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Design of Radon Surveys, Data Interpretation and Measurement of Equilibrium Factor Lluís Font. Grup de Física de les Radiacions Edifici Cc. Universitat.

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Presentation on theme: "Design of Radon Surveys, Data Interpretation and Measurement of Equilibrium Factor Lluís Font. Grup de Física de les Radiacions Edifici Cc. Universitat."— Presentation transcript:

1 Design of Radon Surveys, Data Interpretation and Measurement of Equilibrium Factor Lluís Font. Grup de Física de les Radiacions Edifici Cc. Universitat Autònoma de Barcelona. Spain Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan

2 Radon surveys: design and data interpretation Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan The long-term measurement of the equilibrium factor Contents

3 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Radon surveys The design of the radon survey strongly depends on the main goal: 1)To obtain the annual averaged dose. 2)To identify radon prone areas or houses. 3)To check the usefulness of a given detection technique. 4)To set up the methodology (to be used in a larger survey) 1)To obtain the annual averaged dose. 2)To identify radon prone areas or houses. 3)To check the usefulness of a given detection technique. 4)To set up the methodology (to be used in a larger survey) The results obtained have to be interpreted according to the main goal of the survey The results obtained have to be interpreted according to the main goal of the survey The dosemeter used has to be well calibrated. Intercomparison exercises. The dosemeter used has to be well calibrated. Intercomparison exercises.

4 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Elements of a survey design Type of dosemeter Procedure for installing and collecting the dosemeters Selection of houses. Information to the inhabitants. Exposure time Radon surveys

5 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Radon surveys Dosimeter type If the main goal is to obtain the annual average of indoor radon levels: Passive. Nuclear Track Detector (NTD) of closed type Exposure time As long as possible! The whole year is the best option. Selection of houses. Information Selection of houses. Information According to the distribution of population - Randomly (for big sampling) - Taking into account census data 1 in of the housing stock (UNSCEAR,93) Information sheet to the inhabitants Procedure Installation/collection in the living room and bedrooms of the houses by trained people.

6 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Dosimeter type If the main goal is to identify radon prone areas or houses: Any: NTDs, charcoal cannisters, grab sampling, etc. Exposure time From few hours to several months Short-term may require confirmation Selection of houses. Information Selection of houses. Information According to the distribution of population and to any geologycal, industrial, etc. reason that may suggest the possibility of high radon levels. Information sheet to the inhabitants Procedure Installation/collection in the living room and bedrooms of the houses by trained people. Installation in basements, low-ventilated areas Radon surveys

7 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Dosimeter type If the main goal is to check the usefulness of a given detector: The one that has to be tested Other types if possible Exposure time According to the dosimeter type(s) used Selection of houses. Information Selection of houses. Information According to the distribution of population. Among known people is also possible (optimum losses) Information sheet to the inhabitants Procedure Installation/collection in the living room and bedrooms of the houses by trained people. Installation in basements, low-ventilated areas Radon surveys

8 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Radon surveys Dosimeter type If the main goal is to set up the methodology The one that will be used Other types if possible Exposure time Different exposure times (to avoid saturation) Selection of houses. Information Selection of houses. Information According to the distribution of population. Among known people is also possible (optimum losses) Information sheet to the inhabitants Procedure Installation/collection in the living room and bedrooms of the houses by trained people. Installation in basements, low-ventilated areas

9 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Radon surveys Interpretation of the results obtained Fit to a lognormal distribution Be cautious. Before getting a conclusion: Did you check any other explanation to your findings? Rely on your own results when possible. Did you check if seasonal variations are important? Be cautious. Before getting a conclusion: Did you check any other explanation to your findings? Rely on your own results when possible. Did you check if seasonal variations are important? Do not be too ambitious. Look for the conclusions related to the goals of your survey and that can be demonstrated from your experimental results.

10 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement The equilibrium factor The equilibrium factor between radon and radon daughters is defined as: where C eq is the equilibrium-equivalent radon concentration. It can be obtained from the expression: where C eq is the equilibrium-equivalent radon concentration. It can be obtained from the expression: where is the disequilibrium degree of the i daughter

11 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement Interest The measurement of the equilibrium factor is a direct measurement of the PAEC, which is related to the dose received. Most of the equilibrium factor measurements have been carried out with active detectors. No possibility of using them in radon surveys The results obtained show high variations on F values In the conversion factor from radon concentration to dose, a mean value of F = 0.4 is assumed. Measuring F with NTDs will mean going one step further in the dose estimation.

12 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement Review of existing passive methods Conventional One NTD open One NTD within a diffusion chamber Frank and Benton Nucl. Track Det (1977) 214 Po method Dörschel and Piesch. Radiat. Prot. Dosim.48, 145 (1993) One NTD open One NTD within a diffusion chamber Assuming ventilation rate as the only free parameter

13 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement The measurement of the equilibrium factor by means of NTDs is problematical: Out of 30 measurements carried out by 5 passive detectors, only one result agreed with those obtained with active measuring systems. The measurement of the equilibrium factor by means of NTDs is problematical: Out of 30 measurements carried out by 5 passive detectors, only one result agreed with those obtained with active measuring systems. Miles et al. Results of the 1995 European Comission intercomparison of passive radon detectors, European Comission, Directorate-General XII, Report EUR (1996). Review of existing passive methods However, the conventional or the Po-214 methods are being used to estimate equilibrium factor in some radon surveys.

14 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement The concept of the Reduced Equilibrium Factor Amgarou, Font and Baixeras Nucl. Instr. and Meth. A 506, (2003) Some more previous definitions u and a for unattached and attached to the airborne aerosol particles respectively i (decay constant), p i-1 (recoil factor or desorption probability), a (attachment rate) d (deposition rate) and

15 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement The concept of the Reduced Equilibrium Factor ParameterRange (h -1 ) Vent. ( v ) (0.2 – 2) Aer. Att. ( a ) (5-500) Unattached plate-out ( d u ) (5-110) Attached plate-out ( d a ) ( )

16 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement The concept of the Reduced Equilibrium Factor It is possible to measure F with a good accuracy if independent measurements of Po-218 and Po-214 are carried out.

17 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement Comparison with experimental results 222 Rn 218 Po 214 Pb 214 PoMeasuredFrom F red % deviation From Reineking and Porstendörfer Health Phys. 58, 715 (1990)Concentration values in Bq/m3

18 Third Symposium on Use of Nuclear Techniques in Environmental Studies CTAPS, Yarmouk University, Irbid, Jordan Equilibrium factor measurement How to measure Po-214 and Po-218 with NTDs? Open question. Some kind of alpha spectrometry is required: - Electrochemical etching - Measurements of alpha-track geometry. Some kind of alpha spectrometry is required: - Electrochemical etching - Measurements of alpha-track geometry. A multi-component dosimeter has been set up in our group to measure independently 222Rn, 214Po and 218Po consisting of 3 Makrofol foils: 1 enclosed within the Fzk diffusion chamber and 2 open. It is being currently tested. If you try it,…..GOOD LUCK!!


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