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News Article | May 24, 2017
Site: www.engineeringnews.co.za

National Nuclear Regulator (NNR) CEO Dr Bismark Tyobeka has been elected to serve as president of the sixth review meeting of the Joint Convention on the Safety of Spent Nuclear Fuel Management and Safety of Radioactive Waste Management. The joint convention was adopted on September 5, 1997, and entered into force on June 18, 2001, establishing an international peer review process among contracting parties and providing incentives for nations to take appropriate steps to bring their nuclear activities into compliance with general safety standards and practices. South Africa acceded to the joint convention on November 15, 2006. Tyobeka will work closely with the convention’s two VPs – Geoff Williams from the Australian Radiation Protection and Nuclear Safety Agency and Douglas Tonkay, from the US Department of Energy – to encourage constructive discussions on key issues faced by parties to the convention. He will also engage with regional networks, in particular those that form part of the International Atomic Energy Agency’s Global Nuclear Safety and Security Network to assist member States, who are not already contracting parties to the joint convention to become contracting parties.

Andrady A.L.,North Carolina State University | Torikai A.,Materials Life Society of Japan | Redhwi H.H.,King Fahd University of Petroleum and Minerals | Pandey K.K.,Institute of Wood Science and Technology | Gies P.,Australian Radiation Protection and Nuclear Safety Agency
Photochemical and Photobiological Sciences | Year: 2015

Materials used in the exterior of buildings and in construction are routinely exposed to solar UV radiation. Especially in the case of wood and plastic building materials, the service life is determined by their weather-induced deterioration. Any further increase in ground-level solar UV radiation, UV-B radiation in particular, will therefore reduce the outdoor service life of these products. Any increase in ambient temperature due to climate change will also have the same effect. However, the existing light-stabilizer technologies are likely to be able to mitigate the additional damaging effects due to increased solar UV radiation and maintain the outdoor lifetimes of these materials at the present levels. These mitigation choices invariably increase the lifetime cost of these products. A reliable estimate of what this additional cost might be for different products is not available at the present time. Personal exposure to UV radiation is reduced both by clothing fabrics and glass windows used in buildings and automobiles. This assessment describes how the recent technical advances in degradation and stabilization techniques impact the lifetimes of plastics and wood products routinely exposed to solar UV radiation and the protection to humans offered by materials against solar UV radiation. © The Royal Society of Chemistry and Owner Societies 2015.

Charles P.H.,Queensland University of Technology | Crowe S.B.,Queensland University of Technology | Kairn T.,Queensland University of Technology | Kairn T.,He Wesley Medical Center | And 6 more authors.
Physics in Medicine and Biology | Year: 2013

Due to their small collecting volume, diodes are commonly used in small field dosimetry. However, the relative sensitivity of a diode increases with decreasing small field size. Conversely, small air gaps have been shown to cause a significant decrease in the sensitivity of a detector as the field size is decreased. Therefore, this study uses Monte Carlo simulations to look at introducing air upstream to diodes such that they measure with a constant sensitivity across all field sizes in small field dosimetry. Varying thicknesses of air were introduced onto the upstream end of two commercial diodes (PTW 60016 photon diode and PTW 60017 electron diode), as well as a theoretical unenclosed silicon chip using field sizes as small as 5 mm × 5 mm. The metric Dw,Q/ DDet,Q used in this study represents the ratio of the dose to a point of water to the dose to the diode active volume, for a particular field size and location. The optimal thickness of air required to provide a constant sensitivity across all small field sizes was found by plotting Dw,Q DDet,Q as a function of introduced air gap size for various field sizes, and finding the intersection point of these plots. That is, the point at which Dw,Q DDet,Q was constant for all field sizes was found. The optimal thickness of air was calculated to be 3.3, 1.15 and 0.10 mm for the photon diode, electron diode and unenclosed silicon chip, respectively. The variation in these results was due to the different design of each detector. When calculated with the new diode design incorporating the upstream air gap, k fclin, fmsr Qclin,Qmsr was equal to unity to within statistical uncertainty (0.5%) for all three diodes. Cross-axis profilemeasurements were also improved with the new detector design. The upstream air gap could be implanted on the commercial diodes via a cap consisting of the air cavity surrounded by water equivalent material. The results for the unclosed silicon chip show that an ideal small field dosimetry diode could be created by using a silicon chip with a small amount of air above it. © 2013 Institute of Physics and Engineering in Medicine.

