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Title: Up-to-date radon-thoron discriminative detector for a large scale survey

Abstract

An up-to-date radon-thoron discriminative detector has been developed for conducting a large scale survey. Comparing with our previous detector, some functional problems have been solved. The lowest and highest detection limits of the detector were estimated to be around 5 and 1000 Bq m{sup -3} for radon, and 15 and 1000 Bq m{sup -3} for thoron, respectively, with a 6 month exposure and several theoretical assumptions. Small indoor survey were carried out in Japan and in Hungary using the present detector. The presence of thoron was demonstrated in any indoor surveys by the two results. Since any measurements without discrimination of radon isotopes will result in different risk estimates from actual situations, a special attention should be paid to thoron and its concentration should be accordingly measured as well as the radon concentration.

Authors:
; ; ; ;  [1];  [2]
  1. Radon Research Group, Research Cfenter for Radiation Safety, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)
  2. (Hungary)
Publication Date:
OSTI Identifier:
20723247
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 76; Journal Issue: 11; Other Information: DOI: 10.1063/1.2132270; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; EQUIPMENT; HUNGARY; IONIZATION CHAMBERS; JAPAN; NATURAL RADIOACTIVITY; RADIATION HAZARDS; RADON; RADON 220; SENSITIVITY

Citation Formats

Tokonami, Shinji, Takahashi, Hiroyuki, Kobayashi, Yosuke, Zhuo, Weihai, Hulber, Erik, and Radosys Co., Ltd., Vegyesz u. 17-25, H-1116 Budapest. Up-to-date radon-thoron discriminative detector for a large scale survey. United States: N. p., 2005. Web. doi:10.1063/1.2132270.
Tokonami, Shinji, Takahashi, Hiroyuki, Kobayashi, Yosuke, Zhuo, Weihai, Hulber, Erik, & Radosys Co., Ltd., Vegyesz u. 17-25, H-1116 Budapest. Up-to-date radon-thoron discriminative detector for a large scale survey. United States. doi:10.1063/1.2132270.
Tokonami, Shinji, Takahashi, Hiroyuki, Kobayashi, Yosuke, Zhuo, Weihai, Hulber, Erik, and Radosys Co., Ltd., Vegyesz u. 17-25, H-1116 Budapest. Tue . "Up-to-date radon-thoron discriminative detector for a large scale survey". United States. doi:10.1063/1.2132270.
@article{osti_20723247,
title = {Up-to-date radon-thoron discriminative detector for a large scale survey},
author = {Tokonami, Shinji and Takahashi, Hiroyuki and Kobayashi, Yosuke and Zhuo, Weihai and Hulber, Erik and Radosys Co., Ltd., Vegyesz u. 17-25, H-1116 Budapest},
abstractNote = {An up-to-date radon-thoron discriminative detector has been developed for conducting a large scale survey. Comparing with our previous detector, some functional problems have been solved. The lowest and highest detection limits of the detector were estimated to be around 5 and 1000 Bq m{sup -3} for radon, and 15 and 1000 Bq m{sup -3} for thoron, respectively, with a 6 month exposure and several theoretical assumptions. Small indoor survey were carried out in Japan and in Hungary using the present detector. The presence of thoron was demonstrated in any indoor surveys by the two results. Since any measurements without discrimination of radon isotopes will result in different risk estimates from actual situations, a special attention should be paid to thoron and its concentration should be accordingly measured as well as the radon concentration.},
doi = {10.1063/1.2132270},
journal = {Review of Scientific Instruments},
number = 11,
volume = 76,
place = {United States},
year = {Tue Nov 15 00:00:00 EST 2005},
month = {Tue Nov 15 00:00:00 EST 2005}
}
  • Passive measurements of outdoor radon and thoron concentrations were conducted from June 1992 to June 1993 at a monitoring station over a soil area (10 m x 6 m) in Chiba city, Japan. The measurement period was divided into 4 parts to investigate seasonal variations of radon and thoron concentrations. Ten passive radon-thoron discriminative dosimeters (R-T dosimeters) were placed in duplicate at 5 different altitudes to show the vertical distributions of outdoor radon and thoron concentrations. Outdoor radon concentrations showed no significant difference within 1.0 m above the ground, and the annual average of outdoor radon concentration was 3.85 {+-}more » 0.19 (SE) Bq m{sup {minus}3}. Annual averages of outdoor thoron concentrations at 