Diana Adliene

Levels of 14C in the Terrestrial Environment in the Vicinity of Two European Nuclear Power Plants

Radiocarbon is produced in all types of nuclear reactors. Most of the C-14 released into the environment is in the form of gaseous emissions. Recent data on the C-14 concentration found in terrestrial samples taken in the vicinity of nuclear power plants in Romania and Lithuania are presented. We found increased C-14 levels in the surroundings of both power plants. At the Romanian power plant Cernavoda, we found excess levels of C-14 in grass within a distance of about 1000 in, the highest C-14 specific activity being 311 Bq/kg C (approximately 28% above the contemporary C-14 background) found at a distance of 200 in from the point of release (nearest sampling location). At the Lithuanian power plant Ignalina, samples of willow, pine, and spruce showed a C-14 excess of similar magnitude, while significantly higher values were found in moss samples. The samples were analyzed at the accelerator mass spectrometry facility in Lund, Sweden. (Less)

EVALUATION OF NEW TRANSPARENT TUNGSTEN CONTAINING NANOCOMPOSITES FOR RADIATION PROTECTION SCREENS

Evaluation of the new lead-free optically transparent nanocomposites is provided in this paper along with the introduction to their fabrication technologies and the results of investigation of their X-ray attenuating and optical properties before and after their exposure to high doses. These materials might be considered for the construction of X-ray protective screens that are used to protect medical personnel against scattered X rays during close-to patient operations. Rough selection of possible composites was performed according to X-ray attenuation modelling results. Experimental nanocomposites were prepared dissolving tungstates in different solvents or embedding tungsten structures into polymer matrix. It was found that the lead equivalent thickness of fabricated experimental samples varied from 0.15 to 0.75 mmPb and was higher for samples, containing polyanions of phosphotungstic acid. Transparency of the experimental samples to visible light varied from 20 to 60 % and was slightly increasing with irradiation dose due to radiation-induced processes in polymers.

Master-holograms recorded with pulsed laser on photoresist

Direct write digital holography technique (DWDH) using single pulsed exposures of 440nm pulsed laser has been applied to record master holograms on commercially available photoresists (ma-P1200 and Shipley 1800 series) of different thickness. Method for numerical evaluation of hologram quality, based on diffraction intensity measurement (reflected beam), was proposed and verified. It was found that all investigated photoresists: ma-P1205, ma-P1225 and S1805, were sensitive enough to record holographic structures at low single pulse laser exposures from the range 3.3 ÷ 19.5 mJ/cm2 . Best quality holograms with well – structured holopixels (hogels) were observed on 0.67 μm thick ma- P1205 photoresist exposed to 11.4 mJ/cm2 and on 0.65 μm thick S1805 photoresits exposed to 13 mJ/cm2, where corresponding measured diffraction intensity had its maximum value. In the case of thicker photoresists (ma-P1225, 3.33 μm), comparable quality of the hogel structure was found in the interval 9.8 – 13 mJ/cm2. Investigation has shown a potential of single pulsed laser exposures to record good quality master holograms on commercially available photoresists applying at least 5 times lower exposures values as compared to CW laser exposures usually used to expose photoresist materials in holographic applications. That opens a possibility to use pulsed lasers for quick origination of master-originals for embossed holograms applying DWDH technique or analogue methods.

Investigation of X-Ray Attenuation Properties in Water Solutions of Sodium Tungstate Dihydrate and Silicotungstic Acid

Due to its outstanding photon attenuation features lead (Pb) is the most popular material which is used for radiation shielding and for radiation protection of individuals against ionizing radiation. However, Pb is very toxic and can cause serious health problems. Also recycling of lead containing materials is relative complicated. In order to overcome Pb related problems, researchers are looking for lead free materials possessing similar photon attenuation properties as lead and that can be used for the development and fabrication of radiation shielding elements and radiation protection equipment.

Chapter 9 Nanomaterials and Nanotechnologies for Photon Radiation Enhanced Cancer Treatment

Nanotechnology plays an increasingly important role in the diagnostics, prognostics, theranostic and management of targeted cancer treatments. Radiotherapy is a golden standard for cancer treatment: it requires high accuracy in delivering treatment to cancer patients to reduce toxicity to surrounding tissues and relies on both adequate imaging technologies and precise treatment dose calculations. Since the positive outcome of cancer treatment depends on a proper radiation dose delivery to the target, theoretical dose planning for each patient verified by experimental dose assessment is absolutely necessary. Introduction of the innovative nanotechnologies requires new improved dose delivery concepts that relay on utilization of new nanoscale materials. Materials on the nanoscale such as quantum dots, metal nanoparticles, combined core-shell nanoparticles, drug carriers provide many unique properties and are emerging with promising applications for their implementation in the development of the new cancer treatment strategies.