Two-person game model of long-term safeguards for a final repository for spent nuclear fuel

ABSTRACTThe long-term behavior of the UO2 fuel matrix under conditions of the Belgian “Supercontainer design” was investigated by dissolution tests of high burn-up spent nuclear fuel (SNF) in high alkaline solution under 40 bar of (Ar + 8%H2) atmosphere. Four fragments of SNF, obtained from a pellet previously leached during two years, were exposed to young cement water with Ca (YCWCa) under 3.2 bar H2 partial pressure in four single/independent autoclave experiments for a period of 59, 182, 252 and 341 days, respectively. After a decrease of the concentration of dissolved 238U, which is associated with a reduction of U(VI) to U(IV), the concentration of 238U in solution is constant in the experiments running for 252 and 341 days. These observations indicate an inhibition of the matrix dissolution due to the presence of H2. A slight increase in the concentration of 90Sr and 137Cs in the aqueous solution indicates that there is still dissolution of the grain boundaries. These findings are similar to those reported for spent nuclear fuel corrosion in synthetic near neutral pH solutions.

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Problems of Long Term and Safe Storage of Unloaded and Non-Unloaded Spent Nuclear Fuel for Nuclear Submarines with Liquid-Metal Coolant

Remaining Issues in the Decommissioning of Nuclear Powered Vessels ◽

10.1007/978-94-010-0209-7_37 ◽

2003 ◽

pp. 341-348 ◽

Cited By ~ 1

Author(s):

D. Pankratov ◽

V. Andreyanov ◽

M. Bugrevev ◽

A. Dedoul ◽

Ye. Efimov ◽

...

Keyword(s):

Liquid Metal ◽

Nuclear Fuel ◽

Spent Nuclear Fuel ◽

Liquid Metal Coolant ◽

Safe Storage ◽

Metal Coolant

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Modeling of decay heat removal from CONSTOR RBMK-1500 casks during long-term storage of spent nuclear fuel

Energy ◽

10.1016/j.energy.2018.12.217 ◽

2019 ◽

Vol 170 ◽

pp. 978-985 ◽

Cited By ~ 3

Author(s):

R. Poškas ◽

V. Šimonis ◽

H. Jouhara ◽

P. Poškas

Keyword(s):

Nuclear Fuel ◽

Spent Nuclear Fuel ◽

Heat Removal ◽

Decay Heat ◽

Long Term Storage ◽

Term Storage

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Landscape Modeling for Dose Calculations in the Safety Assessment of a Repository for Spent Nuclear Fuel

11th International Conference on Environmental Remediation and Radioactive Waste Management, Parts A and B ◽

10.1115/icem2007-7115 ◽

2007 ◽

Cited By ~ 1

Author(s):

Tobias Lindborg ◽

Ulrik Kautsky ◽

Lars Brydsten

Keyword(s):

Nuclear Fuel ◽

Safety Assessment ◽

Spent Nuclear Fuel ◽

Landscape Model ◽

Landscape Development ◽

Surface Hydrology ◽

Site Investigations ◽

Time Period ◽

The Individual

The Swedish Nuclear Fuel and Waste Management Co., (SKB), pursues site investigations for the final repository for spent nuclear fuel at two sites in the south eastern part of Sweden, the Forsmark- and the Laxemar site (figure 1). Data from the two site investigations are used to build site descriptive models of the areas. These models describe the bedrock and surface system properties important for designing the repository, the environmental impact assessment, and the long-term safety, i.e. up to 100,000 years, in a safety assessment. In this paper we discuss the methodology, and the interim results for, the landscape model, used in the safety assessment to populate the Forsmark site in the numerical dose models. The landscape model is built upon ecosystem types, e.g. a lake or a mire, (Biosphere Objects) that are connected in the landscape via surface hydrology. Each of the objects have a unique set of properties derived from the site description. The objects are identified by flow transport modeling, giving discharge points at the surface for all possible flow paths from the hypothetical repository in the bedrock. The landscape development is followed through time by using long-term processes e.g. shoreline displacement and sedimentation. The final landscape model consists of a number of maps for each chosen time period and a table of properties that describe the individual objects which constitutes the landscape. The results show a landscape that change over time during 20,000 years. The time period used in the model equals the present interglacial and can be used as an analogue for a future interglacial. Historically, the model area was covered by sea, and then gradually changes into a coastal area and, in the future, into a terrestrial inland landscape. Different ecosystem types are present during the landscape development, e.g. sea, lakes, agricultural areas, forest and wetlands (mire). The biosphere objects may switch from one ecosystem type to another during the modeled time period, from sea to lake, and from lake to mire and finally, some objects are transformed into agricultural area due to favorable farming characteristics.

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NDE of copper canisters for long-term storage of spent nuclear fuel from the Swedish nuclear power plants

10.1117/12.484346 ◽

2003 ◽

Author(s):

Tadeusz Stepinski

Keyword(s):

Nuclear Fuel ◽

Nuclear Power ◽

Power Plants ◽

Nuclear Power Plants ◽

Spent Nuclear Fuel ◽

Long Term Storage ◽

Term Storage

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SR 97: Post-Closure Safety for a KBS 3 Deep Repository for Spent Nuclear Fuel - Overview -

MRS Proceedings ◽

10.1557/proc-663-739 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

Allan Hedin ◽

Ulrik Kautsky ◽

Lena Morén ◽

Jan-Olof Selroos ◽

Patrik Sellin ◽

...

