Release of Radionuclides from the Near Field by Various Pathways. The Influence by the Sorption Properties in the Near Field.

1991 ◽  
Vol 257 ◽  
Author(s):  
Leonardo Romero ◽  
Wars Neretnieks ◽  
Luis Moreno
Keyword(s):  
Near Field ◽  
Chemical Properties ◽  
Compartment Model ◽  
Flowing Water ◽  
Spent Fuel ◽  
Fracture Zones ◽  
Difference Model ◽  
3 Dimensional ◽  
Damaged Zone ◽  
Canister Wall

ABSTRACTRadionuclides from a damaged canister for spent fuel will leak out through a damage in the canister wall and spread through the surrounding backfill. They will further migrate into water bearing fractures in the rock, up through the backfill into the damaged zone around the drift and into the drift itself. Some substance may also diffuse through the rock to adjacent fracture zones. Underway the nuclides will sorb on the materials along the transport paths. This very complex and variable transport geometry has been modelled using a compartment model which is based on simplifying a full 3 dimensional integrated finite difference model. The simplifications are supplemented by introducing analytical and semianalytical solutions at sensitive locations such as entrances and exits from damages and fractures and in the flowing water. The model has been tested against full 3D solutions with good results. Sample calculations are presented and discussed for a nuclide with the chemical properties of Pu-239.

The Near-Field Transport Code Tullgarn and its Use in Performance Assessment

1992 ◽  
Vol 294 ◽  
Author(s):  
Patrik Sellin ◽  
Nils Kjellbert
Keyword(s):  
Performance Assessment ◽  
Near Field ◽  
Steel Corrosion ◽  
List Type ◽  
Spent Fuel ◽  
Radionuclide Migration ◽  
Transport Code ◽  
Damaged Zone ◽  
Chain Decay ◽  
Resistance Network Model

ABSTRACTThe near-field radionuclide migration code Tullgarn has been developed for performance assessment purposes. As a part of the PROPER-code package it has been successfully applied in the SKB 91 safety analysis.The features and processes included in the code are:- Radioactive chain decay- Different canister failure mechanisms (copper corrosion from sulphide attack, steel corrosion, internal overpressure and initially defective canisters) - Spent fuel dissolution. The model is based on the assumption that the dissolution rate is proportional to the α-dose rate- Transport calculations are done with a resistance-network model. Tullgarn calculates the stationary release of radionuclides from a defect in the canister through the buffer and out into a fracture in the rock or up to the damaged zone under the deposition tunnel.Tullgarn can be used as a stand-alone model for near-field release calculations or as a submodel in an integrated assessment. In the SKB 91 analysis, Tullgarn gave the source term to the far-field model.

Reactive transport modelling of a spent fuel repository in a stiff clay formation considering excavation damaged zones

2004 ◽  
Vol 92 (9-11) ◽  
Author(s):  
Laurent De Windt ◽  
Delphine Pellegrini ◽  
Jan van der Lee
Keyword(s):  
Reactive Transport ◽  
Near Field ◽  
Cementitious Materials ◽  
Special Focus ◽  
Spent Fuel ◽  
Transport Modelling ◽  
Pure Diffusion ◽  
Damaged Zone ◽  
Stiff Clay ◽  
Clay Formation

SummaryThe near-field evolution of a spent fuel disposal in a deep stiff clay formation is studied with the coupled chemistry-transport code HYTEC. The study gives an example that such models can be currently used for geometries (2D and 3D) and time scales (100000 y) relevant for performance assessment. The repository consists of short tunnels with MX80 bentonite barriers and cementitious materials for mechanical support. Cesium, iodine and uranium are released from the waste packages considering instant release fractions and congruent dissolution of the fuel pellets. The calculations are carried out with special focus on the excavation damaged zone (EDZ) comparing diffusion process and different advection scenarios in this zone. Cement represents a source of alkaline perturbations but, under the pure diffusion scenario, the alteration of the multi-barrier system remains limited. The presence of the EDZ does not significantly modify radionuclide migration in the pure diffusion case. The advection scenarios, even with very slow flow velocities, illustrate the possibility of preferential pathways through the EDZ for iodine but show almost no effect on the alkaline plume and cesium migration.

Assessment of Geochemical Containment Properties in the Near-field of a Deep Underground Repository

2002 ◽  
Vol 757 ◽  
Author(s):  
Delphine Pellegrini ◽  
Laurent De Windt
Keyword(s):  
Reactive Transport ◽  
Near Field ◽  
Safety Evaluation ◽  
Distribution Coefficients ◽  
Spent Fuel ◽  
Advective Flow ◽  
Transport Modelling ◽  
Migration Pathway ◽  
Excavation Damaged Zone ◽  
Damaged Zone

ABSTRACTFor safety evaluation of deep repositories, the evolution of chemical containment properties of clayey barriers in spent fuel disposal tunnels are assessed using reactive transport modelling. The disturbances related to cement components are more particularly studied for relevant time scales (100,000 years) and dimensions. Theoretical distribution coefficients (Kd) and maximum concentrations are derived for Cs, Tc and U and their sensitivity to the system evolution estimated. Mineralogical transformations and ion sorption are shown to be interdependent mechanisms controlling the intensity and spatial expansion of the alkaline plume. Simulations for a normal diffusive scenario and an altered one involving an advective flow lead to limited perturbations of the mineralogy and containment properties of the multi-barriers system, but emphasize the possibility of a migration pathway through the excavation damaged zone.

