G. Ardisson

CHERNOBYL FALLOUT MEASUREMENTS IN SOME MEDITERRANEAN BIOTAS

The radioactivity of various terrestrial vegetation leaves characteristic of Mediterranean countries has been measured after the Chernobyl accident. In addition, we paid particular attention to lichens and seaweed which are considered as bioindicators of radioactive contamination. Most measurements were performed non-destructively using both coaxial and planar HPGe detectors. For odd mass radionuclides having low energy lines, such as 125Sb or 141Ce the sensitivity of the planar HPGe detector is better than the coaxial detector. The concentration of long-lived fission nuclides remaining three months after the accident were found to be enhanced in needle form leaves and in lichens. The seaweed Sphaerococcus exhibits a strong specific activity for iodine and ruthenium elements and poor concentration for caesium nuclides. The activity ratios of different isotopes of the same element measured in vegetation samples agree well with values found in airborne aerosols by other authors. The activation nuclide 110mAg is found in all samples with the same ratio 110mAg/137Cs = (1.0 +/- 0.2).10(-2) as in the soil deposition.

Radioanalytical determination of actinides and fission products in Belarus soils

Alpha emitting actinides such as plutonium, americium or curium were measured by alpha-spectrometry after radiochemical separation. The short range of alpha-particles within matter requires, after a pre-concentration process, a succession of isolation and purification steps based on the valence states modification of the researched elements. For counting, actinides were electrodeposited in view to obtain the mass-less source necessary to avoid self-absorption of the emitted radiations. Activity concentrations of gamma-emitting fission products were calculated after measurement with high purity germanium detectors (HPGe). These different methods were used to analyse soils sampled in the Republic of Belarus, not far from the Chernobyl nuclear plant.

Radioactive pollution of Turkish biotas one year after the Chernobyl accident

Long-lived fission radionuclides spread out after the Chernobyl accident have been measured in samples collected from the Black Sea and at the Aegean coasts of Turkey between June 15 and September 15, 1987. Nondestructive analysis was performed using high resolution γ-spectroscopy. The activity remaining 16 months after the event was found to be enhanced in coniferous needles as well as in lichens, while foodstuff did not show any appreciable contamination. The relatively high106Ru/134Cs and144Ce/134Cs ratios compared to those found in analogous samples from Southern Europe, might result from a fractionation between refractory and volatile elements.

Chernobyl fallout measurements in some mediterranean biotas

The radioactivity of various terrestrial vegetation leaves characteristic of Mediterrenean countries has been measured after the Chernobyl accident. In addition, we paid particular attention to lichens and seaweed which are considered as bioindicators of radioactive contamination. The measurements were performed by non-destructive way using both coaxial and planar HPGe detectors. For odd mass radionuclides having low energy lines, such as125Sb or141Ce the sensitivity of the planar HPGe detector is better than the coaxial detector. The concentration of long lived fission nuclides remaining three months after the accident were found to be enhanced in needle form leaves and in lichens. The seaweed Sphaerococcus exhibits a strong specific activity for iodine and ruthenium and poor concentration for cesium nuclides. The activity ratios of different isotopes of the same element, measured in vegetation samples agree well with the values found by other authors in airborne aerosols. The activation nuclide110Agm is found in all samples with the same ratio110Agm/137Cs=/1.0±0.2/×10−2, as in the soil deposition.

Plutonium, americium and cesium records in sediment cores from Blelham Tarn, Cumbria (UK)

Abstract238Pu, 239-240Pu, and 241Am were measured, by α-counting after radiochemical separation, in two lake sediment cores. The profiles of these transuranics were compared to those of the fission product 137Cs. Datation of nuclear events and data on behavior of the studied elements were deduced.

Plutonium and americium inventories in atmospheric fallout and sediment cores from Blelham Tarn, Cumbria (UK)

The objective of this paper is to report on the results of a study of 238Pu, 239 + 240Pu and 241Am inventories onto Blelham Tarn in Cumbria (UK). The atmospheric fallout inventory was obtained by analysing soil cores and the results are in good agreement with the literature: 101 Bq m(-2) for 239 + 240Pu; 4.5 Bq m(-2) for 238Pu and 37 Bq m(-2) for 241Am. The sediment core inventory for the whole lake is compared to the atmospheric fallout inventory. The sediment activity is 60-80% higher than the estimated fallout activity, showing a catchment area contribution and in particular the stream input.

γ-Ray spectroscopic reinvestigation of the long lived166Hom decay

The decay of166Hom has been reinvestigated on radiochemically separated sources with the aid of high efficiency HPGe detector. Energies and intensities of 54 γ-lines, of which 10 are new, were carefully measured. All γ-rays can be interpreted as deexciting known166Er levels.

Excited levels in 213Po and 209Pb fed by β-decays of 213Bi (T12 = 45.6 min) and 209Tl (T12 = 2.2 min)

Abstract The γ-decay of radiochemically separated 213 Bi sources (T 1 2 = 45.6 min ) , in equilibrium with 209 Tl (T 1 2 = 2.2 min ) and 213 Po (T 1 2 = 4.2 μ s ) , has been reinvestigated using coaxial HPGe detectors, a LEPS detector and the γ-γ coincidence method. The energies and intensities of 20 γ-lines were measured, of which 11 are reported for the first time. Of the ten γ-rays attributed to 213 Bi β-decay, five are new. All of them were interpreted in a 213 Po level scheme using γ-γ coincidence data. New levels at 292.8, 1003.6 and 1119.5 keV are proposed in 213 Po. In the 209 Tl β-decay, five γ-lines were measured, two of which are new. On the basis of γ-γ coincidence, we suggest that two new levels of 3069.6 and 3388.9 keV are fed into the 209 Pb magic nucleus.

Technetium-99 in the Rhône river water

Abstract99Tc a pure β-particle emitter with long half-life (T=2.13×105 y) was measured in Rhône river water and in Mediterranean sea water near the river mouth. The values obtained in the Rhône river allowed us to show the downstream distribution of the effluents from the nuclear fuel reprocessing plant of Marcoule: the99Tc activity which is low above the plant, 0.016 mBq 1−1, is 0.4 mBq 1−1 at Roquemaure, located 14 km below the plant, and then decreases as a function of distance from the plant.

High resolution study of the γ-ray spectrum following228Ac decay

The decay of228Ac has been reinvestigated by means of high resolution HPGe detectors. Accurate energies and intensities of 242 γ photons were measured, of which 80 were found for the first time.