[en] Electron irradiated poly(methyl methacrylate) (PMMA) and polystyrene (PS) nanoparticles as alternatives to existing sunscreen active ingredients which have safety controversies have been studied. The electron irradiation produces chromophores so that the irradiated polymers turn capable of absorbing ultraviolet (UV) rays. UV-Vis spectroscopy indicates a significant increase in the absorbance in the spectral range of UV and a redshift of the absorption edge is observed at a higher electron fluence. Results of FTIR and Raman studies imply chemical alterations of the irradiated polymers, elucidating the creation of UV absorbing properties. According to results of in vitro 3T3 neutral red uptake (NRU) phototoxicity test in compliance with OECD TG 432, the irradiated PMMA was classified as a non-phototoxic material. In addition, in vitro sun protection factors (SPFs) of formulations containing irradiated polymer nanoparticles in various electron fluence were determined according to ISO 24443. In this study, the effects of electron irradiation and the characteristics of the irradiated polymers are discussed

[en] High quality radiation dosimetry is for workers who rely upon personal dosimeters to record the amount of radiation to which they are exposed. Radiation physicists have been exploring thermoluminescence dosimeter (TLD) for personal monitoring since the mid 1960s, although, widespread use has only occurred in the last 20 years as automated analytical systems and high quality TLD crystals became commercially available. nowadays, multiple TLD (thermoluminescence dosimeter) chips with appropriate physical filters are generally used for measurements of the personal dose equivalent quantities, H_p(d). Though the TLD offers several advantages not possessed by radiological film, it does not offer the some type of advantages as films: re-analysis of an exposure situation is prohibited because the analysis process clears all of the useful dosimetric traps and a record of the luminescence intensity in the form of a glow curve is all that is available after analysis. In addition, the high heating temperatures restrict packaging methods and prevent competitively priced thin films of TLD crystal powders. Optically stimulated luminescence (OSL) technology avoids many engineering limitations imposed by the high heating temperatures used for TLD technology. OSL crystalline powders can be dispersed in various plastics unable to withstand the TLD heating regimen. With uniform dispersion in the plastic, mass-manufacturing techniques can produce large quantities of identically performing detectors. The first proposal conducted by Markey et al. for applications and potentials of α-AI₂O₃:C for OSL dosimetry opened a new era for this phosphor. Pulsed and continuous wave OSL studies carried out on α-AI₂O₃:C have shown that the material seems to be the most promising for routine application of OSL for dosimetric purposes. The main objective of this study is to develop a multi-area personal OSL dosimetry system using α-AI₂O₃:C by taking advantage of its optical properties and energy dependencies. This was done by designing a multi-element filter system for powder layered α-AI₂O₃:C material and an optical reader system based on ultra bright blue LEDs. The main feature of the proposed OSL dosimetry system is that with an appropriate pulsed stimulating scheme and dose assessment algorithm, the personal dose equivalents, H_p(d) can be determined more efficiently and precisely. This dissertation includes various numerical and experimental methods used to design and optimize the performance of the proposed OSL dosimeter may be unfolded from a collection of OSL light emissions following a sequence of optical scanning and dose assessment algorithm. Since the main objective of this work is to obtain the optimum dosimeter system that allows successful measurement of deposited energy distribution, the element's response given as a function of incident photon energy was simulated using a particle transport model, which is calculated using electron/photon Monte Carlo code, MCNP4A. The filtered element responses thus obtained were then used together with angular dependences to design a prototype of the OSL dosimeter. Finally, the experimental response of the designed OSL dosimeter is compared with the original exposure, with good agreement indicating an appropriate dosimetry scheme. Based on the experimental response test of the proposed dosimeter design, it was demonstrated that a multi-area dosimeter system with an LED technology based on α-AI₂O₃:C is suitable to obtain personal dose equivalent information on the mixed radiation fields. With the experimental conditions, the minimum measurable dose was obtained to be 0.1 mGy and that is smaller than the values reported previously. Furthermore, The pulsed blue-LED reader system seems to be quite convenient for OSL measurements from α-AI₂O₃:C and the luminescent output per absorbed dose is larger than the green-LED based system. Therefore, the OSL dosimetry system doveloped in this study can be considered as a compact, reliable and inexpensive system for personal dosimetry. Another work scope of this study is to propose a new dose assessment algorithm for developed multi area OSL dosimetry system. The use of multi-clement dosimeters is necessarily required of a dose assessment algorithm that weights the reading of each element for the evaluation of the personal dose equivalent. In this study, a feed forward neural network using the error back-propagation method was applied for the response unfolding procedure. To replace the simplistic decision tree algorithms by the more sophisticated neural networks, the Bayesian algorithm was introduced to optimize the MLBP (Multi-Layer Back Propagation) neural network. The validation of the proposed algorithm was investigated by unfolding the measured responses of the OSL dosiemter for arbitrary mixed photon field range from 20 keV to 662 keV. Results show that the determined dose values are reproduced with an accuracy better than 89%. With these validation results, it was demonstrated that a multi-element dosimeter system with an unfolding algorithm based on artificial neural intelligence is suitable to obtain spectral information on the incident gamma photons. It was also found that the Bayesian's approach was helpful to optimize the connective weights to solve the abnormal function overfitting. For the unfolding of the multi-element response, merely these weights were applied without carrying out further optimizations. In consequence, the unfolding step requires less than one second, i.e. several orders of magnitude less of computational time in comparison to the optimization step. Therefore, the response unfolding can be carried out frequently and can be implemented either as hardware or as software into the measuring instrument in this topology. The novel approach presented in this study enables the development of the next generation personal dosimetry system using a pulsed optically stimulated luminescence technology

