Demineralized tap water from Seibersdorf (Austria) was used to prepare this sample. The water was screened for artificial nuclides and 210Pb using high resolution gamma spectrometry, and it was found that all nuclides were below the detection limit and far below the spiked values. The water sample was gravimetrically prepared in one batch. A portion of 200 kg demineralized water was acidified with nitric acid to 3% (mass/mass) and spiked with a mixture of certified single radionuclide solutions traceable to the international standard of radioactivity units. A pump with multiple outlets was used to homogenize the bulk water sample in a tank of 600 L. The spiked water was dispensed in plastic bottles of 500 ml.
The final reference massic activity of each radionuclide was established based on the certified activity value of the radionuclide standard solutions used for spiking the water, taking into account the successive dilution steps, the mass of spiking mixture and the amount of water being spiked as determined from weighing. The combined standard uncertainty includes two major components: uncertainty of the certified solution and weighing uncertainty.
Reference date for decay correction: 15 October 2007
| Analyte | Certified Value1,2 [Bq kg-1] | Uncertainty* [Bq kg-1] |
| 54Mn | 4.74 | 0.05 |
| 60Co | 7.52 | 0.07 |
| 65Zn | 13.06 | 0.15 |
| 109Cd | 34.96 | 0.35 |
| 134Cs | 7.65 | 0.10 |
| 137Cs | 8.12 | 0.08 |
| 210Pb | 29.34 | 0.5 |
| 241Am | 7.11 | 0.07 |
1Established based on the certified activity value of the standard solutions used for spiking
2The certified values of massic activities are traceable to the SI through the radioactivity standard solutions used for spiking
*Uncertainty is expressed as a Mixture model median based standard deviation S (MM-median) at 95 % confidence level
The quantity values assigned to the IAEA-445 certified reference material are massic activities of
54Mn,
60Co,
65Zn,
109Cd,
134Cs,
137Cs,
210Pb and
241Am, expressed in the derived SI unit Bq kg
-1. Values were established based on the certified activity values of the standard solutions used for spiking, taking into account the successive dilution steps, the mass of spiking solutions and the amount of matrix being spiked. For all values used in the calculation of the assigned values and associated uncertainties, the evidence on metrological traceability to the SI Units was provided.
References
[1] International Atomic Energy Agency (2011): Certified Reference Materials for Radioactivity Measurements in Environmental Samples of Soil and Water: IAEA-444 and IAEA-445. IAEA Analytical Quality in Nuclear Applications Series No. 21 (IAEA/AQ/21), IAEA, Vienna (report attached).
