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Boyle C.H.,Nuclear Waste Management Organization of Canada | Meguid S.A.,King's College
Nuclear Engineering and Design | Year: 2015

The preferred method for disposal of used nuclear fuel is underground emplacement in a Deep Geological Repository (DGR). Many countries have light water reactor fuels which require large Used Fuel Container or Canister (UFC) designs weighing up to 25 ton for containment. In contrast, Canada exclusively uses heavy water reactor fuel, which is substantially smaller. This has led the Nuclear Waste Management Organization (NWMO) to create a novel UFC, which uses standard pressure vessel grade steel for structural containment and a thick, integrally bonded copper coating applied to the exterior surface for corrosion protection. Currently, the coating is applied using two different methods: electrodeposition and gas dynamic cold spray. This novel copper coating needs to be fully validated to ensure adequate mechanical strength and chemical resistance for use under repository conditions. Detailed mechanical and corrosion testing programs were undertaken. Mechanical tests indicated that adhesion strengths exceeded 45 MPa and tensile properties were comparable to wrought copper. A Finite Element Model (FEM) of the copper-steel composite was created and validated using three point bend tests. This model accurately predicts the response of the composite, including large deformation and debonding failure mechanisms. Now validated, this model will be used to assess the performance of the coating on the full-scale UFC under simulated DGR loading conditions. © 2015 The Authors. Published by Elsevier B.V.

Stroes-Gascoyne S.,Atomic Energy of Canada | Hamon C.J.,Atomic Energy of Canada | Maak P.,Nuclear Waste Management Organization of Canada | Russell S.,Nuclear Waste Management Organization of Canada
Applied Clay Science | Year: 2010

The Canadian approach for long-term management of used nuclear fuel waste is Adaptive Phased Management (APM) which includes development of a Deep Geological Repository (DGR) and placement of nuclear fuel waste in corrosion-resistant copper containers excavated at a depth of 500-1000 m in a suitable host rock formation. The containers would be surrounded by compacted bentonite-based buffers and backfills. This study examined the conditions required to suppress microbial activity in compacted bentonite, such that microbially influenced corrosion (MIC) of copper waste containers in a future DGR would be insignificant. Experiments (of 40-90 days duration) were carried out to determine the effects of dry density and porewater salinity on swelling pressure, water activity (aw) and the culturable and viable microbial community indigenous to MX-80 Wyoming bentonite. A low aw (< 0.96) and a swelling pressure > 2 MPa appear to suppress microbial aerobic culturability below background levels (2.1 × 102 Colony-Forming Units/g) in as-purchased bentonite. To actually impose conditions of aw < 0.96 and swelling pressure > 2 MPa in compacted bentonite in a DGR, dry density needs to be maintained at 1.6 g/cm3 or higher for porewater salinities at ≤ 50 g/L. High porewater salinity (> 100 g/L) also keeps aw < 0.96 and aerobic culturability below background values. Under such conditions, cells likely survive as dormant cells or inactive spores (as suggested by phospholipid fatty acid analysis), which reduces the possibility of significant MIC. Observations in natural clay-rich environments support these findings. The geological timescale of microbial survival in dormant form is at present unknown. Interfacial locations in a DGR could form environments where (temporarily at least) the physical conditions necessary to suppress microbial activity would not always be met. The extent and potential importance of such interfaces with respect to revived microbial activity (and MIC) in a DGR require further study. © 2008 Elsevier B.V. All rights reserved.

Razdan M.,University of Western Ontario | Hall D.S.,University of Western Ontario | Hall D.S.,University of Ottawa | Keech P.G.,University of Western Ontario | And 2 more authors.
Electrochimica Acta | Year: 2012

The present study aims to investigate the electrochemical reduction of a range of H 2O 2 concentrations on a 1.5 at.% SIMFUEL rotating disk electrode over the pH range 1-4. The peroxide reduction mechanism is determined to occur either on a U V-containing surface layer of composition U IV 1-2xU V 2xO 2+x or on an adsorbed U V-containing surface intermediate depending on the surface composition which is determined by solution pH and H 2O 2 concentration. The U IV 1-2xU V 2xO 2+x catalytic surface lattice layer, if formed, is stable and rotation disk studies have demonstrated that H 2O 2 reduction on this surface achieves the diffusion-controlled limit at sufficiently negative overpotentials. However, the adsorbed U V-containing surface intermediate is unstable and can be destroyed by electrochemical reduction to its original state, i.e. UO 2, or by chemical oxidation to U VI prior to dissolution as UO 2 2+. The instability of this surface intermediate limits its availability which prevents significant H 2O 2 reduction and yields currents below the diffusion-controlled limit. The occurrence of both reduction mechanisms demonstrates the influence of locally established surface compositions and the switch from one to the other appears to be controlled by surface diffusion conditions and the bulk pH and H 2O 2 concentrations. © 2012 Elsevier Ltd. All rights reserved.

Sherar B.W.A.,Blade Energy Partners | Keech P.G.,Nuclear Waste Management Organization of Canada | Shoesmith D.W.,University of Western Ontario
Corrosion Science | Year: 2013

Severe corrosion damage may occur when gas transmission pipelines are exposed, at disbonded coating locations, to trapped waters containing sulfide followed by secondary exposure to air. Aerobic corrosion with sulfide was investigated in a long-term corrosion experiment in which corrosion was monitored by measurement of the corrosion potential and polarization resistance obtained from linear polarization resistance measurements. The properties and composition of the corrosion product deposits formed were determined using scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy. A switch from aerobic to aerobic-with-sulfide corrosion doubles the relative corrosion rate. © 2012 Elsevier Ltd.

