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Abstract  

Within the last five years the International Laboratory of Marine Radioactivity at Monaco has organized seven intercomparison exercises worldwide on natural materials of marine origin comprising sea water (SW-N-2), sediment (SD-N-1/1, SD-N-1/2, SD-N-2), seaweed (AG-B-1) and fish flesh (MA-B-3/1, MA-B-3/2). Results on man-made (54Mn,60Co,65Zn,90Sr,99Tc,134Cs,137Cs,238Pu,239,240Pu,241Am) and natural radionuclides were collected and evaluated. Reference values were established for a number of them. In the paper are discussed various aspects of the intercomparison exercises.

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Abstract  

A radiochemical procedure followed by alpha spectrometry has been developed for the determination of237Np present at low activity concentrations in seawater. The analytical procedure is based on concentration of actinides from 1800 1 sea water samples by hydroxide precipitations. Neptunium is isolated by ion exchange, fluoride precipitation and extraction with TTA (thenoyltrifluoroacetone). As a radiochemical yield determinant239Np or235Np is used. Neptunium is electroplated onto stainless steel discs before alpha-spectrometry for about 10 days. The procedure allows for sequential separation of plutonium, americium, technetium and radiocaesium together with neptunium. The radiochemical yield for neptunium is only 20–50%, but the procedure has been applied with success on several samples contaminated with237Np at fallout or close to fallout levels.

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Abstract  

Evidence for the presence of111Ag in Chernobyl fallout at Monaco is given. This fission radionuclide has not been previously reported in Chernobyl fallout. Peak values were as high as 1.9 Bq m–3. Arguments are presented that the observed110mAg content in the fallout originated from volatilisation of silver neutron flux monitors in the reactor rather than production by other nuclear reactions.

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Abstract  

A method of99Tc determination has been developed based on sample decomposition followed by purification from interfering elements by hydroxide and oxide precipitations. Technetium is extracted by TBP and electrodeposited onto stainless steel discs from sodium hydroxide solution.99Tcm is used as yield monitor. The method has been applied to study releases from different sources and contents in different samples of atmospheric, terrestrial and marine origin. Results show enhanced99Tc/137Cs activity ratios for samples collected in recent years which are only expected to be contaminated from fallout from nuclear tests. Integrated fallout measurements did not reflect these enhanced ratios.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
S. Ballestra
,
G. Barci
,
E. Holm
,
J. Lopez
, and
J. Gastaud

Abstract  

This paper describes a radiochemical method for the determination of99Tc in large volumes of rain, river and seawater. The procedure is based on the reduction of technetium to the +4 oxidation state with potassium disulfite in a slightly acidic medium, followed by iron hydroxide precipitation. After oxidation to the +7 oxidation state, the technetium fraction is purified with iron hydroxide and calcium carbonate precipitations. Technetium (+7) is extracted with TBP (xylene) in 3M H2SO4, back extracted in 2M NaOH or ammonia, and the electrodeposition is made in 2M NaOH or H2SO4/NH4OH medium at pH 5–6. The radiochemical yield is determined by gamma counting of the 140 keV gamma ray from99Tcm.99Tc is counted on an anti-coincidence shielded GM-gas flow counter. The purity of the99Tc plated samples is checked by alpha and beta spectrometry using surface barrier detectors and by gamma spectrometry on Ge(HP) detector. The radiochemical yield of 50–150 l water samples is around 20–60%.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
G. Barci-Funel
,
S. Ballestra
,
E. Holm
,
J. Lopez
, and
G. Ardisson

Abstract  

99Tc a pure -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.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
E. Holm
,
S. Ballestra
,
J. Lopez
,
A. Bulos
,
N. Whitehead
,
G. Barci-Funel
, and
G. Ardisson

Abstract  

Samples of macro algae,Codium tomentosum (green),Corallina mediterranea (red),Sphaerococcus coronopifolius (red) andDictyota dichtoma (brown), were collected off Monaco during 1984 and 1988 and analyzed for gamma-emitting radionuclides and transuranium elements. Due to the Chernobyl accident, increased radioactivity in the atmosphere at Monaco was recorded on 30 April 1986 with maximal activity concentrations on 2–3 May. The maximal activity concentrations in sea water occurred on 5–6 May and in the algae on 11 May. The decrease of activity concentrations can be described after May 11 as a single exponential relationship, where elimination rates for different radionuclides and different species specific to the environment can be calculated.The elimination rates thus observed correspond to mean residence times between 70 and 370 days corrected for physical decay. The concentration factors were also estimated and the highest values were found for131I,129Tem, and 110 Agm and lowest for radiocaesium and140Ba. The red algaeSphaerococcus coronopifolius showed generally higher concentration factors than green and brown algae.Regarding transuranium elements, a theoretical contribution from the Chernobyl accident can be made but only242Cm was detected in the algae above previous levels before the accident, due to the relatively small fallout of transuranics.

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