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1
吳楚儀 e Chor-yi Ng. "Radiation hazards of building materials". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B3121051X.
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2
Aldridge, Jesse Philmore. "The role of health physicists in contemporary radiological emergency response". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19434.
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3
Campos, Carlos Austerlitz. "Choice of personnel dosimeter location to assess the effective dose equivalent for various photon irradiations". Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/12916.
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Veinot, Kenneth Guy. "An angular dependent neutron effective-dose-equivalent dosimeter". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17595.
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5
Griffis, Neale Jeff. "Performance evaluation of the Dosicard electronic personal dosimeter". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/16991.
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Johnston, Glen Harvey George. "Evaluation of radiation and dust hazards associated with mineral sand processing". Thesis, Queensland University of Technology, 1988. https://eprints.qut.edu.au/35942/1/35942_Johnston_1988.pdf.
Testo completoAbstract (sommario):
Possible health hazards have been investigated in a mineral sand processing plant to determine the risks to workers contributed by four principal sources:
(i) External gamma radiation ii) Inhaled radioactivity in airborne dust particles (iii) Inhaled activity from airborne radon and radon daughter isotopes
(iv) Respirable free silica Gamma radiation surveys of the plant working environs using
a portable survey meter indicated possible exposure rates
ranging from 70 nSv h-1 to a maximum of 50 μsv h- 1 (near a large pile of monazite sand). The average exposure rate was 400 nSv h-1 • Assuming 100% worker occupancy time under this average rate, then a possible gamma radiation dose of 1 mSv could be received in one working year (2000 hours exposure). Airborne dust sampling in the dry mill of the process plant comprising samples obtained from a portable personal air sampler, stationary high volume samples and cascade impactor samples indicated an average gross alpha-activity or concentration range of 0.02 to 0.16 Bq m-3 (average = .07 Bq m-3 ), with an average activity median aerodynamic diameter (AMAD) of 3.2μm and an activity ratio of 2.4(± 0.4) activity air concentration value average thorium/uranium
1. The average alpha is about 12% of the
recommended derived air concentration limit.
Airborne radon-222 gas released from mineral sand products as detected using solid state nuclear track detectors (CR- 9 plastic). Gas concentrations in the dry mill were found to range from 30 to 220 Bq m~ (average= 35 ± 15 Bq m-3 ). Compared to an equilibrium equivalent recommended limit of
1500 Bq m-3 (International Commission on Radiological
Protection), the average radon-222 concentration is some 2% of the limit. X-ray diffraction measurements on eleven (11) samples of respirable dust revealed four (4) samples having quartz concentrations exceeding the recommended limits. The average percent quartz content in the plant was determined to (by mass) of airborne dust
be (22 + 7)%, with an average quartz mass concentration of 0.8 ± 0.5 mg m-3 •
This may be compared with a mass concentration limit of
0.93 mg m-3 > which places the average quartz concentration
at 86 % of the limit.
Respirable dust in the plant is the chief source of hazard from both a radiological and non-radiological standpoint. General recommendations for reduction of risk include: (i) Reduction of dust from the working environment (possibly enclosing and ventilating dust
producing machinery); (ii) Wearing of efficient respiratory protection apparatus by workers;
(iii)Reduction of worker occupancy time in dust
affected areas.
7
Fulcher, TJ. "The development of an interlock and control system for a clinical proton therapy system". Thesis, Cape Technikon, 1995. http://hdl.handle.net/20.500.11838/1483.
Testo completoAbstract (sommario):
Thesis (Masters Diploma (Technology))--Cape Technikon, Cape Town, 1995The development of a 200 MeV clinical proton therapy facility at the National Accelerator Centre required an interlock and control system to supervise the delivery of radiation to a patient. The interlock and control system is responsible for ensunng that nobody enters the treatment vault during an irradiation, the extraction of the beamstop devices 'from the beam-line to allow the irradiation of the patient and the insertion of those beam-stop devices when an error condition is detected. Because of its nature, the interlock and control system should be designed so that in the event of an error condition being detected, it should fail to a safe state. This is achieved by modelling the interlock and control system with an appropriate modeling method. This thesis describes a graphical modelling method called Petri-nets, which was used to model the system, and the software developed from the model.
8
Tenkate, Thomas D. "Ultraviolet radiation exposure of welders". Thesis, Queensland University of Technology, 1994. https://eprints.qut.edu.au/36715/1/36715_Digitised%20Thesis.pdf.
Testo completoAbstract (sommario):
Ultraviolet radiation (UVR) is a by-product of the welding process and is emitted by the arc formed between the electrode and the base metal. Exposure to UVR can produce acute and chronic effects on the eyes and skin, including photokeratitis and erythema (acute), and pterygium and skin cancer (chronic). The measurement of UVR can be used to determine the level of hazard posed by a particular source.
The personal UVR exposure levels of a group of welders and nearby workers was estimated using a photosensitive polymer film, polysulphone. The polysulphone film was attached to eye protection, the workers clothing and also placed throughout the workarea. The estimated ocular exposures of all subjects were found to exceed the eight-hour maximum permissible exposure limit.
As the main UVR protective measure for welders is a welding helmet, the degree of protection afforded by a range of helmets was investigated in a laboratory experiment. Radiation was found to be reflected off the filter and toward the eye after entering through: (1) an opening between the edge of the shield and the side of the face, and (2) an opening between the top lip of the shield and the top of the head.
The results of this study suggest that welders require ocular protection in addition to welding helmets, and that all exposed skin surfaces of workers in a welding environment should also be protected.
9
Elmukhtar, Yasir Mohamed. "Knowledge and attitude of dentists regarding radiation safety in government dental clinics in Khartoum, Sudan". University of the Western Cape, 2015. http://hdl.handle.net/11394/5037.
Testo completoAbstract (sommario):
Magister Scientiae Dentium - MSc(Dent)The level of knowledge and the attitude of dentists regarding radiation safety will have a direct impact on patient exposure to radiation. Aim: The aim of the present study was to evaluate the knowledge and attitude of dentists regarding radiation safety in government dental clinics in Khartoum, Sudan. Materials and Methods: A cross-sectional study using an administered structured questionnaire was carried out. The questionnaire consisted of 13 questions that included the demographic data of dentists, basic knowledge regarding radiation safety, knowledge of methods of dose reduction and the attitude of dentists regarding radiation safety. One hundred and sixty seven dental practitioners participated in the study. Results: The response rate was 90%. The majority were female, 59%, in the age group younger than 29 years with clinical experience less than 10 years. Only fifteen of the respondents identified themselves as specialist. Half of the respondents did not know that the thyroid gland is the most radiosensitive organ in the head and neck region. Forty four percent believed that the dose for panoramic radiography was higher than that for full mouth periapical radiographs. Forty percent had no idea that a relationship exists between the length of the x-ray cone and the amount of the dose and 44% who knew that the relationship existed, failed to explain that the long cone is more effective for reducing the patient dose. Forty seven percent of the respondents had no idea that there is a relationship between the speed of the film and the amount of dose and 44% who knew that the relationship existed, failed to explain that the fast film is more effective for reducing the patient dose. Sixty six percent had no idea that a relationship exists between collimation of the x-ray tube and patient dose. Forty six percent who knew the relationship existed, failed to explain that rectangular collimation is more effective for dose reduction. Seventy two percent of the dentists did not know what a safe distance from the radiation source was. Forty seven percent did not use film holders when taking periapical radiographs. Conclusions: This study clearly illustrates that there is a lack of knowledge regarding radiation safety in dentists in the government dental clinics in Khartoum, Sudan. Therefore there is a need to increase their knowledge regarding methods of radiation dose reduction (to patient) as well as improving their attitude regarding the radiation safety.
