Reviving MILORD Long-Range Model for Simulating the Dispersion of the Release during Fukushima Nuclear Power Plant Accident

Abstract

This work focuses on long range dispersion using the numerical model MILORD, a Lagrangian particle model capable of simulating transport, dispersion, removal and deposition of tracers. The chosen case study concerns the release of Caesium isotope ¹³⁷Cs from Fukushima Daichi nuclear plant caused by the earthquake and the subsequent tsunami in March 2011. ¹³⁷Cs deposition in the affected area is reproduced from 11 March until the end of that month. In order to evaluate and improve the model, simulations results are compared to station measurements and a sensitivity analysis is performed. A comparison with results of other models is briefly discussed based on a statistical analysis.

Question and Answer

Questioner: Christian Hogrefe

Question: Do you have plans to make further modifications to MILORD and then test it again using observations and other models?

Answer: Several developments and improvements are planned for a number of physical processes, to be then tested on the available datasets already used. For instance, implementing a modulation from the local to the long-range simulation scales in the Langevin equations, to treat more correctly the dispersion of the tracer in proximity of the source; improving the description of the plume rise, not only modulating the emission in space and time but using formulations and parameterizations from literature; introducing more physical parameterizations for the diffusion coefficients K and the PBL height; developing an interface with a mesoscale meteorological model, in order to provide more refined simulations; testing the backward trajectories receptor-source module, not yet applied.