Assessment of the content of tritium and its compounds in soil and vegetation in the region of nuclear power plants with VVER type reactors

Currently, scientists pay great attention to the intake of tritium and its compounds when assessing the impact of radiation-hazardous objects on the environment and humans. Now, there are no acceptable industrial technologies for the effective capture of this radionuclide; therefore, all tritium generated during the operation of nuclear power plants enters the environment with emissions and discharges. Consequently, it leads to an increase in its concentration in environmental objects, including soil and vegetation. This fact determines the need to assess its content in the ground and vegetation. The study aims to develop a method for determining the content of tritium in soil and vegetation. To develop a methodology for assessing the content of tritium in soil and vegetation, we used the technique of preparing counting samples based on burning the selected examples in a specialized Pyrolyser 6-Trio furnace. Previously, scientists conducted some laboratory studies to assess the acceptability of this method of sample preparation. We measured the counting samples on a Tri-CARB 3180 TR/SL liquid scintillation meter. Scientists have developed and certified a method for determining tritium in soil and vegetation. Furthermore, we investigated the content of tritium and its compounds in the environment in the area of the Nuclear Power Plant based on a comprehensive assessment. Researchers found tritium content in soil and vegetation in settlements near nuclear power plants with VVER type reactors. The main routes of entry of tritium and its compounds into vegetation are the air path and the access of tritium from the ground. The presented data determine the need for systematic studies on the accumulation of tritium in environmental objects.

Selection of Fuel Isotope Composition in Heating Injectors of the FNS-ST Compact Fusion Neutron Source

For the FNS-ST compact neutron source, the dependence of the neutron yield on the tritium content in the bulk plasma is analyzed for the operation of the heating injectors with different isotope compositions of the neutral beams. Self-consistent simulations of the FNS-ST operating regimes are performed using the SOLPS4.3 and ASTRA codes for different densities of the bulk plasma and diffusion coefficients. The FC-FNS code is used to calculate the required fluxes of the fuel components into the plasma provided by different injection systems: the pellet injectors and the neutral beams. In simulations, the plasma density is varied in the range ne = (7–10) × 1019 m−3, and the ratio of the diffusivity to the heat conductivity in the range D/χe = 0.2–0.6. For the scenarios with the D + T or D beams, in the window of the operating parameters, the maximum possible fractions of tritium in the bulk plasma are calculated, and the corresponding neutron yields are obtained. For the regimes with the maximum neutron yield (4.5–5.5) × 1017 s−1, the accumulation of tritium at the site (up to 550 g) is calculated for different heating beams.

Radiation Survey in the Area of Peaceful Nuclear Explosion «Takhta-Kugulta»

Purpose: Radiation survey in the area of peaceful nuclear explosion «Takhta-Kagylta» in the Stavropol Region. Material and methods: Radiation survey was performed on the territory of the protected area and on the territory of the 30-km zone from the explosion site. Methods of pedestrian gamma survey with a portable spectrometric complex Multirad-M were used in the course of the survey, along with gamma spectrometric and radiochemical measurements of radionuclide activities in samples and radiochemical separation of 90Sr and 137Cs. The measurement of tritium activity concentration in water was carried out using a low-background liquid alpha-beta radiometer Quantulus-1220. Results: The highest average value of gamma ambient dose equivalent rate was obtained in the area of the peaceful nuclear explosion site. A value of ambient dose equivalent rate at the area between the site and Kevsala village is lower than on the site, but higher than in Kevsala village and in other settlements. The mean value of the surface contamination of soil with 137Cs on the site was 0.43 kBq/m2, while that of 90Sr was 0.055 kBq/m2. Average values of soil surface contamination with radionuclides in the settlements located in the area of the explosion vary over the range between 0.16 and 0.37 kBq/m2 for 137Cs and between 0.035 and 0.066 kBq/m2 for 90Sr. 241Am specific activity values were below the minimum detectable activity (0.01 – 0.04 kBq/m2 at the time of the soil sample measurement of 10–30 h). The contents of 3H, 90Sr and 137Cs radionuclides in drinking water and water of the surface water reservoirs is significantly lower than the intervention levels established in NRB-99/2009. Conclusions: Radiation situation at the location of the technological well complies with the requirements of SanPiN 2.6.1.2819-10 “Radiation Safety and Protection of the Population Living in the Areas of Peaceful Nuclear Explosions (1965 – 1988)”, and does not pose a threat to the health of the population when staying there. It is necessary to arrange the territory of the protection area and technological (charging) well in accordance with the requirements of SanPiN 2.6.1.2819–10. Within the framework of long-term radiation monitoring, it is necessary to provide for the monitoring of the tritium content in the produced gas and in the groundwater of the Krasnogvardeiskoe deposit (located in the direction of the spread of groundwater from the location of the peaceful nuclear explosion).