10
Salikin, Md Saion. "An improved system of damage limitation for better risk control in radiological protection near environmental level". Thesis, University of St Andrews, 1995. http://hdl.handle.net/10023/13372.
Testo completoAbstract (sommario):
In radiological protection, models are used to assess radiation risk by means of extrapolation from high dose and dose rate to low dose and dose rate. In this thesis five main biophysical models of radiation action have been evaluated, appraised and inter-compared. The five models are lethal and potentially lethal (LPL) by Curtis, pairwise lesion interaction (PLI) by Harder, cellular track structure (CTS) by Katz, hit size effectiveness (HSE) by Bond and Varma and track core (TC) by Watt. Each model has been developed based on certain underlying mechanisms or phenomena, to permit interpretation and prediction on the induction of a specified biological endpoint such as cell reproductive death, chromosome aberrations and mutations. Biological systems of interest are, for example, mammalian cells containing deoxyribonucleic acid (DNA). Evidence is mounting that double strand breaks in the DNA are the critical lesions for various biological end points. To proceed with this work the TC model has been chosen. Cancer induction by ionising radiation is the stochastic effect of prime concern in radiological protection. Cancer induction cannot be avoided entirely but its frequency of occurrence may be reduced to acceptable level by lowering the amount of radiation received. The methods of assessment developed by ICRP, in terms of the cancer risk coefficients, are presented in this thesis. In the conventional (legal) system of dosimetry, radiation is quantified by the amount of energy absorbed per unit mass of tissue. Quality factors, superseded by radiation weighting factors, are needed to account for the quality dependence on radiation type. As an alternative, a new dosimetry system is proposed here which is based on the mean free path for primary ionisation along particle tracks and the integral fluence generated by the radiation field, whether directly or indirectly ionising radiation. From the study of cellular data, the mean free path for primary ionisation along particle tracks (lambda) emerges as a parameter which best unifies biological damage data. Radiation effect is found to depend, not on the energy transferred but to depend mainly on the frequency and spatial correlation of interactions. Maximum effect occurs when lambda is equal to lambda0 (2 nanometre, nm). The term 'Absolute Biological Effectiveness' (ABE) is introduced as a parameter which indicates the probability to induce a specified effect, per unit incident fluence. In this endeavour, only direct effects are considered in deriving ABE values for various radiations. However other factors such as indirect effects, inter-track action, repair processes and radiation rate, can be incorporated later if required, in the derivation of ABE. ABE values for photons up to 60Co i.e 1253 keV and neutrons up to 105 keV, have been calculated and presented in this thesis. An attempt has been made to re-express the cancer risk coefficients, derived by ICRP, in the new dosimetry system, in terms of the ABE (Absolute Biological Effectiveness). The hypothesis put forward in this thesis is that the induction of a specified biological-end-point in a biological system due to ionising radiations, is determined not by the amount of energy absorbed per unit mass (dose), but rather by the number of events (ionizations) spatially correlated, along the primary radiation track. Based on this hypothesis, a new unified dosimetry system, independent of radiation type, is proposed. Suggestions are made for possible measuring instruments which have the equivalent response characteristics, namely maximum efficiency of detection for the mean free path Success in devising such types of instrument would ensure the practicability of the new dosimetry system, in operational radiological protection.
11
Jalandoni, D. Jay Moreno. "In-phantom measurement of HE or neutron protection dosimetry". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/16777.
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12
Shika, Matsepane Rebecca. "Radiation safety standards at public hospitals in Limpopo Province, South Africa". Thesis, University of Limpopo (Turfloop Campus), 2012. http://hdl.handle.net/10386/859.
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Murray, Bryon Michael. "Determination of eye dose from personnel monitoring devices in medical institutions". Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17040.
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14
陳木華 e Mok-wah Chan. "Exposures to artificial sources of ionising radiation in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B31208496.
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Zakariya, Nasiru Imam. "Development of nuclear-radiological facility monitoring system". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2182.
Testo completoAbstract (sommario):
Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.The widespread application of nuclear science and technology has been the subject of much concern as well as nuclear safety issues. And to ensure the safety of public life, property and environment, it is indispensable to improve the emergency system for nuclear accidents and the environmental monitoring system for nuclear radiation, so that the occurrence of nuclear accidents, terrorist incidents and the resulting hazards can be prevented or minimized. Due to the benefits of radiation which were earlier and now recognized in the use of X-rays for medical diagnosis and then later with the discoveries of radiation and radioactivity, there was rush in exploiting the medical benefits which eventually led fairly to the recognition of the risks and induced harm associated with it. Thus, only the most obvious harms resulting from high doses of radiation, such as radiation burns, were initially observed and protection efforts were focused on their prevention, mainly for practitioners rather than patients. Subsequently, it was gradually recognized that there were other, less obvious, harmful radiation effects such as radiation-induced cancer, for which there is certain risk even at low doses of radiation.
16
Jeyaretnam, Joseph S. "Occupational hazards and radiation safety in veterinary practice including zoo veterinary practice in Australia". Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2003. https://ro.ecu.edu.au/theses/1306.
