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[en] In the June 2013 edition of the AECL Nuclear Review, Volume 2, Number 1, the last sentence in paragraph three of the Introduction of the article 'The Effect of Irradiation on Ni-containing Components in CANDU Reactor Cores: A Review' was incomplete and has been corrected in this erratum.
[en] To address the question of edibility of fish in the Ottawa River near Chalk River Laboratories (CRL), 123 game fish were collected for analysis from four locations: Mackey and Rolphton (45 km and 35 km upstream of Chalk River Laboratories (CRL), respectively), the Sandspit (Pointe au Bapteme) and Cotnam Island (1.6 km and 45 km downstream of CRL, respectively). Twenty-six to thirty-six game fish were collected at each location in 2007 and samples of flesh or bone were analyzed. Trap nets were used to collect only the fish required, allowing release of management-sensitive species. The focus was on walleye (Sander vitreus) because they are abundant and popular among anglers. A few northern pike (Esox lucius) and a smaller number of smallmouth bass (Micropterus dolomieui) were also collected at three of the four sites. Samples of the fish were analyzed for cesium-137 (137Cs), strontium-90 (90Sr), mercury (Hg), and selected organo-chlorine compounds. Concentrations of 137Cs in the flesh and 90Sr in the bones of sport fish were low and similar at all four locations and appear to reflect the global residuals from nuclear weapons testing (primarily in the 1960's) as opposed to releases from CRL. Possible explanations are: 1) Reductions in radionuclide releases from CRL in recent decades and 2) Relatively large foraging ranges of sport fish. Mercury concentrations were elevated in fishes in the Ottawa River and were significantly higher at the Sandspit and Rolphton than at Mackey and Cotnam Island (p<0.001). Mercury concentrations from the four sites are comparable to concentrations in other Ontario and Quebec lakes. It is advisable therefore, that consumers follow the fish consumption guidelines issued by provincial authorities when eating fish from the Ottawa River. Organo-chlorine compounds were not detected in walleye; however, they were detected in all eight of the pike collected at Cotnam Island. The highest organo-chlorine concentrations were measured in two of the three pike collected at Mackey. PCB values were less than the consumption guideline in all fish analyzed. (author)
[en] Fission product concentration in reactor primary heat transport systems is a common diagnostic indicator for assessing reactor core condition and determining the presence, size, power, location, residence time, burnup, etc., of defected fuel. Typically, diagnostic assessment assumes a priori that measured data (activity concentration measurements and reactor parameters) are accurate; however, this is not always a valid assumption. A set of novel methods has been developed for detecting minor discrepancies in fission product concentration measurements and reactor parameters (such as issues with transit times, purification, and spectral analysis). A variety of techniques are discussed and applied to a variety of reactor types (mainly commercial power plant designs); these techniques and concepts can be modified and applied for research and (or) commercial applications. (author)
[en] Snow washout ratios (WR) for carbon-14 (C-14) and tritiated water vapour (HTO) have been evaluated. Following the establishment of an efficient methodology for handling environmental (small) levels of C-14, WR for C-14 was calculated for the first time (but in a single experiment), with resulting WRC-14 = 3.159 ± 1.396. During 2004-2010 the WR for HTO has been measured in a broad range of meteorological conditions resulting in an average WRHTO = 0.251 ± 0.369. WRHTO has been further analyzed with respect to independent environmental parameters (drivers). No correlation of the WRHTO with precipitation intensity has been observed. A simple empirical relationship between WRHTO and temperature, atmospheric stability and surface roughness was established. (author)
[en] Atomic Energy of Canada Limited (AECL) Chalk River Laboratories (CRL) is a large nuclear research and test establishment with nuclear and non-nuclear facilities located in Chalk River, Ontario. The CRL Environmental Monitoring Program is designed to demonstrate that radiological exposure resulting from releases from the CRL site remain below the public dose limit specified in the regulations (1 mSv/year). This study was conducted to consolidate environmental effects following a continuous atmospheric tritium release observed at CRL. Soil samples were collected at depths of up to 20 cm using soil probes at the CRL site and surrounding areas. The samples were sectioned at 5 cm intervals, and HTO and OBT concentrations were measured in the samples. Prevailing winds at CRL are from NW and SE, which was suggested to be in close relationship with tritium distribution in environmental samples such as soils and plant leaves. The HTO concentration was the highest in surface soil water and plant leaves at a given sampling point. This result suggests that the concentration of tritium in surface soil water and in plants tissue free water essentially reflects the surrounding atmospheric tritium concentration. OBT concentrations in soil were measured at the historical HT release site, Plant Road, Mattawa Road and three background sites near CRL. The top layer of soil generally had the highest OBT concentration among collected soil samples. This result suggests that OBT concentrations are different from HTO concentrations at the same site and can be representative of previously released environmental tritium at the sampling point. The relationship between the OBT concentration in soil and the amount of tritium released into the environment will be useful for the evaluation of environmental tritium effects and the fate of tritium in the terrestrial ecosystem. The study points out that HTO shows shorter-term dynamic conditions, whereas OBT shows longer-term steady-state conditions. (author)
