Determination of iodine-129 and iodine-127 in environmental samples collected in Japan

Analytical method for the determination of¹²⁹I and¹²⁷I in environmental samples has been developed by using radiochemical neutron activation analysis. The¹²⁹I levels in the samples such as soil (0.9–41 mBq/kg), precipitation (0.002–0.11 mBq/kg), pine needles (1.2–32 mBq/kg) and seaweed (<0.1–17 mBq/kg) collected near the nuclear facilities in Tokaimura were higher than those from the other areas in Japan. The highest¹²⁹I concentration was found in surface soil (0–5 cm), and the highest¹²⁹I/¹²⁷I ratios were found in pine needles and precipitation. The¹²⁹I/¹²⁷I ratio was higher in rice paddy soil than those in wheat field soil collected around Tokaimura, while the concentration of¹²⁹I somewhat higher in wheat field soil.     

Determination of I-129 and I-127 in soil and tracer experiments on the adsorption of iodine on soil

Neutron activation analysis of¹²⁹I and¹²⁷I in soil has been studied. The limit of detection for¹²⁹I in soil was about 0.05 mBq/kg or 1×10^–9 as¹²⁹I/¹²⁷I atom ratio. The range of¹²⁹I concentration in surface soils collected around Tokaimura (Ibaraki Prefecture) was 0.9–41 mBq/kg.Tracer experiments on the adsorption of iodine were also carried out, in order to obtain information on the behaviour of iodine in soil-water systems. Different adsorption patterns of iodide and iodate on soil were found. It was supposed that iodide was adsorbed by the soil fraction which became unstable at about 200° C and iodate by the fraction which was relatively stable to heating.     

129I in soil and grass samples around a nuclear reprocessing plant

Neutron activation analysis was used to determine¹²⁹I in soil and grass samples around a reprocessing plant. The method involved wet oxidation of samples, using chromic acid, followed by distillation, collection of iodine in alkaline solution, loading on Dowex-1, irradiation and post-irradiation purification steps. The -activity of¹³⁰I isotope of the purified samples was measured for quantitative determination of¹²⁹I. The experimental results showed that¹²⁹I and the¹²⁹I/¹²⁷I atomic ratio in soil samples varied from 1.09×10^–4 to 5.33×10^–3 pCi g^–1 and 0.10×10^–6 to 6.12×10^–6, respectively. Further, the geometric mean of soil-to-plant transfer factor (Bv) for¹²⁹I was found to be 0.16 which was comparable with other published values.     

Iodine separation procedure for the determination of129I and127I in soil by neutron activation analysis

A radiochemical neutron activation analytical method for the determination of¹²⁹I and¹²⁷I in soil samples was studied. Iodine was separated from the sample prior to the irradiation by volatilization, i.e. by combustion of the sample and trapping of the iodine in an alkaline solution together with a reducing agent. This method enables one to digest samples containing up to 100 g dry matter. The chemical yield was mostly more than 90%. After irradiation the iodine fraction was further purified by solvent extraction. The detection limit of the¹²⁹I/¹²⁷I ratio was 1×10^–9.     

Chemical and nuclear interferences in neutron activation of129I and127I in environmental samples

A combination of neutron activation and gamma-ray coincidence counting technique is used to determine the concentration of both long-lived fission produced¹²⁹I and natural¹²⁷I in environmental samples. The neutron reactions used for the activation of the iodine isotopes are¹²⁹I(n, )¹³⁰I and¹²⁷I(n, 2n)¹²⁶I. Nuclear interferences in the activation analysis of¹²⁹I and¹²⁷I can be caused by production of¹³⁰I or¹²⁶I from other constituents of the materials to be irradiated, i.e. Te, Cs and U impurities and from the¹²⁵I tracer used for chemical yield determination. Chemical interferences can be caused by¹²⁹I and¹²⁷I impurities in the reagents used in the pre-irradiation separation of iodine. The activated charcoals used as iodine absorbers were carefully cleaned. Different chemical forms of added¹²⁵I tracer and¹²⁹I and¹²⁷I constituents of the samples can cause different behaviour of¹²⁵I tracer and sample iodine isotopes during pre-irradiation separation of iodine. The magnitude of the nuclear and chemical interferences has been determined. Procedures have been developed to prevent or control possible interferences in low-level¹²⁹I and¹²⁷I activation analysis. For quality control a number of biological and environmental standard samples were analyzed for¹²⁷I and¹²⁹I concentrations.     

