Predictability of the dispersion of Fukushima-derived radionuclides and their homogenization in the atmosphere

Abstract

Long-range simulation of the dispersion of air pollutants in the atmosphere is one of the most challenging tasks in geosciences. Application of precise and fast numerical models in risk management and decision support can save human lives and can diminish consequences of an accidental release. Disaster at Fukushima Daiichi nuclear power plant has been the most serious event in the nuclear technology and industry in the recent years. We present and discuss the results of the numerical simulations on dispersion of Fukushima-derived particulate 131I and 137Cs using a global scale Lagrangian particle model. We compare concentrations and arrival times, using two emission scenarios, with the measured data obtained from 182 monitoring stations located all over the Northern Hemisphere. We also investigate the homogenization of isotopes in the atmosphere. Peak concentrations were predicted with typical accuracy of one order of magnitude showing a general underestimation in the case of 131I but not for 137Cs. Tropical and Arctic plumes, as well as the early detections in American and European midlatitudes were generally well predicted, however, the later regional-scale mixing could not be captured by the model. Our investigation highlights the importance of the parameterization of free atmospheric turbulence.

Long-distance transport of radioactive plume by nocturnal local winds

“…Therefore, we should continue improving existing numerical models to more accurately represent the local circulation caused by diurnal cycle processes. This finding could also useful to improve the local depositions simulated by a global circulation model31.…”

Model depiction of the atmospheric flows of radioactive cesium emitted from the Fukushima Daiichi Nuclear Power Station accident

“…The accident was caused by the Great East Japan Earthquake, which struck at 14:46 Japan Standard Time (JST; Coordinated Universal Time, UTC+ 9 h) on 11 March 2011. Takemura et al (2011) show that the negative anomaly of a 500-hPa height over the Okhotsk Sea area along 145°E made the westerly jet stronger than the climatological mean during mid-March; consequently, 70 to 80% of the radioactive material from the FDNPS was driven to the Pacific Ocean and the rest of the globe (Takemura et al 2011;Stohl et al 2012;Mészáros et al 2016). The remaining material spread over and deposited onto the land area of Japan, producing characteristic hot spot patterns (Yasunari et al 2011;JAEA 2012;SCJ 2014).…”

Numerical simulations of atmospheric dispersion of iodine-131 by different models

“…The study uses two Lagrangian dispersion models, the HYSPLIT model, one of the most widely used software for atmospheric dispersion simulations [ 9 , 10 ]; and RAPTOR, a Lagrangian model developed at Eötvös Loránd University [ 6 , 11 ]. Lagrangian models calculate atmospheric trajectories of particles originating from the source.…”

“…The evaluation of dispersion models investigates two important aspects: whether and when the predicted plume reached the detection site (arrival time), and what maximum concentration it reached [ 6 – 8 ]. Arrival times and affected areas are usually well predictable with dispersion models, while peak values of concentrations show larger uncertainty.…”