Terrestrial Radionuclides in Environment International Conference on Environmental Protection 16-18 May 2012, Veszprém (Hungary) The Role of Reference Materials in the Measurement of Terrestrial Radionuclides S. Tarjan National Food-chain Safety Office, Hungary tarjan.sandor@gmail.com Collaboration Centre of the IAEA
Topics What is the reference material Proper use of the reference material Reference material production Experiences of the world-wide PT with Moss-Soil What is the accreditation?
The REFERENCE MATERIAL s I. VIM (International Vocabulary of Metrology) JGCM 200:2012 Reference material RM material, sufficiently homogeneous and stable with reference to specified properties, which has been established to be fit for its intended use in measurement or in examination of nominal properties NOTE 1 Examination of a nominal property provides a nominal property value and associated uncertainty. This uncertainty is not a measurement uncertainty. NOTE 2 Reference materials with or without assigned quantity values can be used for measurement precision control whereas only reference materials with assigned quantity values can be used for calibration or measurement trueness control.
The REFERENCE MATERIAL s II. certified reference material CRM reference material, accompanied by documentation issued by an authoritative body and providing one or more specified property values with associated uncertainties and traceabilities, using valid procedures EXAMPLE Human serum with assigned quantity value for the concentration of cholesterol and associated measurement uncertainty stated in an accompanying certificate, used as a calibrator or measurement trueness control material.
The REFERENCE MATERIAL s III. RM CRM CRM may be use as calibrant
Proper use of the RMs (because of the accreditation) Method validation With RM at least two different materials are required With CRM one is enough Method verification To demonstrate the selected methods fulfill the requirements against the validation at given laboratory conditions Internal QC Control chart (regularly) Control of the calibration (occasionaly) Training material Proficiency test material
Terrestrial origin radionuclides in reference matrerial Natural-series RGU-1 (standard uranium ore diluted with quarc) characterised for the uranium content RGTh-1 (thorium ore diluted with quarc) characterised for thorium content Soil type materials Soil (IAEA Soil 6, IAEA 447...) Sediment (Irish Sea Sediment) Industrial waste (phosphogypsum) Characterisation for individual progeny of the decay series
IAEA-447 alias Moss-Soil The site is an old red marble mine area closed in 1962 Colledted: 240 kg Treated: 180 kg
After Before sampling
Be-7 Pb-210 I-125 Cs-137 Air flow: 40000 m 3 /week, counting time 250 000 s, with ULB detector system
210 Pb activity in fall-out, 1998-2006 (Budapest Fogoly u. 13-15.) 40 A, Bq/m 2 35 30 25 20 15 10 5 0 Month
Milling Sieving Homogenising Homogeneity test Final result: 1200 packing units 13
The bulk material (180 kg)
IAEA-447 high organic content soil (moss-soil) 30% rel. eff. ULB detector with carbon-epoxi window
Bulk homogeneity test ANNOVA comparative method by decomposing of uncertainty budget (only for gammaspectrometry) Sources of uncertaity Estimated value Longterm stability sd(ls) Less than 1% Geometry sd(g) 0.5-1% Counting stat. sd(cs) Depend on Heterogeneity sd(ht) It should be less than 1% sd 2 2 2 2 ( ht) sdmeas sdls sdg sdcs
Energies of gamma-ray peaks used for determination of the activity concentrations of the studied radionuclides Series U- series Nuclide 234 Th Energy, kev Yield, % Interfering lines Nuclide energy in kev (Yield,%) Corrections / Remarks 62.88 0.0164 Not used 214 Bi 62.5 (0.011) 227 Th 62.68 (0.007) 63.30 3.75 234 Pa 62.7 (1.5) 234m Pa 62.7 (0.001) 227 Th 64.35 (0.025) 92.38 2.18 92.80 2.15 226 Ra 186.21 3.555 214 Pb 241.99 7.268 295.22 18.41 351.93 35.6 214 Bi 609.32 46.52 1120.3 15.14 1764.5 15.39 Self absorption correction is required. The intensity of the overlapping lines are negligible or the branching ratio is low ( 234 Pa 0.17%) Disturbed by X- rays Not used Disturbed by X- rays Not used 235 U 185.72 (57.0) The disturbing effect of the 235 U is strong 212 Pb 238.63 (43.6) The disturbing effect is strong, not Ra 240.99 recommended line (4.12) 234 Pa 293.7 (3) 210 Tl 296.0 (79) 231 Pa 351.51 (0.007) 234 Pa 351.9 (0.41) 228 Ac 610.58 (0.023) 234 Pa 612.0 (0.389) 234 Pa 1121.7 (0.25) 234m Pa 1765.4 (0.008) Branching ratio is low (0.17%) Branching ratio is low (0.021%) The intensity is negligible Branching ratio is low (0.17%) The intensity is negligible Branching ratio is low (0.17%) Branching ratio is low (0.17%) The intensity is negligible True coincidence factor is 1.00 for the applied geometry Free from true coincidence effect True coincidence correction is required True coincidence factor is 1.006 for the applied geometry
Series Thseries Others Nuclide Energy, kev Yield, % Interfering lines Nuclide energy in kev (Yield,%) 214 Pb 242.0 Corrections / Remarks 212 (7.268) The disturbing effect is strong but there is no Pb 238.63 43.6 224 Ra 240.99 other possibility (4.12) 228 Ac 911.19 26.20 None Free from true coincidence effect 228 Ac 583.41 The intensity is negligible 208 (0.111) Tl 583.19 85.00 234 Pa 584.1 Branching ratio is low (0.17%) (0.18) 40 K 1460.82 10.66 228 Ac 1459.14 Free from true coincidence effect (0.83) 137 Cs 661.66 84.99 214 Bi 661.1 The intensity is Free from true (0.054) negligible coincidence effect 241 Am 59.54 35.92 234 Pa 58.2 Branching ratio is low The self absorption
IAEA-447 high organic content soil (moss-soil) Bulk homogeneity test of 239+240 Pu content 6 samples (10g of each) same process for digestion separation dilution into 25cm 3 volumetric flask preparatum making with Nd co-precipitation preparatum making with electrodeposition- Results in relative values Nd, co-pr. Electro dep. Min 0.7 0.94 Max 1.23 1.05 Average 1.00 1.00 sd 14.78 4.12
Feasibility study Reported results of 40 K-isotope (relative values, moss soil) 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 7 6 1 6a 4 5 3 2 Lab code
Reported results of 137 Cs-isotope (relative values, moss soil) 1.15 1.10 1.05 1.00 0.95 0.90 0.85 0.80 7 6a 6 4 1 5 3 2 Lab code
Characterisation for individual progeny of radioactive decay series
World-wide PT 69 countries 300 lab. Am-241 was 140 reported by laboratories
Application field (an example only) Cross validation using the same material with one reference value and associated uncertainty 210 Pb by gamma-sp 210 Pb+ 210 Bi by LSC 210 Po by alpha sp. Soil erosion study Long term effects by gamma-sp. 137 Cs and 210 Pb Short term effects based on the 210 Pb(ex) and 210 Po equilibrium
What is the accreditation? A strong administration? Any process optimalisation? Any evolution of the laboratory work?
Thank you for your attention!