1 / 18

Presented by: S. M. Hosseini Pooya (PhD) National Radiation Protection Department

Development of a diffusion chamber for passive discriminative measurements of radon/ thoron concentration in dwellings. F. Torabi Nabil , S. M. Hosseini Pooya , M. Taheri , M . Shamsaie Zafarghandi. Presented by: S. M. Hosseini Pooya (PhD) National Radiation Protection Department

nedaa
Télécharger la présentation

Presented by: S. M. Hosseini Pooya (PhD) National Radiation Protection Department

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Development of a diffusion chamber for passive discriminative measurements of radon/thoron concentration in dwellings F. TorabiNabil, S. M. HosseiniPooya, M. Taheri,M. ShamsaieZafarghandi Presented by: S. M. HosseiniPooya (PhD) National Radiation Protection Department Iran Nuclear Regulatory Authority

  2. Introduction • Radon (222Rn) has the most contribution in annually natural exposure of the human via inhalation of the gas. • Thoron (220Rn) may have the same effects (even be more hazardous) due to the long lived of its daughters . • As well most of the radon detectors are also sensitive to the thoron and may be affected on accurate measurements by the presence of thoron in media. • Thus some of the researches are focused on the designing of discriminative systems for separated measurements of these isotopes. • Most of the suggested systems have complicated designs (in active methods) and etching conditions (in passive methods). • A home-made passive diffusion chamber which is based on SSNTD, has been used for many years for passive radon measurements in dwellings in Iran. • In this research first the operation and calibration method of the chamber have been described for both radon and thoron measurements. • Then the design is developed for separated measurements of radon/thoron, and the measurement characteristics of the detector are discussed in detail.

  3. Structure of home-made diffusion chamber: for Radon measurements

  4. 4 Electrochemical Etching (ECE) Voltage:800 V Frequency: 2 kHz Time: 3 hr Temp.:25 ° C H2O)45% + C2H5OH40% + KOH15%Etchant PEW:

  5. Calibration Method The volume of calibration chamber for Radon is 50 liters and for Thoron is 4 liters

  6. The calibration curve of the chamber for Radon The calibration curve of the chamber for Thoron S= 13.55 (Track.cm-2.Bq-1 .l .day-1) S= 0.83 (Track.cm-2.Bq-1 .l .day-1)

  7. Results of the chamber response in the 4th International Intercomparison of Passive Radon Detectors (by NIRS –Japan, 2011)

  8. Developed diffusion chambers for discriminative measurement of radon and thoron Double-filter diffusion chamber & 212Po detector Double-film diffusion chamber

  9. Developed diffusion chamber: Radon detector the outside detector: 212Po detector Double-filter diffusion chamber + 212Po detector Attenuator(Lexan 75µm) • It attenuates only the particles of 8.78 MeV of 212Po to the energies between 0.5 to 1MeV and absorbs all of the other particles of the daughters. Detector(Lexan 250µm) Detector holder

  10. attenuator • The thickness of 75±2 μm has been calculated by Trim Code • The thickness of 75±2μm is achievable by soaking of the 250μm Lexan films in the Aqueous solution of Ethylenediaminefor 4 hours at 25⃘C as : 75% C2H4(NH2)2+25% H2O

  11. Sensitivity of the diffusion chamber for radon measurements The MDL values of the diffusion chamber for radon measurements S= 8.95 (Track.cm-2.Bq-1 .l .day-1)

  12. Sensitivity of the outer Lexan film for 212Po measurements The MDL values of the outer Lexan film for 212Po measurements S=7.96 (Track.cm-2.Bq-1 .m3 .day-1)

  13. Calculation of Thoron Concentration • The outer Lexan film only can measure the concentration of 212Po CTn(Thoron concentration)can be calculated by: The average value of FTn(Equilibrium Factor) is 0.03 in dwellings, 0.913 is the Equilibrium Coefficient, 100/64 is the reverse value of branching ratio in decay chain of 212Po

  14. Cap & fiber glass filter Detector Detector holder Fiber glass filter Filter holder • The upper film detects Radon+ Thoron • The lower film detects only the Radon Detector Detector holder Double-film diffusion chamber

  15. Sensitivity of the diffusion chamber for radon measurements The MDL values of the diffusion chamber for radon measurements S(upper film)=2.06 S(lower film)=1.60

  16. Sensitivity of the diffusion chamber for Thoron measurements The MDL values of the diffusion chamber for Thoron measurements S=0.056(Track.cm-2.Bq-1 .l.day-1)

  17. Conclusion • A home-made passive diffusion chamber which is based on Lexan SSNTD, has been developed for simultaneous measurements of radon/thoron in dwellings. • The sensitivity of the chamber shows that it is appropriate for seasonal measurements of radon in an extended range of concentrations. • The sensitivity of the double-film chamber shows that it is appropriate for seasonal measurements of thoron in areas with high thoron concentrations, while the double-filter method is appropriate for that of low concentration . • The advantages of the method are including its small size, light weight and simple etching process.

  18. Thank you!

More Related