Showing papers by "Atomic Energy of Canada Limited published in 2012"

Nuclear-based hydrogen production with a thermochemical copper–chlorine cycle and supercritical water reactor: equipment scale-up and process simulation

Abstract: SUMMARY Issues related to equipment scale-up and process simulation are described for a thermochemical cycle driven by nuclear heat from Canada's proposed Generation IV reactor (Super-Critical Water-Cooled Reactor; SCWR), which is a CANDU derivative using supercritical water cooling. The copper–chlorine (Cu-Cl) cycle has been identified by Atomic Energy of Canada Limited as the most promising cycle for thermochemical hydrogen production with SCWR. Water is decomposed into hydrogen and oxygen through intermediate Cu-Cl compounds. This article outlines the challenges and design issues of hydrogen production with a Cu-Cl cycle coupled to Canada's nuclear reactors. The processes are simulated using the Aspen Plus process simulation code, allowing the cycle efficiency and possible efficiency improvements to be examined. The results are useful to assist the development of a lab-scale cycle demonstration, which is currently being undertaken at the University of Ontario Institute of Technology in collaboration with numerous partners. Copyright © 2010 John Wiley & Sons, Ltd.

Water Chemistry in a Supercritical Water-Cooled Pressure Tube Reactor

Abstract: The long-term viability of a supercritical water-cooled reactor (SCWR) will depend on the ability of designers and operators to control and maintain water chemistry conditions that will minimize co...

On the development of microstructures and residual stresses during laser cladding and post-heat treatments

Abstract: In this article, laser cladding process with a blown powder feeding was used to deposit nickel-based IN-625 superalloy, cobalt-based hardfacing Stellite 6 alloy and high-vanadium CPM 10V tool steel onto a similar or dissimilar base material, respectively, to investigate the development and controllability of process-induced residual stresses in the clad and to analyse their correlation with microstructural evolutions of the clad and heat-affected zone (HAZ) during cladding and post-heat treatments. The residual stresses were evaluated using the hole-drilling method as per ASTM E837-95, whereas the microstructures were studied using X-ray diffractometer, optical microscope and scanning electron microscope. A particular attention was paid to combined effect of both clad and HAZ on the build-up of residual stresses in the clad. It is expected that the experimental results will form a useful addition to the existing knowledge with respect to the topic and, more significantly, to promote confidence on industrial applications of laser-clad IN-625, Stellite 6 and CPM 10V materials.

Material Performance in Supercritical Water

Abstract: The Supercritical water-cooled reactor (SCWR) design has been selected as one of the Generation IV reactor concepts because of its higher thermal efficiency and plant simplification compared to current light water reactors (LWRs). Reactor operating conditions call for a core coolant temperature between 280 and 620 °C at a pressure of 25 MPa and maximum expected neutron damage levels to any replaceable or permanent core component of 15 dpa (thermal reactor design) and 100 dpa (fast reactor design). Throughout the core, corrosion, stress corrosion cracking, and the effect of irradiation on these degradation modes are critical issues. This chapter reviews the current understanding of the response of candidate materials for SCWR systems, focusing on the corrosion and stress corrosion cracking response, and highlights the design trade-offs associated with certain alloy systems.

Validation of QuickScan dicentric chromosome analysis for high throughput radiation biological dosimetry.

Abstract: Currently, the dicentric chromosome assay (DCA) is used to estimate radiation doses to individuals following accidental radiological and nuclear overexposures when traditional dosimetry methods are not available. While being an exceptionally sensitive method for estimating doses by radiation, conventional DCA is time-intensive and requires highly trained expertise for analysis. For this reason, in a mass casualty situation, triage-quality conventional DCA struggles to provide dose estimations in a timely manner for triage purposes. In Canada, a new scoring technique, termed DCA QuickScan, has been devised to increase the throughput of this assay. DCA QuickScan uses traditional DCA sample preparation methods while adapting a rapid scoring approach. In this study, both conventional and QuickScan methods of scoring the DCA assay were compared for accuracy and sensitivity. Dose response curves were completed on four different donors based on the analysis of 1,000 metaphases or 200 events at eight to nine dose points by eight different scorers across two laboratories. Statistical analysis was performed on the data to compare the two methods within and across the laboratories and to test their respective sensitivities for dose estimation. This study demonstrated that QuickScan is statistically similar to conventional DCA analysis and is capable of producing dose estimates as low as 0.1 Gy but up to six times faster. Therefore, DCA QuickScan analysis can be used as a sensitive and accurate method for scoring samples for radiological biodosimetry in mass casualty situations or where faster dose assessment is required.

