Reprint of "Vertical migration of radio-caesium derived from the Fukushima Dai-ichi Nuclear Power Plant accident in undisturbed soils of grassland and forest"

The vertical distribution of radio-caesium (137Cs and 134Cs) in undisturbed soil profiles of grassland and forest soils, derived from the Fukushima-Daiichi Nuclear Power Plant (FDNPP) accident that occurred on 11 March 2011, was studied. Surface soil and depth profile soil samples were collected from six locations within the 20 km zone of FDNPP, during November 2012 and June 2013. The activity ratio for 137Cs and 134Cs was found to be almost constant about 1 within the soil profiles as well as in the surface soil, indicative of FDNPP accident origin. From soil depth profile distribution of Cs activity, it is observed that Cs is strongly bound to soil materials, which slows Cs migration. N90% of the activity was found to be retainedwithin the upper 5 cmlayer. Retardation of Cs movement has been quantified by measuring sorption of Cs in soil in terms of distribution coefficient (Kd) using the laboratory batch method. Faster migration has been observed in case of forest land soil compared to grassland soil. The empirical migration velocity of Cs radio isotope was estimated fromthe depth profile Cs concentrationand found to vary from 1.1 to 1.7 and 0.85 to 3.5 cm y−1 in grassland and forest soil, respectively. The residential half life for Cs isotopes was found to be 1.03–7.75 y and 1.18–4.67 y for grassland and forest land respectively using a compartmental model. In addition to the empirical analysis of the profiles, analytical modelswere fitted to the data which may help elucidate the physical nature of the transport of trace elements

Uranium Isotope ratios and Sr-90 in Fukushima radiocaesium contaminated soil samples

On 11th March 2011, the Fukushima Daiichi Nuclear Power Station (FDNPS) accident released a massive amount of highly volatile fission products such as 127mTe, 132Te, 131I, 133Xe, 134Cs, 136Cs, and 137Cs caused serious contamination in the atmosphere (aerosol), water, and soils. However, radionuclides such as 90Sr, U and Pu also have a serious concern, because they spread as a result of partial melt-down of the nuclear fuel core including the MOX fuel (mixed U and Pu oxide fuel) in the FDNPS. The chemical toxicity of U is likely to be much more important for human health compared to the risk of cancer from ionizing radiation. The Sr element has the potential to incorporate into the bone structure because its bio-chemically similarity to calcium, thus the 90Sr isotope can cause long-term radiation dose. The principal modes of U and 90Sr intake are from food and water for occupationally unexposed persons. The retention or mobility of U and Sr in soil is highly dependent on soil characteristics in the particular area, due to its large range of distribution coefficient values. The 235U/238U isotope ratio of the soil samples can give fingerprints about the spent fuel used in FDNPS and characterize the fuel melt down. However, due to the relative difficulty of measuring actinide and pure beta particle emitter radionuclides, there is a little data available on U and 90Sr isotopes in and around the Fukushima area. Therefore, studies on U isotope ratio and 90Sr contamination of the contaminated soil samples are important. In the present study, highly radiocaesium contaminated (over 200 Bq g-1) soil samples are used to check the 234U/238U and 235U/238U isotope ratios and 90Sr activity concentration. Further results will be present and discuss in the presentation.VII. Terrestrial Radioisotopes in Environment International Conference on Environmental Protection, 10-13 AUGUST, 2020 (TREICEP 2020

Traces of Pu isotopes originated from burnt-up fuel in Fukushima exclusion zone

The accident in Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released high activity of fission and neutron activation products in the environment. Total amount of released Pu is still unknown. Estimations so far indicates that dispersion from FDNPP is about 0.01 – 0.1 % of total Pu isotopes released from Chernobyl NPP accident. This implies activity of distributed Pu (for FDNPP) at the level GBq. It is assumed that more amount might be deposited close to NPP in early April 2011. However, due to sequence of hydrogen explosion (Unit 3 contained MOX fuel rods) that caused emission of radioactive elements to the atmosphere and depending on meteorological conditions, a highly radioactive plume was moved on the north - western direction of FDNPP. As a consequence of coprecipitation on 15 March 2011, a large area was affected by wet deposition. The highly contaminated area, within 30 km radius of FDNPP was defined as an exclusion zone. This work focused on Pu isotopes as traces of non-volatile elements of burnt-up fuel which were dispersed and could be deposited on that area. Previous papers reported no significant increase of 239+240Pu activity and rather rarely provided information on 238Pu activity concentration in samples from exclusion zone. In the present studies, hot spots (places with high dose rate above 2 μSv h-1) in Namie district were selected. Samples of upper layer soil and plants were collected as well as mud from small “artificial collectors” of water like e.g. small dips below downspout of rain gutter, trench that was a part of road drainage system and dips in the road, etc. The activity level of caesium isotopes (134Cs, 137Cs) in collected samples reached value 5 MBq kg-1 (signature of high and relatively fresh contamination) while 239+240Pu and 238Pu reached 0.3 Bq kg-1 and 0.5 Bq kg-1, respectively. These values were significantly higher than average activity concentration of Pu in Japanese soil estimated as a 0.15 Bq kg-1. The activity ratio, 238Pu and 239+240Pu used as a sources marker, was determined as a 0.5 for Chernobyl accident. Our study reveals higher level of Pu activity ratio in some samples in exclusion zone. That indicates very well the nuclear burnt-up fuel non-volatile elements impact on sampling area. More results in details and their interpretation will be presented at the conference.Plutonium Futures-The Science 201