Transport from the Canister to the Biosphere: Using an Integrated Near-and Far-Field Model

1996 ◽  
Vol 465 ◽  
Author(s):  
B. Gylling ◽  
L. Romero ◽  
L. Moreno ◽  
I. Neretnieks
Keyword(s):  
Field Model ◽  
Near Field ◽  
Coupled Model ◽  
Compartment Model ◽  
Far Field ◽  
Model Concept ◽  
Channel Network ◽  
Transport Barrier ◽  
Damage Level ◽  
Field Release

ABSTRACTA coupled model concept which may be used for performance assessment of a nuclear repository is presented. The tool is developed by integration of two models, one near field and one far field model. A compartment model, NUCTRAN, is used to calculate the near field release from a damaged canister. The far field transport through fractured rock is simulated by using CHAN3D, based on a three-dimensional stochastic channel network concept. The near field release depends on the local hydraulic properties of the far field. The transport in the far field in turn depends on where the damaged canister(s) is located. The very large heterogeneities in the rock mass makes it necessary to study both the near field release properties and the location of release at the same time. In order to demonstrate the capabilities of the coupled model concept it is applied on a hypothetical repository located at the Hard Rock Laboratory in Äspö, Sweden. Two main items were studied; the location of a damaged canister in relation to fracture zones and the barrier function of the host rock. In the study of the near field rock as a transport barrier the effect of different tunnel excavation methods which may influence the damage level of the rock around the tunnel was addressed.

scholarly journals Numerical Prediction of Background Buildup of Salinity Due to Desalination Brine Discharges into the Northern Arabian Gulf

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2284 ◽  
Author(s):  
Aaron C. Chow ◽  
Wilbert Verbruggen ◽  
Robin Morelissen ◽  
Yousef Al-Osairi ◽  
Poornima Ponnumani ◽  
...  
Keyword(s):  
Near Field ◽  
Regional Scale ◽  
Arabian Gulf ◽  
Potential Effect ◽  
Horizontal Resolution ◽  
Point Of View ◽  
Far Field ◽  
Exchange Flow ◽  
3 Dimensional ◽  
Desalination Plants

Brine discharges from desalination plants into low-flushing water bodies are challenging from the point of view of dilution, because of the possibility of background buildup effects that decrease the overall achievable dilution. To illustrate the background buildup effect, this paper uses the Arabian (Persian) Gulf, a shallow, reverse tidal estuary with only one outlet available for exchange flow. While desalination does not significantly affect the long-term average Gulf-wide salinity, due to the mitigating effect of the Indian Ocean Surface Water inflow, its resulting elevated salinities, as well as elevated concentrations of possible contaminants (such as heavy metals and organophosphates), can affect marine environments on a local and regional scale. To analyze the potential effect of background salinity buildup on dilutions achievable from discharge locations in the northern Gulf, a 3-dimensional hydrodynamic model (Delft3D) was used to simulate brine discharges from a single hypothetical source location along the Kuwaiti shoreline, about 900 km from the Strait of Hormuz. Using nested grids with a horizontal resolution, comparable to a local tidal excursion (250 m), far field dilutions of about 28 were computed for this discharge location. With this far field dilution, to achieve a total dilution of 20, the near field dilution (achievable using a submerged diffuser) would need to be increased to approximately 70. Conversely, the background build-up means that a near field dilution of 20 yields a total dilution of only about 12.

Assessment of Redox Conditions in the Near Field of Nuclear Waste Repositories: Application to the Swiss high-level and intermediate level waste disposal concept

2003 ◽  
Vol 807 ◽  
Author(s):  
Paul Wersin ◽  
Lawrence H. Johnson ◽  
Bernhard Schwyn
Keyword(s):  
Solid Phase ◽  
Near Field ◽  
Intermediate Level ◽  
Redox Conditions ◽  
High Level Waste ◽  
Redox Potentials ◽  
Spent Fuel ◽  
Reducing Conditions ◽  
High Level ◽  
Waste Repositories

ABSTRACTRedox conditions were assessed for a spent fuel and high-level waste (SF/HLW) and an intermediate-level waste (ILW) repository. For both cases our analysis indicates permanently reducing conditions after a relatively short oxic period. The canister-bentonite near field in the HLW case displays a high redox buffering capacity because of expected high activity of dissolved and surface-bound Fe(II). This is contrary to the cementitious near field in the ILW case where concentrations of dissolved reduced species are low and redox reactions occur primarily via solid phase transformation processes.For the bentonite-canister near field, redox potentials of about -100 to -300 mV (SHE) are estimated, which is supported by recent kinetic data on U, Tc and Se interaction with reduced iron systems. For the cementitious near field, redox potentials of about -200 to -800 mV are estimated, which reflects the large uncertainties related to this alkaline environment.