Ultra-trace determination of plutonium in urine samples using a compact accelerator mass spectrometry system operating at 300 kV

Abstract: Accelerator mass spectrometry (AMS) is a very sensitive and robust technique for analysis of long-lived radionuclides. Employment of the AMS technique can reduce the demands on sample preparation chemistry, due to its high rejection of interferences and low susceptibility to sample matrix. This is particularly of interest for ultra-trace determination of 239Pu in bioassay and environmental samples, as other mass spectrometric methods such as inductively coupled plasma mass spectrometry (ICP-MS) can suffer from isobaric mass interferences by the presence of uranium in the sample. A rapid sample preparation method for analysis of Pu at femtogram levels in large volume urine samples is described. Using the compact ETH AMS Tandy facility operating at ∼300 kV, the method was validated by analysing urine samples spiked with known amounts of 239/240/241Pu ranging from 1 to 30 fg. The detection limits for the method were estimated to be 0.38 fg for 239Pu, 0.40 fg for 240Pu and 0.08 fg for 241Pu in 1400 mL of urine.

Modeling gas formation and mineral precipitation in a granular iron column.

Abstract: In granular iron permeable reactive barriers (PRBs), hydrogen gas formation, entrapment and release of gas bubbles, and secondary mineral precipitation have been known to affect the permeability and reactivity. The multicomponent reactive transport model MIN3P was enhanced to couple gas formation and release, secondary mineral precipitation, and the effects of these processes on hydraulic properties and iron reactivity. The enhanced model was applied to a granular iron column, which was studied for the treatment of trichloroethene (TCE) in the presence of dissolved CaCO3. The simulation reasonably reproduced trends in gas formation, secondary mineral precipitation, permeability changes, and reactivity changes observed over time. The simulation showed that the accumulation of secondary minerals reduced the reactivity of the granular iron over time, which in turn decreased the rate of mineral accumulation, and also resulted in a gradual decrease in gas formation over time. This study provides a quantitative...

Seasonal Changes In Mineralogy, Geochemistry and Microbial Community of Bacteriogenic Iron Oxides (BIOS) Deposited in a Circumneutral Wetland

Abstract: Changes in the mineralogy, microbial community structure and aquatic geochemistry of bacteriogenic iron oxides (BIOS) deposited at a circumneutral groundwater seep were recorded seasonally. X-ray diffraction and X-ray absorption spectroscopy demonstrated that 2-line ferrihydrite dominated the iron-bearing mineralogy of the BIOS (>60%). Minor proportions of the more crystalline lepidocrocite were also detected in BIOS collected throughout the year (<30%), but goethite (<15%) was only identified in sediments collected during the spring, summer and fall months. Subsurface porewater profiles generally showed an increase in dissolved equilibrium concentrations of Fe(II), indicative of microbial Fe(III) reduction, and the depth at which appreciable levels of dissolved Fe(II) (and to a lesser extent manganese) arose, and sulfate concentrations declined, become shallower as the seasons progressed from spring to fall. Clone libraries constructed from 16S rRNA gene sequence analysis of surficial BIOS showed the pre...

Crystallographic Texture and Volume Fraction of α and β Phases in Zr-2.5Nb Pressure Tube Material During Heating and Cooling

Abstract: The phase transformations in an as-received Zr-2.5Nb pressure tube material were characterized in detail by neutron diffraction. The texture and volume fraction of α and β phases were measured on heating at eight different temperatures 373 K to 1323 K (100 °C to 1050 °C) traversing across the α/(α + β) and (α + β)/β solvus lines, and also upon cooling at 1173 K and 823 K (900 °C and 550 °C). The results indicate that the α-phase texture is quite stable, with little change in the {0002} and $$ \left\{ {11\bar{2}0} \right\} $$ pole figures during heating to 1123 K (850 °C). The β-phase volume fraction increased while a slight change in texture was observed until heating reached 973 K (700 °C). On further heating to 1173 K (900 °C), there appears a previously unobserved α-phase texture component due to coarsening of the prior primary α grains; meanwhile the transformed β-phase texture evolved markedly. At 1323 K (1050 °C), the α phase disappeared with only 100 pct β phase remaining but with a different texture than that observed at lower temperatures. On cooling from the full β-phase regime, a different cooldown transformed α-phase texture was observed, with no resemblance of the original texture observed at 373 K (100 °C). The transformed α-phase texture shows that the {0002} plane normals are within the radial-longitudinal plane of the pressure tube following the Burgers orientation relationship of (110)bcc//(0002)hcp and $$ [\bar{1}11]_{\text{bcc}} //[11\bar{2}0]_{\text{hcp}} $$ with a memory of the precursor texture of the primary α grains observed on heating at 1173 K (900 °C).

