IAEA-465 (BALTIC SEA SEDIMENT) STATUS: CONTRIBUTION OF HELCOM MORS EG and CONTRACTING PARTIES TO CERTIFY REFERENCE MATERIALS FOR RADIONUCLIDES IN MARINE ENVIRONMENTAL STUDIES Pham M.K., Osvath I., Harms A. IAEA-Environmental Laboratories, Monaco Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
Sampling – Bulk material Preparation of the material (freeze-dried, sieved, homogenization, bottling, irradiation) Recheck No Homogeneity test for radionuclides (naturals and homogeneity anthropogenic)? at NAEL Yes No Samples dispatched – measurement campaign Homogeneity Feedback data to NAEL confirmed? Yes Data evaluation - feedback the preliminary results to participants for comments Final report for inter- laboratory run, Diploma Samples sent to expert laboratories Certification process – calculation of “property value” and its uncertainty Continuation of measurement campaign at NAEL Yes No Objectives met? Improvement possible? Yes No Certified reference material Material cannot b e certified General schema for certification process of Environment Laboratories, Monaco reference materials realized at RML-NAEL-IAEA. Department of Nuclear Sciences & Applications
Sediment sample (IAEA-465), collected by HELCOM- MORS from Baltic Sea. Station JML TOTAL DEPTH: 82m, St. JML POS: (N59º34.91, E023º37.608) Persons taking the sample: Pekka Kosloff, Pekka Kotilainen Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
Description of the material (IAEA-465, Baltic Sea Sediment) • 225 kg wet sediment were sampled by box corer (20 × 20 cm) on 26 August 2012, at 82 m depth in the Baltic Sea (at 59 ° 34.91’ N, 23 ° 37.61’ E; station JML of the RV Aranda August 2012 cruise for the HELCOM COMBINE program).. • The sediment was first dried in open air to 108 kg and subsequently in heating cabinets at 85 ° C leaving a total dry mass of 60 kg. • The sample was then ground into a powder, using a micronization technique, homogenized by mixing under nitrogen atmosphere, bottled and sealed in polyethylene flasks (50 g units) and coded as IAEA-465 (for a total of 960 bottles). All bottles were sterilized at 28 kGy ( 60 Co) at an irradiation facility • (Synergy Health, France). The moisture content of the sample was found to be approximately 1.9% by drying 1g of sample at 105 ° C to a constant mass.
Homogeneity tests • Two most important technical consideration in the certification of RMs: Material homogeneity and stability (ISO 35, 2006, Reference materials – General and statistical principles for certification ). • Test of homogeneity for Between–bottles and Within-bottle: Number of bottles used for homogeneity test: 3x15 bottles (for total 960 bottles) taken randomly for the test. • Method used for homogeneity study should have very good repeatability and selectivity. • Analyses done by competent technicians in the lab (consumed a lot of time and human resources). • Homogeneity test performed for: Radionuclides: – The number of Radionuclides used for test as many as possible, as each radionuclide has a different biogeochemical behaviour in the environment. Other components - Trace metals - Elemental compositions
Homogeneity tests (cont’d) Homogeneity test done for : 40 K, 137 Cs, 214 Bi, 226 Ra, U isotopes and 239+240 Pu • Techniques used: • High-resolution low-background gamma-spectrometry, • alpha-spectrometry, • Inductively Coupled Plasma - Mass Spectrometry (ICP-MS), and • Accelerator Mass Spectrometry (AMS). Weight used: 1 st test for between bottles for 3 x 15 bottles, using 5g of sample for • alpha-spectrometry, and 40 g for gamma-spectrometry. 2 nd test for within-bottles heterogeneity test was done for another 10 • aliquots of 10 g of sample for gamma-emitters, and 0.3 g of material for Pu isotopes determination using (AMS) as well as for Uranium isotopes using (ICP-MS) technique. 3 rd test for 20 aliquots of from 20 different bottles (20 g of samples), • counted by gamma spectrometry.
