An approach to discriminatively determine thoron and radon emanation rates for a granular material with a scintillation cell

Abstract

A powder sandwich technique was applied to determine thoron (220Rn) and radon (222Rn) emanation rates for a granular material. The feature of this technique is the sample preparation, in which a granular material is put and fixed between two membrane filters. Airflow is directly given to this sandwich sample, will include thoron and radon emanated from the material, and then is transferred to the detector. This method makes sure that radon as well as thoron emanated is not retained in pore space within the sample volume, which is crucial for the appropriate emanation test. This technique was first introduced by Kanse et al. (2013) with the intention to measure the emanation of thoron-but not of radon-from materials having much higher 224Ra activity than 226Ra. In the present study, the methodology for the discriminative determination of thoron and radon emanation rates from a granular material has been examined using a flow-through scintillation cell and sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron-and radon-associated counts. With a sample of uranium ore, this model was experimentally validated by comparison between the scintillation cell and a reference detector that can discriminatively measure thoron and radon concentrations. Furthermore, the detection limits and uncertainties were evaluated to discuss the characteristics of this method. Key parameters for their improvement were found to be the background radon concentration and the leakage of radon from the measurement system, respectively. It was concluded that the present method is advantageous to a sample that has much higher 226Ra activity than 224Ra if the emanation fractions are similar between thoron and radon.

Comparison of antioxidative effects between radon and thoron inhalation in mouse organs

“…To eliminate the influence of thoron progenies, breeding cages and scintillation cells were equipped with HEPA filters and membrane filters, respectively, and glass filters were placed on the inlet side. The analysis of thoron concentration was calculated based on previous studies (Sakoda et al 2015(Sakoda et al , 2016. Thoron has a short half-life, as mentioned above, and its decay correction in the system was performed accordingly.…”

Seasonal Variations in Radon and Thoron Exhalation Rates from Solid Concrete Interior Walls Observed Using In Situ Measurements

“…These are higher by a factor of six and two than typical values for J Rn (5 × 10 −4 Bq m −2 s −1 ) and J Tn (0.05 Bq m −2 s −1 ) reported in an earlier review paper [20]; however, they fall within their typical ranges of 10 −4 -3 × 10 −3 and 10 −3 -0.2 Bq m −2 s −1 , respectively. The value of α was approximately one order of magnitude greater than a typical value of around 10 −5 s −1 observed in common laboratory tests of rad on emanation and exhalation, where AlphaGUARD or RAD7 was simply connected to an airtight chamber containing a radon-emitting sample (e.g., [21]). This means that the present in situ measurement system was more prone to air leakage, probably because the gap between the accumulation chamber and wall remained unfilled despite the addition of clay to reduce leakage.…”

Influence of various factors on the value of thoron emanation coefficient

“…Some researchers used passive SSNTD detectors for studying the emanation process of thoron [18]. The interesting measurement technique was applied by Sakoda et al [19]. They placed a sample in a closed circuit where air was pumped through the sample and thoron released from the sample was register by a thoron monitor.…”