International Atomic Energy Agency. Department of Nuclear Sciences and Applications. IAEA Environment Laboratories

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1 International Atomic Energy Agency Department of Nuclear Sciences and Applications IAEA Environment Laboratories Vienna International Centre, P.O. Box 100, 1400 Vienna, Austria REFERENCE SHEET CERTIFIED REFERENCE MATERIAL IAEA 447 NATURAL AND ARTIFICIAL RADIONUCLIDES IN MOSS SOIL Certified values for massic activities (Based on dry mass) Radionuclide Certified value Uncertainty* 137 Cs Pb 0.42 x x Po Pb Ra Ac U U Pu Pu * Uncertainty is expressed as a mixture model median based standard deviation S(MM median), k=1 [1] Reference date for decay correction: 15 November 2009 RS_IAEA_447_02/ Page 1 of 5

2 Information values for massic activities (Based on dry mass) Radionuclide Information value Uncertainty* 40 K 0.55 x x Sr Th Am ** Pu * Uncertainty is expressed as a mixture model median based standard deviation S(MM median), k=1 [1] **The value of 241 Am should be corrected for in growth from 241 Pu Reference date for decay correction: 15 November 2009 Origin and preparation of the material In summer 2007, a sample of three hundred kg of the moss soil was collected from an abandoned red marble mine in Gerecse Mountain in the north west part of Hungary by staff of the Radioanalytical Laboratory of the Food and Feed Safety Division (Hungary) in cooperation with the IAEA Terrestrial Environment Laboratory. The groovings in the large marble stone surfaces allowed undisturbed moss growth for the last 40 years, so the 3 5 cm thick fresh soil layer which was produced was mixed with the moss. The mixture of moss soil accumulated radionuclide fall out and thus represents the history or memory record of the radioactive fall out. The cleaned moss soil was dried overnight in an oven at 80 ºC and then milled in a large volume ceramic drum mill. The milled material was sieved to obtain a maximum particle size distribution of 150 µm. The final volume of the treated material was about 180 kg. The material density was measured in 5 test portions and found to be g cm 3. Bottling of IAEA 447 was carried out under normal laboratory conditions. Portions of 150 g were filled into plastic bottles, sealed with security polyethylene caps and labeled with the code IAEA 447. After bottling, the material was sterilized by gamma ray irradiation with a total dose of 25 kgy using a 60 Co source according to EN ISO 13485:2003 to ensure long term stability of the material by inhibiting microbial action. Homogeneity of the material The homogeneity of the material was tested by analyzing 30 test portions using gamma ray spectrometry: three test portions of ca. 30 g each were taken from each of 10 bottles randomly selected from the whole bottling range. 210 Po, 226 Ra, 234 U, 238 U, 238 Pu, Pu and 241 Am were determined by isotope dilution alpha spectrometry, and 210 Pb and 90 Sr by liquid scintillation spectrometry following sample dissolution by wet mixed acids dissolution with microwave digestion and/or molten salt fusion and sequential radiochemical separation procedures. The analysis of the homogeneity study was performed under repeatability conditions to minimize variations. The homogeneity test results provided experimental evidence that satisfactory levels of between and within bottle homogeneity were attained, and that the uncertainties due to between and within bottle heterogeneity were within acceptable limits. Thus the material was considered sufficiently homogeneous for the tested radionuclides [2]. RS_IAEA_447_02/ Page 2 of 5