Detecting high atomic number materials with cosmic ray muon tomography

Abstract: A method is proposed herein to detect high atomic number materials, such as Special Nuclear Materials, within a container based on muon tomography. The container is modeled as a plurality of volume elements. Information related to an initial trajectory and a final trajectory of each muon passing through the container is received. Additionally, a set of initial outer prong vectors and a set of final outer prong vectors are created. Then, a plurality of vector combinations are created from a selected initial vector and a selected final vector. A metric is determined and associated with each vector combination. A subset of the plurality of vector combinations is associated with each volume element and an estimated scattering density is determined and assigned to the volume element. Based on the estimated scattering density assigned to the volume elements, a three dimensional image of the container may be generated.

Rapid determination of 226Ra in urine samples

Abstract: A new radiochemical separation method has been developed for rapid analysis of (226)Ra in urine samples. In this method, radium is separated from urine matrix using cation and anion exchange column chromatography. A (224)Ra tracer is added, together with its parent in the (228)Th standard, for chemical recovery correction. After separation, the sample is precipitated with hydrous titanium oxide and then prepared for counting by creating a thin-layer counting source using BaSO(4) micro-precipitation. The radium isotopes are then counted by alpha spectrometry. Replicate spike and blank samples were analysed for validation of the procedure. The detection limit was determined to be 0.22 Bq l(-1) with 4 h of counting for 20 ml of urine sample. Using this method, the results can be reported within an 8 h turn-around time. This method is suitable for quick dose assessment of (226)Ra exposure following a radiation emergency.

Profiling tool for determining material thickness for inspection sites having complex topography

Abstract: A phased array ultrasonic probe may be mounted to a component to be inspected for wall thickness on an apparatus that includes a split ring adapted to be magnetically held in place on the component. In particular, the probe may be mounted to a carriage connected to the split ring in a manner that allows the carriage to rotate around the split ring while the probe is in operation. Between the probe and the component, a transducer shoe defining, by a flexible membrane, a cavity and an aperture. Conveniently, the construction of the flexible membrane allows wall thickness measurements to be acquired in portions of the component that have complex topography, such as welds. The apparatus is installed on an adaptor assembly for inspection of straight section of pipes. This adaptor assembly is not used in absence of straight section. By acquiring data from multiple output pulse transmitted at multiple incidence angles, processing software may conveniently produce an accurate wall thickness map of the area of interest on the component.

Fatty acid composition of muscle tissue measured in amphibians living in radiologically contaminated and non-contaminated environments.

Abstract: Fatty acid composition was identified as a potential biological indicator of the effects of environmental exposure to radiological contaminants. This end point was measured in muscle tissues of Mink frogs (Rana septentrionalis) obtained from a radiologically contaminated pond and from a non-contaminated pond. It was also measured after the frogs obtained from both ponds were exposed to a 4 Gy 60Co γ radiation dose delivered in vivo at a dose rate of approximately 8 Gy/min. Statistically significant differences for the increase of a couple of polyunsaturated omega-3 fatty acid residues and the decrease of a polyunsaturated omega-6 fatty acid residue were observed between radiologically contaminated and non-contaminated frogs, indicating a partial remodeling of muscle lipids in response to a chronic low-dose tritium exposure. The effects of an acute high-dose exposure to 60Co γ radiation, either for the radiologically contaminated or non-contaminated frogs indicated fast post-irradiation fatty acid changes ...

The Supersafe© Reactor: A Small Modular Pressure Tube SCWR

Abstract: The SUPERSAFE© Reactor (SSR) is proposed as a small modular version of the Canadian supercritical water-cooled reactor (SCWR). The SCWR is Canada’s primary contribution to the Generation-IV (GEN-IV...