Determination of131I,134Cs,137Cs in grass and cheese after Chernobyl accident in Austria

Various samples from Styria /grass/ and Salzburg /cheese/ were analyzed for¹³¹I,¹³⁴Cs and¹³⁷Cs concentration during April–July 1986 by -ray spectrometry. The concentrations are reported in nCi kg^–1 wet weight. The concentration values found for¹³¹I 0.2–17.2 nCi kg^–1 /grass/, 0.1–0.5 nCi kg^–1 /cheese/, for¹³⁴Cs 1.1–6.2 nCi kg^–1 /grass/, 0.2–1.3 nCi kg^–1 /cheese/, for¹³⁷Cs 1.6–15.7 nCi kg^–1 /grass/, 0.3–2.2 nCi kg^–1 /cheese/. While radioactivity of¹³¹I,¹³⁴Cs and¹³⁷Cs in cheese samples increases from May to June, it decreases in grass samples from May to July 1986.     

Distribution and behavior of long-lived radioiodine in soil

The concentration of¹²⁹I in soil in Japan was determined by neutron activation analysis. For the activation analysis, pre-irradiation chemical separation of the iodine was carried out by acid decomposition and distillation and post-irradiation treatment was performed by ion exchange and solvent extraction. The concentration of stable iodine and¹³⁷Cs were also determined and compared with the behavior of¹²⁹I in soil.Soil samples from Ibaraki, Fukui, Fukushima, and Nagasaki Prefectures were analyzed and¹²⁹I was detected in amounts ranging from 10^–7 to 10^–5 Bq/g soil in uncultivated surface soil. There are apparently small variations in the¹²⁹I concentrations in each of the regions analyzed.From depth profile studies in sandy soil, the iodide form of¹²⁹I was found to migrate downward at a relatively rapid rate while other species remain longer in the surface soil.     

Plutonium concentration distribution in bed load sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²³⁸Pu and^{239, 240}Pu were determined in 12 sediment samples collected from the bed of the Romanian Danube river and Black Sea coast during June–September 1994. After the sample material has been properly prepared and²⁴²Pu tracer added, plutonium was separated from americium and curium by anion exchange. After electrodeposition on stainless steel discs the elements were counted with an -spectrometry system with silicon surface-barrier detectors. The^{239, 240}Pu concentrations range between 150 and 800 mBq kg^–1 dry, while the²³⁸Pu concentrations rise up to max 150 mBq kg^–1 dry. Although the chemical yields are rather low (51%) we appreciate the results as valuable since they report for the first time the distribution of the plutonium contamination along the Danube river and the Black Sea coast-Romanian sector.     

Neptunium-237 in the marine environment determination in animal and plant species in the English Channel: Biological indicators and trophic relationships

