Source term estimation for the Fukushima Daiichi Nuclear Power Station accident by combined analysis of environmental monitoring and plant data through atmospheric dispersion simulation

Nagai, Haruyasu; Terada, Hiroaki; Chino, Masamichi; Katata, Genki; Mikami, Satoshi; Saito, Kimiaki

Proceedings of 16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-16) (USB Flash Drive), p.4044 - 4052, 2015/08

JAEA has estimated the atmospheric releases of radionuclide during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric transport and deposition model (ATDM). To improve our source term, we are trying to develop more sophisticated estimation method and use new information from severe accident analysis and observation data. As the first step of new trial, we used Cs/Cs ratios of inventories in FNPS1 reactors Unit 1 to 3 and those in surface deposition. By considering temporal change in Cs/Cs ratio of released plume and ATDM simulations, spatial distribution of Cs/Cs ratio in surface deposition was explained. This result can be used to specify from which reactor the dominant release occurred for each time period, and consequently provide useful information to severe accident analysis for the FNPS1 case.

Development of the emergency system for radioactive source term estimation

Kitabata, Hideyuki*; Chino, Masamichi

JAERI-Data/Code 99-012, 47 Pages, 1999/03

JAERI-Data-Code-99-012.pdf:2.82MB

no abstracts in English

Source term estimation by reverse analysis

Nagai, Haruyasu

no journal, , 

JAEA has estimated the atmospheric releases of radionuclide during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric transport and deposition model WSPEEDI. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has used our source term for estimating levels of radioactive material in the environment and doses to the public. To improve our source term, we recently made detailed source term estimation by using additional monitoring data near the FNPS1 and WSPEEDI including new deposition scheme. The simulation of modified WSPEEDI and the new source term successfully reproduced the local and regional deposition pattern of I and Cs.

Current status of atmospheric dispersion simulation for a nuclear accident

Nagai, Haruyasu; Terada, Hiroaki; Tanimori, Toru*

no journal, , 

no abstracts in English