Development of Radon and Thoron Exposure Systems at Hirosaki University (original) (raw)
Related papers
Thoron versus radon: measurement and dosimetry
International Congress Series, 2005
Two new instruments were developed for the U.S. Department of Energy Environmental Science Management Program (EMSP) to perform more detailed exposure assessment measurements at Fernald, OH. Fernald is a former uranium processing facility undergoing remediation. The instruments are a miniature radon and thoron detector, and a miniature particle size spectrum analyzer. Ongoing measurements of both thoron ( 220 Rn) and radon ( 222 Rn) gas are now being made at four locations: (1) at Fernald; (2) at the New York City National Weather Service site, used as a quality control (QC) site; (3) at a private home in Bangkok used as a QC site; and (4) at a research center and rare earth development facility processing monazite ore near Bangkok. Particle size distribution measurements are presented for two locations: at Fernald and at the Rare Earth Facility near Bangkok. Continuous radon and thoron measurements were made at all sites for at least 1 year and the bronchial dose is reported. D 2004 Published by Elsevier B.V.
Design and construct optimum dosimeter to detect airborne radon and thoron gas: Experimental study
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011
Aim of this work is to design and select optimum dimension of a radon and thoron dosimeter within the measure optimum value of the calibration factor, using CR-39 Nuclear Track Detectors (NTDs). The results show that the best dimension to detect and measure real values of airborne radon and thoron concentrations is 6 cm and 7 cm for diameter and height, respectively. Calibration factors (K) for radon and thoron at this dimension were 2.68 ± 0.03 cm and 0.83 ± 0.01 cm, respectively, and these factors relatively depend on the detector efficiency. Therefore, the efficiency of CR-39NTDs to register alpha particles and their effects on the calibration factor estimated. It is found that the calibration factor increased exponentially with detector efficiency. Moreover, detector efficiency was equal to 80.3 ± 1.23% at the optimum dosimeter.
Journal of Radioanalytical and Nuclear Chemistry, 2013
Gas-flow ionization chambers for radioisotope (RI) monitoring systems at RI institutes throughout Japan are commonly used to measure RIs which leak from the RI institutes. Before the Japan's 2011 Tohoku earthquake [11 March 2011, moment magnitude (M w ) 9.0], ionization current data measured with a gas-flow ionization chamber at the RI institute of Fukushima Medical University were found to change. The question we must raise is whether the variation ionization current can be considered to the variation of outdoor radon concentration. The conversion factors (from ionization current to radon concentration in air) of the gas-flow ionization chamber can be obtained by measuring four levels of radon concentration (outdoor air, indoor air, high level and radon-free gas) with an Alpha-GUARD monitor and the chamber itself. The two gas-flow ionization chambers consist of the air intake and terminal exhaust duct of the RI institute. It was found that the radon concentration in the exhaust air was the same as that in the air intake. This study provided evidence that variations of outdoor radon concentration could be determined using gas-flow ionization chambers for RI monitoring systems.
Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan
Radiation Protection Dosimetry, 2012
Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m 22 s 21 , while the thoron exhalation rate ranged from 40 to 3330 mBq m 22 s 21 . The highest radon exhalation rate (37 mBq m 22 s 21 ) and gamma-ray dose rate (92 nGy h 21 ) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m 23 , which was higher than the average value in Japan (15.5 Bq m 23 ). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m 23 ) to 314 Bq m 23 . The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.
Simultaneous Measurement of Radon and Thoron Released from Building Materials Used in Japan
Progress in Nuclear Science and Technology, 2011
Common building materials used in constructing dwellings are a major source of radon and thoron gases emanation into the indoor environment. Concentrations of the radionuclides 226 Ra and 232 Th and radon/thoron exhalation rates are important parameters for characterizing radon and thoron sources in building materials and comparing the relative contribution of different materials to the total radiation dose. In the present study, concentrations of the radionuclides 226 Ra, 232 Th and 40 K in different kinds of granite used as building materials in Japan were determined by γ-ray spectroscopy, and a common hazard index, the radium equivalent index, was evaluated on the basis of those results. Exhalation rates of radon and thoron were measured by using an accumulation chamber equipped with a solid-state alpha particle detector. The influence of chamber leakage and back diffusion time decay constants on radon exhalation rate was also estimated, and the correlations between radon/thoron exhalation rates and their parent nuclide (radium/thorium) concentrations were examined.
Calibration of commercial radon and thoron monitors at stable activtiy concentrations
Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine, 2014
The upcoming revision of Council Directive 96/29/Euratom in the form of the proposed basic safety standards for protection against the dangers arising from exposure to ionizing radiation (BSS) evokes new challenges for the metrology institutes. In the case of the two radon isotopes, the corresponding public exposure will be part of legal metrology for the first time. Since the levels of activity concentration that are laid down in the draft of the BSS cover the range from 200 Bq/m(3) to 300 Bq/m(3) in general (with an exceptional top level of 1000 Bq/m(3)), new calibration procedures for existing commercial monitors with their limited counting statistic have to be developed. This paper gives an overview how this metrological challenge can be overcome.
