Influence of various factors on the value of thoron emanation coefficient

The “powder sandwich” method was adapted to the measuring equipment at the Laboratory of Radiometric Expertise, IFJ PAN (Kraków, Poland). The versatility of the method has been confirmed. The values of thoron emanation coefficients (f) for 16 materials have been determined. It has been found that the value of thoron emanation coefficient is not directly dependent on the concentration of 224Ra, other factors are also important, e.g. the size of the grains, the inter-grain space and the distribution of radium atoms in the grain. The influence of the grain size on the value of thoron emanation coefficient was investigated.

Radon emission fluctuation as a result of biochar application into the soil

The presented research was focused on the analysis of the impact of biochar application into the soil on the radon exhalation process as a new issue of radiation protection in agriculture. Field measurements of the radon exhalation rate utilizing two methods—active and passive as well as laboratory measurements of the radon emanation coefficient were performed. In laboratory a soil samples with sunflower husk biochar were analysed using the accumulation chamber technique. At the final step the assessment of the effective dose for humans coming from radon exhalation from soil depending on biochar dose applied were evaluated. The doses of biochar applied in the analysed experimental fields were 0, 20, 40, 60, 80, and 100 Mg ha−1. The results show that biochar application into the soil contribute to a decrease in the emanation coefficient from a value around 7% to less than 2% with a simultaneous decrease in the radon exhalation rate from 4.4 to 14.8 mBq m−2 s−1 when the biochar dose increase from 0 to 100 Mg ha−1.

Radon Over Kimberlite Pipes: Estimation of the Emanation Properties of Rocks (Lomonosov Diamond Deposit, NW Russia)

In this paper, using the example of the Lomonosov diamond deposit, experimental studies of rocks were carried out to assess the main radiation and physical factors affecting the formation of the radon field over the kimberlite pipes of the Arkhangelsk diamondiferous province. For various types of rocks, represented by vent kimberlites, tuffaceous-sedimentary rocks of the crater and enclosing and overlying sediments, the following were studied: porosity, density, activity of radium-226, activity of radon in a free state, level of radon production, and emanation coefficient. The research results showed that the greatest amount of radon in a free state is produced by rocks of the near-pipe space, represented by the enclosing Vendian V2 deposits and characterized by high values of the emanation coefficient, radium activity, radon production level and porosity. This fact is associated with the structural and geological features of the near-pipe space, which was exposed to the impact of kimberlite magma on the host rocks. The lowest values of these parameters are characteristic of the kimberlites of the vent facies, which limits the formation of free radon in the body of the pipe. The results of the experimental studies create prospects for the development of emanation methods for searching for kimberlite pipes in the conditions of the Arkhangelsk diamondiferous province.

Preparation of multi-purpose radon emanation sources

The aim of this work was to prepare reference radon emanation sources traceable to primary standards to be used for radon-in-air as well as radon-in-water experiments. The feasibility of making stable radon emanation sources by drop deposition and chemisorption was studied. Experimental emanation coefficients for sources made by drop deposition and chemisorption ranged from 0.10 to 0.74 and from 0.18 to 0.25, respectively. These relatively low emanation coefficient values suggest that further method developments would be desirable. Proposals are made to improve chemisorption yield during source preparation and to obtain more accurate measurements on radon emanation coefficient.

222Rn and 220Rn emanations from powdered samples of samarskite as a function of annealing temperature

Emanation coefficients for radon (222Rn) and thoron (220Rn) were measured from fully metamict samarskite collected from Centennial Cone after 1 h and 24 h annealing in argon from 473 to 1373 K. For the 1 h annealing run, 222Rn emanation coefficients ranged from 5 × 10-6 to 2.1 × 10-5 %, while 220Rn coefficients varied from 6.3 × 10-3 to 2 × 10-2 %. For the 24 h annealing run, 222Rn coefficients ranged from 5.8 × 10-6 to 2.3 × 10-5 %, while 220Rn coefficients varied from 4.1 × 10-3 to 1.5 × 10-2 %. The 222Rn and 220Rn emanation coefficients vs. annealing temperature data can be described by an exponentially decreasing sinusoidal function. Both 222Rn and 220Rn emanation coefficient values after annealing considerably exceeded those measured from an unheated powder reference sample and from the original samarskite sample.