[en] To develop a personal (OSL) optically stimulated luminescence dosimetry system for mixed radiation fields using α-Al₂O₃ : C, a discriminating badge filter system was designed by taking advantage of its optically stimulable properties and energy dependencies. This was done by designing a multi-element badge system for powder layered α-Al₂O₃ : C material and an optical reader system based on high-intensity blue light-emitting diode (LED). The design of the multi-element OSL dosimeter badge system developed allows the measurement of a personal dose equivalent value H_p(d) in mixed radiation fields of β and γ. Dosimetric properties of the personal OSL dosimeter badge system investigated here were the dose response, energy response and multi-readability. Based on the computational simulations and experiments of the proposed dosimeter design, it was demonstrated that a multi-element dosimeter system with an OSL technology based on α-Al₂O₃ : C is suitable to obtain personal dose equivalent information in mixed radiation fields

[en] Recently, a new class of phosphors (Eu²⁺ doped alkali-earth halides) have been introduced which are able to store X-ray information for hours and allow a recovery of this information by optical stimulation within microseconds. This SPP (Storage Photostimulable Phosphor) technology has been investigated for application to medical X-ray imaging and is well proven in molecular biology and radioluminography research. Depending on the application, different requirement exist for the sensitivity and spatial resolution of the film, and these are related to light scattering in the film. The purpose of this study is to investigate the characteristics of the thin SPP plates light propagation mechanism. The influence of the scattering length, absorbance is calculated based on the light diffusion model. The sensitivity, resolution and other image properties are determined from the optical properties. The results indicate that optimizing the image properties of the film can be achieved by a reduction of the absorbance and an increase in film thickness to the penetration depth of the X-rays.

[en] In radiation dosimetry there are numerous problems associated with the measurement of iso-dose curves and depth-dose distributions in high-gradient regions of beams using conventional measuring systems such as ionization chambers, semiconductors, thermo-luminescent detectors (TLDs), and radiographic films. Radiographic film serves several important functions in electron gun calibration, radiation therapy, and radiation protection. It can serve as a radiation detector, relative dosimeter, display device, and an archival medium. Film gives excellent 2D spatial resolution and, in a single exposure, provides information about the spatial distribution of radiation in the area of interest or the attenuation of radiation by objects. It is essential to consider the error of the fitting function as it should be minimized to better optimize the veracity of the film analysis.