Testo completoAbstract (sommario):
This thesis contains reviews and research on the occupational hazards of zoo veterinary practitioners in Australia. Although occupational hazards have long been recognised in the veterinary profession, little information is available on the number and magnitude of injuries to veterinarians in Australia, the United Kingdom or the United States. Apart from anecdotal accounts and some limited data, most of the available information is on occupational zoonoses, generally well recognized by veterinarians. Other occupational hazards to which veterinarians are exposed have received scant attention. The veterinary practitioner in a zoo environment has to treat a range of captive wild species which are much more unpredictable and dangerous than domesticated animals. A comprehensive study on occupational hazards sustained by veterinarians in zoological gardens has not been undertaken in Australia. Only one study had been undertaken in the US amongst zoo veterinarians, while comprehensive may not be able to be transposed to zoos in Australia as the species held in Australian zoos differ from those in the US. Personal communication with some senior veterinarians in the zoological gardens in Australia, have elicited further information on the prevalence of occupational hazards sustained by the zoo and wildlife park veterinarians. The prevalence of physical hazards including radiation, chemical and biological hazards reported by veterinary practitioners and the author's own experience as a veterinary practitioner, chairman of the safety committee, member of the animal ethics committee and manager, research In the zoological gardens in Perth, Western Australia have demonstrated a need for a comprehensive study on occupational hazards prevalent among zoo veterinarians. To investigate the occupational hazards including radiological hazards amongst zoo veterinarians in Australia, a self-administered 14-page comprehensive questionnaire comprising 58 questions was mailed to 27 practising zoo veterinarians in Australia. The questionnaire focused on physical injuries, chemical exposures, allergic and irritant reactions, biological exposures, radiological hazards including problems encountered with x-ray machines, use of protective gear and ancillary equipment for radiography, personnel involved in x-ray procedures and in restraining animals, compliance with the Australian National Health and Medical Research Council (NHMRC) Code of Practice (1982), Radiation Safety Regulations (1988) and National Standard for Limiting Occupational Exposure to Ionising Radiation (1995) The result of the study revealed that 60% of the participants sustained physical injuries such as crushes, bites and scratches inflicted by a range of species with some Injuries requiring medical treatment. Also, 50% of the participants suffered from back injuries while 15% reported fractures, kicks, bites necessitating hospitalization. Ninety percent of the participants sustained needlestick injuries ranging from one to 16+ times. Other significant findings include: necropsy injuries, animal allergies, formaldehyde exposure, musculoskeletal Injuries and zoonotic infections. The survey also identified that veterinary practitioners and their staff were exposed to radiation by not complying with the National Health and Medical Research Council (NHMRC) Australian Code of Practice for the Safe Use of Ionising Radiation (1982) which has been framed to minimize exposure to ionising radiation. The majority of the veterinarians in the study group indicated that radiation exposure Is a major occupational hazard to the veterinary profession. Subsequent to the review and research, discussions were held with few senior zoo veterinarians, the Registrar of the Veterinary Surgeons Board and a number of practising senior veterinarians In Australia to collect information on occupational hazards. Additional information was obtained on occupational injuries sustained by the zoo veterinarians through formal discussions with the Director and the two senior veterinarians In the zoological gardens in Sri Lanka. The discussions with the veterinary practitioners in government and private practice revealed that veterinarians experienced a range of occupational hazards including exposure to rabies. Discussions with the dean and the professor of the animal science department focused on the nature of injuries and preventive strategies. In order to obtain information on occupational hazards in the health care industry, the professor of anatomy of the faculty of medicine and a senior surgeon in Sri Lanka were interviewed. This study identified that the zoo veterinarians are routinely exposed to a wide range of occupational hazards. The literature review among veterinary practitioners In US, UK, Australia and Canada have also identified numerous occupational hazards sustained by the veterinarians. The discussions held in Sri Lanka with the professionals in veterinary and health care industry showed that occupational injuries have been common amongst them and they do not have appropriate preventive guidelines in place. This thesis has incorporated recommendations in the form of preventive strategies for minimizing occupational hazards among veterinary practitioners both in zoological gardens and veterinary practices In Australia and in the developed and developing countries.
17
Ghassemi, Hamed 1964. "Design and simulation of an improved operational amplifier for use in radiation environments". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276987.
Testo completoAbstract (sommario):
The effects of radiation on an operational amplifier were investigated through simulation. The μA 741 was simulated using Spice. Under normal conditions the 741 had the following properties: offset Voltage (Vos) of 0.8 mV, bias current (IB) of 27 nA, offset current (Ios) of 1 nA, and an open loop gain (A0.1.) of 112 dB. When exposed to neutron fluence of 5 x 10¹³ n/cm², these parameters changed to offset voltage of 45 mV, bias current of 1500 nA, offset current of 500 nA, and an open loop gain of 66 dB. A new circuit is proposed that provides improvements in the above parameters. The modified circuit gives a Vos of 3 mV, IB of 200 nA, Ios of 34 nA and A0.1. of 93 dB following exposure to a neutron fluence of 5 x 10¹³n/cm².
18
Van, der Walt Jacobus Gert. "Radiation field shaping through low temperature thermal-spray in radiotheraphy". Thesis, Bloemfontein : Central University of Technology, Free State, 2009. http://hdl.handle.net/11462/116.
Testo completoAbstract (sommario):
Thesis (D. Tech.) -- Central University of Technology, Free State, 2009Superficial cancerous lesions are commonly treated through low energy X-ray or electron radiation in radiotherapy. The treatment units that produce the radiation are equipped with square, rectangular and round applicators of different sizes. These applicators attach to the treatment units and define the radiation field size applied during treatment. An applicator is chosen to fit the shape of the cancerous lesion on the patient as closely as possible. Since cancerous lesions are irregular in shape, there will always be an area of healthy tissue between the edge of the lesion and the edge of the standard field shape. This healthy tissue will be irradiated along with the lesion during treatment which is undesirable since the cancer wound heals through reparative growth of the surrounding healthy tissue after treatment. Traditional techniques that were developed to shield this healthy tissue and thus shape the radiation field to the shape of the lesion present various shortcomings. This study introduces a new thermal-spray process for producing radiation field shaping shields which overcomes most of the shortcomings encountered with the traditional field shaping techniques. Since none of the commercially available thermal-spray equipment could be used to produce field shaping shields, new thermal-spray equipment was designed and fabricated tailor made to the application. Different techniques to determine the contours of the treatment area on the patient were investigated. These included a patient contact technique using a plaster bandage impression and a non-contact technique using 3D laser scanning. From the plaster bandage impression a plaster model can be produced onto which a high density low melt material such as Wood’ s alloy can be thermally sprayed to produce a field shaping mask. A model can also be produced from the 3D laser scanning data through laser sintering (LS) in nylon polyamide powder or through computer numerical controlled (CNC) milling in a block of low density polyurethane. The thermal-spray technique was evaluated by comparing the field shaping ability of radiation shields produced through the technique to the field shaping ability of shields produced through the traditional techniques. Radiographic film was used for this purpose and the results are presented in the form of isodensity charts. The required thicknesses of thermal-sprayed field shaping masks to shield radiation of various energies were also determined. The thicknesses were determined through radiation transmission measurements of known thicknesses of sprayed sheets of Wood’ s alloy. X-ray imaging showed that there were no defects present within thermal-sprayed layers of Wood’ s alloy that may negatively affect the shielding ability of masks produced through the technique.
19
Ho, Wing-kwok, e 何永國. "Solar ultraviolet radiation: monitoring, dosimetry and protection". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31222675.
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Peters, Nazlea Behardien. "Determination of effective dose and entrance skin dose from dose area product values for barium studies in adult patients at a large tertiary hospital in the Western Cape". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2627.
Testo completoAbstract (sommario):
Thesis (MSc (Radiography))--Cape Peninsula University of Technology, 2018.Background and objectives The issue of patient doses received during fluoroscopy procedures, raised concerns for the researcher, as there may have been probable past skin injuries or deterministic injuries that may not have been documented. Amongst the radiology staff, there was very little understanding of what the actual dose area product (DAP) value means in real terms of effective dose and entrance skin dose. The aims of the study were to: i) Measure the radiation doses received by the patient and determine a simple means of defining the DAP value to the radiographer in terms of the dose received by the patient. ii) Determine the effective dose, entrance skin dose and the relationship with the DAP value to assist with developing a conversion co-efficient for dose indicators. Method Direct radiation dose measurements can be obtained through DAP meters attached to the diagnostic equipment, but the DAP value is not an direct indication of the effective dose received by the patient. The DAP values captured from the DICOM header information for barium fluoroscopic procedures at a large tertiary was analysed and Diagnostic Reference levels (DRL) were determined for barium swallow, meal and enema procedures. The effective and skin doses were calculated by means of the Monte Carlo program. The results were compared to published values. The relationship between the entrance skin dose and the DAP value was determined and conversion factors were calculated. Results Correlation between the DAP and entrance skin dose and comparative 75th percentile threshold values were determined for barium swallow (BaS), barium meal (BaM) and barium enema (BaE) procedures. Effective to DAP conversation factors for BaS, BaM and BaE are 0.19, 0.26 and 0.60 respectively and 0.15, 0.11 and 0.14 for entrance skin to DAP. Conclusion The the research showed the relationship between the effective dose, entrance skin dose and DAP value and a simple, practical and applicable explanation of the DAP value by means of conversion factors.
