A Comparison of Neural Networks and Center of Gravity in Muon Hit Position Estimation.

The performance of cosmic-ray tomography systems is largely determined by their tracking accuracy. With conventional scintillation detector technology, good precision can be achieved with a small pitch between the elements of the detector array. Improving the resolution implies increasing the number of read-out channels, which in turn increases the complexity and cost of the tracking detectors.

The Effect of Prestressing and Temperature on Tensile Strength of Basalt Fiber-Reinforced Plywood.

The reinforcement of plywood is demonstrated by laminating pretensioned basalt fibers between veneer sheets, to fabricate so-called prestressed plywood. Belt type basalt fibers bearing a specific adhesion promoting silane sizing were aligned between veneer sheets with 20 mm spacing and were pretensioned at 150 N. Three-layer plywood samples were prepared and tested for tensile strength at room temperature and at 150 °C.

Cost-benefit analysis of health risks caused by indicative dose from drinking water consumption.

The effective dose annual limit in European Union member states for doses above natural background is 1 mSv. This includes ingestion, inhalation and external dose to a member of public. For doses received due to ingestion of drinking water, parametric value for annual indicative dose is 0.

Determination of Ra leachability from filter materials originating from water treatment plant.

NORM (Naturally Occurring Radioactive Material) waste management is a relatively new issue in Estonia. At the present moment, the largest volumes come from water treatment plants, where the Ra isotopes Ra-226 and Ra-228 accumulate in the filter material in the process of water purification. In the absence of prior experience and legislation, the best solution is considered to be the deposition of such material in landfill (Kiisk, 2016).

Long-term monitoring of water treatment technology designed for radium removal-removal efficiencies and NORM formation.

A drinking water treatment plant in Viimsi, Estonia, was monitored over three years for iron, manganese, radium-226, radium-228, as well as their daughter nuclides, in order to determine the efficiency of the treatment process, gain an insight into the removal mechanisms and interactions between radium, iron, and manganese, and assess the overall longevity and performance of the technology along with the possible build-up of NORM in the treatment process. During the study, samples were collected from raw water, first and second stage filtrate, consumer water, backwash water and filter materials. The results show consistent removal efficiency for iron and manganese, as well as an average of over 85% removal for radium with a slight decline over time.

Long-term monitoring of a water treatment technology designed for radium removal - removal efficiencies and NORM formation.

A drinking water treatment plant in Viimsi, Estonia was monitored over three years for iron, manganese, radium-226, radium-228, and their daughter nuclides in order to determine the efficiency of the treatment process, get an insight of the removal mechanisms and interactions between radium, iron, and manganese, and assess the overall longevity and performance of the technology and possible build-up of NORM from the treatment process. During the study, samples were collected from raw water, first and second stage filtrate, consumer water, backwash water, and filter materials. The results show a consistent removal efficiency for iron and manganese, as well as an average of over 85% removal for radium with a slight decline with time.

Enrichment of naturally occurring radionuclides and trace elements in Yatagan and Yenikoy coal-fired thermal power plants, Turkey.

Coal, residues and waste produced by the combustion of the coal contain naturally occurring radionuclides such as U, Ra, Pb, Th and K and trace elements such as Cd, Cr, Pb, Ni and Zn. In this work, coal and its combustion residues collected from Yatagan and Yenikoy coal fired thermal power plants (CPPs) in Turkey were studied to determine the concentrations of natural radionuclides and trace elements, and their enrichments factors to better understand the radionuclide concentration processes within the combustion system. In addition, the utilization of coal fly ash as a secondary raw material in building industry was also studied in terms of radiological aspects.

Long-term modelling of fly ash and radionuclide emissions as well as deposition fluxes due to the operation of large oil shale-fired power plants.

Two of the world's largest oil shale-fired power plants (PPs) in Estonia have been operational over 40 years, emitting various pollutants, such as fly ash, SO, NO, heavy metals, volatile organic compounds as well as radionuclides to the environment. The emissions from these PPs have varied significantly during this period, with the maximum during the 1970s and 1980s. The oil shale burned in the PPs contains naturally occurring radionuclides from the U and Th decay series as well as K.

Temporal changes in radiological and chemical composition of Cambrian-Vendian groundwater in conditions of intensive water consumption.

Intensive groundwater uptake is a process at the intersection of the anthroposphere, hydrosphere, and lithosphere. In this study, groundwater uptake on a peninsula where only one aquifer system - the Cambrian-Vendian (CmV) - is available for drinking water uptake is observed for a period of four years for relevant radionuclides and chemical parameters (Cl, Mn, Fe, δO). Intensive groundwater uptake from the CmV aquifer system may lead to water inflow either from the sea, through ancient buried valleys or from the under-laying crystalline basement rock which is rich in natural radionuclides.

