Numerical simulation of radionuclides migration in the far field of a geological repository

Safety conditions associated with geological repositories must be guaranteed also in the case of radionuclides migrating from the near field to the far field of a geological repository and to the external environment. For this reason the migration process of radionuclides and the factors affecting the process patterns have a crucial importance. In the present article, in order to simulate the migration process of radionuclides in the far-field of a geological repository, the groundwater simulation code PMWIN (Processing Modflow) is used, following a methodology applied by the same authors in a previous work. The present case study refers to a non-uniform groundwater flow field and shows the influence of two important parameters, the distribution coefficient and the hydraulic gradient. The results are compared with the ones previously obtained for the uniform flow case and the different scenarios are discussed

Fate of Some Common Radionuclides Found in Dardanelle Lake

Four factors influence the concentrations of radionuclides in Dardanelle Lake water: injections due to fallout and discharge from Nuclear I coupled with losses due to decay, to dilution and to sedimentation. It is possible to estimate the first three factors and to measure monthly changes in the concentrations of Sr-89, Ce-141, Cs-137, Co-38, Ce-144, and Sr-90 - Y-90 during periods when the concentrations of these nuclides are abnormally high (after large releases or the Chinese weapons tests) or abnormally low (during reactor refueling)

Deposition patterns of atmospheric 7Be, 210Pb, 40K in cost of west Mediterranean sea, Málaga (Spain)

The deposition of radionuclides on the ground is an essential process to understand atmospheric transportation, sedimentation and geological process, being the major removal pathway for airborne particulates. To predict the long-term radiological consequences of an accidental deposition of the radionuclides to the ground, it is a prerequisite to know the environmental long-term behaviour of these radionuclides and a relatively large number of values are required for statistically meaningful conclusions. Nuclides of the natural decay chains, especially for 238U decay chain, are widely applied into atmospheric research, oceanography and marine geology. Atmospheric depositional fluxes of 7Be, 210Pb and 40K were simultaneously measured in monthly interval for eleven years (from January 2005 to December 2015 at Málaga (4 º28´ 8W; 36º 43´40N). Samples were collected monthly in an area of 1 m2 using a collector that is a slightly tilted stainless steel tray and filling 25 or 50 L polyethylene vessels with bulk deposition. The radionuclides present in all samples are 7Be, 210Pb and 40K appears approximately in 50% of the samples. The temporal variations of radionuclides in bulk deposition exhibit similar seasonal behaviour with low values in winter-autumn months and maximum values in spring-summer months. The time variations of the different radionuclides have been discussed in relation to various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at different latitudes. Bulk depositional fluxes of 7Be, 210Pb and 40K have been evaluated for period of measurements. Bulk depositional fluxes of 7Be , 210Pb and 40K varied between 3 and 1779 Bq m-2 month-1 (annual mean = 1247 Bq m-2 year-1 ), and 1 to 102 Bq m-2 year-1 (annual mean = 140 Bq m-2 year-1) and 0,5 to 81 Bq m-2 year-1 ( annual mean = 65 Bq m-2 year-1). Data on the atmospheric depositions of radionuclides in Málaga show clear seasonal variations which can be attributed to the meteorological conditions affecting the transport and deposition processes. The amount of rainfall controls mainly the depositional fluxes. .There is a statistically relationship between 7Be and 210Pb fluxes indicating that removal behaviour from the atmosphere is relatively similar.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Tracer Applications of Noble Gas Radionuclides in the Geosciences

The noble gas radionuclides, including 81Kr (half-life = 229,000 yr), 85Kr (11 yr), and 39Ar (269 yr), possess nearly ideal chemical and physical properties for studies of earth and environmental processes. Recent advances in Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, have enabled routine measurements of the radiokrypton isotopes, as well as the demonstration of the ability to measure 39Ar in environmental samples. Here we provide an overview of the ATTA technique, and a survey of recent progress made in several laboratories worldwide. We review the application of noble gas radionuclides in the geosciences and discuss how ATTA can help advance these fields, specifically determination of groundwater residence times using 81Kr, 85Kr, and 39Ar; dating old glacial ice using 81Kr; and an 39Ar survey of the main water masses of the oceans, to study circulation pathways and estimate mean residence times. Other scientific questions involving deeper circulation of fluids in the Earth's crust and mantle also are within the scope of future applications. We conclude that the geoscience community would greatly benefit from an ATTA facility dedicated to this field, with instrumentation for routine measurements, as well as for research on further development of ATTA methods

The Search for Supernova-produced Radionuclides in Terrestrial Deep-sea Archives

An enhanced concentration of 60Fe was found in a deep ocean's crust in 2004 in a layer corresponding to an age of ~2 Myr. The confirmation of this signal in terrestrial archives as supernova-induced and detection of other supernova-produced radionuclides is of great interest. We have identified two suitable marine sediment cores from the South Australian Basin and estimated the intensity of a possible signal of the supernova-produced radionuclides 26Al, 53Mn, 60Fe and the pure r-process element 244Pu in these cores. A finding of these radionuclides in a sediment core might allow to improve the time resolution of the signal and thus to link the signal to a supernova event in the solar vicinity ~2 Myr ago. Furthermore, it gives an insight on nucleosynthesis scenarios in massive stars, the condensation into dust grains and transport mechanisms from the supernova shell into the solar system

Detailed plan for the COMET WP3 initial research activity - list of research projects and goals, participants and timing

Detailed plan for the COMET Work Package (WP) 3