S. Ballestra

Radiometric investigations of Kara Sea sediments and preliminary radiological assessment related to dumping of radioactive wastes in the Arctic Seas

There has been world-wide concern over the possible health and environmental impacts of the dumping of radioactive wastes in shallow waters of the Kara and Barents Seas. During 1992, IAEA-MEL participated in a joint Russian-Norwegian expedition to the region and collected a suite of sediment cores for characterization of downcore radioactivity distribution patterns and inventories with the aim of assessing past and present inputs of radionuclides. The 137Cs, 238Pu, 239,240Pu, and 241Am contents of the 0–1 cm sections range from 17 to 32, 0·01 to 0·06, 0·4 to 1·3 and 0·2 to 0·5 Bq kg−1 (dry wt), respectively. The 238Pu/239,240Pu and 241Am/239,240Pu activity ratios are consistent with those reported for global fallout. Detailed information on downcore radionuclide distribution patterns and inventories, as well as an account of sedimentation parameters, are presented. A preliminary assessment of the long-term radiological impact of radioactive waste disosal in the Arctic Seas, on global and regional scales, has been made. The modelling results suggest that the global radiological impact of the disposals will be comparable to or less than those resulting from other anthropogenic and natural sources of radioactivity. However, radiological effects on the regional scale may be of importance. IAEA is carrying out a 4 year International Arctic Seas Assessment Project (IASAP) that will comprehensively cover all aspects of radioactive dumping in the Arctic Seas and it will be reported to the London Convention in 1996. The IAEA-MEL study described here represents a preliminary contribution to IASAP.

Fallout deposition at Monaco following the chernobyl accident

Increased atmospheric radioactivity from the Chernobyl accident was first detected on air filters taken in Monaco on 30 April 1986, with maximum activities of 10, 2·9, 1·5 and 0·84 Bqmdash3 for 132Te, 131 I, 137Cs and 134Cs, respectively, occurring about 1–3 May 1986. About one week later the activities had fallen to about 1% of peak values. A total of 33 radioisotopes were detected. The integrated inventories were significantly less than at other sites to the east. Preliminary results of plutonium analyses are also presented, together with other deposition data in rain and soil.

Radiochemical measurements of99Tc: Sources and environmental levels

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.

Chernobyl radionuclides in shellfish

Abstract Radionuclides from the Chernobyl accident arrived at Monaco on 30 April, 1986. A sample of Mytilus galloprovincialis collected six days later showed near-maximum levels of most radionuclides. Monitoring continued for seven months thereafter, peak concentrations being transiently as high as 480 Bq kg−1 (all soft parts, wet weight) for 103Ru. Other radionuclides detected included 132Te, 129mTe, 131I, 106Ru, 134Cs, 137Cs, 110mAg, 140Ba, 125Sb, 95Nb and 141Ce. Biological half-lives for elimination in this environment were generally around 10 days or longer and most elimination curves contained a number of components. Radionuclide contents of the mussels were predicted quite accurately from concentrations observed on air filters collected simultaneously, but were not satisfactorily explained relative to total radionuclide concentrations in the seawater even three days after peak air filter activities. The use of concentration factors from the literature did not improve the latter predictions. This suggests that the radionuclides were absorbed very rapidly from the fallout particles, rather than from radionuclides first solubilised from particles. Patella lusitanica specimens contained activities about 20–50 times higher than those in the mussels.

Air radionuclide patterns observed at Monaco from the Chernobyl accident

Radionuclide concentrations in air filters taken in Monaco for several weeks after the Chernobyl accident on April 26, 1986 have been carefully examined. Unusual radionuclides such as 105Ru, 111Ag, 125Sn and 126Sb were identified as being present in small amounts. Nuclides of the more volatile elements I, Te, and Ag peaked 6–24 hours earlier than the average, whereas the refractory elements exhibited a different distribution. Radionuclide concentrations seen in air at Chernobyl compared with those observed at Monaco show that 134,137Cs was least removed by environmental processes between the two sites and rare earths the most. The second (4–5 May) peak of activity released from the Chernobyl reactor was characterised by a relatively higher content of refractory elements, also observed at Monaco. The different phases of such an accident can thus be observed even at distances approaching 2000 km.

Low-level measurements of actinides and long-lived radionuclides in biological and environmental samples

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%.

The presence of man-made radionuclides in the marine environment in the South of Spain

Abstract In this paper, levels of 137Cs, 99Tc, Pu-isotopes and 241Am in a wide group of seaweed species collected in the southern Spanish marine environment are given. Atmospheric fallout seems to be responsible for the presence of such radionuclides in the zone. However, it is shown that additional amounts of transuranic nuclides are present in the neighbouring coasts of Palomares. These are interpreted to be a consequence of the aircraft accident which occurred there during 1966.

Summary of IAEA-MEL's investigation of Kara Sea radioactivity and radiological assessment

IAEA-MEL participated in five expeditions to the Kara Sea with the aim of assessing the radiological consequences of dumped radioactive wastes in the Novaya Zemlya Bays and Trough. The programme included sampling, in-situ underwater investigations, laboratory analyses of water, sediment and biota samples, the development of a marine radioactivity database, modelling and radiological assessment, the organization of intercomparison exercises and the evaluation of distribution coefficients. Radiometric investigations have shown that no radiologically significant environmental contamination has occurred. Leakages which have led to locally increased levels of radionuclides in sediment have only been observed in Stepovoy and Abrosimov Bays. Computer modelling results suggest that only radiological effects on local and regional scales may be of importance. The global radiological impact of the disposals in the Arctic Seas will be negligible.

Radionuclides in macro algae at Monaco following the Chernobyl accident

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.

Determination of237Np in large volume samples of sea water by a radiochemical procedure

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.