RADIOISOTOPES

Show abstractHide abstract

Possibility of the application of the Welch test on the radioactivity measurements was discussed.
Recently, the measurements of the radioactivities in the seawater and/or marine products are often carried out by the local governments.
It is very important to compare these data and to know whether any significant differences exist between them.
The various kinds of correction must be done for all the radioactivity data, for example, background subtraction, counting efficiency, and so on, depending on the measuring places and instruments.
The test of the significance of the data must be done under the assumption that the variances of the data are different each other, although the parent means of the radioactivities can be assumed to be equal. Therefore, the Welch tests are often used for the radioactivity data.
The author has attempted Monte-Carlo simulations to know the distribution of the normalized statistic which corresponds to that for the Welch test, and concluded that the statistic was not of the t-distribution but of the normal one.
It is therefore concluded that the Welch test is not suitable to the test of the radioactivity data and involves much risks not to reject the significantly different data.

View full abstract

Download PDF (691K)

One of the main purposes of Super-Kamiokande is the observation of solar neutorinos. The radon concentration in the detector water should be less than about 5 mBq/m³, because low energy background events in this experiment are dominated by radon daughters. We developed a high sensitive radon detector with an electrostatic collection method and a PIN photodiode to measure the energy of a particles from the daughter nuclei of ²²²Rn. We constructed a calibration system to study high voltage dependence and absolute humidity dependence of the detector. As a result, the absolute humidity dependence was clearly observed at the region less than 1.6 g/m³. The calibration factor at 0.08 g/m³ was 1.8±0.1 (count/d) / (mBq/m³) . The detection limit was 13 mBq/m³ by the Curie's method.

View full abstract

Using autoradiographic analysis or a direct count of ¹²⁵I in the various organs, we examined the distribution of Na¹²⁵I in various mouse organs. KI in saline, or saline alone was orally administered to mice for 3 days, and then Na¹²⁵I was injected into the tail vein. Na¹²⁵I in various organs of mice at 5 day after injection was measured. The accumulation of ¹²⁵I in the submaxillary gland and stomach of the KI group was 5 times higher than that of the saline group. In conclusion, these results indicate that the administration of KI specifically enhances the accumulation of ¹²⁵I in the submaxillary gland and stomach.

View full abstract

For the purpose of educational use of environmental ionizing radiations, we have made a simple γ-ray counter consisted of a portable survey meter and a pocket-computer. The interface circuit of survey meter and pocket-computer was handmade. The relative intensities of environmental γ-rays were measured along the road in Fukui. The intensities increased, when passing through tunnels or by cliffs, and the geological effects were observed at Wakasa district. We can use this system as a teaching material of computer-assisted measurement.

View full abstract

Register with J-STAGE for free!