Pb-210 and Po-210 atmospheric releases via fly ash from oil shale-fired power plants.

During high temperature processes in the furnace volatile and semi-volatile elements and radionuclides are partially emitted to the environment, depending on their chemical form in the original fuel, the technological set-up of the combustion system, and the prevailing combustion conditions. Two of the world's largest oil shale-fired power plants (PPs) have been operational in Estonia from the 1960s, during which time creation of significant environmental emissions and waste containing naturally occurring radionuclides has occurred. Pb-210 and Po are considered natural radionuclides with the highest emission rates from PPs and possess elevated potential radiation exposure risks to humans and the environment.

Radionuclide concentration variations in the fuel and residues of oil shale-fired power plants: Estimations of the radiological characteristics over a 2-year period.

Several multi-day samplings were conducted over a 2-year period from an oil shale-fired power plant operating with pulverized fuel type of boilers that were equipped with either novel integrated desulphurization system and bag filters or with electrostatic precipitators. Oil shale, bottom ash and fly ash samples were collected and radionuclides from the U and Th series as well as K were determined. The work aimed at determining possible variations in the concentrations of naturally occurring radionuclides within the collected samples and detect the sources of these fluctuations.

Pb-210 and fly ash particles in ombrotrophic peat bogs as indicators of industrial emissions.

Peat cores were collected from a Sphagnum-dominated Selisoo bog, which is located about 40 km from the large oil shale-fired power plants (PPs) in Estonia. These PPs have been operational from the 1960's and had the largest negative impact on the surrounding environment during the 1970's and 1980's. Nearby ombrotrophic peatlands are good indicators of atmospheric pollution due to their properties of effectively adsorbing mineral matter and pollutants.

Behaviour mechanisms and correlation between lead (Pb) and its isotope (210)Pb in industrial residue as an indicator for waste characterization.

Total lead and (210)Pb concentrations were determined in various ash fractions (collected from two of the world's largest oil shale-fired power plants) by inductively coupled plasma mass-spectrometry (ICP-MS) and gamma spectrometry. Results show a clear increase in total lead (values up to 193 ppm in filter ashes) and (210)Pb (values up to 148 Bq kg(-1) in filter ashes) concentrations in the ash fractions from the furnace towards the filter ashes. A strong positive linear correlation (Pearson's bivariate correlation remained between 0.

The enrichment behavior of natural radionuclides in pulverized oil shale-fired power plants.

The oil shale industry is the largest producer of NORM (Naturally Occurring Radioactive Material) waste in Estonia. Approximately 11-12 million tons of oil shale containing various amounts of natural radionuclides is burned annually in the Narva oil shale-fired power plants, which accounts for approximately 90% of Estonian electricity production. The radionuclide behavior characteristics change during the fuel combustion process, which redistributes the radionuclides between different ash fractions.

(226)Ra measurement by LSC as a tool to assess the efficiency of a water treatment technology for removing radionuclides from groundwater.

A simple (226)Ra analysis procedure by LSC with an extractive scintillator was tested for evaluating the long-term radionuclides removal efficiency of a water treatment facility at Viimsi, Estonia. During the 14 months of operation, total radium removal efficiency of the treatment process has stayed over 90%, but the removal efficiencies of the different purification steps have varied notably. This demonstrates the need for routine monitoring of radium content in the water treatment plant.

Groundwater treatment as a source of indoor radon.

New Viimsi Parish water treatment plant (Northern Estonia) was investigated in order to determine whether the open filter columns serve as a source of (222)Rn generation in the treatment process and whether they influence indoor air (222)Rn activity concentrations. (222)Rn measurements of indoor (222)Rn were performed at different locations of the treatment plant; water samples from incoming raw water, from all the purification stages, consumers water and solid filter material from two filtration stages were analyzed.

The enrichment of natural radionuclides in oil shale-fired power plants in Estonia--the impact of new circulating fluidized bed technology.

Burning oil shale to produce electricity has a dominant position in Estonia's energy sector. Around 90% of the overall electric energy production originates from the Narva Power Plants. The technology in use has been significantly renovated - two older types of pulverized fuel burning (PF) energy production units were replaced with new circulating fluidized bed (CFB) technology.

Radon leakage as a source of additional uncertainty in simultaneous determination of ²²⁶Ra and ²²⁸Ra by gamma spectrometry--validation of analysis procedure.

A series of validation experiments was carried out to assess robustness, repeatability, and trueness of an analysis procedure for simultaneous determination of (226)Ra and (228)Ra in water samples. The study revealed instabilities in the radon holding capacity of the sample matrix (epoxy resin). The discovered effect is a new additional component in the uncertainty budget which should be considered when (226)Ra is measured via its progeny in similar sample matrices.