21
Meldrum, Lennox R. "Estimate of lifetime UV exposure for selected workers in South East Queensland". Thesis, Queensland University of Technology, 1998.
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22
Seydaliev, Marat Radikovich. "Development and Test of a GEM-Based TEPC for Neutron Protection Dosimetry". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14607.
Testo completoAbstract (sommario):
The effective dose equivalent, H (or the effective dose, E ) to an individual is the primary limiting quantity in radiation protection. However, techniques for measuring H for neutrons have not been fully developed. In this regard a new tissue equivalent proportional counter (TEPC) based on a gas electron multiplier (GEM) for measuring H*(10), which is a conservative estimate of H, for neutrons was designed and constructed.
The deposited energy distribution for two different neutron sources (a Cf-252 source and a AmBe source) was measured using the new TEPC. The measurements were performed using two different proportional gases: P-10 gas and a propane-based tissue equivalent gas at various pressures. A computer simulation of the new TEPC, based on the Monte Carlo method, was performed in order to obtain the pulse height distributions for the two neutron sources. The simulated results and the measured results were compared. Results show that the experimental results agree with the computational results within 20% of accuracy for both Cf-252 and AmBe neutron sources.
A new model GEM-based TEPC was developed for use in obtaining H*(10). The value of H*(10) for the Cf-252 source and for the AmBe source using experimental measurements was obtained. These results are presented in this study. The study shows that the GEM-based TEPC can successfully estimate H*(10). With these results and some refinements, this GEM-based TEPC can directly be used as a neutron rem meter.
23
Ho, Chi-wai, e 何志偉. "Radiation dose due to indoor radon and its progeny in Hong Kong and a study of mitigation methods to control indoor radon exposure". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31236972.
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Vishvakarman, Devasenapathy. "Occupational exposure to ultraviolet radiation in Central Queensland". Thesis, Queensland University of Technology, 1999.
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Jeffries, Cameron. "Radiological exposure due to radioactivity carrying aerosols in a mineral sand processing plant". Thesis, Queensland University of Technology, 2002. https://eprints.qut.edu.au/37123/7/37123_Digitised%20Thesis.pdf.
Testo completoAbstract (sommario):
Mineral sand processing involves a radiological risk due to uranium and thorium series isotopes. Characterising the radioactive aerosol requires measurement of the activity size distribution and the isotopic composition of the aerosol. This is a time consuming process requiring long sampling times and sample counting after a suitable delay time. As a result a number of weeks are required to complete analysis of the activity size distribution. Instrumentation is now available that determines the number and mass distribution within a matter of minutes.
Measurements of activity, number and mass distribution and total activity concentration were made at six sites in the Consolidated Rutile Limited dry processing mill at Pinkenba, Queensland. The activity distribution was measured using a cascade impactor. The number distribution was measured using an Aerodynamic Particle Sizer. The mass distribution was measured with the impactor of two samples and was calculated from the measured number size distributions. The activity distribution was counted twice with a six month gap to test the effect of in growth of 210Po from attached 210Pb. It was concluded that 210Po in growth has a negligible effect on the measured activity size distributions.
The activity and mass distributions measured by the impactor were compared. The impactor measured mass distribution was compared to the APS calculated mass distribution. The activity distribution was compared with the number and mass distributions determined by the APS. Agreement was found between the activity and APS mass distribution. The results show that the activity distribution could be determined quickly by measuring the mass distribution with the APS and applying the total activity concentration.
26
Lopes, Pedro Henrique Silvestre. "Utilização do mapa espacial de radiação e dose acumulada como ferramenta para otimização de doses em pacientes e trabalhadores nas clínicas de medicina nuclear". Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1705.
Testo completoAbstract (sommario):
Esse estudo tem por objetivo geral propor um mapa espacial de doses como ferramenta auxiliar na avaliação da necessidade de otimização de ambientes em serviços de medicina nuclear e, por objetivos específicos, avaliar as dosimetrias individuais dos trabalhadores; analisar a estrutura física dos serviços de medicina nuclear; avaliar as taxas de dose do ambiente. A pesquisa realizada se caracteriza como um estudo de caso, de natureza exploratória e explicativa, em três Serviços de Medicina Nuclear estabelecidos na região Noroeste do Estado do Paraná. Os resultados obtidos indicaram que as taxas de dose avaliadas e a dosimetria dos trabalhadores, em todas as dependências dos serviços pesquisados, respeitam os limites de doses anuais, mas algumas excedem os limites de investigações preconizados na norma NN-CNEN 3.01 (2014). Concluiu-se que o mapa espacial de dose é uma ferramenta importante para os serviços de medicina nuclear, pois facilita a visualização das áreas com maior concentração de radiação, bem como a revisão contínua de tais medidas e recursos para identificar quaisquer falhas e deficiências na sua aplicação, corrigi-las e evitar suas repetições, além de verificar regularmente se os objetivos de proteção radiológica estão sendo alcançados.This study has as general aim to propose a spatial map of doses as an auxiliary tool in assessing the need for optimization of the workplace in nuclear medicine services. As specific aims, we assessed the workers individual dosimetry; we analyzed the facilities of the nuclear medicine services; and we evaluated environment exposure rates. The research is characterized as a case study, with an exploratory and explanatory nature. It was conducted in three Nuclear Medicine Services, all established in the Northwest of the Paraná State. Results indicated that the evaluated dose rates and workers dosimetry, in all the dependencies of the surveyed services, are within the limits of annual doses. However some exceeded the limits recommended in the standard CNEN-NN 3:01 (2014). It was concluded that the spatial map dose is an important tool for nuclear medicine services because it facilitates the visualization of areas with highest concentration of radiation, and also helps in the constant review of these measures and resources, aiding in the identification of any failures and shortcomings, providing resources to correct any issues and prevent their repetition. The spatial map dose is also important for the regular inspection, evaluating if the radiation protection objectives are being met.
27
Stoneham, Melissa J. "Healthy public policy in local government facilitating and inhibiting factors: Shade creation as a case study". Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/36761/1/36761_Digitised%20Thesis.pdf.
Testo completoAbstract (sommario):
Sun safe behaviour is a modifiable behaviour and therefore the potential for change is large. Targeted interventions that use multi-strategy or healthy public policy approaches may be successful at increasing sun safe behaviours and creating supportive environments that promote positive health outcomes. This research considered sun safety, and more specifically shade creation, within the domain of public places that integrate human leisure-time exposure to ultraviolet radiation (UVR). It was felt that the potential for behaviour change through the adoption of healthy public policy was probably greatest in this domain. Specifically this research considered the creation of shade as a complementary strategy to individual sun safe behaviours, and investigated how best local governments can create shade at public facilities. Policy considerations that have the potential to increase shade creation were identified within the many activities at the local government level. For example, legislation and regulations that control a community's infrastructure may be modified to mandate shade for walkways, public parks and swimming pools for new communities. Policy changes may also promote or change behaviours related to sun safety. Authors have stated that strategies such as governmental legislation and policies that are being used to diffuse an innovation should be investigated to determine the factors that have played crucial roles in the process (Oldenburg, Hardcastle & Kok, 1997a). This research considered these comments and aimed to identify public health efforts to increase shade that expanded beyond targeting individuals, to include activities that create complex changes in community design and facilities through the introduction of healthy public policies.
