Triple Play of Band Gap, Interband, and Plasmonic Excitations for Enhanced Catalytic Activity in Pd/HxMoO3 Nanoparticles in the Visible Region.

Plasmonic photocatalysis has been limited by the high cost and scalability of plasmonic materials, such as Ag and Au. By focusing on earth-abundant photocatalyst/plasmonic materials (HxMoO3) and Pd as a catalyst, we addressed these challenges by developing a solventless mechanochemical synthesis of Pd/HxMoO3 and optimizing photocatalytic activities in the visible range. We investigated the effect of HxMoO3 band gap excitation (at 427 nm), Pd interband transitions (at 427 nm), and HxMoO3 localized surface plasmon resonance (LSPR) excitation (at 640 nm) over photocatalytic activities toward the hydrogen evolution and phenylacetylene hydrogenation as model reactions. Although both excitation wavelengths led to comparable photoenhancements, a 110% increase was achieved under dual excitation conditions (427 + 640 nm). This was assigned to a synergistic effect of optical excitations that optimized the generation of energetic electrons at the catalytic sites. These results are important for the development of visible-light photocatalysts based on earth-abundant components.

Natural radioactivity of residues from groundwater treatment facilities in Finland.

The accumulation of naturally occurring radionuclides in solid residues was investigated from groundwater treatment facilities (GTFs) in Finland. Natural radionuclides U-238, Ra-226, Pb-210 and Ra-228 were found in various precipitates, sludges and filters at concentrations exceeding the general clearance level of 1 kBq kg-1used for solid materials in the European directive 2013/59/Euratom. The accumulation of natural radionuclides in different solid residues was observed even when the activity concentrations in the untreated groundwater were relatively low, and when there was no measurable change in the concentrations between raw and treated groundwater within analytical uncertainties. Based on mass and activity balance considerations this is thought to be due to the large volumes of treated water per year. The exposure of workers to natural radiation from solid residues in the regular use of a groundwater facility was found not to be likely to exceed 0.3 mSv a-1if the activity concentrations are <10 kBq kg-1for U-238, Ra-226, Pb-210 and Ra-228. The worker exposure from solid residues is therefore likely to remain below the reference level of 1 mSv a-1, and indoor radon is more of a concern for the radiation protection of workers at GTFs. However, the natural radionuclide content in the different solid residues from groundwater treatment needs to be characterised properly to be able to ensure safety in the final use of the residues with respect to the potential exposure of the public.

The issue of Cs-137 in firewood and biomass combustion: a review.

In large parts of Europe, the Chernobyl accident of 1986 caused fallout of Cs-137. This led to the uptake of Cs-137 in trees or other materials used for bioenergy production or as firewood for domestic purposes. This Cs-137 may concentrate in the ashes of the combustion process in such a way that the clearance level of 100 Bq per kg, defined in Directive 2013/59/Euratom (EU BSS), may consequently be exceeded. There is currently no clear consensus in Europe regarding the regulatory approach to this issue: should the import and use of Cs-137 contaminated biomass and its ashes be considered as a planned exposure situation or rather as an existing exposure situation? If considered as an existing exposure situation, which reference level should be applied? We compare the approaches in various European countries, such as Finland, Norway, Sweden, Belgium and the Netherlands. Results of a recent measurement campaign performed in Belgium on firewood imported from Belarus, Ukraine and other countries show a quite large range of Cs-137 activity concentration in firewood. Analysis of samples from biomass combustion confirms that the clearance level of 100 Bq per kg Cs-137 may be exceeded even when the activity concentration in the initial pellet is trivial. A review of dose-assessment studies performed by STUK and from the literature is presented. The general context of biomass energy production is sketched: for instance, in the Netherlands, 40 large biomass firing plants (capacity > 10 MW) are operational and some 20 more are already planned. The fly ashes from the biomass combustion may be a valuable resource for the construction industry, and the issue of Cs-137 contamination is connected with the requirements of the EU BSS regarding the natural radioactivity of building materials. Assessing the impact of Cs-137 contamination and clarifying regulations in the frame of a graded approach are important elements in this context.

