J. Dalmasso

Reinvestigation of the decay of the long-lived odd-odd 176Lu nucleus

Abstract The decay of the naturally occuring 176Lu nucleus has been reinvestigated using coaxial and planar HPGe detectors. Energy and intensity values of the three main γ rays are given with an improved precision. The 401.04-keV γ-ray was measured in single γ-spectra and its intensity I = 0.48% was deduced. The 176Lu half life was measured using a 133Ba standard γ-activity source mixed with the Lu2O3 sample, found to be T 1 2 = (3.73 ± 0.05)×10 10 years. A revised 176Lu decay scheme has been derived.

Study of the transfer of radionuclides in trees at a forest site

The transfer of radionuclides such as 137Cs and 90Sr from soil to trees (conifers) was studied in a forest area, the Boreon massif, 30 km north of Nice in South Eastern France. This area has been highly contaminated after the Chernobyl accident. Besides the γ-emitting fission products, the α-emitters 238Pu and 239+240Pu and the pure β-emitter 90Sr were measured in different parts of the studied trees (roots, branches, twigs, etc.). As has already been reported by other authors, the radionuclide activities in the tree rings are not correlated with the fallout deposition. They were found varying according to the sap flux in the tree and higher in sapwood than in heartwood. For cesium the root absorption was found to be lower than the atmospheric deposition. Soil-to-plant concentration factors were calculated for 137Cs, 90Sr and 239+240Pu.

One step ion exchange process for the radiochemical separation of americium, plutonium and neptunium in sediments

A radiochemical separation is presented for americium, plutonium and neptunium from sediment samples by using an unique anionic exchange process. An oxidation-reduction step was introduced in the classical procedure of the radiochemical determination of transuranic elements in order to control the valence of the separated elements.

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.

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.

Indirect determination of241Pu activity in soils using low energy photon spectrometers

Actinides activity levels deposited after the Chernobyl accident on the coastal Mediterranean area at Monaco have been recently measured (1). The values obtained are low. However, our γ-measurements on humic soils from the southern Alps revealed high137Cs level contamination areas and urged us to evaluate241Pu activity levels. The indirect determination of241Pu was based on the γ-activity measurement of the241Am in situ ingrown.

Simultaneous detection of short-lived 201Tl, 99Tcm and 131I isotopes in sewage sludge using low energy photon spectrometry

Abstract The low-energy photon spectrometry has been applied to measure the activity concentration of radionuclides in sludge samples from the sewage treatment plant in Nice city. Short-lived 201 Tl, 99 Tc m and 131 I isotopes which are currently used in nuclear medicine were detected at levels included between 1 and 250 Bq/kg. 134 Cs and 137 Cs due to the Chernobyl fallout are also detected.