NATURALLY OCCURRING RADIONUCLIDES AND SELECTED RARE EARTH ELEMENTS IN AIR PARTICULATES OF AN INDIAN HIGH RADIATION BACKGROUND AREA

Naturally occurring radionuclides of terrestrial origin are present in the earth’s crust. In most places on the earth, the natural radioactivity varies only within narrow limits, but in some places there are wide deviations from normal levels because of abnormally high levels of radioactive minerals. The presence of thorium and uranium and their decay products in minerals such as monazites, ilmenite, rutile, silimanite and zircon result in enhanced natural background radiation fields in the deposit areas are widely known as high background radiation area (HBRA). Monazite is one of the principal sources of rare earth elements (REEs) and present in the continental crust. Thus it is necessary to facilitate data on HBRAs to predict radiation patterns in the environment toincrease awareness. Radiological investigations have been carried out in the eastern coastal area of Odisha state, India to measure the extra terrestrial gamma dose rate, natural radionuclide (226Ra, 228Ac and 40K) concentration in selected surface soil samples. Based on thoron and its progeny measurements in the houses, air particulates were collected using cascade impactor. REEs, U and Th were measured from air particulates using an inductively coupled plasma mass spectrometry (ICP-MS) for a better understanding to trace the origin of sources.9th International Conference on High Level Environmental Radiation Areas-For Understanding Chronic Low-Dose-Rate Radiation Exposure Health Effects and Social Impacts (ICHLERA 2018

Sr-90 analysis in Fukushima water samples

The main contaminants released from the Fukushima Daiichi Nuclear Power Station accident is the volatile radioisotopes of caesium (137Cs ~15 PBq, 134Cs ~15 PBq) with the non-volatile 90Sr (~0.14 PBq). The 90Sr (T1/2 = 28.8 y) is a pure beta particle emitter artificial radionuclide, produced by the fission of U and Pu isotopes. Low level (some Bq kg-1 or mBq kg-1) 90Sr contamination exists in different environmental matrices as a result of nuclear weapon tests and nuclear accidents. For the public, radiation dose resulted from external beta particles exposure is not relevant because the low penetration efficiency of beta particles and limited radionuclide deposition on human skin. However, radiation dose due to beta emitter radionuclide incorporation via ingestion and inhalation into human body must be considered in case of a nuclear accident. Basically, Sr element has no biological role in the human body, however it is an alkaline earth metal with similar bio-chemical properties of calcium thus can attach into the bone structure causing long-term radiation dose. From the view point of public health and natural radiation protection, 90Sr monitoring in various environmental, samples is essential.In this work 90Sr contamination was determined in well and ground water samples collected from the Fukushima exclusion zone using a multi-collector thermal ionization mass spectrometry instrument equipped with wide aperture retardation potential (WARP) energy filter and Daly ion-counter. 90Sr could not detected in the water samples since the concentration of the 90Sr was below 30 mBq kg-1 (minimum detectable activity concentration). Considering the radiation protection of the population, the radiation dose from 90Sr ingestion is negligible.VII. Terrestrial Radioisotopes in Environment International Conference on Environmental Protection, 10-13 AUGUST, 2020 (TREICEP 2020

Fate of Cs, Sr and U in soils affected by Fukushima Daiichi Nuclear Power Station Accident

On March 11, 2011 a massive earthquake and ensuing tsunami severely damaged the Fukushima–Daiichi Nuclear Power Station (FDNPS) resulting in hydrogen explosions at nuclear reactors. Although it is believed that nuclear material such as plutonium and uranium isotopes must have remained largely inside reactor, the chances of their release in environment should be considered. Consequently, the study of fate of radionuclides that could be present due to FDNPP accident is of great importance from the viewpoint of radioecology.In order to understand migration behavior of Cs, Sr and U, determination of sorption-desorption characteristics in contaminated soils from exclusion zone in Okuma town has been carried out in present work. Kd (distribution coefficient) values were established using batch method with stable isotopes as tracers. To estimate the source of contamination in soils, isotope ratios of uranium were measured using TIMS. Analytical chemical separation of U from digested soils was carried out with AER (AG 1 x 8)-UTEVA resins. Characterization of different soil parameters like particle size distribution, pH, organic content, cation exchange capacity (CEC), CaCO3, elemental and oxide composition of soil has been determined.Sorption coefficient, Kd(S) of Cs and Sr was found to be in the range of 65 to 2100 and 15 to 130 L/kg respectively. Kd(S) - U values varied from 30-36000 L/kg i.e. three orders of magnitude difference. High values of Kd(S) reflect more sorption capacity of soil for U and Cs than Sr. Values of desorption coefficient, Kd(D) for Cs and U were higher than values in the sorption process. This shows irreversibility of Cs and U sorption in soil as well as good retention capacity for actinides like U. The 235U/238U ratio did not show any enrichment of 235U in Fukushima soils. The 236U/238U isotope ratio value of the order of 10-7 in Fukushima soil showed mixing effect of global fallout and FDNPS accident. Details of the work will be presented in the conference.VII. Terrestrial Radioisotopes in Environment International Conference on Environmental Protection 10-13 AUGUST, 2020 (TREICEP 2020

