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Pilgrim D.,Atomic Energy of Canada Ltd
Topical Meeting Held by the ANS Nuclear Criticality Safety Division, NCSD 2013 - Criticality Safety in the Modern Era: Raising the Bar | Year: 2013

Atomic Energy of Canada Limited (AECL) is Canada's premier nuclear science and technology organization. AECL has two locations where criticality safety is considered, Whiteshell Laboratories (WL) and Chalk River Laboratories (CRL). Between the two sites AECL has approximately 3280 employees. Its workforce is very diverse in that the company employs those with engineering, science, technology, administrative and business backgrounds as well as those in skilled trades. However there is also a contingent of employees who do not have post secondary education. The diversity of skills and educational background of AECL's workforce made it challenging to meet the intent of ANS 8.20 standard "Nuclear Criticality Safety Training" and the Canadian regulatory commitments that require all AECL employees to be trained in criticality safety. Nuclear Criticality Safety Program personnel at AECL decided the best approach to provide training for such a diverse community would be on a graded approach. Four categories were created in which every employee could be placed based on their required duties. This ranged from Category A, whose work could not impact criticality safety, to Category D, whose work could have serious consequences to criticality safety. A guidance document was issued directing the AECL management team to categorize their employees. The training outlined in the guidance document was a combination of pre-existing course material and material that needed to be developed. This material included awareness for all staff that covered a high level introduction to criticality safety, computer based training for emergency responders, and a revision to the nuclear criticality safety course that better aligned with ANS-8.20, Nuclear Criticality Safety Training. A graded approach to training began in 2009 and since then there has been a threefold increase in the number of employees receiving the full day training program and approximately 22 per cent of AECL staff has received basic awareness. With the aid of computer-based learning it is expected that the number of employees that will receive basic awareness will increase significantly over the coming year.

Banath J.P.,Cancer Agency Research Center | Klokov D.,Cancer Agency Research Center | Klokov D.,Atomic Energy of Canada Ltd | MacPhail S.H.,Cancer Agency Research Center | And 2 more authors.
BMC Cancer | Year: 2010

Background: Evidence suggests that tumor cells exposed to some DNA damaging agents are more likely to die if they retain microscopically visible γH2AX foci that are known to mark sites of double-strand breaks. This appears to be true even after exposure to the alkylating agent MNNG that does not cause direct double-strand breaks but does produce γH2AX foci when damaged DNA undergoes replication.Methods: To examine this predictive ability further, SiHa human cervical carcinoma cells were exposed to 8 DNA damaging drugs (camptothecin, cisplatin, doxorubicin, etoposide, hydrogen peroxide, MNNG, temozolomide, and tirapazamine) and the fraction of cells that retained γH2AX foci 24 hours after a 30 or 60 min treatment was compared with the fraction of cells that lost clonogenicity. To determine if cells with residual repair foci are the cells that die, SiHa cervical cancer cells were stably transfected with a RAD51-GFP construct and live cell analysis was used to follow the fate of irradiated cells with RAD51-GFP foci.Results: For all drugs regardless of their mechanism of interaction with DNA, close to a 1:1 correlation was observed between clonogenic surviving fraction and the fraction of cells that retained γH2AX foci 24 hours after treatment. Initial studies established that the fraction of cells that retained RAD51 foci after irradiation was similar to the fraction of cells that retained γH2AX foci and subsequently lost clonogenicity. Tracking individual irradiated live cells confirmed that SiHa cells with RAD51-GFP foci 24 hours after irradiation were more likely to die.Conclusion: Retention of DNA damage-induced γH2AX foci appears to be indicative of lethal DNA damage so that it may be possible to predict tumor cell killing by a wide variety of DNA damaging agents simply by scoring the fraction of cells that retain γH2AX foci. © 2010 Banáth et al; licensee BioMed Central Ltd.