3 Characterization study The IAEA 447 Certified Reference Material was characterized on the basis of results reported by the IAEA Terrestrial Environment Laboratory in Seibersdorf, Austria. In addition, the material was analyzed by two expert laboratories (Radioanalytical Laboratory, Food and Feed Safety Division, Budapest, Hungary, and Laboratory of Radiological Measurements, Jožef Stefan Institute, Ljubljana, Slovenia). Each laboratory was asked to determine the measurands of interest in three different bottles. The results obtained from the expert laboratories were used to confirm the IAEA certified values. In total, 30 bottles were analyzed in the Terrestrial Environment Laboratory and expert laboratories during the characterization campaign of the moss soil material. The IAEA derived reference values were in agreement with the expert laboratories results. The following methods were used for the charaterization of the reference material: gamma ray spectrometry for the measurement of the gamma emitting radionuclides; liquid scintillation counting for the measurement of 90 Sr, 210 Pb and 241 Pu after radiochemical separation; alpha spectrometry for the measurement of 210 Po, 226 Ra, 234 U, 238 U, 238 Pu, Pu, and 241 Am after radiochemical separation; inductively coupled plasma mass spectrometry for the measurement of 232 Th [2,3]. 228 Ra was not independently determined, its value is derived from 228 Ac at secular equilibrium. Assignment of values Certification procedure The assigned certified values were established on the basis of results reported by the IAEA Terrestrial Environment Laboratory in Seibersdorf, Austria and confirmed by two expert laboratories [2]. The information values were established by measurements at a single laboratory, namely the IAEA Terrestrial Environment Laboratory in Seibersdorf, Austria. The details concerning all reported results as well as the criteria for certification can be found in the report Worldwide Open Proficiency Test: Determination of Natural and Artificial Radionuclides in Moss Soil and Water, IAEA CU , IAEA, Vienna, 2012 [2], which may be downloaded free of charge from: AQ 22_web.pdf. All other documents are available upon request. Statement on metrological traceability and uncertainty of assigned values The property values assigned to the IAEA 447 Certified Reference Material are calculated as massic activities of each radionuclide, expressed in the derived SI unit Bq kg 1. The measurement uncertainty associated with individually assigned values is expressed as a mixture model median based standard deviation S(MM median) [1]. Utmost care was taken regarding the metrological traceability of the property values assigned to this reference material already at the planning phase and during the entire characterization process. Intended use This Certified Reference Material is intended to be used for quality assurance/quality control in the determination of massic activities of listed natural and artificial radionuclides for samples of similar matrix composition and density. The material is also suitable for method development and validation of analytical procedures, including potential bias evaluation, and for training purposes. This material is not to be used as a calibrator. RS_IAEA_447_02/ Page 3 of 5

4 Instructions for use The reference material is supplied in 150 g units. Homogeneity is guaranteed if a minimum test portion of 0.5 g and 30 g is used for radiochemical analysis and gamma spectrometry respectively. To overcome segregation effects due to storage or transportation, the material should be mixed before opening the bottle. All necessary precautions should be taken when opening the bottle to prevent any spread of the fine powder in the laboratory. Dry mass determination The average moisture content of the material was determined by drying several test portions of 2 g in an oven at 105 C for 12 hours and was found to be approximately 3.4 %. Since moisture content can vary with ambient humidity and temperature, it is recommended to check it prior to analysis and to report all results on a drymass basis. Handling and storage The original unopened bottle should be stored securely at ambient temperature in a dark and dry place. It is recommended to avoid direct exposure to sunlight or to a source of heat. Issue and expiry date The issue date of this reference material is May Based on experience with similar materials, the expiry date is May The IAEA is monitoring the long term stability of the material and customers will be informed in case of any observed change. Legal disclaimer The IAEA makes no warranties, expressed or implied, with respect to the data contained in this reference sheet and shall not be liable for any damage that may result from the use of such data. Compliance with ISO Guide 31:2000 The content of this IAEA Reference Sheet is in compliance with the ISO Guide 31:2000: Reference materials Content of certificates and labels [4]. Citation of this reference sheet It is suggested to cite this reference sheet according to the following example, as appropriate to the citation format used: INTERNATIONAL ATOMIC ENERGY AGENCY, Reference Sheet for CRM IAEA 447, Natural and artificial radionuclides in moss soil. IAEA, Vienna, 5 pp. (The latest version published applies; see Note below). Note Certified values as stated in this reference sheet may be updated if more information becomes available. Users of this material should ensure that the reference sheet in their possession is current. The current version may be found in the IAEA s Reference Materials online catalogue: In case of any discrepancies with other published material related to the IAEA 447 CRM, the certified values given in the current version of the reference sheet shall be considered. RS_IAEA_447_02/ Page 4 of 5

5 Further information: For further information regarding this material, please contact: Head, Terrestrial Environment Laboratory International Atomic Energy Agency Environment Laboratories Vienna International Centre P.O. Box 100, A 1400 Vienna, Austria Tel.: E mail: NAEL Reference Materials.Contact Point@iaea.org REFERENCES [1] DUEWER, D.L., A Robust Approach for the Determination of CCQM Key Comparison Reference Values and Uncertainties, Working document CCQM/04 15, BIPM, pdf [2] INTERNATIONAL ATOMIC ENERGY AGENCY, Worldwide Open Proficiency Test: Determination of Natural and Artificial Radionuclides in Moss soil and Water, IAEA CU , IAEA, Vienna (2012). [3] SHAKHASHIRO, A. et al., IAEA 447: A new certified reference material for environmental radioactivity measurements, Appl. Rad. Isot. 70 (2012) [4] INTERNATIONAL ORGANIZATION FOR STANDARDIZATION, Reference materials Content of certificates and labels, ISO Guide 31: 2000, ISO, Geneva (2000). Mr Ales Fajgelj Chair, RM Certification Committee Ms Alessia Ceccatelli Project Officer, Terrestrial Environment Laboratory RS_IAEA_447_02/ Page 5 of 5