Aims: The research described in this thesis was designed to provide local governments throughout Australia, and more specifically Queensland, with information and a model of how best to develop and adopt healthy public policy to ensure public health issues that had no legal standing were integrated into their core business.
An important aspect of the study was to investigate local governments that were at different stages of the policy process to enable the identification of a range of inhibiting and facilitating factors.
Methods: This research relied on case studies of local governments that examined the variables such as policy design, key stakeholders, resources, sources of diffusion, community involvement, environment receptivity, policy outcomes and barriers to successful healthy public policy development, adoption and where possible, implementation. In total, fifteen local governments were included in this study.
Qualitative research methods were used extensively to gather data within each case study setting. Open-ended questionnaires were used to target three groups of professionals. These included key informants, additional stakeholders and professionals external to the local government setting. Key informants were identified as the primary policy adopter. Additional stakeholders had the potential to influence shade creation within the Local government context, and the professionals external to the local government were identified as being able to assist in developing, adopting and implementing shade creation policies within the community setting.
Data were predominantly analysed through content analysis where major themes were identified in responses, coded and counted to identify the leading trends.
Relation to Previous Work: All Queensland local governments (n=125) were forwarded a copy of "Shade Creation for Local Government - Policy Guidelines" (AIEH, 1995) which contained a model shade creation policy, in 1995. This dissemination occurred prior to this research commencing.
Results: This research subsequent to this dissemination of information identified a number of facilitating and inhibiting factors for the development and adoption of healthy public policy at the local government level. The facilitating factors that promoted policy development and adoption included the nature and position of local government within the community, the perceived priority of the policy process, the disposition of local government Officers and the extent of community or external stakeholder input. Five primary barriers to the development and adoption of healthy public policy at the local level included deficiencies in policy design, inadequate political support, organisational barriers, resource constraints and external factors such as the risk of vandalism.
Based on these findings a systems model was developed with the objective of guiding the development and adoption of healthy public policy at the local level.
Conclusion: This research identified that although many local governments have been creating shade for many years, this has been occurring on an ad hoc basis, without support from formal policies or procedures. Without formal policy, there is little galvanising infrastructure to ensure shade creation activities occur into the future, regardless of staffing levels and interests or funding.
This research investigated this process and identified a number of factors that inhibit and facilitate the healthy public policy process in the local government setting.
28
Flaspoehler, Timothy Michael. "FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45743.
Testo completoAbstract (sommario):
In the following work, the MAVRIC sequence of the Scale6.1 code package was tested for its efficacy in calculating a wide range of shielding parameters with respect to HTGRs. One of the NGNP designs that has gained large support internationally is the VHTR. The development of the Scale6.1 code package at ORNL has been primarily directed towards supporting the current United States' reactor fleet of LWR technology. Since plans have been made to build a prototype VHTR, it is important to verify that the MAVRIC sequence can adequately meet the simulation needs of a different reactor technology. This was accomplished by creating a detailed model of the VHTR power plant; identifying important, relevant radiation indicators; and implementing methods using MAVRIC to simulate those indicators in the VHTR model.
The graphite moderator used in the design shapes a different flux spectrum than water-moderated reactors. The different flux spectrum could lead to new considerations when quantifying shielding characteristics and possibly a different gamma-ray spectrum escaping the core and surrounding components. One key portion of this study was obtaining personnel dose rates in accessible areas within the power plant from both neutron and gamma sources. Additionally, building from professional and regulatory standards a surveillance capsule monitoring program was designed to mimic those used in the nuclear industry. The high temperatures were designed to supply heat for industrial purposes and not just for power production. Since tritium, a heavier radioactive isotope of hydrogen, is produced in the reactor it is important to know the distribution of tritium production and the subsequent diffusion from the core to secondary systems to prevent contamination outside of the nuclear island.
Accurately modeling indicators using MAVRIC is the main goal. However, it is almost equally as important for simulations to be carried out in a timely manner. MAVRIC uses the discrete ordinates method to solve the fixed-source transport equation for both neutron and gamma rays on a crude geometric representation of the detailed model. This deterministic forward solution is used to solve an adjoint equation with the adjoint source specified by the user. The adjoint solution is then used to create an importance map that can weight particles in a stochastic Monte Carlo simulation. The goal of using this hybrid methodology is to provide complete accuracy with high precision while decreasing overall simulation times by orders of magnitude. The MAVRIC sequence provides a platform to quickly alter inputs so that vastly different shielding studies can be simulated using one model with minimal effort by the user. Each separate shielding study required unique strategies while looking at different regions in the VHTR plant. MAVRIC proved to be effective for each case.
29
Santos, Romilda Prado dos. "Exposição ocupacional às radiações ionizantes durante cirurgias ortopédicas guiadas fluoroscopicamente". Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/331.
Testo completoAbstract (sommario):
A Radiologia tem sido considerada uma das áreas da Medicina que mais se desenvolve, especialmente com o aporte de novas tecnologias. Entre as aplicações da Radiologia Intervencionista destaca-se a utilização da fluoroscopia no centro cirúrgico em complemento às cirurgias ortopédicas, objeto da presente pesquisa. Entretanto, alguns complexos e longos procedimentos guiados fluoroscopicamente podem resultar em altos níveis de exposição ocupacional às radiações ionizantes para equipe de cirurgia ortopédica e trabalhadores de saúde, induzir sérios danos à saúde. Levando em conta esses aspectos, o objetivo geral dessa pesquisa consiste em determinar a exposição ocupacional da equipe de cirurgia ortopédica em procedimentos guiados por fluoroscopia e verificar dentre as cirurgias observadas a que oferece maior exposição ocupacional às radiações ionizantes, como também, a aplicação dos princípios básicos de proteção radiológica nestes procedimentos. A metodologia utilizada para essa pesquisa foi a qualiquantitativa do tipo exploratória. A pesquisa foi realizada no Hospital de Clínicas da Universidade Federal de Curitiba (UFPR). Os sujeitos pesquisados foram os membros da equipe de cirurgia ortopédica, ou seja, médicos ortopedistas, residentes, anestesias, instrumentador cirúrgico, técnicos e auxiliares de enfermagem, e enfermeiros. A coleta de dados foi realizada de 01 de janeiro a 30 de maio de 2011. Contribuíram para a pesquisa, 44 trabalhadores que responderam uma entrevista coletiva, e um questionário com 25 perguntas fechadas. foi constituídos quatro grupos de onze participantes cada, seguida de análise documental e de monitoração da área pesquisada e individual. Os resultados mostraram que os profissionais de saúde do setor pesquisado expõem-se às radiações ionizantes, devido à demanda de cirurgias guiadas por equipamentos emissores de radiação ionizantes fluoroscopicamente, e a falta de conhecimento em radioproteção. Diante dessas constatações foram sugeridas pelos grupos medidas de prevenção a essas exposições de modo a minimizar possíveis efeitos biológicos das radiações ionizantes. Foi concluído que existe exposição ocupacional com os trabalhadores do setor pesquisado, os mesmos tem pouco conhecimento quanto ao uso dos equipamentos de radioproteção nos procedimentos cirúrgicos com equipamentos emissores de radiações ionizantes, não usam corretamente os monitores individuais.Radiology has been considered one of the areas of medicine that most devel-ops, especially with the contribution of new technologies. Among the applications of Interventional Radiology highlights the use of fluoroscopy in the surgical center in addition to co-orthopedic surgeries, the object of the present research. Entretan-to some complex and lengthy fluoroscopically guided procedures can result in high levels of occupational exposure to ionizing radiation for e-quipe orthopedic surgery and health workers, induce serious damage to health. Considering these aspects, the general objective of this research is to de-termine the occupational exposure of the team of orthopedic surgery proce-dures guided by fluoroscopy and verify observed among the surgeries that offer greater occupational exposure to ionizing radiation, but also the application of basic principles of radiological protection in these procedures. The methodology for this research was the qualitative and quantitative exploratory type. The research was conducted at Hospital de Clinicas, Federal University of Curitiba (UFPR). Study subjects were members of the team of orthopedic surgery, or orthopedic doctors, residents, anesthesia, surgical instrumentator, technicians and nursing assistants, and nurses. Data collection was performed from January 1 to May 30, 2011. Contributors to the survey, 44 workers who answered a news conference, and a questionnaire with 25 closed questions of. was divided in four groups of eleven participants each, followed by document analysis and monitoring of the area and searched individually. The results we-strated that the health sector professionals surveyed were exposed to ionizing radiation, due to demand-driven surgery equipment emitting ionizing radiation fluoroscopically, and the lack of knowledge in radioprote-tion. Before these findings were suggested by the groups pre-vention measures of these exposures to minimize possible biological effects of ionizing radiation-tions. It was concluded that occupational exposure exists with re-worked in the sector researched, they have little knowledge about the use of radiation protection equipment in surgical procedures with equipment emitting ionizing radiation, properly use the monitors indi-tions.
