ISO 11665-7-2012 Measurement of radioactivity in the environment - Air radon-222 - Part 7 Accumulation method for estimating surface exhalation rate《环境辐射性测量 空气 .pdf

1、 ISO 2012 Measurement of radioactivity in the environment Air: radon-222 Part 7: Accumulation method for estimating surface exhalation rate Mesurage de la radioactivit dans lenvironnement Air: radon 222 Partie 7: Mthode destimation du flux surfacique dexhalation par la mthode daccumulation INTERNATI

2、ONAL STANDARD ISO 11665-7 First edition 2012-07-15 Reference number ISO 11665-7:2012(E) ISO 11665-7:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or

3、by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-

4、mail copyrightiso.org Web www.iso.org Published in Switzerland ISO 11665-7:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 T erms, definitions and symbols 1 3.1 T erms and definitions . 1 3.2 Symbols . 2 4 Principle of the meas

5、urement method for estimating surface exhalation rate 2 5 Equipment . 4 6 Accumulation of radon in a container . 5 6.1 Accumulation characteristics 5 6.2 Accumulation duration 5 7 Sampling 5 7.1 Sampling objective . 5 7.2 Sampling characteristics . 5 7.3 Sampling duration . 6 7.4 Volume of air sampl

6、ed 6 8 Detection method 6 9 Measurement 6 9.1 Procedure 6 9.2 Influence quantities 7 10 Expression of results . 7 10.1 Radon surface exhalation rate . 7 10.2 Standard uncertainty 7 10.3 Decision threshold and detection limit . 7 10.4 Limits of the confidence interval . 8 11 Test report . 8 Annex A (

7、informative) Example of a sample results sheet 10 Annex B (informative) Estimation of radon surface exhalation rate using a continuous measurement method 12 Annex C (informative) Estimation of radon surface exhalation rate using a spot measurement method 18 Bibliography .23 ISO 11665-7:2012(E) Forew

8、ord ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a techni

9、cal committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of e

10、lectrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to

11、the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for i

12、dentifying any or all such patent rights. ISO 11665-7 was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies, and radiological protection, Subcommittee SC 2, Radiological protection. ISO 11665 consists of the following parts, under the general title Measurement of radioa

13、ctivity in the environment Air: radon-222: Part 1: Origins of radon and its short-lived decay products and associated measurement methods Part 2: Integrated measurement method for determining average potential alpha energy concentration of its short-lived decay products Part 3: Spot measurement meth

14、od of the potential alpha energy concentration of its short-lived decay products Part 4: Integrated measurement method for determining average activity concentration using passive sampling and delayed analysis Part 5: Continuous measurement method of the activity concentration Part 6: Spot measureme

15、nt method of the activity concentration Part 7: Accumulation method for estimating surface exhalation rate Part 8: Methodologies for initial and additional investigations in buildings The following parts are under preparation: Part 9: Method for determining exhalation rate of dense building material

16、s Part 10: Determination of diffusion coefficient in waterproof materials using activity concentration measurement iv ISO 2012 All rights reserved ISO 11665-7:2012(E) Introduction Radon isotopes 222, 220 and 219 are radioactive gases produced by the disintegration of radium isotopes 226, 224 and 223

17、, which are decay products of uranium-238, thorium-232 and uranium-235 respectively, and are all found in the earths crust. Solid elements, also radioactive, followed by stable lead are produced by radon disintegration 1 . Radon is today considered to be the main source of human exposure to natural

18、radiation. The UNSCEAR (2006) report 2suggests that, at the worldwide level, radon accounts for around 52 % of global average exposure to natural radiation. The radiological impact of isotope 222 (48 %) is far more significant than isotope 220 (4 %), while isotope 219 is considered negligible. For t

19、his reason, references to radon in this part of ISO 11665 refer only to radon-222. The radon-222 half-life (3,8 days) is long enough for it to migrate from the rock producing it, through the soil, to the air 3 . The radon atoms in the soil are produced by the disintegration of the radium-226 contain

20、ed in the mineral grains in the medium. Some of these atoms reach the interstitial spaces between the grains: this is the phenomenon of emanation. Some of the atoms produced by emanation reach the soils surface by diffusion and convection: this is the phenomenon of exhalation 345 . These mechanisms

21、are also brought into play in materials (building materials, walls, etc.). The quantity of radon-222 reaching the open air per unit of time and per unit of surface is called the radon-222 surface exhalation rate and depends on the physical characteristics of the soil and weather conditions. When the

22、 ground is covered in snow or a layer of water, or is frozen, this surface exhalation rate can become very weak. Values of the radon-222 surface exhalation rate observed in France, for example, vary between 1 mBq/m 2 /s and about 100 mBq/m 2 /s 67 . In uranium-bearing ground, radon-222 surface exhal

23、ation rates in the order of 50 000 mBq/m 2 /s can be observed. By way of comparison, the United Nations Scientific Committee estimates the average surface exhalation rate on the surface of the globe at 20 mBq/m 2 /s 8 . NOTE The origin of radon-222 and its short-lived decay products in the atmospher

24、ic environment and other measurement methods are described generally in ISO 11665-1. ISO 2012 All rights reserved v Measurement of radioactivity in the environment Air: radon-222 Part 7: Accumulation method for estimating surface exhalation rate 1 Scope This part of ISO 11665 gives guidelines for es

25、timating the radon-222 surface exhalation rate over a short period (a few hours), at a given place, at the interface of the medium (soil, rock, laid building material, walls, etc.) and the atmosphere. This estimation is based on measuring the radon activity concentration emanating from the surface u