Larsson C.-M.,Australian Radiation Protection and Nuclear Safety Agency | Higley K.A.,Oregon State University | Real A.,CIEMAT
Annals of the ICRP | Year: 2015

The International Commission on Radiological Protection (ICRP) established Committee 5 in 2005 in response to the need to provide direct demonstration of environmental protection from radiation in accordance with national law and international agreements. The development of the ICRP system for environmental protection was facilitated by research over the previous decades, as well as by ICRP’s evaluation of the ethical and philosophical basis for environmental protection as laid out in ICRP Publication 91. The 2007 Recommendations (Publication 103) incorporated environmental protection as one of the integral elements of the radiation protection system. Over a relatively short time, the system has evolved to incorporate a set of 12 Reference Animals and Plants (RAPs), which is a small enough number to develop comprehensive databases for each RAP, but wide ranging enough to provide some insight into radiation impact and protection against such impact, as appropriate, in terrestrial, freshwater, and marine ecosystems. As necessary, the databases can be used to derive supplementary databases for Representative Organisms typical for a particular exposure situation of concern or under study. The system, to date, details biology of the RAPs (Publication 108); outlines transfer factors for estimation of internal concentrations of radionuclides of environmental significance under different situations (Publication 114); provides further information (Publication 108) on dosimetry, biological effects, and derived consideration reference levels (bands of environmental dose rates where potential detrimental effects may deserve attention); and provides information on application of the system in planned, emergency, and existing exposure situations (Publication 124). Currently, a review of experimental determinations of relative biological effectiveness, to guide derivation of specific weighting factors for use in environmental radiation protection if possible and necessary, is being concluded, as is work on improved dosimetry. Further work in this area involves consolidation of databases, recommendations for derivation of specific databases for Representative Organisms on the basis of the RAP data, and recommendations for application of the system to environmental protection in relation to certain human activities of potential environmental concern. Consideration needs to be made for the wider range of ecosystem effects that may be covered in ecological risk assessments, which incorporate the complete suite of stressors that result from human activity, and their effects, to understand the role of radiation effects in this context. © The International Society for Prosthetics and Orthotics Reprints and permissions: sagepub.co.uk/journalsPermissions.nav

Simpson Jr. S.,Menzies Research Institute | Taylor B.,Menzies Research Institute | Blizzard L.,Menzies Research Institute | Ponsonby A.-L.,Murdoch Childrens Research Institute | And 5 more authors.
Annals of Neurology | Year: 2010

Objective: A protective association between higher vitamin D levels and the onset of multiple sclerosis (MS) has been demonstrated; however, its role in modulating MS clinical course has been little studied. We investigated whether higher levels of serum 25-hydroxyvitamin D (25-OH-D) were associated with a lower risk of relapses in people with MS. Methods: We conducted a prospective cohort study of 145 participants with relapsing-remitting MS from 2002 to 2005. Serum 25-OH-D levels were measured biannually, and the hazard of relapse was assessed using survival analysis. Results: There was an inverse linear relationship between 25-OH-D levels and the hazard of relapse over the subsequent 6 months, with hazard ratio (HR) 0.91 (95% confidence interval [CI]: 0.85-0.97) per 10nmol/l increase in 25-OH-D level (p = 0.006). When variation due to timing of blood collection was removed by estimating 25-OH-D at the start of each season, this association persisted, with HR 0.90 (95% CI, 0.83-0.98) per 10nmol/l increase (p = 0.016). Taking into account the biological half-life of 25-OH-D, we estimated 25-OH-D at monthly intervals, resulting in a slightly enhanced association, with HR 0.88 (95% CI, 0.82-0.95) per 10nmol/l increase (p = 0.001). Adjusting for potential confounders did not alter these findings. Interpretation: In this prospective population-based cohort study, in a cohort largely on immunomodulatory therapy, higher 25-OH-D levels were associated with a reduced hazard of relapse. This occurred in a dosedependent linear fashion, with each 10nmol/l increase in 25-OH-D resulting in up to a 12% reduction in risk of relapse. Clinically, raising 25-OH-D levels by 50nmol/l could halve the hazard of a relapse. © 2010 American Neurological Association.

Brady Z.,RMIT University | Cain T.M.,Royal Childrens Hospital | Johnston P.N.,RMIT University | Johnston P.N.,Australian Radiation Protection and Nuclear Safety Agency
Journal of Medical Imaging and Radiation Oncology | Year: 2011

Introduction: The use of CT has rapidly increased since its introduction. Although an important medical tool for diagnosis and treatment, CT is recognised as being among the highest contributors to population radiation exposure. As the risks associated with exposure are higher for children than for adults, this study assessed the impact of paediatric CT in Australia by analysing imaging trends. Methods: CT imaging trends were derived from Medicare data. Comparable data from a dedicated paediatric hospital (Royal Children's Hospital Melbourne (RCH)) were analysed to determine the validity of utilising Medicare statistics in the younger age groups. The resulting trends reflect the situation for paediatric CT imaging in Australia. Results: In 2009, 2.1 million CT services were billed to Medicare in Australia for children and adults. The average annual growth in the number of CT services provided since 1994 was 8.5%, compared with population growth of 1.4%. Comparison of RCH and Medicare data revealed that only one third of paediatric CT imaging is captured by Medicare. Combining the data sets showed that over the last 20 years, there has been an average annual increase of 5.1% in the CT imaging rate for 0 to 18-year-olds. However, in recent years, growth in the imaging rate for 11 to 18-year-olds has slowed, while for 5 to 10-year-olds the imaging rate has declined. Conclusions: The significant growth in CT services is attributable to incre3ased demand from the adult demographic. Conversely, increases in the imaging rate for paediatric patients have slowed overall. In fact, for some age groups the rate has fallen. © 2011 The Royal Australian and New Zealand College of Radiologists.