30
Wooten, Hasani Omar. "Time-Dependent Neutron and Photon Dose-Field Analysis". Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7153.
Testo completoAbstract (sommario):
A unique tool is developed that allows the user to model physical representations of complicated glovebox facilities in two dimensions and determine neutral-particle flux and ambient dose-equivalent fields throughout that geometry. The code Pandemonium, originally designed to determine flux and dose rates only, has been improved to include realistic glovebox geometries, time-dependent source and detector positions, time-dependent shielding thickness calculations, time-integrated doses, a representative criticality accident scenario based on time-dependent reactor kinetics, and more rigorous photon treatment. The photon model has been significantly enhanced by expanding the energy range to 10 MeV to include fission photons, and by including a set of new buildup factors, the result of an extensive study into the previously unknown "purely-angular effect" on photon buildup. Purely-angular photon buildup factors are determined using discrete ordinates and coupled electron-photon cross sections to account for coherent and incoherent scattering and secondary photon effects of bremsstrahlung and florescence.
Improvements to Pandemonium result in significant modeling capabilities for processing facilities using intense neutron and photon sources, and the code obtains comparable results to Monte Carlo calculations but within a fraction of the time required to run such codes as MCNPX.
31
De, Brouwer Christophe. "Analyse des diverses réglementations concernant la radioprotection: sur les plans international et national et examen de leurs cohérences par rapport aux données actualisées de radiobiologie". Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211530.
Testo completo
32
Porto, Lorena Elaine. "Avaliação da dose em pacientes pediátricos submetidos a exame de tomografia computadorizada". Universidade Tecnológica Federal do Paraná, 2014. http://repositorio.utfpr.edu.br/jspui/handle/1/1070.
Testo completoAbstract (sommario):
CAPESA dosimetria em tomografia computadorizada (TC) envolve desde a determinação de grandezas dosimétricas específicas de TC até a estimativa de dose absorvida e dose efetiva. Entretanto, deve-se considerar que por envolver radiação ionizante no seu processo, este procedimento apresenta riscos inerentes e sua utilização deve ponderar o custo e o benefício propiciado pelo procedimento. A proteção de pacientes submetidos a exames radiológicos, de uma maneira geral, é determinada pelos princípios da “justificação” e “otimização”. Desta forma, torna-se importante o conhecimento dos níveis de radiação nas exposições durante um procedimento tomográfico. Estes níveis foram observados através da estimativa das grandezas específicas para tomografia computadorizada, tais como o Índice de kerma no ar (C100,ar), o Índice de kerma ponderada (Cw) e o produto kerma comprimento (PKL,CT), e em estimados os níveis de dose efetiva e risco para o estudo tomográfico computadorizado de crânio, tórax e abdômen realizado com múltipla varredura. Os valores obtidos foram comparados com os obtidos por simulação computacional por Monte Carlo. Eles foram utilizados, neste estudo, no cálculo da Dose Efetiva e risco e para comparação com o nível de referência de dose estabelecido pela Comunidade Européia. Utilizando-se o programa de simulação computacional Dosecal X_CT e o protocolo ICRP 103, foram determinadas as grandezas de radioproteção relevantes para o estudo que são os valores de dose efetiva referente ao procedimento. O nível do Produto kerma comprimento (PKL,CT), utilizando-se o C100,ar previamente estabelecido, foi também obtido e comparado com o nível de referência de dose estabelecido pela comunidade europeia. Os valores encontrados até agora estão dentro dos limites dos Níveis de Referência.
The computed tomography (CT) dosimetry involves measurements of specific quantities of CT, which are part of CT quality control procedures, as well as calculation of absorbed and effective doses to a patient submitted to CT examinations. Since CT uses ionizing radiation, it should be considered that a precise balance between risks and benefits must be achieved in order to justify the adoption of such technique. Radiation protection of patients undergoing radiological exams is established based on the justification and optimization principles. Nowadays, it is important to know the dose radiation levels to which a patient is exposed during a tomographic procedure. Those are given by the estimation of specific dosimetric quantities called the computed tomography kerma index in air, C100,air, the weighted computed tomography kerma index Cw, kerma length product, PKL,CT and then the levels of effective dose and risk to the computerized CT scan study of skull, thorax and abdomen with a multiple scanning. The values obtained were compared with those obtained by computer simulation using Monte Carlo method. The protection quantities organ absorbed dose, effective dose and risk for comparison with the reference dose level established by the European Community. Using computational simulation program of the Dosecal X_CT and the ICRP 103 Protocol, were certain quantities of radiation protection relevant to study which are the values of effective dose for the procedure. The dose length product PKL,CT level was calculated from the C100,air and compared to the reference dose level established by the European Community. The values found so far are within the limits of the reference levels.
33
Modiba, Reshoketswe Mokgadi. "Compliance to radiation safety standards by radiographers and dental professionals in Waterberg District Hospitals, Limpopo Province". Thesis, 2014. http://hdl.handle.net/10386/1369.
Testo completoAbstract (sommario):
Thesis (MPH. ) --University of Limpopo, 2014This dissertation reports on findings from a qualitative research that sought to investigate adherence and compliance to radiation safety protocols by radiographers and dental professionals in the Waterberg District. The study also sought to determine the knowledge the participants had on the chronic ill-effects of occupational exposure to radiation, safety protocols and their professional experience in dealing with occupational exposure to radiation. Altogether 60 participants from 8 health institutions in the Waterberg district took part in the study. They were compromised of males and females with ages ranging from 22-60 years. The response rate was 75% (n=45/60). The empirical data of the study shows a consistent yet disconcerting pattern among practitioners about safety compliance, safety protocols and their understanding of long term effect of occupational exposure to radiation. Despite their impressive knowledge of X-rays being a source of ionizing radiation, the level of their understanding of ill-effects thereof was of great concern. The general failure by both professionals in complying with the most basic safety protocols is worrisome. In a nutshell, yet some of the practitioners were found to be greatly exposed to radiation, their daily practices were found not consistent with procedures dictated by the guidelines on the use of medical X-ray equipment. Overall, only 59% of radiographers always wore their dosimeters, a basic monitoring and protective tool to measure their radiation exposure. In the study, only 38% of the dentists were found to be compliant and overwhelmingly alluded this to their employers being unable to supply them with crucial protective clothing, a finding that the researcher cannot dispute as indicated in the responses by the two groups. The failure of the employer in enforcing monitoring and assuring safety to the employees, patients and the general public emerged from this study. Various non-compliance patterns could be attributed to the participants and others to the employer. Protocols as clearly stipulated in R1332 of Hazardous Substance Act 15 of 1973 and other guidelines are not adhered to.
