Simultaneous resolution of reactive radioactive decay, non-isothermal flow, and migration with application to the performance assessment for HLW repositories

2010 ◽  
Vol 98 (6) ◽  
Author(s):  
R. Juncosa ◽  
I. Font ◽  
J. Delgado
Keyword(s):  
Ion Exchange ◽  
Radioactive Decay ◽  
Chemical Species ◽  
High Level Waste ◽  
Chemical Components ◽  
Clay Material ◽  
Decay Series ◽  
And Migration ◽  
High Level ◽  
Radioactive Species

AbstractRadioactive decay is an important subject to take into account when studying the thermo-hydro-dynamic behavior of the buffer clay material used in the containment of radioactive waste. The modern concepts for the multibarrier design of a repository of high level waste in deep geologic formations consider that once canisters have failed, the buffer clay material must ensure the retention and/or delay of radionuclides within the time framework given in the assessment studies. Within the clay buffer, different chemical species are retarded/fixed according to several physicochemical processes (ion exchange, surface complexation, precipitation, matrix diffusion, ...) but typical approaches do not consider the eventuality that radioactive species change their chemical nature (The radioactive decay of an element takes place independently of the phase (aqueous, solid or gaseous) to which it belongs. This means that, in terms of radionuclide fixation, some geochemical processes will be effective scavengers (for instance mineral precipitation of crystal growth) while others will not (for instance ion exchange and/or sorption).In this contribution we present a reactive radioactive decay model of any number of chemical components including those that belong to decay series. The model, which is named FLOW-DECAY, also takes into account flow and isotopic migration and it has been applied considering a hypothetical model scenario provided by the project ENRESA 2000 and direct comparison with the results generated by the probabilistic code GoldSim. Results indicate that FLOW-DECAY may simulate the decay processes in a similar way that GoldSim, being the differences related to factors associated to code architecture.

Transparent Tools for Uncertainty Analysis in High Level Waste Disposal Facilities Safety

2007 ◽  
Author(s):  
Francisco Luiz de Lemos ◽  
Karl-Heinz Helmuth ◽  
Terry Sullivan
Keyword(s):  
Fuzzy Logic ◽  
Uncertainty Analysis ◽  
Waste Disposal ◽  
Computational Models ◽  
Cognitive Mapping ◽  
Data Interpretation ◽  
High Level Waste ◽  
Rock Interaction ◽  
And Migration ◽  
High Level

In this paper some results of a further development of a technical cooperation project, initiated in 2004, between the CDTN/CNEN, The Brazilian National Nuclear Energy Commission, and the STUK, The Finnish Radiation and Nuclear Safety Authority, are presented. The objective of this project is to study applications of fuzzy logic, and artificial intelligence methods, on uncertainty analysis of high level waste disposal facilities safety assessment. Uncertainty analysis is an essential part of the study of the complex interactions of the features, events and processes, which will affect the performance of the HLW disposal system over the thousands of years in the future. Very often the development of conceptual and computational models requires simplifications and selection of over conservative parameters that can lead to unrealistic results. These results can mask the existing uncertainties which, consequently, can be an obstacle to a better understanding of the natural processes. A correct evaluation of uncertainties and their rule on data interpretation is an important step for the improvement of the confidence in the calculations and public acceptance. This study focuses on dissolution (source), solubility and sorption (sink) as key processes for determination of release and migration of radionuclides. These factors are affected by a number of parameters that characterize the near and far fields such as pH; temperature; redox conditions; and other groundwater properties. On the other hand, these parameters are also consequence of other processes and conditions such as water rock interaction; pH and redox buffering. Fuzzy logic tools have been proved to be suited for dealing with interpretation of complex, and some times conflicting, data. For example, although some parameters, such as pH and carbonate, are treated as independent, they have influence in each other and on the solubility. It is used the technique of fuzzy cognitive mapping is used for analysis of effects of variations on one parameter on the others in a system. This technique uses the concept of fuzzy sets to represent the “quality” of the relation between parameters rather then deterministic numbers.