We have studied the uptake of²³⁷Np in marine plants and animals belonging to several phyla, and collected samples from the end of January 1986 to March 1986, in a sampling station situated near the outlet of the irradiated fuel reprocessing plant at La Hague.We determined the²³⁷Np by neutron activation analysis. This method is very sensitive, with a limit of detection of 5×10^–10 mg, 1.3×10^–2 mBq. The method consists of the following steps:Reduction of the neptunium to the tetravalent state by treatment with a mixture of hydrazine sulfate and ferrous iron-chromatographic separations on Dowex 1×10 resin in a nitric medium, then in a hydrochloric medium-neutron irradiation in a nuclear reactor-purification of the neptunium by chromatography on Dowex 1×10 resin in a nitric then hydrochloric medium-measurement of the isotope²³⁸Np by gamma ray spectrometry using a Ge(Li) detector. The species were collected at Goury, at the northwest extremity of the Cotentin Peninsula, 5 km from the outlet of the reprocessing plant at La Hague. The levels of²³⁷Np were as follows: red algaeCorallina officinalis 64 mBq kg^–1 wet weight; andChondrus crispus 18 mBq kg^–1 wet weight; the spongeHalichondria panicea 14 mBq kg^–1 wet weight; the ascidianDendrodoa grossularia 12 mBq kg^–1 wet weight. The bivaive molluscsPatella vulgata andGibbula umbilicalis (the flesh ofP. vulgata andG. umbilicalis: 4 and 7 mBq kg^–1 wet weight respectively) also prove to be interesting biological indicatorsThe transfer modes of²³⁷Np to the various species as a function of their trophic levels are discussed as well as the distribution among the organs in the species consumed and the radiological impact of human consumption.     

Determination of131I,134Cs,137Cs in plants and cheese after Chernobyl accident in Roumania

Various samples from the south-east region of Roumania/greens, fodder, cheese/were analyzed for¹³¹I,¹³⁴Cs and¹³⁷Cs concentrations in May and July 1986 by -ray spectrometry. The concentrations are reported in nCi. kg^–1 wet weight. For greens, a considerable decrease was observed for¹³¹I/to 3.0–7.0 nCi. kg^–1/,¹³⁴Cs/to 0.5–2.0 nCi.kg^–1/ and¹³⁷Cs /to 1.0–4.0 nCi. kg^–1/ from the first half /5–15 May/ till the end of May 1986. For cheese, maximum values were measured between 5 and 15 May /sheep cottage cheese: 500–800 nCi.kg^–1 for¹³¹I, 25–50 nCi. kg^–1 for¹³⁴Cs, 40–80 nCi. kg^–1 for¹³⁷Cs/; at the beginning of July a considerable decrease /to 5–10 nCi. kg^–1 for¹³¹I, 1.2–2.0 nCi.kg^–1 for¹³⁴Cs, 2.2–3.0 nCi. kg^–1 for¹³⁷Cs/ was observed. In autumn 1986 a small increase up to 2.0–3.0 nCi. kg^–1 for¹³⁴Cs and 3.4–5.0 nCi. kg^–1 for¹³⁷Cs /in November/ was reported. The population's internal possible contamination was strongly limited by the authorities' severe control of the food-stuff.     

Determination of uranium and thorium isotopes in mineral spring waters

Concentrations levels of uranium and thorium isotopes have been analyzed in the m mineral spring waters of a high background region of Brazil: Poços de Caldas and Águas da Prata. The procedure was based on the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th and²²⁸Th by -spectrometry after separation and purification of the isotopes of interest by using anion-exchange chromatography and preparation of the samples for -measurements by electrodeposition. The concentration varied from <1.1 to 28.4 mBq.l^–1 and from <1.6 to 141 mBq.l^–1 for²³⁸U and²³⁴U, respectively. Thorium isotope measurements varied from <0.2 to 1.8 mBq.l^–1 from <0.3 to 4.9 mBq.l^–1 and from <0.8 to 19.9 mBq.l^–1 for²³²Th,²³⁰Th and²²⁸Th, respectively. Calculations of thorium and uranium isotopic activity ratios were carried out giving values ranging from 1.9 to 7.2, from 1.2 to 3.0 and from 7.7 to 15.3 for²³⁴U/²³⁸U,²³⁰Th/²³²Th and²²⁸Th/²³²Th, respectively. The effective doses due to the intake of²³⁸U and²³⁴U present in these waters are expected to reach values up to 1.4×10^–3 mSv y^–1 and 8.0×10^–3 mSv y^–1, respectively.     

