Inverse modeling of the 137Cs source term of the Fukushima Dai-ichi Nuclear Power Plant accident constrained by a deposition map monitored by aircraft

Keiya Yumimoto, Yu Morino, Toshimasa Ohara, Yasuji Oura, Mitsuru Ebihara, Haruo Tsuruta, Teruyuki Nakajima

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The amount of 137Cs released by the Fukushima Dai-ichi Nuclear Power Plant accident of 11 March 2011 was inversely estimated by integrating an atmospheric dispersion model, an a priori source term, and map of deposition recorded by aircraft. An a posteriori source term refined finer (hourly) variations comparing with the a priori term, and estimated 137Cs released 11 March to 2 April to be 8.12 PBq. Although time series of the a posteriori source term was generally similar to those of the a priori source term, notable modifications were found in the periods when the a posteriori source term was well-constrained by the observations. Spatial pattern of 137Cs deposition with the a posteriori source term showed better agreement with the 137Cs deposition monitored by aircraft. The a posteriori source term increased 137Cs deposition in the Naka-dori region (the central part of Fukushima Prefecture) by 32.9%, and considerably improved the underestimated a priori 137Cs deposition. Observed values of deposition measured at 16 stations and surface atmospheric concentrations collected on a filter tape of suspended particulate matter were used for validation of the a posteriori results. A great improvement was found in surface atmospheric concentration on 15 March; the a posteriori source term reduced root mean square error, normalized mean error, and normalized mean bias by 13.4, 22.3, and 92.0% for the hourly values, respectively. However, limited improvements were observed in some periods and areas due to the difficulty in simulating accurate wind fields and the lack of the observational constraints.

Original languageEnglish
Pages (from-to)1-12
Number of pages12
JournalJournal of Environmental Radioactivity
Volume164
DOIs
Publication statusPublished - 2016 Nov 1
Externally publishedYes

Fingerprint

Nuclear Power Plants
Aircraft
nuclear power plant
Nuclear power plants
Accidents
accident
aircraft
Particulate Matter
modeling
suspended particulate matter
wind field
Mean square error
Tapes
Time series
time series
filter

Keywords

  • Atmospheric dispersion
  • Fukushima Daiichi Nuclear Power Plant accident
  • Inverse modeling
  • Source term
  • Surface deposition

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis

Cite this

Inverse modeling of the 137Cs source term of the Fukushima Dai-ichi Nuclear Power Plant accident constrained by a deposition map monitored by aircraft. / Yumimoto, Keiya; Morino, Yu; Ohara, Toshimasa; Oura, Yasuji; Ebihara, Mitsuru; Tsuruta, Haruo; Nakajima, Teruyuki.

In: Journal of Environmental Radioactivity, Vol. 164, 01.11.2016, p. 1-12.

Research output: Contribution to journalArticle

Yumimoto, Keiya ; Morino, Yu ; Ohara, Toshimasa ; Oura, Yasuji ; Ebihara, Mitsuru ; Tsuruta, Haruo ; Nakajima, Teruyuki. / Inverse modeling of the 137Cs source term of the Fukushima Dai-ichi Nuclear Power Plant accident constrained by a deposition map monitored by aircraft. In: Journal of Environmental Radioactivity. 2016 ; Vol. 164. pp. 1-12.
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