Impact of soil incorporation of biochar on radon emission

<p>Biochar (charcoal made from biomass in the pyrolysis process) has found broad application in agriculture. The research performed with biochar revealed the positive impact of biochar application for chemical and physical properties of soil. Biochar was also used as an material for decontamination of soil from heavy metals and pesticides. The improved water retention of soil after biochar application was shown as well. There are particular research concerning the usage of biochar as an material for decontamination of soil from anthropogenic radioactive material including Cs-137 and Sr-90 deposited after nuclear weapon test. However, the biochar find the most practical application in agriculture for improvement of crops efficiency and water retention of soils. The typical application amount of biochar for agricultural purpose varies from 40 to 100 Mg ha<sup>-1</sup>.</p><p>Actually, there are numerous research activities focused on the direct impact of biochar on physical and chemical soil properties. Simultaneously lack of information are available for issue if and how biochar impact for environment radioactivity. As one of that impact could be  the influence on radon emission from soil surface. The aim of presented work was to investigate the impact of biochar application into the soil for the radon emission process.</p><p>The research objects were soil samples collected from experimental fields with biochar applied at doses from 1 to 100 Mg ha<sup>-1</sup>. Two type of biochar were investigated – first biochar produced from sunflower husk at temperature of 650°C and second biochar produced from wood chips at temperature of 650°C. The radon emanation coefficient were assessed using active cumulative technique incorporating AlphaGUARD instrument equipped with sealed accumulation box.  In addition, we directly measured radon exhalation rate at the experimental fields. As the emanation coefficient calculation require the information on Ra-226 activity concentration, the gamma spectrometry analysis using HPGe detector were performed for samples collected on particular field.  </p><p>The results of activity concentration assessments shown that the most visible effect of biochar application into the soil is associated with the reduction of soil bulk density by this material. No significant changes in activity concentration depending on the biochar dose applied were observed for Ra-226. Fluctuation in radon exhalation rate as well as in emanation coefficient, depending on the biochar dose (from 1 to 100 Mg ha<sup>-1</sup>) were observed and presented.</p><p>The research was partially conducted under the projects “Water in soil – satellite monitoring and improving the retention using biochar” no. BIOSTRATEG3/345940/7/NCBR/2017, which was financed by the Polish National Centre for Research and Development in the framework of “Environment, agriculture and forestry” – BIOSTRATEG strategic R&D programme.</p>

Effect of grain size on radon emanation coefficient, surface and mass exhalation rates and the correlation coefficient between them in different masses of soil and phosphate fertilizer

It is important to study the behavior of recoiling radon atoms 222Rn after decay of parent 226Ra and the effect of parameters on their access to the surrounding medium. The present study was carried out using CR-39 detector to study the effect of grain size on the correlation between surface and mass exhalation rates and the correlation between emanation coefficient and exhalation rate at different masses of soil and phosphate fertilizer. In addition, the relationship between emanation coefficient and the sample mass was studied for different grain sizes (0.1, 0.3, 0.5 and 1 mm). The results showed that there is no effect of grain sizes on the correlation coefficient between surface and mass exhalation rates in soil and fertilizer. The correlation coefficient between emanation coefficient and exhalation rate in different masses of soil was slightly influenced by the grain sizes. While the correlation coefficient between emanation coefficient and exhalation rate in different masses of phosphate fertilizer samples was not affected by the grain sizes (0.1, 0.3 and 0.5 mm). However, it was found that the emanation coefficient decreases exponentially with the mass for soil and phosphate fertilizer. This relationship was not significantly affected by grain size in soil except grain size 1 mm. While this relationship was affected by grain size >0.3 mm in phosphate fertilizer.