Ismail Y.,University of Montreal | Ismail Y.,Atomic Energy of Canada Ltd | Mccormick S.,U.S. Department of Agriculture | Hijri M.,University of Montreal
FEMS Microbiology Letters | Year: 2013

Trichothecenes are an important family of mycotoxins produced by several species of the genus Fusarium. These fungi cause serious disease on infected plants and postharvest storage of crops, and the toxins can cause health problems for humans and animals. Unfortunately, there are few methods for controlling mycotoxin production by fungal pathogens, and most rely on chemicals, creating therefore subsequent problems of chemical resistance. We tested the impact of the symbiotic arbuscular mycorrhizal fungus Glomus irregulare on a trichothecene-producing strain of Fusarium sambucinum isolated from naturally infected potato plants. Using dual in vitro cultures, we showed that G. irregulare inhibited the growth of F. sambucinum and significantly reduced the production of the trichothecene 4, 15-diacetoxyscirpenol (DAS). Furthermore, using G. irregulare-colonized potato plants infected with F. sambucinum, we found that the G. irregulare treatment inhibited the production of DAS in roots and tubers. Thus, in addition to the known beneficial effect of mycorrhizal symbiosis on plant growth, we found that G. irregulare controlled the growth of a virulent fungal pathogen and reduced production of a mycotoxin. This previously undescribed, biological control of Fusarium mycotoxin production by G. irregulare has potential implications for improved potato crop production and food safety. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Le T.,McMaster University | Ewing D.,McMaster University | Schefski C.,Atomic Energy of Canada Ltd | Ching C.Y.,McMaster University
Nuclear Engineering and Design | Year: 2014

Flow-Accelerated Corrosion (FAC) is a major degradation mechanism affecting carbon steel piping systems in nuclear power plants (NPPs). Flow and mass transfer conditions determine the local distribution of wall thinning, even though chemistry and materials determine the overall potential for FAC. Different localized thinning rates in back-to-back elbow configurations between the first and second elbows have been noted at NPPs, and this difference depends on the distance between elbows, flow conditions, and the configuration of the back-to-back elbows (S-, C-, or out of plane). This paper will focus on mass transfer measurements for back-to-back elbows arranged in an out of plane configuration for different elbow separation distances under single-phase flow conditions. The mass transfer measurements were performed using a mass dissolution technique of gypsum test sections in water. The experiments were performed at a Reynolds number of 70,000 and a resulting Schmidt number of 1280, which is similar to that for the diffusion of the iron magnetite layer of carbon steel piping in water, providing a mass transfer environment analogous to that in NPPs. Experiments were performed with 0, 1, 2 and 5 pipe diameters in length between the elbows. The mass transfer results show regions of higher mass transfer in the second elbow in comparison to the first elbow. The maximum mass transfer enhancement factor decreased from 2.7 to 2.1 as the separation distance increased from 0 to 5 pipe diameters. Flow streaks on the second elbow surface indicated swirling flow and its strength decreased with increasing separation distances. The relative roughness in the upstream pipe was found to be 0.003-0.004. The roughness level in the second elbow is 1.5 times higher than the upstream pipe and decreases with increasing bend separation distance. © 2014 Elsevier B.V.

Pietralik J.M.,Atomic Energy of Canada Ltd | Schefski C.S.,Atomic Energy of Canada Ltd
Journal of Engineering for Gas Turbines and Power | Year: 2011

The three groups of parameters that affect flow-accelerated corrosion (FAC) are the flow conditions, water chemistry, and materials. Nuclear power plant (NPP) data and laboratory tests confirm that, under alkaline water chemistry, there is a close relationship between local flow conditions and FAC rates in the piping components. The knowledge of the local flow effects can be useful for developing targeted inspection plans for piping components and predicting the location of the highest FAC rate for a given piping component. A similar evaluation applies also to the FAC in heat transfer equipments such as heat exchangers and steam generators. The objective of this paper is to examine the role of the flow and mass transfer in bends under alkaline FAC conditions. Bends experience increased FAC rates compared with straight pipes, and are the most common components in piping systems. This study presents numerical simulations of the mass transfer of ferrous ions and experimental results of the FAC rate in bends. It also shows correlations for mass transfer coefficients in bends and reviews the most important flow parameters affecting the mass transfer coefficient. The role of bend geometry and, in particular, the short and long radii, surface roughness, wall shear stress, and local turbulence, is discussed. Computational fluid dynamics calculations and plant artifact measurements for short- and long-radius bends are presented. The effect of the close proximity of the two bends on the FAC rate is also examined based on CANDU (CANDU is a registered trademark of the Atomic Energy of Canada Limited) NPP inspection data and compared with literature data.

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