Kinetics and mechanisms of the reactions of thiosulphato-amine complexes of cobalt(III). Part I. Isomerization and base hydrolysis ofcis andtrans isomers of dithiosulphatobis(ethylenediamine) cobalt(III) ion in aqueous solution

Summary Investigations were carried out on the isomerization and base hydrolysis ofcis andtrans forms of dithiosulphatobis-(ethylenediamine)cobalt(III) ions. Thecis form isomerizes to thetrans form in neutral aqueous medium, rates being 1.15, 2.30 and 4.0×10^–5s^–1, respectively at 42, 50 and 58 °C. Thetrans complex isomerizes to thecis form in basic solution only, the rate varying with pH in a sigmoid pattern. In presence of OH^–, an acid-base equilibrium of the complex ion sets in, but only the basic form takes part in the isomerization reaction. Hydrolysis of thecis isomer proceeds through a base-dependent path only, but that of thetrans isomer proceeds both through base-dependent and base-independent paths. The mechanisms are associative in nature. Thetrans form reacts faster thancis in all cases.     

Background levels of238U and226Ra in atmospheric aerosols

The²³⁸U and²²⁶Ra contents of small-volume aerosols are determined by a chemical analysis technique. Mean activity concentrations of²³⁸U and²²⁶Ra in aerosols over approximately ten years are 0.29·10^–5 and 0.93·10^–5 Bq/m³, respectively. The yearly variation of²³⁸U and²²⁶Ra in aerosols is small. The concentrations of²²⁶Ra are always larger than those of²³⁸U in the same sampling time. The correlation of²³⁸U and²²⁶Ra cannot be recogonized (r=0.18). The concentrations of summer samples are greater than those of winter samples for²³⁸U. One of the causes of seasonal difference may be due to the fact that the components of aerosols are different according to soil size, soil components, weathering states, etc.     

131I,134Cs and137Cs concentrations in 1986 for some Roumanian foodstuffs

Results of post-Chernobyl measurement on some foodstuff samples /eggs, meat, fruit, honey, medicinal herbs/ from South-Eastern Roumania are presented. Gamma-ray spectrometry was used; the radioactive concentration values are given in nCi.kg^–1 wet weight. A strong decrease in concentrations for eggs from 6–7 May /3.0–7.4 nCi for¹³¹I, 0.25–0.40 nCi for¹³⁴Cs, 0.40–0.85 nCi for¹³⁷Cs per one egg, mainly in the yolk/ to 19–25 May /0.3–1.0 nCi for¹³¹I, 0.15–0.25 nCi for¹³⁴Cs, 0.25–0.40 nCi for¹³⁷Cs/ was observed. The mean values for lamb meat /joint muscle/ were 500 nCi.kg^–1 for¹³¹I, 12 nCi.kg^–1 for¹³⁴Cs, 22 nCi.kg^–1 for¹³⁷Cs /18–25 May/. Relatively reduced values were found for fruits, e.g. compared to dairy products¹. In May–June 1986, the food consumption in Roumania was strictly limited and controlled by competent authorities.     

Natural radioactivity in Zambian building materials collected from Lusaka

Samples of natural and manufactures building materials collected around Lusaka have been analyzed for natural radionuclides using -spectrometry. A simple comparison of the specific radioactivities of primordial radionuclides in these materials to the world averages for soil (25 Bq kg^{–1 238}U, 25 Bg kg^{–1 232}Th, 370 Bq kg^{–1 40}K and 89 Bq kg^–1 Ra_eq) shows that, of the nine types of samples analyzed, only burnt clay bricks (for²³⁸U,²³²Th and⁴⁰K), cement roofing tiles (for²³⁸U), building and river sands (for²³²Th and⁴⁰K) have greater activities than does soil. Radiological evaluation of specific radioactivities in these materials indicates that all materials meet the external -ray dose limitation of 1.5 mSv y^–1, that is, all samples have a radium equivalent activity of less than 370 Bq kg^–1.     

