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Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*
Radiation Measurements, 89, p.8 - 13, 2016/06
Times Cited Count：2 Percentile：19.71(Nuclear Science & Technology)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 so-called sandwich sample. The mathematical model was developed to differentiate total alpha counts into thoron- and radon-associated counts. This method was experimentally validated, and then the detection limits and uncertainties were evaluated to characterize this method. It was concluded that the present method is advantageous to a sample that has much higher 
Ra activity than 
Ra if the emanation fractions are similar between thoron and radon.
Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*
Radiation Measurements, 77, p.41 - 45, 2015/06
Times Cited Count：8 Percentile：56.13(Nuclear Science & Technology)When a scintillation cell is used for radon measurement, detection efficiencies for individual alpha emitters (
Rn, 
Po and 
Po) are required depending on the methods of data analysis. The present study describes an attempt to obtain an empirical parameter which is necessary to calculate their individual detection efficiencies in the flow-through cell: the fraction of the progeny generated in the cell which is deposited onto the wall. As a result, an empirical formula was acquired to estimate the deposition fraction of Po as a function of flow rate. This result is helpful in understanding the characteristics of the scintillation cell. The empirical formula derived in this study can also be applied to predicting the behavior of thoron progeny (
Pb and its progeny) in continuous thoron measurements with the flow-through scintillation cell.
Okura, Takehisa; Feistenauer, P.*; Meisenberg, O.*; Shinonaga, Taeko*; Tschiersch, J.*
no journal, ,
The atmospheric radioactivity monitoring at Nuclear Science Research Institute, following the Fukushima accident was reviewed in this study. Comparison with measurement result of the filters at Helmholz Zentrum Muenchen (Germay) was made in order to discuss how to make an estimate of background under contaminated circumstance soon after the accident. Values of each other for samples with important level to estimate internal exposure was consistent; this points to that the adopted method to estimate background was appropriate. But some of samples with relative lower level were incompatible with each other. Penetration of radiocesium aerosols through HE-40TA was discussed with size distribution of radiocesium aerosols and characteristics of HE-40TA. Size distributions of radiocesium aerosols were evaluated experimentally, separated from HE-40TA and collected into a cascade impactor. The penetration was estimated by about 1% - 5%.
Okura, Takehisa; Meisenberg, O.*; Feistenauer, P.*; Shinonaga, Taeko*; Tschiersch, J.*
no journal, ,
Atmospheric radioactivity monitoring was made at Nuclear Science Research Institute, JAEA, following the Fukushima accident. Aerosol-bound radiocesium (Cs) was collected on paper filter (HE-40TA). In this study, to evaluate size distribution of the Cs, radioactive aerosols collected on HE-40TA was removed into distilled water, and then radioactive aerosols were extracted from the solution with a nebulizer and collected into a cascade impactor. The size distribution soon after the accident has one peak which is found around 0.3 
m. Corresponded temporal decreasing Cs concentration, the second peak which has median of 1-2 m was developed besides ca. 0.3-m-median peak at sites around field. The size distribution collected at a site in woods has only one peak after also significant decreasing of Cs concentration. It is presumed that the coarser-median peak was attributed to resuspended radioactivity, considered on the basis of distribution of radioactive aerosols on the filters observed with autoradiography and reference articles.
Sakoda, Akihiro; Meisenberg, O.*; Tschiersch, J.*
no journal, ,
The powder sandwich technique was recently developed to measure thoron (Rn-220) emanation fraction from a sample with high Ra-224 concentration. In this method, a sample was set between two filters, and then air passing through the filters was directly introduced to a detector. In the present study, this technique was expanded to discriminatively measure radon (Rn-222) and thoron emanation fractions using a scintillation cell. First, we made theoretical models that predict counts per time for each nuclide (radon, thoron, or their progeny). Then, analytical solutions for these models were fitted to experimental data to obtain radon and thoron emanation rates. This presentation describes mainly the rationale of our approach. Measurement examples for some samples are also shown and discussed.
