抄録
Recently many Japanese wear jewelry as personal ornaments, particularly bracelets. The jewelry is made of gems, jewels, noble metals and so on. Some kinds of jewelry include much amount of radioactive elements more than that of natural range in ores which are in our living-environment. The radioactive concentrations of 25 kinds of jewels and gems, which were easily purchased on a market or through the Internet, were analyzed by HPGe. The bracelet which was made of ceramics showed the highest radioactive concentration and it was estimated as approx. 800 Bq g-1 of 232Th and 140 Bq g-1 of 238U by assuming radioactive equilibrium among the nuclides in the decay series. Moreover, there was a high radioactive concentration gem including 60 Bq g-1 of 232Th and 300 Bq g-1 of 238U. The radioactive materials added in the ceramics should be monazite analyzed by a prompt gamma-ray activation analysis method. Though the ceramics became the object of the NORM management by the concentration, the radioactivity of one bracelet does not exceed 8,000 Bq. So, all these jewelry samples do not have to manage as NORM as consumer products according to the guideline by Japanese government. However, the jewelry's activity by deliberate addition of radioactive materials is deemed to be unjustified exposure, that the ICRP led the consideration. It is considered that the NORM guideline should take in the consideration of ICRP and prohibit the addition of radioactive materials to jewelry.