34
Fundak, Robert. "Rapid establishment of emergency action areas as a consequence of large scale radioactive material releases from fixed nuclear facilities". Thesis, 1995. http://hdl.handle.net/1957/35225.
Testo completoAbstract (sommario):
Rapid emergency response decisions from a radiation release are necessary in
order to prevent the general public from being exposed to a potential radiation hazard.
A one meter exposure rate measurement is all that is necessary to establish relocation
and food control areas when the ground is contaminated at the Protective Action Guide
minimum response levels. With the results of these calculations, a known one meter
exposure rate is all that is necessary to establish relocation and food control areas for a
release from the WNP-2 commercial nuclear power plant or a release from a waste
tank at the Hanford site. The calculated one meter exposure rate for WNP-2 is 1.32
��R/hr at twenty-four hours. The calculated one meter exposure rate for the Hanford
tanks is 14.97 ��R/hr.Graduation date: 1995
35
Kros, Charles. "Radiological dose assessment for the leaking coil replacement on the Necsa radioactive effluent evaporator facility". Thesis, 2014.
Cerca il testo completoAbstract (sommario):
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2013.In this study a dose assessment is used to demonstrate conformance to national and international dose limits for workers and meets the Necsa ALARA goals for a radiological repair task. The dose assessment methodology is based on international standards, principles and criteria and involves the process of determining radiological dose, through the use of exposure scenarios, bioassay results, monitoring data, source term information, and pathway analysis. The radiological task is the replacement of the leaking steam coil on the radioactive effluent evaporator facility at Necsa. The effluent treatment facility, its operation, the origin of the radioactive effluent and hazards associated with the leaking coil are discussed. The dose assessment is supported by measurement of actual radiological conditions in the area where the task will be performed using suitable and calibrated instrumentation. The assumptions were limited to the physical phenomena associated with the behaviour of materials and available from national and international studies. The importance of proper planning of all the tasks associated with the replacement task as well as sources of inaccuracy and uncertainty associated with the calculated doses are discussed. The results of the assessment are evaluated in terms of ALARA, namely the safety fundamental principles of justification, optimisation and limitation of facilities and activities. Other dose reduction options, such as personal protective clothing and equipment, were considered to show that the doses conform to the ALARA objectives of Necsa and other operation optimisation measures.
36
Feeney, Donovan L. "An analysis of secondary radiation doses in a South African neonatal high care unit". Thesis, 2019. https://hdl.handle.net/10539/29854.
Testo completoAbstract (sommario):
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand,
Johannesburg, in partial fulfillment of the requirements for the degree of Master of Medicine in
Diagnostic Radiology
Johannesburg 2019Introduction: Neonates in a neonatal ICU or high care unit are a high-risk population. Besides a vulnerability to medical and surgical conditions, which often require radiological investigation, they are also at risk from the effects of radiation used in imaging. These risks increase with radiation dose. Numerous studies have assessed the dose due to primary radiation, however few have assessed the secondary radiation dose, and none have quantified the dose over time. Aim: To quantify the secondary radiation dose in our neonatal high care unit in order to determine if additional protective measures from secondary radiation are necessary. Method: A prospective analytic study was undertaken using multiple thermoluminescent devices in a cubicle of a neonatal high care unit, and control dosimeters outside the unit. Dosimeters were deployed for a 4 week period. Simultaneously, data was collected on patient numbers, and the X-rays performed in the unit. Results were compared to reference ranges for primary and secondary radiation (2-3 mSv per annum). Results: The average secondary radiation dose was 0.108mGy (p=0.6553) over 4 weeks, less than the expected background radiation dose of 0.17 – 0.25mGy. There was a large number of patients moving through the unit during the study period (89), with an average of 14 patients in the unit at a time, however this did not result a large number of X-ray exposures. Twenty one percent of patients were in the unit for less than a day, and 49 % were admitted for less than 3 days. Sixteen patients (18%) had X-ray investigations, with a total of 21 investigations and 30 exposures. Thirty percent of primary radiation dose was due to repeat exposures. Patients receiving X-rays had an average of 2 X-ray examinations (range: 1 to 4 studies) performed, with an average Entrance Skin Dose of 196.7µSv (0.197mGy) – range 77 to 554µSv (0.077mGy to 0.554mGy). There was no statistically significant difference between weeks or zones (p=0.1060 and p=0.8237 respectively), and differences in primary radiation doses was likely due to chance. Conclusion: Additional measures to protect patients in the unit from secondary radiation are unnecessary. There was a low probability of patients having a radiological investigation in the neonatal high care unit, and secondary radiation doses were not measurably higher than background radiation.
TL (2019)
37
Kegopotsemang, Onalenna. "Evaluation and redesign of radiation shielding in a radionuclide production facility at a particle accelerator / Onalenna Kegopotsemang". Thesis, 2004. http://hdl.handle.net/10394/11338.
Testo completoAbstract (sommario):
iThemba LABS is a particle accelerator facility housing a radionuclide production facility that uses a 66 MeV proton beam to produce radionuclides for medical and industrial use. Ionising radiation is produced by a variety of sources at Themba LABS. Ionising is a health hazard. High doses can cause acute radiation syndrome, i.e. "radiation sickness". Lower doses cannot cause acute symptom, but carry a risk of radiation-related cancer. Ionising radiation is also detrimental to materials, and can damage polymers and lubricants e.g. Shielding is used to reduce radiation levels to values that should be safe for the intended level of human occupancy. Shield performance is vital to human health and the life expectancy of polymers and lubricants, so that quality management in shield design is very important. However, until 2003, there has been no formal system at iThemba LABS to evaluate and improve all radiation shield designs and layouts from a radiation protection perspective. This study deals with evaluating and redesigning radiation shielding in the radionuclide production facility of iThemba LABS. There are several designs and layouts in the radionuclide production building of iThemba LABS that lead to unnecessary exposure of personnel to ionising radiation. The shielding in these areas are sub-standard. Performance criteria for radiation shields are developed. Inadequate radiation shields are identified. The identified inadequate shields are: the processing hotcells, the target store room and the hotcells in the radiopharmaceutical dispensing laboratory, Point-Kernel radiation shielding calculations are done to specify materials and material thickness that will adequately protect workers against ionising radiation.Thesis (MSc. ARST) North-West University, Mafikeng Campus, 2004
38
Bartolo, William Charles Francis Safety Science Faculty of Science UNSW. "Radioisotope laboratory safety auditing, compliance and associated problems in NSW". 2007. http://handle.unsw.edu.au/1959.4/40787.