The geological research in France - The Dosssier 2005 Argile

2006 ◽  
Vol 985 ◽  
Author(s):  
Frederic Plas ◽  
Jacques WENDLING
Keyword(s):  
Near Field ◽  
Concept Design ◽  
Dose Calculations ◽  
Spent Fuel ◽  
Geological Medium ◽  
Source Data ◽  
Underground Research Laboratory ◽  
Broad Outline ◽  
Geological Research

AbstractAt the end of fifteen years of researchs defined by the French act of December 30, 1991 on radwaste management, Andra gave a report, “Dossier Argile 2005”, which concluded with the feasibility of a reversible disposal in the argillaceous Callovo-Oxfordien formation studied by means of an underground research laboratory at Meuse/Haute-Marne site. Starting from source data like the characteristics of the geological medium and the waste inventory, the process followed by Andra to achieve at this conclusion is of type sequential and iterative between concept design, scientific knowledge, in particular that of the phenomenological evolution of the reposiroty and its geological environment from operating period to long term, and Safety assessment. The “Dossier Argile 2005” covers a broad radwaste inventory, ILLW, HLW and Spent Fuel, so that it makes it possible to cover whole of the technological, scientific and safety topics. This article will give an overview of the geological disposal studies in France and draw the main conclusion of the Dossier 2005 Argile. It will be focused on the near field (Engineering components and near field host rock), while considering if necessary its integration within the whole system. After a short description of the concepts (incl. waste inventory and the characteristics of the Meuse/Haute the Marne site) and the functions of the components of repository and geological medium, one will describe successively the broad outline of the phenomenological evolution of repository and the geological medium in near field, by in particular releasing the time scales of processes and uncertainties of knowledge. On this basis, one will indicate the safety scenarios which were considered and the broad outline of performance and dose calculations. Lessons learn from the Dossier 2005 Argile will be discussed and perspective and priority for future will be indicated.

The Integrated Project NF-PRO: Recent Advances in European Research on the Near-Field System

2007 ◽  
Author(s):  
Alain Sneyers ◽  
Bernd Grambow ◽  
Pedro Herna´n ◽  
Hans-Joachim Alheid ◽  
Jean-Franc¸ois Aranyossy ◽  
...  
Keyword(s):  
European Commission ◽  
Near Field ◽  
Framework Programme ◽  
European Research ◽  
Spent Fuel ◽  
Field System ◽  
Geological Repository ◽  
Integrated Project ◽  
High Level ◽  
Sixth Framework Programme

The Integrated Project NF-PRO (Sixth Framework Programme by the European Commission) investigates key-processes in the near-field of a geological repository for the disposal of high-level vitrified waste and spent fuel. The paper discusses the project scope and content and gives a summary overview of advances made by NF-PRO.

Zirconia Inert Matrix Fuel for Plutonium and Minor Actinides Management in Reactors and as an Ultimate Waste Form

2008 ◽  
Vol 1104 ◽  
Author(s):  
Claude Degueldre ◽  
Wolfgang Wiesenack
Keyword(s):  
Near Field ◽  
Fission Products ◽  
Minor Actinides ◽  
Spent Fuel ◽  
Geological Disposal ◽  
Inert Matrix Fuel ◽  
Inert Matrix ◽  
Fuel Pellets ◽  
Reducing Conditions ◽  
Deep Geological Disposal

AbstractA plutonia stabilised zirconia doped with yttria and erbia has been selected as inert matrix fuel (IMF) at PSI. The results of experimental irradiation tests on yttria-stabilised zirconia doped with plutonia and erbia pellets in the Halden research reactor as well as a study of zirconia solubility are presented. Zirconia must be stabilised by yttria to form a solid solution such as MAz(Y,Er)yPuxZr1-yO2-ζ where minor actinides (MA) oxides are also soluble. (Er,Y,Pu,Zr)O2-ζ (with Pu containing 5% Am) was successfully prepared at PSI and irradiated in the Halden reactor. Emphasis is given on the zirconia-IMF properties under in-pile irradiation, on the fuel material centre temperatures and on the fission gas release. The retention of fission products in zirconia may be stronger at similar temperature, compared to UO2. The outstanding behaviour of plutonia-zirconia inert matrix fuel is compared to the classical (U,Pu)O2 fuels. The properties of the spent fuel pellets are presented focusing on the once through strategy. For this strategy, low solubility of the inert matrix is required for geological disposal. This parameter was studied in detail for a range of solutions corresponding to groundwater under near field conditions. Under these conditions the IMF solubility is about 109 times smaller than glass, several orders of magnitude lower than UO2 in oxidising conditions (Yucca Mountain) and comparable in reducing conditions, which makes the zirconia material very attractive for deep geological disposal. The behaviour of plutonia-zirconia inert matrix fuel is discussed within a burn and bury strategy.

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