Entity

Time filter

Source Type

Petawawa, Canada

Chalk River Laboratories is a Canadian nuclear research facility located in Deep River, Renfrew County, Ontario, near the village of Chalk River, about 180 km north-west of Ottawa.CRL is a site of major research and development to support and advance nuclear technology, in particular CANDU reactor technology. CRL has expertise in physics, metallurgy, chemistry, biology, and engineering and unique research facilities. For example, Bertram Brockhouse, a professor at McMaster University, received the 1994 Nobel Prize in Physics for his pioneering work in neutron spectroscopy while at CRL from 1950-1962. Sir John Cockcroft was an early director of CRL and also a Nobel laureate. CRL produces about one-third of the world's supply of medical radioisotopes. It is owned and operated by Atomic Energy of Canada Limited. Wikipedia.


Rowan D.J.,Chalk River Laboratories
Journal of Environmental Radioactivity | Year: 2013

Steady state approaches, such as transfer coefficients or bioaccumulation factors, are commonly used to model the bioaccumulation of 137Cs in aquatic foodwebs from routine operations and releases from nuclear generating stations and other nuclear facilities. Routine releases from nuclear generating stations and facilities, however, often consist of pulses as liquid waste is stored, analyzed to ensure regulatory compliance and then released. The effect of repeated pulse releases on the steady state assumption inherent in the bioaccumulation factor approach has not been evaluated. In this study, I examine the steady state assumption for aquatic biota by analyzing data for two cesium isotopes in the same biota, one isotope in steady state (stable 133Cs) from geologic sources and the other released in pulses (137Cs) from reactor operations. I also compare 137Cs bioaccumulation factors for similar upstream populations from the same system exposed solely to weapon test 137Cs, and assumed to be in steady state. The steady state assumption appears to be valid for small organisms at lower trophic levels (zooplankton, rainbow smelt and 0+ yellow perch) but not for older and larger fish at higher trophic levels (walleye). Attempts to account for previous exposure and retention through a biokinetics approach had a similar effect on steady state, upstream and non-steady state, downstream populations of walleye, but were ineffective in explaining the more or less constant deviation between fish with steady state exposures and non-steady state exposures of about 2-fold for all age classes of walleye. These results suggest that for large, piscivorous fish, repeated exposure to short duration, pulse releases leads to much higher 137Cs BAFs than expected from 133Cs BAFs for the same fish or 137Cs BAFs for similar populations in the same system not impacted by reactor releases. These results suggest that the steady state approach should be used with caution in any situation where reactor releases are episodic or pulse in nature, even if the magnitude of these releases is small. © 2012 . Source


Guzonas D.A.,Chalk River Laboratories | Cook W.G.,University of New Brunswick
Corrosion Science | Year: 2012

Interest in materials degradation in supercritical water (SCW) increased significantly after the Generation IV International Forum selected the supercritical water-cooled reactor as one of six concepts for investigation. While a significant body of literature now exists on alloy corrosion in SCW, most studies have focused on the metal side of the metal-water interface. Using new data and a selective review of corrosion in SCW, this paper highlights how changes in SCW density change the corrosion mechanism, and highlights the close link between corrosion in SCW and high-temperature steam above 500°C. Key issues in test methodologies are also discussed. © 2012. Source


This paper speculates on the role of infection in modifying a young child's risk of promoting precursor B-cell acute lymphoblastic leukemia (ALL). It is suggested that the heat shock instigated by infections, particularly in infancy, stimulates Th1 pro-inflammatory cytokines and an apoptosis-inhibitory environment. This infective stress also increases the number of cooperating oncogenic mutations in pre-leukemic cells, especially if the primary adaptive immune response is delayed. The glucocorticoid release that follows leads to acute thymic involution, a decline in antitumor immunity, and maturation arrest of B-lymphocytes. The infective lymphoid recovery hypothesis addresses an apparent contradiction-that a non-hygienic environment primes the adaptive immune response and is protective against childhood ALL, while multiple infections occurring later increase the risk of childhood ALL. In affluent (compared to less-affluent) societies, the characteristic ALL incidence peak in early childhood, and the shortened time to diagnosis, arise from surviving recurrent infections and the accumulated loss and recovery of lymphoid tissue. Evidence supporting the hypothesis, such as the role of lymphoid tissue reconstitution cytokines that stimulate proliferation stress on B-cell progenitors, comes from the study of children with congenital syndromes that are susceptible to leukemia. © 2011. Source


Richardson R.B.,Chalk River Laboratories
Cell Cycle | Year: 2013

TP53's role as guardian of the genome diminishes with age, as the probability of mutation increases. Previous studies have shown an association between p53 gene mutations and cancer. However, the role of somatic TP53 mutations in the steep rise in cancer rates with aging has not been investigated at a population level. This relationship was quantified using the International Agency for Research on Cancer (IARC) TP53 and GLOBOCAN cancer databases. The power function exponent of the cancer rate was calculated for 5-y age-standardized incidence or mortality rates for up to 25 cancer sites occurring in adults of median age 42 to 72 y. Linear regression analysis of the mean percentage of a cancer's TP53 mutations and the corresponding cancer exponent was conducted for four populations: worldwide, Japan, Western Europe, and the United States. Significant associations (P ≤ 0.05) were found for incidence rates but not mortality rates. Regardless of the population studied, positive associations were found for all cancer sites, with more significant associations for solid tumors, excluding the outlier prostate cancer or sex-related tumors. Worldwide and Japanese populations yielded P values as low as 0.002 and 0.005, respectively. For the United States, a significant association was apparent only when analysis utilized the Surveillance, Epidemiology, and End Results (SEER ) database. This study found that TP53 mutations accounts for approximately one-quarter and one-third of the aging-related rise in the worldwide and Japanese incidence of all cancers, respectively. These significant associations between TP53 mutations and the rapid rise in cancer incidence with aging, considered with previously published literature, support a causal role for TP53 according to the Bradford-Hill criteria. However, questions remain concerning the contribution of TP53 mutations to neoplastic development and the role of factors such as genetic instability, obesity, and gene deficiencies other than TP53 that reduce p53 activity. © 2013 Landes Bioscience. Source


Duffey R.B.,Chalk River Laboratories | Ha T.,Candesco Corporation
IEEE Transactions on Power Systems | Year: 2013

Power restoration following a large outage or widespread blackout is time critical and complex. A new method is presented for determining the timing and chance of electric power recovery and restoration. The present advance over previous work is explicitly integrating human, component and system reliability, which unifies the topic of power system restoration with the general theory for errors, accidents and outcomes for other technological systems. © 2012 IEEE. Source

Discover hidden collaborations