Medical Radiology and Radiation Safety. 2013. Vol. 58. No. 6. P. 5-13

RADIATION SAFETY

R.M. Alexakhin¹, V.G. Sychev²

Radioecological Aspects of Agricultural Remediation Following the Accident at the Fukushima Daichi NPP

1. All-Russian Institute of Agricultural Radiology and Agroecology of RAAS, Obninsk, Russia. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. ; 2. D.N. Pryanishnikov All-Russian Research Institute of Agriculture and Soil Science, Moscow, Russia

Abstract

The accident at the Fukushima Daichi NPP (FDNPP) in Japan on 11 March 2011 has resulted in the extensive areas’ contamination, considerable part of which is occupied by agricultural and forested lands. The territories to be remediated cover the areas of 500 km² (exposure doses above 20 mSv/year) and 1300 km² (5–20 mSv/year). In the range of countermeasures of great importance are protective measures in agriculture which is connected with the essential role of contaminated agricultural products consumption, as a source of human irradiation, and social-psychological significance of the products’ decontamination where the concentrations of radioactive substances exceed the permitted levels.

The major exposure pathways for the population on the affected territory are: external irradiation, inhalation and internal irradiation (radionuclide uptake with food and drinking water). The main  doseforming radionuclides in the accidental area are: ¹³¹I and ¹³⁷Cs. The role of the dietary source is defined by the diet composition and time after radionuclide fallout. The importance of this source of exposure, in comparison with external irradiation, is an increasing with the distance from the FDNPP. In case of the thyroid gland irradiation the dietary pathway of ¹³¹I transfer is dominating.

The main option when mitigating consequences of the FDNPP accident was decontamination (cleanup) of soils (soil-plant cover) which is achieved by removal of the top most affected horizon (up to 4–5 cm). Since the territory to be remediated is large, this rehabilitation measure produces great amounts of radioactive wastes. Their estimated amounts may reach volumes of solid domestic waste produced annually in Japan. The above main principle of mitigating consequences of the accident in Japan differs significantly from the approaches to solving similar tasks after the Kyshtym and Chernobyl disasters where the main options were retargeting of the agricultural branches on farmland, high chemicalization, use of special sorbents in animal feeding and area allocation for farming branches based on ¹³⁷Cs contamination density, as well as temporary exclusion of the most affected lands from the use.

Various protective agricultural measures have been studied (soil washing, application of potassium fertilizers, radical amelioration of meadow-pasture lands, etc.). Some of these measures have been found to be ineffective (phytoremediation, removal of forest litter, plant washing).

A comprehensive set of measures in agriculture in the accidental region has been recognized as the key way for the affected area remediation.

Key words: accident at the Fukushima-1 NPP, agricultural production, area decontamination, countermeasures, population, exposure