Hartmut Nies

A comparison of doses from 137Cs and 210Po in marine food: A major international study

Radioactivity levels of natural 210Po and anthropogenic 137Cs in sea water and biota (fish and shellfish) have been estimated for the FAO fishing areas on the basis of measurements carried out in recent years. Collective doses resulting from seafood consumption are calculated for each FAO area using radioactivity data for water and biota. Good agreement is observed between the results calculated by these two methods, with the exception of the doses from 210Po via shellfish consumption. The collective effective dose commitment from 137Cs in marine food in 1990 has been estimated at 160 man Sv with an uncertainty of 50%. The corresponding dose from 210Po is 30000 man Sv with an estimated uncertainty of a factor of 5. The results confirm that the dominant contribution to doses derives from natural 210Po in fish and shellfish and that the contribution from anthropogenic 137Cs (mainly originating from nuclear weapons tests) is negligible.

Dry and wet deposition of 7Be, 210Pb and 137Cs in Monaco air during 1998–2010: Seasonal variations of deposition fluxes

Temporal variations of (7)Be, (210)Pb and (137)Cs activity concentrations in precipitation in Monaco from 1998 to 2010 showed that maxima of (7)Be and (210)Pb deposition fluxes coincide with the peaks of precipitation amounts observed in different months of a year, and most of (7)Be and (210)Pb was washout from the atmosphere by precipitation. The seasonal variations were not uniform from year to year, and the amount of precipitation controlled the deposition fluxes of (7)Be and (210)Pb, which was not the case for (137)Cs. The fractional deposition fluxes of (7)Be and (210)Pb in different seasons were in the order fall > spring > winter > summer, while the fractional amount of precipitation followed the order fall > winter > spring > summer. The fractional deposition fluxes of (137)Cs were found in the order spring > fall > summer > winter. The precipitation-normalized deposition fluxes of (7)Be, (210)Pb and (137)Cs were generally higher during summer. The highest (7)Be/(210)Pb activity ratio was observed in 2010, and the smallest one in 2001, following the influence of the modulation of cosmic rays on the production rates of (7)Be in the atmosphere by solar activity. Activity ratios of (7)Be/(210)Pb observed in winter and fall were generally higher than during summer and spring.

The contamination of the north sea by artificial radionuclides during the year 1987

Abstract The activity concentrations of the caesium isotopes 137 Cs and 134 Cs and of the radionuclide strontium-90 in the seawater of the North Sea during the year 1987 are presented. Isotopes originating from the reactor disaster at Chernobyl are detectable in the water of the North Sea only at very low activities. At some positions in the North Sea, plutonium isotopes, americium and curium have been determined. The main source of these artificial nuclides are the reprocessing plants at Sellafield (UK) and La Hague (France). Due to the installation of new reprocessing facilities at Sellafield, a constant downward trend of contamination from 137 Cs in the central North Sea can be established.

A new Certified Reference Material for radionuclides in Irish sea sediment (IAEA-385)

A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra, (230)Th, (232)Th, (234)U, (238)U, (238)Pu, (239+240)Pu and (241)Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides ((90)Sr, (210)Pb((210)Po), (235)U, (239)Pu, (240)Pu and (241)Pu). Results for less frequently reported radionuclides ((60)Co, (99)Tc, (134)Cs, (155)Eu, (224)Ra and (239)Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes.

A new comparison of marine dispersion model performances for Fukushima Dai-ichi releases in the frame of IAEA MODARIA program.

A detailed intercomparison of marine dispersion models applied to the releases from Fukushima Dai-ichi nuclear power plant was carried out in the frame of MODARIA program, of the IAEA. Models were compared in such a way that the reasons of the discrepancies between them can be assessed (i.e., if they are due to the hydrodynamic part, the dispersion part, and the ultimate reasons). A sequential chain of dispersion exercises was carried out with this purpose. The overall idea is to harmonize models, making them run with the same forcing in a step-by-step procedure, in such a way that the main agent in producing discrepancy between models can be found. It was found that the main reason of discrepancies between models is due to the description of the hydrodynamics. However, once this has been suppressed, some variability between model outputs remains due to intrinsic differences between models (as numerical schemes). The numerical experiments were carried out for a perfectly conservative radionuclide and for (137)Cs (including water/sediment interactions). Model outputs for this radionuclide were also compared with measurements in water and sediments.