Corrosion issues in pressurized heavy water reactor (PHWR/CANDU®) systems

Abstract: Although the CANDU pressurized heavy water reactor (PHWR) design differs from that of light water reactors (LWRs), many of the materials degradation issues are similar. Materials common to both designs are carbon steels, low alloy steels, stainless steels and zirconium alloys. However, these materials are used for systems and components that may be quite different between these two designs. The major difference is the use of fuel channels to contain the fuel in a CANDU. These zirconium alloy fuel channels are assembled into a stainless steel ‘calandria’ vessel, which holds the heavy water moderator. Corrosion issues associated with these fuel channels are discussed in further detail in this chapter. Steam generator, heat transport and balance of plant piping and components in CANDUs are similar in materials and function to those in LWRs, but some unique aspects of operating these systems in CANDU reactors will be discussed. Finally, monitoring advances are outlined, along with a discussion of future trends in ‘smart’ technologies for improved CANDU design and operation.

Proliferation Resistance Considerations for Remote Small Modular Reactors

Abstract: Remotely located Small Modular Reactors at the low end of energy production (on the order of 10 MWe, referenced here as Very Small Modular Reactors or VSMRs) present unique proliferation resistance advantages and challenges. Addressing these challenges in the most efficient manner may not only be desirable, but necessary, for development of this technology. Incorporation of safeguards considerations early in the design process (Safeguards by Design) along with safety, security, economics and other key drivers, is of importance. This approach raises the possibility of increased monitoring of operational data for verification purposes (Operational Transparency), which may become a useful aspect of the safeguards approach for such systems.

Towards large scale automated interpretation of cytogenetic biodosimetry data

Abstract: Cytogenetic biodosimetry is the definitive test for assessing exposure to ionizing radiation It involves manual assessment of the frequency of dicentric chromosomes (DCs) on a microscope slide, which potentially contains hundreds of metaphase cells We developed an algorithm that can automatically and accurately locate centromeres in DAPI-stained metaphase chromosomes and that will detect DCs In this algorithm, a set of 200–250 metaphase cell images are ranked and sorted The 50 top-ranked images are used in the triage DC assay (DCA) To meet the requirement of DCA in a mass casualty event, we are accelerating our algorithm through parallelization In this paper, we present our finding in accelerating our ranking and segmentation algorithms Using data parallelization on a desktop system, the ranking module was up to 4-fold faster than the serial version and the Gradient Vector Flow module (GVF) used in our segmentation algorithm was up to 8-fold faster Large scale data parallelization of the ranking module processed 18,694 samples in 1140 hr Task parallelization of Image ranking with parallelized labeling on a desktop computer reduced processing time by 20% of a serial process, and GVF module recoded with parallelized matrix inversion reduced time by 70% Overall, we estimate that the automated DCA will require around 1 min per sample on a 64-core computing system Our long-term goal is to implement these algorithms on a high performance computer cluster to assess radiation exposures for thousands of individuals in a few hours

Graphene-Based Composite Anodes for Lithium-Ion Batteries

Abstract: Graphene has emerged as a novel, highly promising material with exceptional properties and potential application in a wide range of technologies As an anode material for lithium-ion batteries, it was shown that it cannot be used in the pure form due to its large irreversible capacity but as part of a composite with other active materials Transition metal oxides, silicon, and tin have been explored as active anode materials to replace graphite because of their high theoretical capacities However, these materials have large volume changes during cycling that leads to the failure of the batteries To resolve this problem, additives have been added to these materials to mitigate this volume change In recent years, graphene has been employed as an encapsulating agent for these materials In this chapter, an overview of the work exploring composites made of graphene as a novel support for nanoscale materials that react with lithium and provide high capacities will be presented

Portable detection apparatus and method

Abstract: A portable detection apparatus can include a housing, a first detector for detecting ionizing radiation from a first subject and a second detector within the housing for the detecting the background radiation. A shield within the housing can surround the first and second detectors and define a shield aperture around the first and second detectors for radiation from the subject to enter the housing. A radiation blocking member can substantially block at least a portion of the ionizing radiation from reaching the second detector, whereby radiation detected by the second detector comprises substantially only the background radiation. A processor module can be connected to the first and second detectors for determining the amount of ionizing radiation detected by the first detector attributable to secondary radiation.