26、nder investigation and accumulated in a container of a known volume for a known duration. This method is estimative only, as it is difficult to quantify the influence of many parameters in environmental conditions. This part of ISO 11665 is particularly applicable, however, in case of an investigati

27、on, a search for sources or a comparative study of exhalation rates at the same site. This part of ISO 11665 does not cover calibration conditions for the rate estimation devices. The measurement method described is applicable for radon exhalation rates greater than 5 mBq/m 2 /s. NOTE The uncertaint

28、y relating to the estimation of the result obtained by applying this part of ISO 11665 cannot guarantee that the true flux value is included in the uncertainty domain. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated referenc

29、es, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 11665-1, Measurement of radioactivity in the environment Air: radon-222 Part 1: Origins of radon and its short-lived decay products and associated measure

30、ment methods ISO 11665-5, Measurement of radioactivity in the environment Air: radon-222 Part 5: Continuous measurement method of the activity concentration ISO 11665-6, Measurement of radioactivity in the environment Air: radon-222 Part 6: Spot measurement method of the activity concentration ISO/I

31、EC 17025, General requirements for the competence of testing and calibration laboratories IEC 61577-1, Radiation protection instrumentation Radon and radon decay product measuring instruments Part 1: General principles 3 T erms, definitions an d symbols 3.1 T erms and definition s For the purposes o

32、f this document, the terms and definitions given in ISO 11665-1 and the following apply. 3.1.1 accumulation container recipient with known geometric characteristics used to accumulate the radon, with one open face in contact with the surface under investigation INTERNATIONAL STANDARD ISO 11665-7:201

33、2(E) ISO 2012 All rights reserved 1 ISO 11665-7:2012(E) 3.1.2 accumulation duration time elapsed between installation of the container after air tightness is achieved and the end of sampling 3.1.3 bac k di f fus ion mechanism responsible for the transport of radon from the accumulation container atm

34、osphere into the material under investigation 3.1.4 effective surface internal surface of the open face of the container that is in contact with the surface under investigation 3.1.5 effective volume available internal volume for radon accumulation after the container is installed 3.2 Symbols For th

35、e purposes of this document, the symbols given in ISO 11665-1 and the following apply. C activity concentration in the accumulation container at time t, in becquerels per cubic metre S effective surface, in square metres t elapsed time since the start of the accumulation process, in seconds U expand

36、ed uncertainty calculated by Uk u with k = 2 u standard uncertainty associated with the measurement result u rel relative standard uncertainty V effective volume, in cubic metres B time constant of back diffusion, per second i decay constant of the nuclide i, per second V time constant of leakage, p

37、er second surface exhalation rate, in becquerels per square metre per second decision threshold of the surface exhalation rate, in becquerels per square metre per second # detection limit of the surface exhalation rate, in becquerels per square metre per second lower limit of the confidence interval

38、 of the surface exhalation rate, in becquerels per square metre per second upper limit of the confidence interval of the surface exhalation rate, in becquerels per square metre per second 4 Principle of the measurement method for estimating surface exhalation rate The measurement method for estimati

39、ng the radon surface exhalation rate is based on the following elements: a) accumulating radon in a radon-free accumulation container applied to the surface under investigation for a known duration; 2 ISO 2012 All rights reserved ISO 11665-7:2012(E) b) sampling a volume of air representative of the

40、air contained in the accumulation container; c) measuring the radon activity concentration in this air sample; d) calculating the surface exhalation rate. An estimate of the surface exhalation rate is calculated from the following elements: the variation in the radon activity concentration inside th

41、e accumulation container between two given moments; the effective surface of the accumulation container in contact with the surface under investigation; the effective volume of the accumulation container. The radon activity concentration in the accumulation container increases over time depending on

42、 the surface- related exhalation rate, the volume of the accumulation container and influencing factors such as inadequate air tightness (leakage) and back diffusion. The increase of radon activity concentration can be fitted with an exponential function: Ct S V t 1e (1) where Rn222 BV(2) Since the

43、background radon activity concentration in the container is close to zero at the beginning of the accumulation process, the initial slope of the curve is independent of back diffusion 910 . Assuming that radon loss by leakage is negligible, the accumulation phase can be approximated by a linear incr

44、ease of radon activity concentration in the accumulation container (see the example in Figure 1) as described by Formula (3): Ct S V t (3) Figure 1 Example of changes in radon activity concentration in the accumulation container For outdoor measurements, the analysis of the measurement results can r

45、equire detailed knowledge of climatic conditions. For example, the radon surface exhalation rate measurements carried out during snow or rain are only representative of these weather conditions. ISO 2012 All rights reserved 3 ISO 11665-7:2012(E) For soil investigations, the surface area, topography,

46、 geology, pedology, vegetation, etc. all need to be taken into account. The humidity content of the ground at the time of sampling may be determined (see ISO 11465). Several measurement methods meet the requirements of this part of ISO 11665. They can be distinguished by the way the air is sampled f

47、rom the accumulation container. 5 Equipment The apparatus shall include the following components. a) An accumulation container with known geometric characteristics (see Figure 2): The accumulation container characteristics shall be chosen so that any irregularities of the surface under investigation

48、 do not introduce an uncertainty of more than 10 % into the effective volume of the accumulation container. The effective surface of the accumulation container shall be selected to ensure that measurements are the most representative possible of the surface under investigation (i.e. the effective su

49、rface shall be appropriate for the surface area under investigation). The effective volume of the accumulation container shall be at least 10 times greater than the volume of air sampled from the accumulation container by the radon measuring device. The material used in the accumulation container shall not allow the radon to be diffused towards the outside of the container during the accumulation p