Laboratory and Modelling Studies of Sodium Benionite Grounmater Interaction

1986 ◽  
Vol 84 ◽  
Author(s):  
M. Sneujman ◽  
H. Uotiia ◽  
J. Rantanen
Keyword(s):  
Near Field ◽  
Chemical Species ◽  
Fluid Phase ◽  
High Level Waste ◽  
Sodium Bentonite ◽  
Model Calculations ◽  
Buffer Material ◽  
Modelling Studies ◽  
Calcite Saturation ◽  
High Level

AbstractAccording to the present Finnish concept sodium bentonite will be used as a buffer material in the repository for high-level waste. Experimental and theoretical studies treating the effect of bentonite upon the chemical conditions in a repository have been initiated with the object of specifying the chemistry of the near field.Sodium bentonite was let react with water under anaerobic conditions at 25°C for 540 days, during which time six fluid samples were extracted for the chemical analysis of 15 chemical species. The generated fluid phase was alkaline (PH = 9…10) and contained a high amount of bicarbonate. Also a low redox-potential was measured. The fluid phase chemistry was investigated using the geochemical code PHREEM. Calcite saturation was observed in all fluid samples.A modelling of sodium bentonite interaction with water based on the main mineral components of bentonite was also performed with PHREEQE. A fairly good agreement between experimental results and model calculations was observed.

Studies of the Fundamental Chemistry of Hanford Tank Sludges

2003 ◽  
Author(s):  
Gregg J. Lumetta ◽  
Brian M. Rapko ◽  
Herman M. Cho
Keyword(s):  
Complex Mixture ◽  
Chemical Species ◽  
Department Of Energy ◽  
High Level Waste ◽  
Resonance Spectroscopy ◽  
X Ray Diffraction ◽  
Hanford Site ◽  
Mineral Phases ◽  
Fe Oxyhydroxides ◽  
High Level

The U.S. Department of Energy has embarked on an effort to retrieve, immobilize, and dispose of the 2.1 × 105 m3 of radioactive tank wastes that were generated during weapons production and other operations at the Hanford Site in Washington State. One of the major challenges associated with this effort is the processing of the 4.2 × 104 m3 of high-level waste sludges. These sludges consist of a complex mixture of amorphous and crystalline mineral phases. The current plan for processing the sludge solids consists of leaching with aqueous NaOH, washing out the NaOH and dissolved components, then vitrifying the solids in borosilicate glass. The purpose of the NaOH leaching step is to remove components such as Al, Cr, and P that can lead to the production of an unacceptable quantity of high-level waste glass. In this paper, we will discuss the chemistry underlying the leaching and washing processes, focusing on the specific mineral phases present in the sludge solids and how these phases respond to the leaching process. The chemical phases present in the Hanford tank sludge solids have been identified through microscopy coupled with electron diffraction and through powder X-ray diffraction. We have also recently been applying nuclear magnetic resonance spectroscopy to characterize chemical species in tank sludge solids. Numerous chemical species have been identified including the aluminum oxy/hydroxides gibbsite and boehmite, aluminosilicates, iron oxy/hydroxides, and mixed Cr/Fe oxyhydroxides. Identification of these phases has led to a more fundamental understanding of the behavior of the various sludge components during leaching; in turn, this understanding will allow for improved process flow sheets. For example, we have shown that certain tank sludges are high in boehmite, Υ-AIOOH. This mineral phase is much more refractory than other AI phases such as gibbsite. Thus, more severe leaching conditions (e.g., increased temperature, NaOH concentration, and leaching duration) are required to remove AI from wastes high in boehmite.

Properties of Bentonite Clay as Buffer Material in High-Level Waste Geological Disposal. Part I: Chemical Species Contained in Bentonite

1987 ◽  
Vol 76 (2) ◽  
pp. 221-228 ◽  
Author(s):  
Masanori Takahashi ◽  
Masayuki Muroi ◽  
Atsuyuki Inoue ◽  
Masahiro Aoki ◽  
Makoto Takizawa ◽  
...  
Keyword(s):  
Chemical Species ◽  
Bentonite Clay ◽  
High Level Waste ◽  
Geological Disposal ◽  
Buffer Material ◽  
High Level

scholarly journals On the Temperature Response in Ice Sheets to Radioactive Waste Deposits