Lye J.E.,Australian Radiation Protection and Nuclear Safety Agency | Lye J.E.,RMIT University | Butler D.J.,Australian Radiation Protection and Nuclear Safety Agency | Ramanathan G.,Australian Radiation Protection and Nuclear Safety Agency | Franich R.D.,RMIT University
Physics in Medicine and Biology | Year: 2012

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has installed an Elekta Synergy platform linac to establish a direct megavoltage primary standard calibration service, instead of relying on calibrations derived from 60Co. One of the 6 MV beams of the ARPANSA linac has been approximately matched to the Varian high energy platform 6 MV photon beam. The electron beam energy was adjusted to match the percentage depth dose (PDD) curve and TPR 20,10. This work calculates the error introduced when using a calibration factor from this Elekta Synergy Platform linac on a Varian high-energy platform beam at 6 MV. Monte Carlo models of the Varian and matched Elekta accelerator accurately predict the measured PDDs and profiles, but show significantly different energy spectra, resulting mainly from differences in target thickness between the two accelerators. Monte Carlo modelling of the energy correction factor k Q of a secondary standard NE2561 chamber shows a difference of 0.4% between the Varian and the Varian-matched Elekta beams. Although small, this is a significant discrepancy for primary standard calibrations. Similar variations are expected for chambers of similar construction, and additional variations may occur with other linac manufacturers. The work has also investigated the design of a custom flattening filter to precisely match the energy spectrum of the Varian beam on the Elekta platform. © 2012 Institute of Physics and Engineering in Medicine.

Larsson C.-M.,Australian Radiation Protection and Nuclear Safety Agency
Annals of the ICRP | Year: 2012

The approach to protection of the environment may vary considerably depending on ethical basis, methodological approach, and identification of endpoints and protective targets. The International Commission on Radiological Protection (ICRP) reviewed these issues in Publication 91, 'A framework for assessing the impact of ionising radiation on non-human species', published in 2003. At the same time, ICRP proposed that a possible future ICRP system addressing environmental assessment and protection would focus on biota, that the system should be effect-based so that any reasoning about adequate protection would be derived from firm understanding of harm at different exposure levels, and that the system should be based on data sets for Reference Animals and Plants. ICRP has thus chosen to approach environmental protection on the basis of biology, and further developed the approach in Publications 103, 108 and 114. This paper explores the biological basis for the ICRP system of environmental protection from the viewpoints of: the effects endpoints of concern; the hierarchy of biological organisation; adequate and appropriate protective targets; and the derivation of benchmark dose (rates) to guide protective efforts. © 2012.

Larsson C.-M.,Australian Radiation Protection and Nuclear Safety Agency
Annals of the ICRP | Year: 2015

Protection of the environment is integral to the system of radiological protection, as outlined in the 2007 Recommendations of the International Commission on Radiological Protection (ICRP, Publication 103). The Commission’s activities in this area are mainly pursued by Committee 5 and its associated Task Groups. Publication 91 broadly outlines the approach to radiological protection of the environment, and its alignment with approaches to environmental protection from hazardous substances in general. Publications 108 and 114 provide the cornerstones of the environmental protection system and relevant databases. Publication 124 considers its application in planned, existing, and emergency exposure situations. The system centres on 12 Reference Animals and Plants (RAPs) with broad relevance for environmental protection based on their ubiquity and significance as well as other criteria, as described in Publication 108. The databases comprise general biology of the RAPs, transfer parameters, dose conversion coefficients, and effects data. Derived Consideration Reference Levels (DCRLs) were established for each RAP; a DCRL represents a band of dose rates that might result in some deleterious effects in individuals of that type of RAP. Newly established Task Group 99 will compile the RAP-specific reference information into monographs, with the view of updating information and improving the applicability of the system in different exposure situations. For certain scenarios, more precise and ecosystem-specific protection benchmarks may be justified, which would have to be informed by consideration of representative organisms (i.e. representative of a particular ecosystem and relevant to the specific scenario; Publication 124). Committee 5 will explore this further, making use of a limited number of case studies. © 2016, © The International Society for Prosthetics and Orthotics.

Karipidis K.K.,Australian Radiation Protection and Nuclear Safety Agency
Radiation Protection Dosimetry | Year: 2014

An important consideration in surveys of residential magnetic fields is whether the sample of homes measured is representative of the population. This study assessed the potential bias in a survey of magnetic fields conducted in 296 homes randomly selected from the telephone directory in Melbourne. The choice of the telephone directory as the sampling frame introduced some bias when compared with census information. There was also evident self-selection bias with residents twice as likely to participate if they lived in the vicinity of visible electrical infrastructure such as transmission lines. However, when corrected for bias the corrected magnetic fields were only slightly lower than the measurements with a percentage difference in the range of 2.8-6.0 %. These results provide confidence that the measurements in the survey were good estimates of the distribution of residential magnetic fields in Melbourne. © The Author 2014.

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