Tools for harmonized data collection at exposure situations with naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) contribute to the dose arising from radiation exposure for workers, public and non-human biota in different working and environmental conditions. Within the EURATOM Horizon 2020 RadoNorm project, work is ongoing to identify NORM exposure situations and scenarios in European countries and to collect qualitative and quantitative data of relevance for radiation protection. The data obtained will contribute to improved understanding of the extent of activities involving NORM, radionuclide behaviours and the associated radiation exposure, and will provide an insight into related scientific, practical and regulatory challenges. The development of a tiered methodology for identification of NORM exposure situations and complementary tools to support uniform data collection were the first activities in the mentioned project NORM work. While NORM identification methodology is given in Michalik et al., 2023, in this paper, the main details of tools for NORM data collection are presented and they are made publicly available. The tools are a series of NORM registers in Microsoft Excel form, that have been comprehensively designed to help (a) identify the main NORM issues of radiation protection concern at given exposure situations, (b) gain an overview of materials involved (i.e., raw materials, products, by-products, residues, effluents), c) collect qualitative and quantitative data on NORM, and (d) characterise multiple hazards exposure scenarios and make further steps towards development of an integrated risk and exposure dose assessment for workers, public and non-human biota. Furthermore, the NORM registers ensure standardised and unified characterisation of NORM situations in a manner that supports and complements the effective management and regulatory control of NORM processes, products and wastes, and related exposures to natural radiation worldwide.

A methodology for the systematic identification of naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) are present worldwide and under certain circumstances (e.g., human activities) may give radiation exposure to workers, local public or occasional visitors and non-human biota (NHB) of the surrounding ecosystems. This may occur during planned or existing exposure situations which, under current radiation protection standards, require identification, management, and regulatory control as for other practices associated with man-made radionuclides that may result in the exposure of people and NHB. However, knowledge gaps exist with respect to the extent of global and European NORM exposure situations and their exposure scenario characteristics, including information on the presence of other physical hazards, such as chemical and biological ones. One of the main reasons for this is the wide variety of industries, practices and situations that may utilise NORM. Additionally, the lack of a comprehensive methodology for identification of NORM exposure situations and the absence of tools to support a systematic characterisation and data collection at identified sites may also lead to a gap in knowledge. Within the EURATOM Horizon 2020 RadoNorm project, a methodology for systematic NORM exposure identification has been developed. The methodology, containing consecutive tiers, comprehensively covers situations where NORM may occur (i.e., minerals and raw materials deposits, industrial activities, industrial products and residues and their applications, waste, legacies), and thus, allows detailed investigation and complete identification of situations where NORM may present a radiation protection concern in a country. Details of the tiered methodology, with practical examples on harmonised data collection using a variety of existing sources of information to establish NORM inventories, are presented in this paper. This methodology is flexible and thus applicable to a diversity of situations. It is intended to be used to make NORM inventory starting from the scratch, however it can be used also to systematise and complete existing data.

Radioactivity of residues from waste incineration facilities in Finland.

Waste incineration in Europe has been increasing in the past few decades as there is a need to reduce the burden on landfills and their associated environmental concerns. While incineration reduces the volume of the waste, the volume of slag and ash is still substantial. To find out potential radiation risks that incineration residues could set to workers or the public, the levels of radioactive elements in these residues were investigated from nine waste incineration plants in Finland. Natural and artificial radionuclides were detected in the residues, but in general the activity concentrations were low. This study shows that the level of Cs-137 in the fly ash from municipal waste incineration follows the pattern of 1986 fallout zones in Finland, although the levels are significantly lower than in ash from bioenergy production from the same areas. Am-241 was also detected in many samples, although the activity concentrations were very low. Based on the findings in this study, the typical ash and slag residues from municipal waste incineration do not need radiation protection measures for workers or the public even in regions that received up to 80 kBq m-2of Cs-137 fallout in 1986. The further use of these residues need not be restricted due to radioactivity. Hazardous waste incineration residues and other special cases need to be considered separately, depending on the original waste composition.

Laboratory-scale X-ray absorption spectroscopy of 3d transition metals in inorganic thin films.

In this paper we present laboratory-scale X-ray absorption spectroscopy applied to the research of nanometer-scale thin films. We demonstrate the Cu K edge X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of CuI and CuO thin films grown with atomic layer deposition. Film thicknesses in the investigated samples ranged from 12 to 248 nm. Even from the thinnest films, XANES spectra can be obtained in 5-20 minutes and EXAFS in 1-4 days. In order to prove the capability of laboratory-based XAS for in situ measurements on thin films, we demonstrate an experiment on in situ oxidation of a 248 nm thick CuI film at a temperature of 240 °C. These methods have important implications for novel and enhanced possibilities for inorganic thin film research.

Operando Laboratory-Based Multi-Edge X-Ray Absorption Near-Edge Spectroscopy of Solid Catalysts.

Laboratory-based X-ray absorption spectroscopy (XAS) and especially X-ray absorption near-edge structure (XANES) offers new opportunities in catalyst characterization and presents not only an alternative, but also a complementary approach to precious beamtime at synchrotron facilities. We successfully designed a laboratory-based setup for performing operando, quasi-simultaneous XANES analysis at multiple K-edges, more specifically, operando XANES of mono-, bi-, and trimetallic CO2 hydrogenation catalysts containing Ni, Fe, and Cu. Detailed operando XANES studies of the multielement solid catalysts revealed metal-dependent differences in the reducibility and re-oxidation behavior and their influence on the catalytic performance in CO2 hydrogenation. The applicability of operando laboratory-based XANES at multiple K-edges paves the way for advanced multielement catalyst characterization complementing detailed studies at synchrotron facilities.

