Wyniki wyszukiwania - BazTech

1

Indoor and outdoor 222Rn and 220Rn and their progeny levels surrounding Bayan Obo mine, China

Wang Nanping, Hu Miao, Zeng Weihua, Yu Cong, Jia Binlin, Yang Zhijie

Nukleonika

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2020

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Vol. 65, No. 2

145--148

EN

More than half of the total natural ionizing radiation dose received by the human population is caused by radon and thoron (Rn and Tn) and their progeny. To estimate the level of radiation due to radon and thoron and their progeny, an investigation was conducted in a residential area near the world’s largest open-pit mine of Bayan Obo in Inner Mongolia, China. The concentration of Rn, Tn, and their decay products in air and soil were studied by using AlphaGUARD, RAD7, and ERS-RDM-2S for a discrete period of time in three different locations. The average indoor concentration of radon and thoron was 62.6 ± 44.6 Bq/m3 and 108.3 ± 94.5 Bq/m3 respectively, and the outdoor concentration was 12.9 ± 6.3 Bq/m3 and 55.8 ± 18.5 Bq/m3 , respectively. Relatively high concentrations were recorded in the area near to the mine, with a significant increasing trend observed in indoor thoron concentration. A prominent hotspot in thoron concentration was found in a single-story house with values 747 ± 150 Bq/m3 . The equilibrium equivalent thoron concentration (EECTn) varies from 0.48 Bq/m3 to 2.36 Bq/m3 with an arithmetic mean of 1.37 ± 0.64 Bq/m3 , and comparatively higher than EECRn. Concluding that the mining activity at Bayan Obo mine is significantly increasing the level of indoor thoron and its progeny in surroundings. It is suggested to further systematically investigate the indoor Rn and Tn progeny concentrations in the residential dwellings of the Bayan Obo mining area, and 232Th content of the building materials, to provide a basis for calculating the radiation dose.

2

Exposures from radon, thoron, and thoron progeny in high background radiation area in Takandeang, Mamuju, Indonesia

Saputra Miki Arian, Nugraha Eka Djatnika, Purwanti Tri, Arifianto Rokhmat, Laksmana Roza Indra, Hutabarat Richard P., Hosoda Masahiro, Tokonami Shinji

Nukleonika

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2020

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Vol. 65, No. 2

89--94

EN

The exposure from radon, thoron, and thoron progeny was measured for 45 dwellings in high background radiation area in Takandeang, Indonesia with ambient dose equivalent rate ranging from 0.34 µSv•h-1 to 1.90 µSv•h-1 . The measurement was taken using passive radon and thoron discriminative detector and thoron progeny detector. This measurement was taken from November 2018 to October 2019, and within one month the detector would be replaced with a new detector. The concentrations of radon, thoron, and thoron progeny were calculated as 42–490 Bqm−3 , 20–618 Bqm−3 , and 4–40 Bqm−3 , respectively. The concentrations for outdoor were 49–435 Bqm−3 , 23–457 Bqm−3 , and 4–37 Bqm−3 , respectively, and the annual effective dose was 9.8–28.6 mSv•y-1 . Based on the result of Spearman’s correlations analysis between the indoor radon and thoron concentrations and between the indoor thoron progeny and thoron concentrations, we suggest that exposure to thoron cannot be predicted from exposure to radon, and the equilibrium equivalent thoron concentration has a large uncertainty when it is estimated from thoron concentration assuming a single thoron equilibrium factor.

3

Deconvolution of alpha spectra from air filters applied for measurements of the short-lived radon progeny concentration

Skubacz K.

Nukleonika

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2017

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Vol. 62, No. 3

229--234

EN

The paper contains a description of a method for the analysis of the complex alpha spectra generated during the measurement of the activity of filters outside of a vacuum chamber under environmental conditions. The peaks corresponding to the energies of alpha particles emitted by the specific isotopes are particularly large on the low-energy side of the peak maximum, and the energy resolution strongly depended on the applied filters. The analysis was based on the non-linear regression to a function designed for four, six and eight parameters. Satisfactory results were obtained for each of these functions, and the best-fitting results were achieved for the eight-parameter function. In addition, the uncertainties related to the estimated parameters, as well as the signals corresponding to functions that describe the shape of the energy peak, have been evaluated. There are also examples of the implementation of the method with respect to short-lived radon progeny and thoron decay products.

4

Filtration approach to mitigate indoor thoron progeny concentration

Wang J., Meisenberg O., Chen Y., Karg E., Tschiersch J.

Nukleonika

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2010

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Vol. 55, No. 4

445-450

EN

This study investigates filtration of air as potential mitigation method of thoron progeny exposure. The experiments were conducted in a model room (volume 7.1 m3) which was equipped with a pump and an HEPA (high efficiency particulate air) filter. Filtration at a rate of 0.2, 0.4, 0.5 and 0.8 h–1 during 88 h proved an effective practice in reducing the total indoor thoron decay product concentration. The results indicate that 0.4–0.8 h–1 filtration rate had almost the same filtration efficiency in decreasing the total thoron EEC (equilibrium equivalent concentration) by 97 per cent while 80 per cent of total thoron EEC were reduced by 0.2 h–1 filtration rate; meanwhile, the unattached thoron EEC rose significantly by 190, 270, 290 per cent, respectively under 0.4–0.8 h–1 filtration rate, whereas 0.2 h–1 filtration rate increased unattached thoron EEC by 40 per cent. The aerosol number size distribution variation reveals that filtration operation removes smaller particles faster or earlier than the larger ones. The annual effective dose calculated was reduced by 91–92 per cent at a filtration rate of 0.4–0.8 h–1 while 75 per cent reduced at 0.2 h–1 filtration rate after 88 h filtration process.