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- 저자 : Tokonami Shinji (검색결과 4 건)
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Saïdou,Shinji Tokonami,Masahiro Hosoda,Augustin Simo,Joseph Victor Hell,Olga German,Esmel Gislere Oscar Meless 대한방사선방어학회 2022 방사선방어학회지 Vol.47 No.4
Background : The current study reports measurements of activity concentrations of radon (222Rn) and thoron (220Rn) in dwellings , followed by inhalation dose assessment of the public , and then by the development of regulation and the national radon action plan (NRAP) in Cameroon . Materials and Methods : Radon , thoron , and thoron progeny measurements were carried out from 2014 to 2017 using radon-thoron discriminative detectors (commercially RADUET) in 450 dwellings and thoron progeny monitors in 350 dwellings . From 2019 to 2020 , radon track detectors (commercially RADTRAK) were deployed in 1 , 400 dwellings . It was found that activ- ity concentrations of radon range in 1 , 850 houses from 10 to 2 , 620 Bq/m3 with a geometric mean of 76 Bq/m3 . Results and Discussion : Activity concentrations of thoron range from 20 to 700 Bq/m3 with a geometric mean of 107 Bq/m3 . Thoron equilibrium factor ranges from 0 . 01 to 0 . 6 , with an arithmetic mean of 0 . 09 that is higher than the default value of 0 . 02 given by UNSCEAR . On average , 49% , 9% , and 2% of all surveyed houses have radon concentrations above 100 , 200 , and 300 Bq/m3 , respectively. The average contribution of thoron to the inhalation dose due to radon and thoron exposure is about 40% . Thus , thoron cannot be neglected in dose assessment to avoid biased results in radio-epidemiological studies . Only radon was considered in the drafted regulation and in the NRAP adopted in October 2020 . Reference levels of 300 Bq/m3 and 1 , 000 Bq/m3 were recommended for dwellings and workplaces . Conclusion : Priority actions for the coming years include the following : radon risk mapping , promotion of a protection policy against radon in buildings , integration of the radon prevention and mitigation into the training of construction specialists , mitigation of dwellings and workplaces with high radon levels , increased public awareness of the health risks associated with radon , and development of programs on the scientific and technical aspects .
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Comparative analysis of radon, thoron and thoron progeny concentration measurements
Janik, Miroslaw,Tokonami, Shinji,Kranrod, Chutima,Sorimachi, Atsuyuki,Ishikawa, Tetsuo,Hosoda, Masahiro,Mclaughlin, James,Chang, Byung-Uck,Kim, Yong Jae Oxford University Press 2013 Journal of radiation research Vol.54 No.4
<P>This study examined correlations between radon, thoron and thoron progeny concentrations based on surveys conducted in several different countries. For this purpose, passive detectors developed or modified by the National Institute of Radiological Sciences (NIRS) were used. Radon and thoron concentrations were measured using passive discriminative radon-thoron detectors. Thoron progeny measurements were conducted using the NIRS-modified detector, originally developed by Zhuo and Iida. Weak correlations were found between radon and thoron as well as between thoron and thoron progeny. The statistical evaluation showed that attention should be paid to the thoron equilibrium factor for calculation of thoron progeny concentrations based on thoron measurements. In addition, this evaluation indicated that radon, thoron and thoron progeny were independent parameters, so it would be difficult to estimate the concentration of one from those of the others.</P>
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Nkoulou II Joseph Emmanuel Ndjana,Engola Louis Ngoa,Dallou Guy Blanchard,Saïdou,Bongue Daniel,Hosoda Masahiro,Njock Moïse Godefroy Kwato,Tokonami Shinji 대한방사선방어학회 2023 방사선방어학회지 Vol.48 No.2
Background : This study aims to reevaluate natural radiation exposure , following up on our previous study conducted in 2019 , and to assess the associated risk of lung cancer to the public residing in the gold mining areas of Betare-Oya , east Cameroon , and its vicinity. Materials and Methods : Gamma-ray spectra collected using a 7 . 62 cm × 7 . 62 cm in NaI(Tl) scintillation spectrometer during a car-borne survey, in situ measurements and laboratory mea- surements performed in previous studies were used to determine the outdoor absorbed dose rate in air to evaluate the annual external dose inhaled by the public . For determining internal exposure , radon gas concentrations were measured and used to estimate the inhalation dose while considering the inhalation of radon and its decay products . Results and Discussion : The mean value of the laboratory-measured outdoor gamma dose rate was 47 nGy/hr, which agrees with our previous results (44 nGy/hr) recorded through direct mea- surements (in situ and car-borne survey) . The resulting annual external dose (0 . 29 ± 0 . 09 mSv/yr) obtained is similar to that of the previous study (0 . 33 ± 0 . 03 mSv/yr) . The total inhalation dose resulting from radon isotopes and their decay products ranged between 1 . 96 and 9 . 63 mSv/yr with an arithmetic mean of 3 . 95 ± 1 . 65 mSv/yr. The resulting excess lung cancer risk was esti- mated ; it ranged from 62 to 216 excess deaths per million persons per year (MPY) , 81 to 243 ex- cess deaths per MPY, or 135 excess deaths per MPY, based on whether risk factors reported by the U. S . Environmental Protection Agency, United Nations Scientific Committee on the effects of Atomic Radiation , or International Commission on Radiological Protection were used , re- spectively. These values are more than double the world average values reported by the same agencies . Conclusion : There is an elevated level of risk of lung cancer from indoor radon in locations close to the Betare-Oya gold mining region in east Cameroon . Therefore , educating the public on the harmful effects of radon exposure and considering some remedial actions for protection against radon and its progenies is necessary.
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Siraz M.M. Mahfuz,Alam M.S.,Jubair A.M.,Das S.C.,Ferdous J.,Hossain Z.,Das S.,Khandaker Mayeen Uddin,Bradley D.A.,Tokonami Shinji,Yeasmin S. 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.8
Radon is a naturally occurring carcinogenic agent, poses a serious health hazard when inhaled or ingested in significant amounts. The water of the Padma river will be used as a tertiary coolant for the soon-to-be-commissioned ‘Rooppur Nuclear Power Plant’. Hence, it is important to assess the radiological status of the river prior to the commission of this power plant. Therefore, for the first time, 25 samples of water were collected from various locations of the Padma River and analyzed for radon concentration using the RAD H2O (DURRIDGE) radon monitoring device. The radon concentrations were found in the range from 0.077 ± 0.036 to 0.494 ± 0.211 Bq/L with a mean of 0.250 ± 0.093 Bq/L. All the concentrations were found to be below the recommended limits of WHO (100 Bq/L) and USEPA (11.1 Bq/ L). The mean annual effective dose due to the radon exposure via inhalation and ingestion pathways were 0.638 mSv/y and 0.629 mSv/y, respectively, which were all well below the annual effective dose recommended by WHO (0.1 mSv/y). Since Bangladesh lacks a national safety limit of radon in water, this pioneering study provides baseline data on radon levels for the environment around Rooppur Nuclear Power Plant.
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