[en] The thermal neutron activation of deuterium inside a heavy-water-moderated or -cooled nuclear reactor produces a build-up of tritium in the heavy water. The in situ decay of tritium can, for certain reactor types and operating conditions, produce potentially useable amounts of 3He, which can be directly extracted via the heavy-water cover gas without first separating, collecting and storing tritium outside the reactor. It is estimated that the amount of 3He available for recovery from the moderator cover gas of a 700 MWe class Pressurized Heavy Water Reactor (PHWR) ranges from 0.1 to 0.7 m3 (STP) per annum, varying with the tritium activity buildup in the moderator. The harvesting of 3He would generate approximately 12.7 m3 (STP) of 3He, worth more than $30M at current market rates, over a typical 25-year operating cycle of the PHWR. This paper discusses the production of 3He in the moderator of a PHWR and its extraction from the 4He moderator cover gas system using conventional methods. (author)
[en] This paper describes an experimental approach where reactor kinetics experiments are used to study reactor physics phenomena that are normally investigated using static-measurement techniques. This approach provides validation data relating to these phenomena for a range of core reactivities, rather than only providing data at critical conditions. Sub-critical and super-critical transient measurements were performed in the ZED-2 reactor. The transients were analyzed using a point kinetics model to derive the reactivity states that induced the transients. The reactor physics phenomenon of interest for the current study is Coolant Density Induced Reactivity. Initial measurements were performed using an air-cooled (i.e., voided) ZED-2 lattice; the measurements were then repeated using the same lattice cooled with light water. These measurements yielded reactivity values for both coolant conditions in the lattice for a range of supercritical and sub-critical states. This investigation avoids the inherent assumption of static-measurement analyses that the bias in predicting criticality for the two coolant conditions is identical to the bias in predicting the phenomenon of Coolant Density Induced Reactivity itself. The measured reactivity values are compared with calculations employing the 3-D stochastic neutron transport reactor code MCNP. (author)
[en] This article gives a review of the Canadian nuclear sector and examines the opportunities that may lie ahead for this sector. Canada is amongst a small number of countries with a comprehensive nuclear sector. With its commitment to nuclear energy it has nuclear utilities operating in three provinces. These utilities are consistently rated amongst the best in the world for safe reliable performance. Canada has internationally respected, independent regulator operating in a coherent legislative and legal framework which meets and exceeds international expectations. Canada has a robust supply chain from mining through manufacturing and services anchored by a domestic reactor original equipment manufacturer (OEM).
[en] As so-called second-generation power reactors are approaching the end of their original design lives, assessments are being made to determine the feasibility and economics of extending plant life. Although components exposed to neutron and gamma irradiation are often those of most concern in terms of in-service ageing and continued fitness for service, ageing of out-of-core components can also limit the possibility of extended service life beyond design life. In CANDU reactors, life extension decisions occur when the Zr-2.5Nb pressure tubes reach end of life, typically after about 25 years of service for the first CANDU-6 units. At the time of pressure tube replacements, the remaining life predictions for several other major components or systems provide the information required to determine life extension feasibility. Several CANDU reactors are currently being refurbished, with others planned, and experience to date shows that the steam generators, heat transport system piping and various balance of plant piping systems are typically those requiring careful assessment to ensure successful refurbishment. In this paper, we discuss AECL R and D that is oriented towards providing the chemistry and materials inputs required to assess current condition and predict future ageing of CANDU reactor out-of-core components and systems, and in particular steam generators (Alloy 800 tubing and carbon steel internals), feeder pipes and related heat transport system piping (carbon steel flow accelerated corrosion, feeder cracking). Systems and components that may impact future life will also be discussed, along with the related R and D, and this includes balance of plant system piping (feedwater piping and buried piping), cables and concrete structures. (author)
[en] The Ottawa River has received nuclear reactor effluent from Chalk River Laboratories (CRL) for more than 60 years, including releases from a NRX accident in 1952. Recent interest in the potential impact of these historical releases and the possible need for remediation of a small region immediately downstream from the release point has led to comprehensive studies to assess risk to people and wildlife. In this paper, the results of an extensive survey of gamma-emitting anthropogenic radionuclides in Ottawa River sediment in the vicinity of CRL are presented. Anthropogenic radionuclides detected in Ottawa River sediment include 60Co, 94Nb, 137Cs, 152Eu, 154Eu, 155Eu and 241Am. Concentrations of all anthropogenic radionuclides decline rapidly with distance downstream of the process outfall, reaching stable concentrations about 2 km downstream. All of these radionuclides are found at some sites within 2 km upstream of the process outfall suggesting limited upstream transport and sedimentation. Comparison of anthropogenic radionuclides with several representative primordial radionuclides shows that with the exception of sites at the process outfall and within 2 km downstream of the process outfall, primordial radionuclide concentrations greatly exceed CRL derived anthropogenic radionuclide concentrations. Thus, over 60 years of radionuclide releases from operations at CRL have had little impact on radionuclide concentrations in Ottawa River sediment, except at a few sites immediately adjacent to the process outfall. (author)