Mantagaris E.,Nuclear Waste Management Organization of Canada
Canadian Nuclear Society - 35th Annual Conference of the Canadian Nuclear Society and 38th CNS/CNA Student Conference 2015 | Year: 2015

This Panel provides an international focus on long-term plans for managing used nuclear fuel. The Panel brings together representatives from a range of organizations mandated to advance progress with the long-term management of used nuclear fuel. Specifically, the Panel discussion will highlight the status of national policies and programs through presentations from Europe and North America.

Hatton C.,Nuclear Waste Management Organization of Canada
Canadian Nuclear Society - 35th Annual Conference of the Canadian Nuclear Society and 38th CNS/CNA Student Conference 2015 | Year: 2015

The Nuclear Waste Management Organization (NWMO) is responsible for the implementation of Adaptive Phased Management (APM), the federally-approved plan for the safe long-term management of Canada's used nuclear fuel. Under the APM plan, used nuclear fuel will ultimately be placed within a deep geological repository in a suitable rock formation. In implementing APM, the NWMO is committed to ensure consistency with international best practices in the development of its repository system, including any advances in technology. In 2012, the NWMO undertook an optimization study to look at both the design and manufacture of its engineered barriers. This study looked at current technologies for the design and manufacture of used fuel containers, placement technologies, repository design, and buffer and sealing systems, while taking into consideration the state of the art worldwide in repository design and acceptance. The result of that study is the current Canadian engineered barrier system, consisting of a 2.7 tonne used fuel container with a carbon-steel core, copper-coated surface and welded spherical heads. The used fuel container is encapsulated in a bentonite buffer box at the surface and then transferred underground. Once underground, the used fuel is placed into a repository room which is cut into the rock using traditional drill-and-blast technologies. This paper explains the logic for the selection of the container and sealing system design and the development of innovative technologies for their manufacture including the use of laser welding, cold spray and pulsed-electrodeposition copper coating for the manufacture of the used fuel container, isostatic presses for the production of the one-piece bentonite blocks, and slip-skid technologies for placement into the repository.

Mantagaris E.,Nuclear Waste Management Organization of Canada
Canadian Nuclear Society - 35th Annual Conference of the Canadian Nuclear Society and 38th CNS/CNA Student Conference 2015 | Year: 2015

The Transportation Panel brings together six representatives from a range of Canadian and international organizations involved in the shipment of used nuclear fuel. The panel will highlight the robustness of the package used to ensure safety, the extensive experience transporting used nuclear fuel around the world, and the important role of the regulators. In addition, Canada's technical and engagement programs for transporting used nuclear fuel will be presented. © Copyright 2015 by the Canadian Nuclear Society. All rights reserved.

Clark I.D.,University of Ottawa | Al T.,University of New Brunswick | Jensen M.,Nuclear Waste Management Organization of Canada | Kennell L.,Nuclear Waste Management Organization of Canada | And 3 more authors.
Geology | Year: 2013

Consideration of the geosphere for isolation of nuclear waste has generated substantial interest in the origin, age, and movement of fluids and gases in low-permeability rock formations. Here, we present profiles of isotopes, solutes, and helium in porewaters recovered from 860 m of Cambrian to Devonian strata on the eastern flank of the Michigan Basin. Of particular interest is a 240-m-thick, halite-mineralized, Ordovician shale and carbonate aquiclude, which hosts Br--enriched, post-dolomitic brine (5.8 molal Cl) originating as evaporated Silurian seawater. Authigenic helium that has been accumulating in the aquiclude for more than 260 m.y. is found to be isolated from underlying allochthonous, 3He-enriched helium that originated from the rifted base of the Michigan Basin and the Canadian Shield. The Paleozoic age and immobility of the pore fluids in this Ordovician aquiclude considerably strengthen the safety case for deep geological repositories, but also provide new insights into the origin of deep crustal brines and opportunities for research on other components of a preserved Paleozoic porewater system. © 2013 Geological Society of America.

Keech P.G.,Nuclear Waste Management Organization of Canada
14th International High-Level Radioactive Waste Management Conference, IHLRWMC 2013: Integrating Storage, Transportation, and Disposal | Year: 2013

Within ongoing work, NWMO is demonstrating that copper remains a viable corrosion barrier for used fuel nuclear containers, emplaced in a deep geological repository. Coated samples, manufactured via cold spray and electrodeposition have been produced. Corrosion testing for coated samples and wrought samples reveals that cold spray samples behave similar to wrought samples in 3 mol/L NaCl solution at room temperature. When oxygen is absent, corrosion has not been observed. When higher salinity and temperatures are used, wrought copper samples produce a small amount of hydrogen, consistent with corrosion on the order of a few nm/y during the first few months of exposure testing in bulk solutions.

Boyle C.,Nuclear Waste Management Organization of Canada
14th International High-Level Radioactive Waste Management Conference, IHLRWMC 2013: Integrating Storage, Transportation, and Disposal | Year: 2013

The Nuclear Waste Management Organization is advancing its reference Used Fuel Container design as well as investigating novel alternative designs. The structural evaluation of the containers must follow best international practices, demonstrated via the use of national and international codes and standards. However, none currently address the unique challenges of disposal containers. This work proposes the use of applicable subsections of the American Society of Mechanical Engineers' Boiler and Pressure Vessel Code with modifications for disposal containers. This methodology was then utilized to evaluate and size a conceptual Used Fuel Container designed specifically for CANDU fuel. The inclusion of initial geometric imperfections as required by the code reduced the plastic collapse load by up to 13.6%; however, the proposed container still met all acceptance criteria.

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