Certified reference material IAEA-446 for radionuclides in Baltic sea seaweed

A Certified Reference Material (CRM) for radionuclides in seaweed (Fucus vesiculosus) from the Baltic Sea (IAEA-446) is described and the results of the certification process are presented. The (40)K, (137)Cs, (234)U and (239+240)Pu radionuclides were certified for this material, and information values for 12 other radionuclides ((90)Sr, (99)Tc, (210)Pb ((210)Po), (226)Ra, (228)Ra, (228)Th, (230)Th, (232)Th, (235)U, (238)U, (239)Pu and (240)Pu) are presented. The CRM can be used for Quality Assurance/Quality Control of analysis of radionuclides in seaweed and other biota samples, as well as for development and validation of analytical methods, and for training purposes.

A one-dimensional dispersion model for radionuclides in the marine environment applied to the chernobyl fallout over the Northern Baltic Sea

Abstract The Baltic Sea was the marine ecosystem most affected by Chernobyl fallout. The occurrence of ‘hot spots’ at the water surface was characteristic of the contamination. A one-dimensional vertical dispersion model has been used to explain the distribution of the radionuclides, cesium-137 and cesium-134, in the water column of the central Bothnian Sea for the first six months after the contamination event. In addition to physical dispersion processes, specific chemical characteristics of the radionuclides were taken into account. The simulation shows that, in the six-month period, 5% of the cesium-137 and cesium-134 was trapped in the sediment, while 50% of the plutonium-239/240 activity was deposited. The activity concentration of plutonium in the water column was, however, close to the limit of detection.

A comparison of marine radionuclide dispersion models for the Baltic Sea in the frame of IAEA MODARIA program.

Four radionuclide dispersion models have been applied to simulate the transport and distribution of (137)Cs fallout from Chernobyl accident in the Baltic Sea. Models correspond to two categories: box models and hydrodynamic models which solve water circulation and then an advection/diffusion equation. In all cases, interactions of dissolved radionuclides with suspended matter and bed sediments are included. Model results have been compared with extensive field data obtained from HELCOM database. Inventories in the water column and seabed, as well as (137)Cs concentrations along 5 years in water and sediments of several sub-basins of the Baltic, have been used for model comparisons. Values predicted by the models for the target magnitudes are very similar and close to experimental values. Results suggest that some processes are not very relevant for radionuclide transport within the Baltic Sea, for instance the roles of the ice cover and, surprisingly, water stratification. Also, results confirm previous findings concerning multi-model applications.

Main results of the 2012 joint Norwegian–Russian expedition to the dumping sites of the nuclear submarine K-27 and solid radioactive waste in Stepovogo Fjord, Novaya Zemlya

This paper reports the main results of the 2012 joint Norwegian-Russian expedition to investigate the radioecological situation of the Stepovogo Fjord on the eastern coast of Novaya Zemlya, where the nuclear submarine K-27 and solid radioactive waste was dumped. Based on in situ gamma measurements and the analysis of seawater and sediment samples taken around the submarine, there was no indication of any leakage from the reactor units of K-27. With regard to the radioecological status of Stepovogo Fjord, activity concentrations of all radionuclides in seawater, sediment and biota in 2012 were in general lower than reported from the previous investigations in the 1990s. However in 2012, the activity concentrations of (137)Cs and, to a lesser extent, those of (90)Sr remained elevated in bottom water from the inner part of Stepovogo Fjord compared with surface water and the outer part of Stepovogo Fjord. Deviations from expected (238)Pu/(239,240)Pu activity ratios and (240)Pu/(239)Pu atom ratios in some sediment samples from the inner part of Stepovogo Fjord observed in this study and earlier studies may indicate the possibility of leakages from dumped waste from different nuclear sources. Although the current environmental levels of radionuclides in Stepovogo Fjord are not of immediate cause for concern, further monitoring of the situation is warranted.

Modelling of marine radionuclide dispersion in IAEA MODARIA program: Lessons learnt from the Baltic Sea and Fukushima scenarios☆

State-of-the art dispersion models were applied to simulate (137)Cs dispersion from Chernobyl nuclear power plant disaster fallout in the Baltic Sea and from Fukushima Daiichi nuclear plant releases in the Pacific Ocean after the 2011 tsunami. Models were of different nature, from box to full three-dimensional models, and included water/sediment interactions. Agreement between models was very good in the Baltic. In the case of Fukushima, results from models could be considered to be in acceptable agreement only after a model harmonization process consisting of using exactly the same forcing (water circulation and parameters) in all models. It was found that the dynamics of the considered system (magnitude and variability of currents) was essential in obtaining a good agreement between models. The difficulties in developing operative models for decision-making support in these dynamic environments were highlighted. Three stages which should be considered after an emergency, each of them requiring specific modelling approaches, have been defined. They are the emergency, the post-emergency and the long-term phases.