1976 ◽  
Vol 16 (74) ◽  
pp. 89-98
Author(s):  
K. Philberth
Keyword(s):  
Radioactive Waste ◽  
Temperature Increase ◽  
Nuclear Energy ◽  
Thermal Power ◽  
Radioactive Decay ◽  
Ice Sheet ◽  
Temperature Response ◽  
High Level Waste ◽  
The Mean ◽  
High Level

AbstractDisposal of the the radioactive waste from the peaceful use of nuclear energy in the central region of the ice sheet of Greenland or Antarctica has been proposed. This paper demonstrates that an area only 100 km2 on the ice divide is sufficient to dispose of the high-level waste of the whole world for the next 30 years without hazard. The thermal power of the radioactive decay makes the waste containers melt down to a depth of 2 km. Thus the total disintegration heat is spread through a volume of 100 km2 × 2 km. The mean temperature increase in this volume is a few degrees. The temperature increase does not influence the rheology of the ice sheet at any time: for a few ten-thousand years after the dumping the area concerned is too small; later the temperature increase is too small.

Characterization of Electroactive Cs Ion-Exchange Materials using XAS

1996 ◽  
Vol 465 ◽  
Author(s):  
N. J. Hess ◽  
J. H. Sukamto ◽  
S. D. Rassat ◽  
R. T. Hallen ◽  
R. J. Orth ◽  
...  
Keyword(s):  
Ion Exchange ◽  
High Level Waste ◽  
Cubic Phase ◽  
Loaded State ◽  
Single Use ◽  
Exchange Resins ◽  
High Level ◽  
Initial Results ◽  
Deposition Conditions

ABSTRACTVarious ion exchange materials have been proposed for the removal of Cs from high level waste streams produced during the reprocessing of fuel rods. Cs can be released from loaded traditional exchange resins by elution and then the resin can be reused. However large quantities of secondary wastes are generated. Another class of “single use” exchangers is directly incorporated in the loaded state into a solid waste form (e.g. borosilicate glass logs). A third alternative is electroactive ion-exchange materials, where the uptake and elution of Cs are controlled by an applied potential. This approach has several advantages over traditional reusable ion-exchange resins including much reduced secondary waste, higher Cs selectivity, and higher durability.XAS experiments were conducted at the Fe K-edge and Cs Lm-edge on a series of electrochemically produced nickel ferrocyanide films to determine the effects of deposition conditions and subsequent alkali exchange on structural and chemical aspects of the films. The deposition conditions include methods described in the literature and PNNL proprietary procedures. Although the performance and the durability of the films do vary with processing conditions, Fe K-edge EXAFS results indicate that all deposition conditions result in the. formation of the cubic phase. Initial results from Cs Lm-edge EXAFS analysis suggest that the Cs ion is present as a hydrated species.

Selective Radionuclide (Cs+, Sr2+, and Ni2+) Ion-exchange by K2xMgxSn3-xS6(x=0.5-0.95) (KMS-2)

2010 ◽  
Vol 1265 ◽  
Author(s):  
Joshua Leighton Mertz ◽  
Emmanouil J. Manos ◽  
Mercouri Kanatzidis
Keyword(s):  
Ion Exchange ◽  
Inductively Coupled Plasma ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
High Level Waste ◽  
Inductively Coupled ◽  
Inorganic Ion ◽  
The Stability ◽  
High Level

Abstract137Cs and90Sr, both byproducts of the fission process, make up the majority of high-level waste from nuclear power plants.63Ni is a byproduct of the erosion-corrosion process of the reactor components in nuclear energy plants. The concentrations of these ions in solution determine the Waste Class (A,B, or C) and thus selective removal of these ions over large excesses of other ions is necessary to reduce waste and cut costs. Herein we report the use of the Inorganic Ion Specific Media (ISM) K2xMgxSn3-xS6(x=0.5-0.9) (KMS-2) for the ion exchange of Cs+, Sr2+, and Ni2+in several different conditions. We will also report the stability of this new material in the general conditions found at nuclear power plants (pH ˜6-8) and DOE sites (pH>10). Measurements at low concentrations were conducted with inductively coupled plasma mass spectrometry and Kd values are reported for each of the ions in a variety of conditions.

Sign in / Sign up

Export Citation Format

Share Document