RADIOISOTOPES

“Zuiki” is the stem of a taro plant containing natural radioactive potassium-40. Several zuiki stems were peeled, dried, and micronized; then, the compression and formation method was used to make ten disk-shaped sources. These sources were measured as to their weight, thickness, diameter, and radiation count (using a GM-survey meter). The counted radiation was mainly attributed to β-rays from ⁴⁰K. The averages (SD’s) of the weight, thickness, diameter, and radiation count were 15.1(0.03) g, 9.98(0.1) mm, 35.2(0.01) mm and 163.4(10.5) cpm, respectively. The usability of the sources for educational purposes was examined in three tests on the dependence of the radiation count versus time, distance, and shielding. Furthermore, the statistical fluctuation of the radiation counts was examined by making 50 measurements. It was concluded that the zuiki radiation sources were useful for demonstrating the three principles of radiation protection and the statistical fluctuation of radiation counts.