0.04, 0.15, 0.25, 0.70, and 1.0 m above the ground were 40.5 {+-} 4.4, 22.5 {+-} 3.7, 13.9 {+-} 3.1, 9.5 {+-} 2.9 (SE) Bq m{sup {minus}3}, and < 9.0 Bq m{sup {minus}3}; the lower detection limit of the dosimeter, respectively, and their vertical profiles, n(z) (Bq m{sup {minus}3}), were expressed well by the formula n(z) = {alpha}z{sup B}. Vertical profiles of the atmospheric turbulent diffusion coefficient were also estimated from the observed thoron profiles, as expressed by the power function K(z) = A z{sup B}, of which B values were estimated to vary from 1.034 to 1.609 if averaged thoron exhalation rates during the measurement period were within 0.3 to 2.8 (Bq m{sup {minus}2} s{sup {minus}1}). 45 refs., 6 figs., 3 tabs.« less
  • During a one-year long measurement period, radon and thoron data obtained by two different passive radon-thoron discriminative monitors were compared at subsurface workplaces in Hungary, such as mines (bauxite and manganese ore) and caves (medical and touristic). These workplaces have special environmental conditions, such as, stable and high relative humidity (100%), relatively stable temperature (12°C–21°C), low or high wind speed (max. 2.4 m s{sup −1}) and low or elevated aerosol concentration (130–60 000 particles m{sup −3}). The measured radon and thoron concentrations fluctuated in a wide range among the different workplaces. The respective annual average radon concentrations and their standard deviations (inmore » brackets) measured by the passive radon-thoron discriminative monitor with cellulose filter (CF) and the passive radon-thoron discriminative monitor with sponge filter (SF) were: 350(321) Bq m{sup −3} and 550(497) Bq m{sup −3} in the bauxite mine; 887(604) Bq m{sup −3} and 1258(788) Bq m{sup −3} in the manganese ore mine; 2510(2341) Bq m{sup −3} and 3403(3075) Bq m{sup −3} in the medical cave (Hospital Cave of Tapolca); and 6239(2057) Bq m{sup −3} and 8512(1955) Bq m{sup −3} in the touristic cave (Lake Cave of Tapolca). The respective average thoron concentrations and their standard deviation (in brackets) measured by CF and SF monitors were: 154(210) Bq m{sup −3} and 161(148) Bq m{sup −3} in the bauxite mine; 187(191) Bq m{sup −3} and 117(147) Bq m{sup −3} in the manganese-ore mine; 360(524) Bq m{sup −3} and 371(789) Bq m{sup −3} in the medical cave (Hospital Cave of Tapolca); and 1420(1184) Bq m{sup −3} and 1462(3655) Bq m{sup −3} in the touristic cave (Lake Cave of Tapolca). Under these circumstances, comparison of the radon data for the SF and CF monitors showed the former were consistently 51% higher in the bauxite mine, 38% higher in the manganese ore mine, and 34% higher in the caves. Consequently, correction is required on previously obtained radon data acquired by CF monitors at subsurface workplaces to gain comparable data for SF monitors. In the case of thoron, the data were unreliable and no significant tendency was seen during the comparison therefore comparison of previously obtained thoron data acquired by either CF or SF is doubtful. There was probable influence by relative humidity on the detection response; however, the effects of the high wind speed and elevated aerosol concentration could not be excluded. The results of this study call attention to the importance of calibration under extreme environmental conditions and the need for using reliable radon-thoron monitors for subsurface workplaces.« less
  • The EPA conducted a survey of indoor radon levels in homes located in 10 states. The states surveyed included Alabama, Colorado, Connecticut, Kansas, Kentucky, Michigan, Rhode Island, Tennessee, Wisconsin, and Wyoming. The highest concentration of radon was found in northern Alabama where the local geology is the explanation for this problem. Homes in Wisconsin, Wyoming and Colorado also had high levels of radon.
  • A method is described for checking film and film products for the presence of microdefects passing through the film. The method does not involve a positive gas pressure inside the product, and the effect of gaseous diffusion through the product is eliminated. This is brought about by the use of the radioactive inert gas thoron (/sup 220/Rn/sub 86/) which has a short half-life (T = 54.5 sec). The possibility of creating a highly sensitive device for monitoring the hermetic sealing of films and film products, which is free from radiation hazard, is shown.