Keyword(s):

Nuclear Fuel ◽

Spent Nuclear Fuel ◽

Bentonite Clay ◽

High Strength ◽

Functional Requirements ◽

Future Evolution ◽

Site Investigations ◽

Base Scenario ◽

Shed Light

ABSTRACTIn preparation for coming site investigations for siting of a deep repository for spent nuclear fuel, the Swedish Nuclear Fuel and Waste Management Company, SKB has carried out the long- term safety assessment SR 97, requested by the Swedish Government. The repository is of the KBS-3 type, where the fuel is placed in isolating copper canisters with a high-strength cast iron insert. The canisters are surrounded by bentonite clay in individual deposition holes at a depth of 500 m in granitic bedrock. Geological data are taken from three sites in Sweden to shed light on different conditions in Swedish granitic bedrock.The future evolution of the repository system is analyzed in the form of five scenarios. The first is a base scenario where the repository is postulated to be built entirely according to specifications and where present-day conditions in the surroundings, including climate, persist. The four other scenarios show the evolution if the repository contains a few initially defective canisters, in the event of climate change, in the event of earthquakes, and in the event of future inadvertent human intrusion.The principal conclusion of the assessment is that the prospects of building a safe deep repository for spent nuclear fuel in Swedish granitic bedrock are very good. The results of the assessment also serve as a basis for formulating requirements and preferences regarding the bedrock in site investigations, for designing a program for site investigations, for formulating functional requirements on the repository's barriers, and for prioritization of research.

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Depleted Uranium Oxides and Silicates as Spent Nuclear Fuel Waste Package Fill Materials

MRS Proceedings ◽

10.1557/proc-465-615 ◽

1996 ◽

Vol 465 ◽

Cited By ~ 2

Author(s):

C. W. Forsberg

Keyword(s):

Nuclear Fuel ◽

Spent Nuclear Fuel ◽

Chemical Species ◽

Fission Products ◽

Depleted Uranium ◽

Improve Performance ◽

Waste Package ◽

Reducing Conditions ◽

Nuclear Fuel Waste

ABSTRACTA new repository waste package (WP) concept for spent nuclear fuel (SNF) is being investigated. The WP uses depleted uranium (DU) to improve performance and reduce the uncertainties of geological disposal of SNF. The WP would be loaded with SNF. Void spaces would then be filled with DU (∼0.2 wt % 235U) dioxide (UO2) or DU silicate-glass beads.Fission products and actinides can not escape the SNF UO2 crystals until the UO2 dissolves or is transformed into other chemical species. After WP failure, the DU fill material slows dissolution by three mechanisms: (1) saturation of WP groundwater with DU and suppression of SNF dissolution, (2) maintenance of chemically reducing conditions in the WP that minimize SNF solubility by sacrificial oxidation of DU from the +4 valence state, and (3) evolution of DU to lower-density hydrated uranium silicates. The fill expansion minimizes water flow in the degraded WP. The DU also isotopically exchanges with SNF uranium as the SNF degrades to reduce long-term nuclear-criticality concerns.

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Fracture smectite as a long-term sink for natural radionuclides – indications from unusual U-series disequilibria

Radiochimica Acta ◽

10.1524/ract.2000.88.9-11.763 ◽

2000 ◽

Vol 88 (9-11) ◽

Cited By ~ 6

Author(s):

N. Marcos ◽

J. Suksi ◽

H. Ervanne ◽

K. Rasilainen

Keyword(s):

Nuclear Fuel ◽

Chemical Stability ◽

Spent Nuclear Fuel ◽

Activity Ratio ◽

Near Field ◽

Natural Radionuclides ◽

Mineral Component ◽

Considerable Part ◽

Preferential Loss

Occurrence of natural U in fracture smectite (main mineral component of bentonite) was studied as an analogue to radionuclide behaviour in the near-field of spent nuclear fuel repository. Elevated U content (57 ppm) was observed in fracture smectite sampled from the surface of water-carrying fracture in granite pegmatite at a depth of 70 m. The current groundwater conditions are oxidising at the sampled point. The U-234/U-238 activity ratio (AR) measured in the bulk U and in its sequentially extracted phases, displays unusually low value (around 0.30). Low AR indicates preferential loss of the U-234 isotope from the system. Because the U-234 loss can also be seen in the Th-230/U-234 activity ratio (clearly over 1), the selective removal of the U-234 isotope must have taken place more recently than what is needed to equilibrate Th-230/U-234 pair (i.e. 350000 a). To explain the selective U-234 loss from the smectite we postulate that bulk U is in reduced +4 form and a considerable part of the U-234 isotope in easily leachable oxidised +6 form. This study suggests that the long-term chemical stability of the bulk U in the smectite is due to irreversible fixation of U in the reduced +4 form.

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