Study on Radioactivity and Negative Ion Originated from a Thoron Artificial Hot Spring

• Published in: RADIOISOTOPES 2005/09/15, Vol.54(9), pp.375-383
• Main Authors: SAKODA, Akihiro, KATAOKA, Takahiro, HANAMOTO, Katsumi, YAMAOKA, Kiyonori
• Format: Article
• Language: eng ; jpn
• Subjects: high-purity germanium detector; ion distribution; leaching rate of radon; monazite; negative air ion; pH dependence; relative humidity dependence; thoron; water content
• ISSN: 0033-8303; 1884-4111
• DOI: 10.3769/radioisotopes.54.375

To elucidate the various characteristic and their availabilities of the radioactivity and negative air ion originated from an artificial thoron hot spring, we simulated a hot spring condition using a monazite powder and measured the negative air ions and radioactivities in the condition. In the result, the radioactivity of the thorium series nuclide (208Tl) in monazite was 5.3 times of that of the uranium series nuclide (214Bi) . For the pH (3.5-12.5) dependence of the leaching nuclides from monazite in water, the thorium series nuclides (228Ac, 212Pb) were well leached on the strong acid side because the monazite includes the rare earth element (REE) which was high ionization tendency and was substituted by the radioactive nuclide. On the other side, the uranium series nuclides (214Bi, 214Pb) leached in water were not detected because the specific activities of the uranium series nuclide are lower relative to those of the thorium series nuclide. Moreover, there were many negative air ions originated from monazite in the place within 10 cm away from the monazite surface. This is suggested that most negative ions exist within the range of the radiated α rays. Negative air ions increased with increasing atmospheric relative humidity (35-60%) . This is suggested that negative air ions stably existed in the hydration type such as O-2 (H2O) n. Furthermore, for the hydrous rate dependence of the negative air ions originated from monazite, the negative air ions without supernatant fluid were larger than those with supernatant fluid, because a rays ionized water on the surface of monazite.