Radioactivity and radon emanation fraction of the granites sampled at Misasa and Badgastein

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Abstract

The chemical composition was analyzed and the radioactivity, radon exhalation rate and emanation fraction were measured to investigate the characteristics of the granites sampled at Misasa and Badgastein, world famous for radon therapy. The Misasa granite was probably composed of quartz, albite and microcline. The Badgastein granite was probably composed of quartz and muscovite. The radon exhalation rates and emanation fractions of the Misasa granite were much higher than those of the Badgastein granite, regardless of the 226Ra activity concentrations.

Introduction

The hot spring at Misasa in Japan and the gallery at Badgastein in Austria are world famous for radon therapy (Mitsunobu et al., 2005; Zötl, 1995). Patients with rheumatic diseases, etc. inhale radon and its progenies for therapeutic purposes (Falkenbach et al., 2005). Many investigations have been made to clarify the mechanism of radon therapy (Yamaoka, 2006). However, the mechanism has not yet been understood because the generation and behavior of radon and its progenies in the environment and the internal movement of inhaled radon and its progenies are not entirely obvious (Porstendörfer, 1994; Ishikawa et al., 2003). We previously reported the leaching rate of radon from the rocks into water, which were sampled at the region where radon therapy is practiced (Sakoda et al., 2007a, Sakoda et al., 2007b). On the other hand, to our knowledge, there is no information on the radon exhalation rate and emanation fraction of these rocks. Therefore, it is important to obtain the radon exhalation rate and emanation fraction of the radioactive rock as a radon source.

In this study, as part of the study to elucidate the mechanism of the radon therapy, the chemical composition was analyzed and the 226Ra activity, radon exhalation rate and emanation fraction were measured to investigate the characteristics of two granites sampled at Misasa and Badgastein. The 232Th and 40K activity was also measured. In addition, the difference in the radon emanation fraction between the two granites was also discussed. Here, it is noted that in this paper “radon” means 222Rn, and “emanation fraction” means the quantity better known under “emanation power”.

Section snippets

Sample

Two granites were used in this study. One (Misasa granite) was collected at the hot bathing hall with high concentration of radon at Misasa Medical Center of Okayama University Medical School. In the corner of the bathing hall, there is a well in which the granite is transported underground and deposited. The granite of varied grain size was sampled from there. The other one (Badgastein granite) was collected near the gallery of the Gasteiner Heilstollen in Austria. A block of the granite was

Chemical composition

Fig. 2 shows the XRD patterns of the samples. Most peaks of the Misasa granite corresponded to the diffraction patterns of quartz (SiO2), albite (NaAlSi3O8) and microcline (KAlSi3O8) and most peaks of the Badgastein granite corresponded to the diffraction patterns of quartz (SiO2) and muscovite (KAl2(Si3Al)O10(OH)2). Table 1 shows the major elements in the samples determined by ICP-AES. The Misasa granite was composed of SiO2, Al2O3, Fe2O3, Na2O, K2O and CaO and the Badgastein granite was

Conclusions

The chemical composition of the two granites was analyzed and the radioactivity, radon mass exhalation rate and emanation fraction were measured, which were sampled at Misasa in Japan and Badgastein in Austria. The Misasa granite was probably composed of quartz, albite and microcline. The Badgastein granite was probably composed of quartz and muscovite. The radon mass exhalation rates of the Misasa granite were 1.9 times higher than those of the Badgastein granite although the 226Ra activity

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