Sediment profile dating and reconstructing nuclear events from annually laminated lake sediments in northern Finland.

The sediments deposited in Lake Kevojärvi (69°45N, 27°00'E) in northernmost Finland were investigated for radioactivity. Freeze cores recovered from the 35-m deep basin has preserved a distinct succession of annual laminations deposited between 1909 and 2015. The basic varve structure is composed of a detrital snowmelt layer and an organic-rich post-snowmelt layer lying on top of the snowmelt layer. The past nuclear events have been preserved in the lake sediment. In order to study these, sediment freeze with annual sediment laminations were recovered from the lake bottom and measured for gamma emitting radionuclides. A total of 53 sediment subsamples, each incorporating sediment from one to two varves i.e. sediment deposited during one to two years, were taken for gamma spectroscopy measurements using low-background HPGe detector system. The measurements showed large variations in 137Cs and 241Am concentrations between different laminae marking different nuclear events in history. This highly resolved profile revealed a detailed record of anthropogenic radioactive fallout from atmospheric nuclear weapons testing during 1950s and 1960s and the Chernobyl accident in 1986. The measured 137Cs concentrations varied between 0.6 and 229 Bq/kg dry weight (dw) while the measured 241Am concentrations varied between 0.6 and 6.4 Bq/kg dw. The 137Cs showed downward migration in the sediment column since 137Cs was also found in varves dating before 1945. The first clear increase in 137Cs concentration was observed in 1956 varve and the 137Cs concentrations were found to peak in the 1964, 1970 and 1986 varves. The 241Am was first observed in 1957 varve and the concentrations peaked in 1960-1962, 1964 and 1970 varves. This demonstrated that 241Am can be a complementary chronostratigraphic marker to 137Cs in sediment. A time delay of one to two years was observed between the years of intensive atmospheric nuclear weapons testing and the increased 137Cs and 241Am concentrations in the sediment varves. In the 210Pb concentrations long-time periods of low (~1930-1950 and ~1990-2000) and high concentrations (~1950-1980) were observed. The reason for large variation was the amount of sediment input. The Constant rate of supply (CRS) model results showed good agreement with the varve counting. The model results showed that the 210Pb deposition has been constant over the last 80 years and no effect of climate change to the 210Pb deposition was observed.

Johann-type laboratory-scale x-ray absorption spectrometer with versatile detection modes.

We present a low-cost laboratory X-ray absorption spectrometer that uses a conventional X-ray tube source and bent Johann-type crystal monochromators. The instrument is designed for X-ray absorption spectroscopy studies in the 4-20 keV range which covers most K edges of 3d transition metals and L edges of 5d transition metals and actinides. The energy resolution is typically in the range of 1-5 eV at 10 keV depending on the crystal analyser and the Bragg angle. Measurements can be performed in transmission, fluorescence, and imaging modes. Due to its simple and modular design, the spectrometer can be modified to accommodate additional equipment and complex sample environments required for in situ studies. A showcase of various applications is presented.

Transfer factors and effective half-lives of (134)Cs and (137)Cs in different environmental sample types obtained from Northern Finland: case Fukushima accident.

The Fukushima NPP accident caused a small but detectable cesium fallout in northern Finland, of the order of 1 Bq/m(2). This fallout transferred further to soil, water, flora and fauna. By using modern HPGe detector systems traces of (134)Cs from the Fukushima fallout were observed in various samples of biota. In northern Finland different types of environmental samples such as reindeer meat, berries, fish, lichens and wolf were collected during 2011-2013. The observed (134)Cs concentrations varied from 0.1 Bq/kg to a few Bq/kg. By using the known (134)Cs/(137)Cs ratio observed in Fukushima fallout the increase of the Fukushima accident to the (137)Cs concentrations was found to vary from 0.06 % to 6.9 % depending on the sample type. The aggregated transfer factors (Tag) and effective half-lives (Teff) for (134)Cs and (137)Cs were also determined and then compared with known values found from earlier studies which are calculated based on the fallout from the Chernobyl accident. Generally, the Tag and Teff values determined in this study were found to agree with the values found in the earlier studies. The Teff values were sample-type specific and were found to vary from 0.91 to 2.1 years for (134)Cs and the estimates for (137)Cs ranged between 1.6 and 19 years. Interestingly, the ground lichens had the longest Teff whereas the beard lichen had the shortest. In fauna, highest Tag values were determined for wolf meat ranging between 1.0 and 2.2 m(2)/kg. In flora, the highest Tag values were determined for beard lichens, ranging from 1.9 m(2)/kg to 3.5 m(2)/kg.