March 2011 than expected by the rate of radiocesium decay.