An Overview of Instrumentation for Measuring Radon in Environmental Studies
Journal of Radiation and Nuclear Applications
A number of techniques have been used to measure the concentrations of (222 Rn) and their decay products in the environment. Three characteristics were used to describe the radon measurement techniques: (i) whether the technique measures 222 Rn or its daughter products; (ii) time resolution and (iii) radioactive detection of the type of emission either alpha, or beta particles or gamma radiation resulting from radioactive decay. Most common methods rely on detection of alpha particles. Sometimes a single alpha particle (e.g., 218 Po for 222 Rn) is detected to measure radon isotopes (as in air-inmonitors, RAD7, Durridge, USA) or by counting all three alpha particles produced in the decay of 222 Rn (i.e., 222 Rn, 218 Po, and 214 Po) using scintillation counters. Some methods are based on the detection of gamma-ray emitted radionuclides during radioactive decay of the progeny of 222 Rn (214 Bi, 214 Pb) and only a few methods utilize beta decays. The present work discusses the various methods available for radon measurements from different matrices causing radon release to the environment, wherever applicable, the sensitivity and quality assurance/quality control (QA/QC) aspects of these techniques are also explored.
2019
Mathura is a city in the north Indian prefecture of Uttar Pradesh. Mathura oil processing plant sited in the city is one of the utmost petroleum treatment facilities in Asia which was built up in 1978. The Mathura petroleum processing plant discharges harmful gases and arranges squander into the waterways making the region filthy and undesirable. In the present study attention has been given to the estimation of radon and its descendants to know the effect of radioactivity in nearby homes due to refinery waste. Radiological significance of radon and its descendants have been recognized quite a while back, thoron had frequently been disregarded because of its short half-life. Numerous investigations demonstrate that Thoron and its progeny is likewise a noteworthy contributor to the Residential buildings in some Asian and American nations. The present investigation was completed using Solid State Nuclear Track Detectors (SSNTD's) based twin chamber dosimeters. Radon concentration ...
Measurements of Radon Concentrations and Dose
Measurements of radon gas concentrations with their progeny and the annual effective dose indoor the building of Al-Mustansiriyah University College of Science-Chemistry Department have been carried out by using time-integrated passive radon dosimeters solid state nuclear track detector CR-39 technique. The detectors with 1cm x1cm have been distributed over 58 places and suspended for sitting (1m) and standing (1.75m) positions in each location under study. The dosimetric measurements are made over a period of 100 days from 30 January 2014 to 10 May 2014. The calibration process has been done using radium-226 source with known activity radiation. It has found that the indoor radon gas concentrations varying from 35.220±5.935Bg/m 3 to 71.673±8.466Bg/m 3 with an average value 49.129±6.969Bg/m 3 at 1m, and varying from 31.794±5.639Bg/m 3 to 68.246±8.261Bg/m 3 with an average value 45.487±6.696Bg/m 3 at 1.75m which are within the worldwide limits 148Bg/m 3 (EPA, 2003) and 200-300Bg/m 3 (ICRP, 2009). The annual effective dose of the inhalation exposure to radon gas has been estimated and this vary from 0.370mSv/y to 0.753mSv/y with an average value 0.516mSv/y at 1m, and varying from 0.334mSv/y to 0.717mSv/y with an average value 0.478mSv/y at 1.75m which are within the worldwide permissible limits 3-10mSv/y (ICRP, 1993). The potential alpha energy concentration found to vary from 3.808mWL to 7.748mWL with an average value 5.311mWL at 1m and vary from 3.437mWL to 7.378mWL with an average value 4.918mWL at 1.75m which are less than the recommended value 53.33mWL (UNSCEAR, 1993). The lung cancer cases per million person per year vary from 6.664 to 13.562per million person per year with an average value 9.296per million person per year at 1m and vary from 6.016 to 12.913per million person per year with an average value 8.607per million person per year which are less than the recommended range 170-230 per million person per year (ICRP, 1993). The number of decays per-minute using swabs measurements technique have been used for selected units within two swabs from building materials walls for each unite, with area of 100cm 2 using Ludlum 3030, the average of three swabs measurements have been calculated. Hence, the effectiveness of emitted alpha particles from the walls has been calculated to be varied from 0.00556 to 0.02222Bq/cm 2 with an average value 0.01154Bq/cm 2 at 1m and 0.00000Bq/cm 2 to 0.01667Bq/cm 2 with an average value 0.00983Bq/cm 2 at 1.75m respectively which is within the permissible limit 0.04Bq/cm 2 (Danial, 2010).
Comparative analysis of radon, thoron and thoron progeny concentration measurements
Journal of Radiation Research, 2013
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.