Tritium in the aquatic environment of Ozersk

Introduction. The article presents data on tritium concentrations in various types of aquatic environments (rainfall, snowfall, water from the Irtyash, B. Nanoga, Kyzyltash lakes, and the source of the Techa river, tap water, ice from the refrigerator, and urine) within the city of Ozersk and on the territory immediately adjacent to it in the impact zone of Mayak Production Center in the Southern Urals. Material and methods. For the quantitative determination of tritium in various aqueous media, sampling was carried out from 2002 to 2016. Samples were analyzed by the scintillation method using a single-stage electrolytic enrichment procedure. Results. Almost all aquatic environments in Ozersk in terms of their tritium content exceed the technogenic background established for the Ural region. On average, this excess is by 14, 11, 9, 19, 4, 6, 19 times for rainfall, snowfall, drinking water of residential premises, ice, the water of the Irtyash and B. Nanoga lakes, water from the source of the river Techa accordingly. Elevated concentrations of tritium in the urine of Ozersk people and the adjacent territory were noted in comparison with literature data for other regions of the world. Conclusion. The obtained research results revealed the levels of pollution of the aquatic environment of Ozersk with tritium relative to the level of technogenic background. These works indicate the need to develop a method for cleaning tritium emissions and discharges by nuclear enterprises to reduce the risk to the population.

Hydrogeological Behaviour and Geochemical Features of Waters in Evaporite-Bearing Low-Permeability Successions: A Case Study in Southern Sicily, Italy

Knowledge about the hydrogeological behaviour of heterogeneous low-permeability media is an important tool when designing anthropogenic works (e.g., landfills) that could potentially have negative impacts on the environment and on people’s health. The knowledge about the biogeochemical processes in these media could prevent “false positives” when studying groundwater quality and possible contamination caused by anthropogenic activities. In this research, we firstly refined knowledge about the groundwater flow field at a representative site where the groundwater flows within an evaporite-bearing low-permeability succession. Hydraulic measurements and tritium analyses demonstrated the coexistence of relatively brief to very prolonged groundwater pathways. The groundwater is recharged by local precipitation, as demonstrated by stable isotopes investigations. However, relatively deep groundwater is clearly linked to very high tritium content rainwater precipitated during the 1950s and 1960s. The deuterium content of some groundwater samples showed unusual values, explained by the interactions between the groundwater and certain gases (H2S and CH4), the presences of which are linked to sulfate-reducing bacteria and methanogenic archaea detected within the saturated medium through biomolecular investigations in the shallow organic reach clayey deposits. In a wider, methodological context, the present study demonstrates that interdisciplinary approaches provide better knowledge about the behaviour of heterogeneous low-permeability media and the meaning of each data type.

Tritium contaminated soil in sites for Semipalatinsk above-ground nuclear tests

Semipalatinsk above-ground nuclear tests caused atmospheric fallout and radioactive contam-ination of the environment that resulted in the synthesis of great amount of radioisotopes. Triti-um was the basic isotope generated in the soil as a result of above-ground nuclear tests. Previ-ously many researchers believed that tritium contamination of the soil occurred in sites for un-derground nuclear tests only. The research of tritium content in areas for above-ground nuclear tests was not taken into consideration. However, during the work in the site for above-ground tests “Experimental Field”, we examined the tritium content in soil and numerically estimated the specific activity of 3H. Because the radioisotope may be produced from the following activa-tion reactions while nuclear explosions: 6Li3 + n → 4He2 + 3Н; 10B5 + n → 24He2 + 3Н; 14N + n → 12C + 3Н, as well as 151Eu63 + n → 152Eu63 , we selected soil samples to test for 3H, as well as for 152Eu. Then analysis results were compared for establishing relationship between the isotopes and investigating the mechanism of 3H production. The article presents results of detailed study of soil contaminated with tritium in the “Experimental Field” site. 3H content in soil and the iso-tope distribution in epicenter zones of technical sites and in sites located in different distance from the epicenter are presented. Correlated dependence of the 3Н content on the 152Eu content that allowed us to discover the basic mechanism of the tritium production, that was a neutron-activation reaction occurred at the time of above-ground nuclear tests.

Isotopic composition of precipitation in Poland: a 44-year record

Isotopic composition of precipitation (2H/1H and 18O/16O isotope ratios, tritium content) is nowadays widely used in numerous applications of environmental isotopes—most notably in hydrology, climatology and biogeochemistry. Here we present a long record (44 years) of stable isotope composition and tritium content in monthly precipitation available for the Krakow station (southern Poland). Krakow is the only site in Poland for which long-term record of the isotopic composition of monthly precipitation is available. The tritium data are discussed here in the context of generally declining levels of bomb tritium in the global atmosphere and growing influence of technogenic emissions of this isotope. Two aspects of temporal variability of stable isotope composition of precipitation collected in Krakow are discussed here: (i) seasonality and (ii) interannual changes of δ18O and δ2H signal. Whereas the seasonality of stable isotope signal is generated mainly by seasonally varying the degree of rainout of air masses bringing moisture from the source regions (subtropical Atlantic Ocean) to the centre of the European continent, the North Atlantic Oscillation seems to govern interannual changes of δ18O and δ2H on the decadal timescale. Progressing warming of the local atmosphere, in the order of 1.8 °C in the past four decades, leaves its imprint in stable isotope signal measured in Krakow precipitation; the slope of isotope–temperature relationship is in the order of 0.50‰/°C for δ18O and 3.5‰/°C for δ2H.