Testo completoAbstract (sommario):
This thesis reports on the modification of the "Safecode" computer-program to monitor the safety of radio-isotope laboratories, and its application to 24 compliance audits in NSW during the period 1999 to 2006. Additionally, an attempt was made to predict the level of risk to persons working within those laboratories. Based on the current NSW radiation control legislation and the relevant Australian Standards a comprehensive audit checklist was developed for this project. Each safety requirement in those documents was used to develop a question, resulting in 187 questions in the checklist. The questions were grouped into the following seven Topic Elements: Licensing and Registration; Radiation Safety Administration; Personal and Area Monitoring; Dose Limit Compliance; Documentation/Records; RSO/RSC Qualifications and Duties; and Facilities. A novel feature was the allocation of "weighting factors" to individual questions and Elements. The computer program facilitated analysis of data and provided output in spreadsheet and graphical form. .The on-site physical audits were conducted using the project check-list, and were supplemented by discussions with the client's representative. The results showed significant variation between sites with overall compliance scores ranging from 37% to 94%. The reasons for this large variation stem from differences in local management regime; the appointment of an RSO at one site; variation in the extent of adoption of relevant codes of practice; and legislative weaknesses. Further analysis of the data presented legal, advisory and combined scores for each Element for each site; and variations over time. The graphic displays of the results were appreciated by client management. The formula developed to predict risk, based on the physical parameters alone, showed little relationship to the total audit scores. Statistical analysis of the two data groups by correlation coefficient confirmed this general finding. Development of the formula however served to indicate deficiencies in the Question Set, and the importance of human factors in achieving a high degree of safety.
39
Doodoo-Amoo, David Nii. "Development of composite materials for non-leaded glove for use in radiological hand protection". 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3077629.
Testo completo
40
Mallory, Stacy L. "An analysis of shielding requirements in conjunction with current radiographic imaging practices". Thesis, 2003. http://hdl.handle.net/1957/30865.
Testo completoAbstract (sommario):
The National Council of Radiation Protection and Measurements
Report No. 49, originally issued on September 15, 1976, has been the
primary design guide for diagnostic x-ray structural shielding in the
United States. To further protect the public from various areas of
medical radiation exposure, NCRP issued Report 116 in 1987 to
decrease the public exposure limits. These new limits used in
conjunction with NCRP 49 to determine shielding requirements for
diagnostic radiological rooms can be shown to over-shield based on
current technologies and protocols.
This paper explores the NCRP conservative assumptions that
physicists specifying barrier requirements for diagnostic x-ray facilities
normally utilize. These evaluated assumptions, which are incorporated
in the methodology and attenuation data presented in NCRP Report 49
formulas, include relatively high single kVp's, a "one size fits all"
workload default, and the lack of attenuation factors by the patient, the
wall, and the film. In essence, an analysis of the conservative nature of
NCRP 49 is demonstrated.
An example of Primary and Secondary Shielding Methodology
utilizing NCRP 49 and NCRP 116 dose limits is provided as well as the
cost factors associated with the results. These examples are further
evaluated using a Monte Carlo software program.
In addition, an analysis of actual current radiographic conditions
in an imaging room is performed. This is done to determine first, the
actual mA utilized for specific exams; secondly, the actual mA-min
weekly workload; and thirdly, the tangible exams performed per week
in small and large medical facilities.
Based on the information and analysis presented, this paper
concludes that the formulas for NCRP 49 and NCRP 116 need to be
reexamined. Furthermore, this paper also demonstrates once again
that NCRP 49, utilizing NCRP 116 dose limits is extremely
conservative.Graduation date: 2004
41
Gerstenmaier, Jan Frank. "Public health implications of medical diagnostic radiation exposure". Diss., 2012. http://hdl.handle.net/10500/6085.
Testo completoAbstract (sommario):
Radiation from Computed Tomography (CT) is now the major contributor to population
radiation dose. Despite controversy around the dose-effect relationship of radiation from
CT, the linear non-threshold (LNT) theory is endorsed by many authorities, and
constitutes the basis of cancer risk estimates. The purpose of this study was (1) a
literature review of radiobiological theories, and methods of dose saving stategies in
CT; (2) to highlight the importance of dose saving in CT, and to demonstrate how dose
can be saved in a radiology department: Following a 40% reduction in reference X-ray
tube current for a CT of the urinary tract, the effecitve dose and estimated lifetime
attributable risk of incident cancer due to this CT in a group (n=103) were reduced by
37% and 38% in an age and sex-matched group respectively. The literature review
showed that the public health implications of CT radiation exposure remain uncertain.Health Studies
M.A. (Public Health)
42
Shih, Han. "Step-growth thiol-ene photopolymerization to form degradable, cytocompatible and multi-structural hydrogels". Thesis, 2014. http://hdl.handle.net/1805/3842.
Testo completoAbstract (sommario):
Indiana University-Purdue University Indianapolis (IUPUI)Hydrogels prepared from photopolymerization have been used for a variety of tissue engineering and controlled release applications. Polymeric biomaterials with high cytocompatibility, versatile degradation behaviors, and diverse material properties are particularly useful in studying cell fate processes. In recent years, step-growth thiol-ene photochemistry has been utilized to form cytocompatible hydrogels for tissue engineering applications. This radical-mediated gelation scheme utilizes norbornene functionalized multi-arm poly(ethylene glycol) (PEGNB) as the macromer and di-thiol containing molecules as the crosslinkers to form chemically crosslinked hydrogels. While the gelation mechanism was well-described in the literature, the network properties and degradation behaviors of these hydrogels have not been fully characterized. In addition, existing thiol-ene photopolymerizations often used type I photoinitiators in conjunction with an ultraviolet (UV) light source to initiate gelation. The use of cleavage type initiators and UV light often raises biosafety concerns. The first objective of this thesis was to understand the gelation and degradation properties of thiol-ene hydrogels. In this regard, two types of step-growth hydrogels were compared, namely thiol-ene hydrogels and Michael-type addition hydrogels. Between these two step-growth gel systems, it was found that thiol-ene click reactions formed hydrogels with higher crosslinking efficiency. However, thiol-ene hydrogels still contained significant network non-ideality, demonstrated by a high dependency of hydrogel swelling on macromer contents. In addition, the presence of ester bonds within the PEGNB macromer rendered thiol-ene hydrogels hydrolytically degradable. Through validating model predictions with experimental results, it was found that the hydrolytic degradation of thiol-ene hydrogels was not only governed by ester bond hydrolysis, but also affected by the degree of network crosslinking. In an attempt to manipulate network crosslinking and degradation rate of thiol-ene hydrogels, different macromer contents and peptide crosslinkers with different amino acid sequences were used. A chymotrypsin-sensitive peptide was also used as part of the hydrogel crosslinkers to render thiol-ene hydrogels enzymatically degradable. The second objective of this thesis was to develop a visible light-mediated thiol-ene hydrogelation scheme using a type II photoinitiator, eosin-Y, as the only photoinitiator. This approach eliminates the incorporation of potentially cytotoxic co-initiator and co-monomer that are typically used with a type II initiator. In addition to investigating the gelation kinetics and properties of thiol-ene hydrogels formed by this new gelation scheme, it was found that the visible light-mediated thiol-ene hydrogels were highly cytocompatible for human mesenchymal stem cells (hMSCs) and pancreatic MIN6 beta-cells. It was also found that eosin-Y could be repeatedly excited for preparing step-growth hydrogels with multilayer structures. This new gelation chemistry may have great utilities in controlled release of multiple sensitive growth factors and encapsulation of multiple cell types for tissue regeneration.