[en] With current waste monitoring technology it is reasonable to assume that much of the material designated as low level waste (LLW), generated within nuclear facilities, is in fact uncontaminated. This may include operational wastes, metal and rubble, office waste and discrete items from decommissioning or decontamination operations. Materials that contain only trivial quantities of radionuclides could realistically be exempted or released from regulatory control for recycle or reuse. A criterion for uncontrolled disposal of low-level radioactive contaminated waste is that the radiation exposure of the public and of each individual caused by this disposal is so low that radiation protection measures need not be taken. The International Atomic Energy Agency (IAEA) suggests an annual effective doses of 10 μ Sv as a limit for the individual radiation dose. In 1990, new recommendation on radiation protection standards was developed by International Commission on Radiological Protection (ICRP) to take into account new biological information related to the detriment associated with radiation exposure. Adoption of these recommendations necessitated a revision of the Commission's secondary limits contained in Publication 30, Parts 1 ∼ 4. This study summarized the potential radiation exposure from valuable scrap metal considered to uncontrolled recycle by new ICRP recommendations. Potential exposure pathways to people following were analyzed and relevant models developed. Finally, concentrations leading to an individual dose of 10 μ Sv/yr were calculated for 14 key radionuclides. These potential radiation exposures are compared with the results of an IAEA study. 12 refs., 6 tabs., figs

[en] In this paper, the implementation techniques of intelligent nuclear material surveillance system based on the COM (Component Object Model) and SOM (Self Organized Mapping) was described. The surveillance system that is to be developed is consist of CCD cameras, neutron monitors, and PC for data acquisition. To develop the system, the properties of the COM based software development technology was investigated, and the characteristics of related platform APIs was summarized. This report could be used for the developers who want to develop the intelligent surveillance system for various experimental environments based on the DVR and sensors using Borland C++ Builder

[en] In this report, a preliminary study on the safeguardability of ACP (Advanced spent fuel Conditioning Process) was conducted with Los Alamos National Laboratory. The proposed ACP concept is an electrometallurgical treatment technique to convert oxide-type spent nuclear fuels into metal forms, which can achieve significant reduction of the volume and heat load of spent fuel to be stored and disposed of. For the safeguardability analysis of the ACP facility, sub-processes and their KMPs (Key Measurement Points) were defined first, and then their material flows were analyzed. Finally, the standard deviation of the Inventory Difference (ID) value of the facility was estimated with assumption by assuming international target values for the uncertainty of measurement methods and their uncertainty. From the preliminary calculation, we concluded that if the assumptions regarding measurement instruments can be achieved in a safeguards system for the ACP facility, the safeguards goals of International Atomic Energy Agency (IAEA) could be met. In the second phase of this study, further study on sensitivity analyses considering various factors such as measurement errors, facility capacities, MBA periods etc. may be needed

[en] In this paper, the implementation techniques of nuclear material surveillance system based on the digital video capture board and digital counter was described. The surveillance system that is to be developed is consist of CCD cameras, neutron monitors, and PC for data acquisition. To develop the system, the properties of the PCI based capture board and counter was investigated, and the characteristics of related SDK library was summarized. This report could be used for the developers who want to develop the surveillance system for various experimental environments based on the DVR and sensors using Borland C++ Builder

[en] This report describes the development of the nod-destructive nuclear material assay for ACP. The main story includes the design of ACP safeguards Neutron Counter(ASNC) by MCNP code and the test results of the prototype ASNC. The prototype ASNC is composed of 20 He-3 tubes, a high density PE, a Pb shield, a C neutron reflector and Cd neutron absorbers. Its mean neutron detection efficiency in z-axial direction is 19% and the error is 2%. These value satisfies the design criteria of 14% efficiency and 2% error. The ASNC test includes the measurement of the counting efficiency as increasing HV, the measurement of the counting efficiency and the error in z-axial direction and the HV test before/after the PDT threshold adjustment. The MCNP code calculation for the ASNC of the ACP Hot Cell is performed again because the metal ingot size is changed to 15 cm. From the MCNP code calculation, the counting efficiency is 21.7% and the error is 0.98% in z-axial direction