Radon exhalation rates from building materials using electret ion chamber radon monitors in accumulators

Pilot Study of Thoron Concentration in an Underground Thorium Mine

The Steenkampskraal mine in the Western Cape Province in South Africa provides some interesting challenges for radiation protection practitioners in view of the high thoron values encountered in this mine. The mine contains high natural thorium concentrations that lead to high thoron activity concentrations, as will be shown in this paper. The influence of ventilation has been studied, and the source term has been investigated by considering the thorium content of the rocks and the thoron exhalation. The thoron activity concentrations are around 10 kBq m -3 at a monazite seam, and the thorium exhalation is consistent with these levels. The thoron concentrations can be reduced by ventilation but not eliminated. However, the thoron progeny can probably be reduced dramatically. Issues that affect the thoron levels are also discussed. Further studies are needed, but the thoron may well not be a radiation protection problem despite the high thoron concentrations.

Phosphogypsum recycling in the building materials industry: assessment of the radon exhalation rate

Phosphogypsum can be classified as a Naturally Occurring Radioactive Material (NORM) residue of the phosphate fertilizer industry. One of the main environmental concerns of its use as building material is the radon exhalation. The aim of this study is to measure the radon exhalation rate from plates and bricks manufactured with phosphogypsum from three installations of the main Brazilian producer, Vale Fertilizantes, in order to evaluate the additional health risk to dwellers. A simple and reliable accumulator method involving a PVC pipe sealed with a PVC pipe cover commercially available with CR-39 radon detector into a diffusion chamber was used for measuring radon exhalation rate from phosphogypsum made plates and bricks. The radon exhalation rate from plates varied from 0.19 ± 0.06 Bq m^-2 h^-1, for phosphogypsum from Bunge Fertilizers, from 1.3 ± 0.3 Bq m^-2 h^-1, for phosphogypsum from Ultrafertil. As for the bricks, the results ranged from 0.11 ± 0.01 Bq m^-2 h^-1, for phosphogypsum from Bunge Fertilizers, to 1.2 ± 0.3 Bq m^-2 h^-1, for phosphogypsum from Ultrafertil. The results obtained in this study for the radon exhalation rate from phosphogypsum plates and bricks are of the same order of magnitude than those from ordinary building materials. So, it can be concluded that the recycling of phosphogypsum as building material is a safe practice, since no additional health risk is expected from the radiological point of view.

Determining the radon exhalation rate from a gold mine tailings dump by measuring the gamma radiation

The mining activities taking place in Gauteng province, South Africa have caused millions of tons of rocks to be taken from underground to be milled and processed to extract gold. The uranium bearing tailings are placed in an estimated 250 dumps covering a total area of about 7000 ha. These tailings dumps contain considerable amounts of radium and have therefore been identified as large sources of radon. The size of these dumps make traditional radon exhalation measurements time consuming and it is difficult to get representative measurements for the whole dump. In this work radon exhalation measurements from the non-operational Kloof mine dump have been performed by measuring the gamma radiation from the dump fairly accurately over an area of more than 1 km(2). Radon exhalation from the mine dump have been inferred from this by laboratory-based and in-situ gamma measurements. Thirty four soil samples were collected at depths of 30 cm and 50 cm. The weighted average activity concentrations in the soil samples were 308 ± 7 Bq kg(-1), 255 ± 5 Bq kg(-1) and 18 ± 1 Bq kg(-1) for (238)U, (40)K and (232)Th, respectively. The MEDUSA (Multi-Element Detector for Underwater Sediment Activity) γ-ray detection system was used for field measurements. The radium concentrations were then used with soil parameters to obtain the radon flux using different approaches such as the IAEA (International Atomic Energy Agency) formula. Another technique the MEDUSA Laboratory Technique (MELT) was developed to map radon exhalation based on (1) recognising that radon exhalation does not affect (40)K and (232)Th activity concentrations and (2) that the ratio of the activity concentration of the field (MEDUSA) to the laboratory (HPGe) for (238)U and (40)K or (238)U and (232)Th will give a measure of the radon exhalation at a particular location in the dump. The average, normalised radon flux was found to be 0.12 ± 0.02 Bq m(-2) s(-1) for the mine dump.

Predicted indoor radon concentrations from a Monte Carlo simulation of 1,000,000 granite countertop purchases

Previous research examining radon exposure from granite countertops relied on using a limited number of exposure scenarios. We expanded upon this analysis and determined the probability that installing a granite countertop in a residential home would lead to a meaningful radon exposure by performing a Monte Carlo simulation to obtain a distribution of potential indoor radon concentrations attributable to granite. The Monte Carlo analysis included estimates of the probability that a particular type of granite would be purchased, the radon flux associated with that type, the size of the countertop purchased, the volume of the home where it would be installed and the air exchange rate of that home. One million countertop purchases were simulated and 99.99% of the resulting radon concentrations were lower than the average outdoor radon concentrations in the US (14.8 Bq m(-3); 0.4  pCi l(-1)). The median predicted indoor concentration from granite countertops was 0.06 Bq m(-3) (1.59 × 10(-3) pCi l(-1)), which is over 2000 times lower than the US Environmental Protection Agency's action level for indoor radon (148 Bq m(-3); 4 pCi l(-1)). The results show that there is a low probability of a granite countertop causing elevated levels of radon in a home.

Accurate measurement of the radon exhalation rate of building materials using the closed chamber method

The construction department of the Chinese government is now discussing the possibility of reducing indoor radon exposure through controlling the radon exhalation rate of building materials. However, which quantity is suitable for control and how to specify and measure this quantity are still not clear. A comparison of a theoretical model and measurement process of radon exhalation between the surface of soil and building materials was carried out. As a result, the so-called intrinsic exhalation rate is thought to be a suitable quantity for control. Through theoretical analysis and experimental comparisons of different pre-treatment methods, it was indicated that the closed chamber method could be used to measure the intrinsic exhalation rate of building materials. Measurement results show that the average intrinsic radon exhalation rate of building materials commonly used in Beijing is 4.891 mBq m(-2) s(-1), with a range of 0.323-21.250 mBq m(-2) s(-1), and the average diffusion length is 16.448 cm, with a range of 2.371-41.960 cm.