Determination of 226Ra in TENORM Sample Considering Radon Leakage Correction

Background: Phosphogypsum is material produced as a byproduct in fertilizer industry and is generally used for building materials. This material may contain enhanced radium-226 (226Ra) activity concentration compared to its natural concentration that may lead to indoor radon accumulation. Therefore, an accurate measurement method is proposed in this study to determine 226Ra activity concentration in phosphogypsum sample, considering the potential radon leakage from the sample container.Materials and Methods: The International Atomic Energy Agency (IAEA) phosphogypsum reference material was used as a sample in this study. High-purity germanium (HPGe) gamma spectrometry was used to measure the activity concentration of the 226Ra decay products, i.e., 214Bi and 214Pb. Marinelli beakers sealed with three different sealing methods were used as sample containers. Due to the potential leakage of radon from the Marinelli beaker (MB), correction to the activity concentration resulted in gamma spectrometry is needed. Therefore, the leaked fraction of radon escaped from the sample container was calculated and added to the gamma spectrometry measured values.Results and Discussion: Total activity concentration of 226Ra was determined by summing up the activity concentration from gamma spectrometry measurement and calculated concentration from radon leakage correction method. The results obtained from 214Bi peak were 723.4 ± 4.0 Bq· kg-1 in MB1 and 719.2 ± 3.5 Bq· kg-1 in MB2 that showed about 5% discrepancy compared to the certified activity. Besides, results obtained from 214Pb peak were 741.9 ± 3.6 Bq· kg-1 in MB1 and 740.1 ± 3.4 Bq· kg-1 in MB2 that showed about 2% difference compared to the certified activity measurement of 226Ra concentration activity.Conclusion: The results show that radon leakage correction was calculated with insignificant discrepancy to the certified values and provided improvement to the gamma spectrometry. Therefore, measuring 226Ra activity concentration in TENORM (technologically enhanced naturally occurring radioactive material) sample using radon leakage correction can be concluded as a convenient and accurate method that can be easily conducted with simple calculation.

Radiation Safety Exploration Using Radio-photoluminescence Dosimeter for Crookes Tubes in Junior and Senior High School in Japan

Background: Crookes tube is utilized in junior high and high schools in Japan to study the character of electrons and current, and not for radiological education. There is no official guideline or regulation for these radiation source to the public. Therefore, most teachers have no information about the leakage of X-rays from Crookes tube. The peak energy of X-rays is approximately 20 keV, and it is impossible to measure using conventional survey meters.Materials and Methods: Each leakage dose of low energy X-rays from 38 Crookes tube in the education field, such as junior and senior high schools in Japan, was explored by the teachers in the school using radio-photoluminescence (RPL) dosimeters. Before and after the measurements, the dosimeters were sent by postal mails.Results and Discussion: At the exploration in this study, it was estimated that the 70 μm dose equivalent, Hp(0.07) of X-rays from 31 Crookes tubes were smaller than 100 μSv in 10 minutes, at the distance of 1 m, where the Crookes tube was usually observed. However, the highest dose was estimated as 0.69 mSv by an equipment with the full power. Furthermore, one Crookes tube exhibited 0.62 mSv with minimum output power of the induction coil. This relatively large dose was reduced by the shorter distance of discharge electrodes of the induction coil.Conclusion: The leakage dose of low energy X-rays from 38 Crookes tube was explored using RPL dosimeters. It was estimated that the Hp(0.07) of X-rays from 31 Crookes tubes were smaller than 100 μSv in 10 minutes at the distance of 1 m, while some equipment radiated a higher dose. With this study, the provisional guideline for the safety operation of Crookes tube is established.