SORPTION CHARACTERISTICS OF CAESIUM, STRONTIUM AND URANIUM IN FUKUSHIMA CONTAMINATED SOIL SAMPLES

In March 2011, the Fukushima Daiichi Nuclear Power Plant accident led to largest release of anthropogenic radionuclides in the environment [1]. It consisted of several radionuclides viz., 131I, 137Cs, 134Cs, 132Te, 132I, 136Cs, etc., as well as radioactive noble gases (133Xe and 135Xe). A large area was contaminated mainly due to deposition of radio Cs isotopes. Environmental monitoring with respect to different radionuclides is important to understand the cause of accident [2]. Most of the nuclear fission radionuclides are carcinogenic in nature whereas some are hazardous to biotic system. From the viewpoint of radiological safety in a living environment, radionuclides e.g. 137Cs, 90Sr with long half lives (t1/2~30y) are of major concern due to solubility in aqueous solution under normal condition. Hence the investigation of sorption behaviour of sorbed radionuclides plays an important role to predict transport and diffusion in soil-water system [3]. Sorption includes various processes by which dissolved radionuclide ion can bind to solid surfaces. For sorption assisted diffusion processes, Kd (Distribution Coefficient by batch method) is one of the important parameters for the measurement of migration of radionuclides in the soil column during any nuclear accident.In the present work, sorption behaviour of Cs, Sr and U has been examined by quantification of solid-liquid distribution coefficients (Kd) using batch method in soil samples contaminated due to FDNPP accident. To establish the fate and transfer of radionuclides, site specific distribution coefficient (Kd) were measured in the soil samples using standard method. Log Kd values for Cs, Sr and U were found to be ~1, 2 and 3 respectively. Different soil parameters like particle size distribution, pH, organic content, cation exchange capacity (CEC), CaCO3, elemental and oxide composition of soil has been carried out to understand the geochemical behaviour of these radionuclides. The characteristics of Kd will be discussed in detail during presentation.16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere (MIGRATION 2017)

ESTIMATION OF URANIUM ISOTOPES IN SOIL AFFECTED BY FUKUSHIMA NUCLEAR POWER PLANT ACCIDENT AND ITS MOBILITY BASED ON DISTRIBUTION COEFFICIENT AND SOIL PROPERTIES

An extraordinary earthquake of magnitude 9.0 followed by Tsunami on 11 March 2011 caused serious nuclear accident occurred at the Fukushima Daiichi Nuclear Power Plant (FDNPP) about 250 km north to Tokyo, capital of Japan. This has resulted radioactive contamination in a large area due to deposition of long-lived radionuclides. Contaminated soil can cause an enhanced radiation exposure even after many years and depending upon environmental conditions can be mobilized to aquatic systems. Therefore, the fate and transfer of these radionuclides in the soil water system is very important for radiation protection and dose assessment. In the present study, emphasis has been given on isotope ratio measurement of uranium which can give us the idea about its contamination during accident. Soil and water samples were collected from contaminated areas around FDNPP. Inductively coupled plasma mass spectrometry (ICPMS) is used for total uranium concentration and thermal ionization mass spectrometry (TIMS) has been used for uranium isotopes measurement. Extraction chromatography has been used for the separation of uranium. We have observed, isotope ratio 235U/238U is of natural origin, however in a few soil samples 236U has been detected. For the migration behavior, its distribution coefficient (Kd) has been determined using laboratory batch method. Depleted uranium is used as tracer for uranium Kd estimation. Chemical characterization of soil with respect to different parameters has been carried out. The effect of these soil parameters on distribution coefficient of uranium has been studied in order to explain the radionuclide mobility in this particular area. The distribution coefficient values for uranium are found to vary from 30-35679 L/Kg. A large variation in the distribution coefficient values shows the retention or mobility of uranium is highly dependent on soil characteristics in the particular area. This variation is explained with respect to pH, Fe, Mn, CaCO3 and organic content. There is a very good correlation of uranium Kd obtained with Fe content. There is a variation with uranium activity ratio where as no enrichment of 235U has been noticed in the studied area. However contaminated water used for cooling the reactor vessel stored near the reactor after accident, may contain radioactive uranium. Therefore, it is of a concern to understand leaching of U in the groundwater system. In that context, this study will be very much useful.International Conference on RADIOECOLOGY & ENVIRONMENTAL RADIOACTIVITYに参加し、ESTIMATION OF URANIUM ISOTOPES IN SOIL AFFECTED BY FUKUSHIMA NUCLEAR POWER PLANT ACCIDENT AND ITS MOBILITY BASED ON DISTRIBUTION COEFFICIENT AND SOIL PROPERTIESの発表を行