Determination of129I in soils of Germany using radiochemical neutron activation analysis

At 5 sampling sites distributed throughout Germany the¹²⁹I concentrations in soils have been measured in individual depth intervals to a depth of 60 cm. These measurements are used to determine the total amount of¹²⁹I in a soil column of 60 cm depth. The data indicate that the¹²⁹I concentrations and the¹²⁹I/¹²⁷I isotope ratios are higher at the sampling locations near the coast compared to the sampling locations in Southern Germany. The total¹²⁹I inventories in the top 60 cm of soils are correlated with the¹²⁹I deposition through rainfall.     

Determination of the129I content of the primary coolant of nuclear power reactors

A neutron activation determination of the content of¹²⁹I in the cooling water of nuclear power reactors is described.¹²⁹I is coprecipitated as PbI₂. After neutron irradiation the gamma-spectrum of PbI₂ is measured. The detection limit for¹²⁹I is 2.9 mBq/dm³. The applicability of X-ray spectrometry for¹²⁹I determination is also evaluated. The proposed methods are applied for determination of the¹²⁹I content of the cooling water of WWR-440 type reactors at the nuclear power station Kozloduy, Bulgaria     

Measurement of uranium in total diet samples: Daily intake for Japanese

Diet samples were collected by a duplicate portion study of Japanese adults in two districts, a newly-rising town and an established seaside village, of Ishikawa Prefecture, which faces the Sea of Japan. Uranium concentrations in a total of 80 diet samples were determined by -spectrometry after chemical separation. No marked differences between the two districts were found regarding characteristics of food consumption in thirteen categories and in daily intake of²³⁸U per person. The daily intake of²³⁸U per person ranged from 1.1 to 40 mBq with a geometric mean value of 9.6±2.1 mBq. The²³⁴U/²³⁸U activity ratios ranged from 0.7–1.5, with most being from 1.0–1.2. The internal dose estimation system (IDES) was completed with Japanese physical parameters and other parameters of ICRP Publication 30, and then the annaul effective dose equivalent was estimated as 3·10^–7 Sv for²³⁸U in a Japanese adult.     

Measurements of210Pb and210Po in Japanese human hair

²¹⁰Pb and²¹⁰Po in human hair have been measured to serve as an aid in order to estimate the dietary intake and body burden of these radionuclides of Japanese. The²¹⁰Po concentrations found in 83 hair samples were ranging from 4.0 to 59.3 mBq/g with a mean (median) value of 18.2±12.2 (14.9) mBq/g as compared to the²¹⁰Pb concentrations from 0.7 to 6.5 mBq/g with a mean (median) value of 2.3±1.1 (2.0) mBq/g. The²¹⁰Po/²¹⁰Pb activity ratios (mean: 8.7±5.1, median: 7.1) were surprisingly higher compared with the available literature value of about 2. The high concentration of²¹⁰Po in human hair of Japanese may be due to the ingestion of animal protein mainly in the form of seafood.     

Iodine-129 and natural iodine-127 in deer thyroids from the environment of a small nuclear fuel reprocessing plant and from sites remote from nuclear facilities

Concentrations of the fission product¹²⁹I and natural¹²⁷I were determined in deer thyroids collected in the environment of the small Karlsruhe nuclear fuel reprocessing plant (WAK) and in a region remote from¹²⁹I sources of nuclear facilities. The isotopic ratio¹²⁹I/¹²⁷I in thyroids from the environment of WAK varies from 1.0×10^–6 to 12.9×10^–6, which is about one order of magnitude higher than the¹²⁹I/¹²⁷I ratios in thyroids from deer in a region remote from nuclear facilities. These ratios were between 0.2×10^–6 and 0.7×10^–6.