Showing papers by "Atomic Energy of Canada Limited published in 2016"

Semiconductivity of steam generator tubing alloys in simulated crevice chemistries containing lead and sulphur

Abstract: Semiconductivity of passive films on steam generator (SG) tubing alloys, Alloys 690 and 800, in simulated crevice chemistries containing lead and sulphur was investigated using the Mott–Schottky analysis. The interaction of the above species with other ions on the properties of passive film and the correlation between the semiconductivity and the breakdown of passive film were discussed. Experimental results revealed that semiconductivity could be either n or p type semiconductor; both Pb and S can incorporate into the passive layer, depending on the solution pH and alloy compositions. For n type semiconductors formed on Alloy 800, they are easily broken down but more resistant to anodic dissolution; for p type passive films formed on Alloys 690 and 800, they are not easily broken down but more prone to anodic dissolution. It is concluded that the semiconductivity of passive film on SG tubing alloys was dependent on the alloy compositions, the solutions, temperature and film formation potentials.

Investigation of the Thermal Stability of NdxScyZr1-x-yO2-δ Materials Proposed for Inert Matrix Fuel Applications

Abstract: Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

Performance of Chemical Vapor Deposition and Plasma Spray-Coated Stainless Steel 310 in Supercritical Water

Abstract: In this study, aluminized and NiCrAlY plasma-sprayed AISI 310 stainless steel samples were tested in supercritical water (SCW) at 500°C. The microstructure after SCW exposure was analyzed using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Weight measurements were taken before and after exposure to provide quantitative comparison of the two coatings on AISI 310 base metal. The results showed that aluminized and bare 310 stainless steel experienced similar weight gain, in the range of 0.02-0.08 mg/cm2 after 1550 hr. The aluminized sample had a slight weight decrease as exposure progressed. Oxide formation, in the forms of Al2O3 and (Fe; Cr)2O3, was found on the aluminized surface along with surface cracking after 1550 hr testing in SCW. NiCrAlY-coated 310, however, had the most consistent weight increase and oxide formation (mainly Al2O3) on the surface. Based on the results from this study, the aluminized coating has limitations in providing surface protection due to surface cracking and weight loss. The NiCrAlY plasma-sprayed coating with alumina formation on the surface has the potential to provide long-term surface protection to the substrate material in SCW.

Cs-137 in milk, vegetation, soil, and water near the former Soviet Union's Semipalatinsk Nuclear Test Site.

Abstract: The present study was carried out to evaluate Cs-137 activity concentration in soil, water, vegetation, and cow's milk at 10 locations within three regions (Abai, Ayaguz, and Urdzhar) to the southeast of the Semipalatinsk Nuclear Test Site (SNTS) in Kazakhstan. Cs-137 activity concentrations, determined using a pure Ge gamma-ray spectrometer, showed that, all samples collected did not exceed the National maximum allowable limits of 10,000 Bq/kg for soil, 100 Bq/kg for cow's milk, 74 Bq/kg for vegetation, and 11 Bq/kg for water. Cs-137 is, therefore, not considered a health hazard in these regions. The highest levels of contamination were found in the Abai region, where the highest activity concentration of Cs-137 was 18.0 ± 1.0 Bq/kg in soil, 7.60 ± 0.31 Bq/kg in cow's milk, 4.00 ± 0.14 Bq/kg in the vegetation, and 3.00 ± 0.24 Bq/kg in water. The lowest levels were measured within the Urdzhar region, where 4.00 ± 0.14 Bq/kg was found in the soil, 0.30 ± 0.02 Bq/kg in the cow's milk, 1.00 ± 0.03 Bq/kg in the vegetation, and 0.20 ± 0.02 Bq/kg in the water.

Nickel-chromium-iron alloys with improved resistance to stress corrosion cracking in nuclear environments

Abstract: A Ni-Cr-Fe alloy with improved resistance to stress corrosion cracking in nuclear environments, the alloy comprising 23-28 wt% Cr, 25-35 wt% Ni, 0.35 wt% Ti, 0.15-0.45 wt% A1, <0.75 wt% Cu, and balance Fe and incidental impurities. The alloy may be used in steam generator tubing of a nuclear reactor. A method of producing an article includes: providing the alloy as disclosed herein; forming the alloy into the article by cold working the alloy to 20%; and heat treating the article.

