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The radiation tolerance and development of robotic platforms for nuclear decommissioningNancekievill, Matthew January 2018 (has links)
There is an increasing desire to deploy low-cost robotic systems in nuclear decommissioning environments. These environments include long-standing nuclear fuel storage ponds such as those at the Sellafield site in Cumbria, UK as well as areas affected by expulsion of radioactive material from sites such as the Fukushima accident in Japan 2011. An area of concern for the successful deployment of robotic platforms in a radioactive field is their radiation tolerance. It is necessary to understand how the low-cost components used within robotic platforms react to radiation exposure in a nuclear decommissioning environment. This thesis discusses the radiation tolerance of multiple commercial-off-the-shelf (COTS) components that are commonly used within a robotic platform up to an expected yearly total dose of 5 kGy(Si). It was found that COTS voltage regulators are susceptible to gamma exposure, however, development of a discrete voltage regulator showed an increased tolerance to radiation under certain load and temperature conditions. Inertial measurement units were also investigated and found to be susceptible to a total ionising dose.
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Interface and Size Effects on TiN-based Nanostructured Thin FilmsKim, Ickchan 2011 May 1900 (has links)
Titanium nitride coatings have been widely applied and studied as high temperature diffusion barrier for silicon devices in microelectronics, wear resistant coatings in turbine blade materials, and materials for future high temperature nuclear reactors. In order to enhance the material property, superlattices is one of artificially engineered protective coatings, such as AlN/TiN and TaN/TiN multilayered films. Epitaxial cubic multilayer films, TaN/TiN and AlN/TiN nanolayers were grown on Si(001) by Pulsed Laser Deposition (PLD) with various nanolayer thicknesses and number of interfaces. Microstructural studies include X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution TEM with ion-irradiation experiments. Electrical, mechanical and thermal property studies were conducted for the interface and size effects on the nanolayers by using nanoindentation and Transient Thermo-Reflectance (TTR) methods. The microstructural and hardness study on TaN/TiN films with ion irradiation (12 keV and 50 keV He ) suggest no obvious microstructural or mechanical behavior change due to ion irradiation. In addition, titanium nitride that serves as effective diffusion barrier to prevent the inter-diffusion between the nuclear fuel and the cladding material was studied in order to enhance the lifetime of the fuels and the reliability of the fuel claddings. The TiN has good adhesion with the stainless steel and higher hardness than that of bulk TiN on the stainless steel. Thermal conductivity test demonstrates that thin TiN film has compatible thermal conductivity as the MA957 and HT-9 bars. The size effect on electrical resistivity is dominant in both of the epitaxial cubic and the polycrystalline TiN thin films in the thickness ranged from ~60 nm down to ~35nm. In the TaN/TiN multilayer, the grain scattering effect on resistivity is dominant rather than interface influence on the resistivity with comparing epitaxial cubic phase and polycrystalline phase. The microstructure and hardness studies of the AlN/TiN multilayer films with He implantation present that the suppression of amorphization in AlN layers and the reduction of radiation-induced softening were achieved in all nanolayer films. Radiation tolerance was found to be size dependent and the layer thickness leading to the highest radiation tolerance was around 10 nm. In addition, the embedded epitaxial cubic AlN with cladding TiN nanolayers showed higher effective thermal conductivity than that of AlN single layer as well as the embedded polycrystalline AlN in the thickness ranged from 10 nm down to 2 nm. It confirms a suppressed size effect, which reduces the amount of decrease in through-plane thermal conductivity.
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Enhanced Radiation Tolerance in Sputtered Cu/V MultilayersFu, Engang 2009 August 1900 (has links)
High energy particle (neutron, proton and He ions) irradiation to materials
typically leads to deteriorating properties, including void swelling, blistering,
embrittlement, fracture and exfoliation of surfaces. This dissertation examines size
dependent radiation damage in nanostructured metallic multilayers synthesized by the
magnetron sputtering technique at room temperature. It reveals the roles of interface in
achieving enhanced radiation tolerance in metallic materials. The microstructure and
mechanical properties of as-deposited Cu/V multilayer films are systemically
investigated, providing the basis for studying radiation damage mechanisms.
Sputter-deposited Cu/V multilayers are subjected to helium (He) ion irradiation at
room temperature with a peak dose of 6 displacements per atom (dpa). The average
helium bubble density and lattice expansion induced by radiation decrease significantly
with decreasing h, where h is individual layer thickness. The magnitude of radiation
hardening decreases with decreasing h, and becomes negligible when h is 2.5 nm or
less. The interactions between interfaces and radiation induced point defects and the
evolution of microstructurs and mechanical behavior are discussed. This study indicates that nearly immiscible Cu/V interfaces spaced a few nm apart can effectively reduce the
concentration of radiation induced point defects.
Dose dependent radiation damage at room temperature in these Cu/V multilayers
is systematically investigated with a peak dose in the range of 1-12 dpa. Peak bubble
density increases with increasing dose, but it is much lower in Cu/V 2.5 nm multilayers
than that in Cu/V 50 nm specimens. A similar radiation hardening trend is observed in
multilayers irradiated at different fluences. Radiation hardening increases with dose and
seems to reach saturation at a peak dose of 6 dpa. Negligible hardening for fine ( h less than/equal to 2.5
nm) multilayers is observed at all dose levels.
