Consequences of radioactive releases into the sea resulting from the accident at the Fukushima Dai-ichi nuclear power plant - Evolution of expert investigation according to the data available

Abstract

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in March2011 led to an unprecedented direct input of artificial radioactivity into the marine environment. The Institute for Radioprotection and Nuclear Safety was requested by the French authorities to investigate the radioecological impact of this input, in particular the potential contamination of products of marine origin used for human consumption. This article describes the close link between the responses provided and the availability of the data, as well as their nature and ability to meet the requirements of expert investigation. These responses were needed: (i) to evaluate the inputs of radionuclides into the marine environment, (ii) to understand their dispersion in seawater, and (iii) to estimate their transfer to the biota and sediments. Three phases can be distinguished which characterise these processes during the accident and post-accident periods. The first phase corresponds to an emergency phase during which no measurements were available on samples from the marine environment. It involved the formulation of hypotheses based solely on the expertise of the Institute for Radioprotection and Nuclear Safety. The second phase started when the Japanese authorities provided measurements of the concentrations of radionuclides in seawater. Although these data were not yet adapted to addressing the problems of radioecology, the scenarios could then be refined and the estimates developed in more detail. During the third phase, the accumulation of data over the course of time made it possible to study the phenomena in an appropriate way. The chronology of the events shows that it is essential to have (i) significant measurements of concentration from samples collected in the various matrices of the marine environment, regularly updated and sufficiently well-documented, (ii) samples of seawater collected at the earliest opportunity as close as possible to the damaged site to characterise the source term, and (iii) a numerical tool allowing rapid modelling 424 RADIOPROTECTION -VOL. 47 -N°3 (2012) of the dispersion of radionuclides in seawater, as well as their transfer to sediments and the biota, ultimately for the purpose of estimating the dose to humans.

Fukushima’s Forgotten Radionuclides: A Review of the Understudied Radioactive Emissions

“…37 Further purification is performed by solvent extraction or coprecipitation techniques, as described in ref 37. The extraction chromatography technique using Eichrom's TEVA resin is especially useful to purify 99 Tc and remove 106 Ru (interference in radiometric measurements) or 99 Ru (interference in ICP-MS). 37,95,96 Gamma-emitting 95m Tc is a suitable radiotracer to determine the recovery of the separation.…”

“…In a few samples taken in the period of 21−31 March, approximately 100 Bq/L 99m Tc were determined in a few seawater samples−this is the only report we could find for Fukushima-Tc in seawater. 106 ■ IODINE-129…”

“…For a short discussion of the "orphan" radionuclides 103 Ru and 106 Ru as well as 36 Cl, the reader is referred to the SI. 37,98,106 In summary, the above examples illustrate the variety of scientific challenges, the multitude of target nuclides that call for monitoring and further investigation.…”

“…For a short discussion of the "orphan" radionuclides 103 Ru and 106 Ru as well as 36 Cl, the reader is referred to the SI. 37,98,106 In summary, the above examples illustrate the variety of scientific challenges, the multitude of target nuclides that call for monitoring and further investigation. Unfortunately, some for some radionuclides, important information can no longer be gathered because of the radionuclides' relatively short half-lives, for example, the radioxenon isotopes 131m Xe, 133m Xe, 133 Xe, and 135 Xe, as well as 103 Ru, 35 S or 89 Sr.…”

Comparison between modelling and measurement of marine dispersion, environmental half-time and 137Cs inventories after the Fukushima Daiichi accident

“…The seawater measurements reported here come from a compilation of monitoring data (Laguionie et al 2012) provided on the Internet by TEPCO (TEPCO 2011), Ministry of Education, Culture, Sports, Science and Technology (MEXT) (MEXT 2011), Fukushima Prefecture, Hokkaido University and already published results (Inoue et al 2012;Buesseler et al 2012;Honda et al 2012;Aoyama et al 2012;Caffrey et al 2012). The database includes 948 significant measurements of 137 Cs activity in seawater (above the detection limit, which varies with time) carried until to 20 July 2011 and the results from more than 7000 seawater samples analysed until May 2012.…”