Investigation of the Thermal Stability of NdxScyZr1-x-yO2-δ Materials Proposed for Inert Matrix Fuel Applications.

Abstract: Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

Cross-over fluid coupling

Abstract: A cross-over fluid coupling includes a first coupling end and a second coupling end. A plurality of first conduits have inner ends disposed toward the first coupling end and outer ends spaced apart from the inner end toward the second coupling end and being outboard of the inner end. A plurality of second conduits have outer ends that are disposed toward the first coupling end and positioned laterally outboard of the inner end of at least one of the first conduits, and inner ends that are spaced apart from the outer end toward the second coupling end in the axial direction and is laterally inboard of the outer end of the at least one of the first conduits.

Hydrogen storage assembly

Abstract: A hydrogen storage assembly includes at least one wafer formed of a substrate material that produces metal hydride when exposed to a hydrogen-rich carrier fluid. The wafer can be supported by a housing and arranged so that the hydrogen-rich carrier fluid can flow over a reaction surface of the wafer. At least one heating element can be arranged to transfer heat to the wafer to attain an operating temperature suitable for hydrogen charging on the reaction surface. A de-activation material may be provided on the reaction surface for inhibiting formation of surface oxide that impedes hydrogen absorption during charging and hydrogen desorption during discharging. The at least one wafer can include a plurality of monolithic plate wafers spaced apart about a central axis of the assembly. The at least one wafer can include a plurality of monolithic disc wafers in at least one stacked arrangement.

Valve packing assembly having shape-memory member

Abstract: A packing assembly for a valve includes a first segment having at least one first guiding surface, and a second segment having at least one second guiding surface in engagement with at least a portion of the at least one first guiding surface. A shape-memory member couples the first and second segments. The shape-memory member may be formed of a material that is responsive to changes in temperature, so that, in response to a change in temperature, the shape-memory member may cause relative movement of the first and second segments in a first direction. In response to the movement, the first and second guiding surfaces may cause relative displacement of the first and second segments in a second direction.

Portable detection apparatus and method

Abstract: A portable detection apparatus includes a fluid inlet to acquire a stream of fluid, a fluid outlet and a fluid flowpath therebetween. A pump circulates the fluid through the fluid flowpath. A gamma spectrometer and a mercury analyzer engage the fluid flowpath to analyze and detect radiation emitted by the fluid. A filter trap is in the fluid flowpath downstream from the gamma spectrometer and the mercury analyzer. The filter trap includes a valve assembly and at least a first and second filter for collecting gaseous constituents from the fluid. Each filter is removably connected to the first valve assembly. The valve assembly has a first configuration, in which the first filter is fluidly connected to the fluid flowpath and the second filter is fluidly isolated from the fluid flowpath, and a second configuration, in which the second filter is fluidly connected to the fluid flowpath and the first filter is fluidly isolated from the fluid flowpath.

A study on the effect of the internal exposure to (210)Po on the excretion of urinary proteins in rats.

Abstract: This study was designed to assess the feasibility of a noninvasive urine specimen for the detection of proteins as indicators of internal exposure to ionizing radiation. Three groups of rats (five in each group) were intravenously injected with 1601 ± 376, 10,846 ± 591 and 48,467 ± 2812 Bq of 210Po in citrate form. A sham-exposed control group of five rats was intravenously injected with sterile physiological saline. Daily urine samples were collected over 4 days following injection. Purification and pre-concentration of urinary proteins were carried out by ultrafiltration using a 3000 Da molecular weight cutoff membrane filter. The concentration of common urinary proteins, namely albumin, alpha-1-acid glycoprotein, immunoglobulins IgA and IgG, was measured by an enzyme-linked immunosorbent assay. Urinary excretion of albumin decreased dose-dependently (p < 0.05) 96 h post-injection relative to the control group. In contrast, no statistically significant effects were observed for other proteins tested. The dose-dependent decrease in urinary excretion of albumin observed in this study underscores the need for further research, which may lead to the discovery of new biomarkers that would reflect the changes in the primary target organs for deposition of 210Po.