Thermal stability of Cu/V multilayers is revealed by in situ annealing inside a
transmission electron microscope. During isothermal annealing at 600 degrees C grain boundary
grooving occurs across layer interfaces in Cu/V 50 nm specimens, whereas Cu/V 5 nm
multilayers appear rather stable. Annealing of Cu/V multilayers at 400 degrees C leads to
hardening of multilayers, whereas softening occurs in Cu/V multilayers annealed at 600
degrees C. The evolution of mechanical properties during annealing is correlated to the
degradation of the layer interface and the consequent reduction of interface resistance to
the transmission of single dislocation.
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Development of a predictive DNA double strand break assay for the identification of individuals with high normal tissue radiosensitivity /Brown, Emma Jane Hay. January 2008 (has links)
Thesis (M.D.) - University of St Andrews, November 2008. / Restricted until 12th November 2010.
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In vitro prediction of inherent cellular radiosensitivitySmit, Kathleen Ann January 2005 (has links)
Thesis (MTech (Biomedical Technology))--Cape Peninsula University of Technology, 2005 / The principal objective in irradiating tumours is to permanently inhibit their
reproductive ability. More than half of all malignancies are primarily treated
with radiation but tumours of different histologies differ greatly in response to
radiotherapy as well as individual patients displaying great variability in
response to treatment. The need for reliable assays predicting tumour and
normal tissue response to radiation is therefore a prime objective of clinical
oncology. The requirement of such a test would be that it would relate to
clinical outcome Le. the possibility of recurrence of disease or of tumour
control as well as indicating whether the treatment should be administered
more aggressively or not. These are important factors that, if known, could be
used as part of the treatment planning in radiotherapy and selection of best
therapy modality.
The colony forming c1onogenic assay has been shown to be a reliable
reflection of a cells ability to maintain reproductive integrity after radiation
exposure. In this study it has successfully been used to demonstrate the
surviving fraction of cells but has the limitation of cells needing to process the
ability to form colonies. Cells from primary tumours do not readily form
colonies and may display poor anchorage making this assessment of
radiosensitivity in the clinic less desirable. These data are presented together
with unpublished data obtained using the micronucleus assay. Micronuclei
frequency (MNF) varies in different cell types with test doses and provides a
means to rank the cell in terms of response to radiation. In normal cells a
linear inverse correlation exits between MNF and cell survival. However, MNF
does not rank malignant cells according to their intrinsic survival to radiation
displaying a weak correlation between MNF and cell survival.
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Development of a predictive DNA double strand break assay for the identification of individuals with high normal tissue radiosensitivityBrown, Emma Jane Hay January 2008 (has links)
A genetically determined high level of intrinsic normal tissue radiosensitivity may account for the 5% of patients who experience unexpectedly severe normal tissue side effects following radiotherapy. The pre-treatment identification of these individuals by a diagnostic test or “predictive assay “ may allow appropriate modification of treatment plans and improve the therapeutic index of radiotherapy. Results from studies of cell-based assays measuring the response of a single cell type taken from patients to in vitro irradiation have been inconsistent, leading to the opinion of many that they are of no value in the prediction of normal tissue radiosensitivity. A systematic review of the literature presented here, however, suggests that poor methodology of study design often with inadequate control for those factors other than normal tissue radiosensitivity which influence radiotherapy toxicity and lack of reporting of assay precision means that it is difficult to form any conclusions, positive or negative about the diagnostic accuracy of the cell-based assays studied so far. Analysis of individual patient data extracted from these studies suggests that at least some of these assays may possess some discriminatory value. This finding justified an attempt to develop a novel cell-based assay based on the kinetics of radiation-induced .H2AX in peripheral blood lymphocytes. Assay failure rate was high and intra- and inter-sample assay reproducibility was poor for quantification by microscopy but were better for flow cytometric analysis. A study of 8 volunteers, however, demonstrated that intra-individual variation was higher than inter-individual variation in assay results, strongly suggesting that poor assay reproducibility due to technical or biological factors may limit the assay’s potential to identify radiosensitive individuals. This suspicion needs to be confirmed in a clinical study of patients of known radiosensitivity. As blood sample storage conditions affect assay results these will need to be standardized to prevent confounding of results.
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Description and prediction of clinical radiosensitivity : emphasis on normal tissue reactions /Tell, Roger, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.
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Accurate description of heterogeneous tumors for biologically optimized radiation therapy /Nilsson, Johan, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Univ., 2004. / Härtill 4 uppsatser.
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Evaluating the role of lymphocyte radiosensitivity and variants in double-strand break repair genes, checkpoint kinase 2 (CHEK2) and nibrin (NBN), in the predisposition to prostate cancer : a dissertation /Deming, Brenda Boon. January 2007 (has links)
Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2007. / Vita. Includes bibliographical references.
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G₂ chromosomal radiosensitivity in childhood and adolescent cancer survivors and their offspring /Curwen, Gillian B. January 2008 (has links)
Thesis (Ph.D.) - University of St Andrews, January 2008.
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