Homogeneity tests (cont’d) IAEA-465, test of homogeneity Cs-137 1.10 1.05 St. dev. Relative value 95% conf. lim. Mean 1.00 95% conf. lim. St. dev. 0.95 0.90 No446 No561 No250 No371 No921 No90 No841 No229 No781 No3 No137 No120 No611 No489 No801 Sample Number
Homogeneity tests (cont’d) Table 1 – Homogeneity uncertainty 20 samples of IAEA-465 Nuclide u bb (%) u meas (%) u int (%) u hom (%) 137 Cs 1.5 1.0* 1.1 1 40 K 1.1 1.7* 1.2 0 where u bb (%) is relative standard deviation between bottles (or uncertainty of the between-bottle hetegeneity) u meas (%) is uncertainty of measuerement u int (%) is repeatability of the measurement u hom (%) is homogeneity uncertainty of xx (20) samples taken randomly from a total of 960 bottles (a combine uncertainty of ubb and umeas) * represents value used to calculate u hom (uc(bb) or uhom) is a combined uncertainty of the between-bottle heterogeneity (ubb) and the measurement variation (umeas)
Sample dispatch and data feedback • 26 selected participants received samples on May 2016 • 26 feedback, the last one received at the end of March 2017 • Sending out the draft report to participants for their comments and correction if any. HELCOM-MORS participants: • Denmark (DTU Nutech,Technical University of Denmark): DM • Finland (STUK – Radiation and Nuclear Safety Authority): FI • Germany (6 participants from Germany, some belong to HELCOM contracting party: (i) Johann Heinrich von Thünen-Institut (GE (i)), Institut für Fischereiökologie, (ii) Federal Maritime and Hydrographic Agency (FMHA) (GE (ii)) and (iii) Landesmessstelle für Radioaktivität (GE (iii)) • Poland (3 participants from Poland, two belong to HELCOM: (i) Central Laboratory for Radiological Protection (PO (i)) and (ii) Institute of Meteorology and Water Management, Maritime Branch (PO (ii)) • IAEA
Sample dispatch and data feedback • Detail report requested from participating laboratories: • • (1) average weight of sample used for analysis; • (2) number of analyses; (3) massic activity (Bq kg -1 ) corrected for blank, background, etc.; • • (4) estimation of the combined uncertainties; • (5) description of chemical procedures and counting equipment; • (6) standard solutions used for analysis; • (7) chemical recoveries (if any), counting time and decay corrections. • The reference date for reporting activities was set-up (sampling date- 26 th August 2012 ).
Criteria for assigning values and uncertainties_ ISO Guide 13528 • The obtained data were first checked for compliance with the certification requirements, and then for their validity based on technical reasoning. • All accepted set of results were used for robust statistical calculation. Robust statistics as described in ISO Guide 13528 (ISO, 2005) were used for the determination of the assigned values, where the robust mean and robust standard deviations were calculated as per Algorithm A as described in Annex C.1 of ISO 13528. • A certified value was assigned when at least 5 independent results were available and the relative expanded uncertainty was less than 15 %. The number 15 % chosen based on the homogeneity test of different radionuclide, and would reach maximum 20% for activities lower than 1 Bq kg -1 • For the radionuclides where these criteria were not fulfilled, the robust mean and relative expanded uncertainties were given only as information values.
Criteria for assigning values and uncertainties_ Cont’d • These criteria were fulfilled for: 40 K, 137 Cs, 210 Pb ( 210 Po), 226 Ra, 228 Ra, 228 Th, 230 Th, 232 Th, 234 Th, 234 U, 235 U, 238 U, 239+240 Pu and 241 Am (alpha technique only) • and the information values are given to other 238 Pu and 241 Am (both gamma and radionuclides alpha techniques used).
Data distribution for Cs-137 in IAEA-465 160 137 Cs (IAEA-465) 150 GE (ii) 140 PO (ii) DM 130 IAEA 120 110 Bq kg-1 100 90 80 PO (i) GE (i) GE (iii) 70 FI 60 50 18 9 19 21 24 20 17 13 22 11 23 14 7 18 25 3 6 16 10 5 15 12 22 8 4 1 Laboratories Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
Data distribution for Pu-239+240 in IAEA-465 3.5 DM 3.0 GE (iii) GE (i) FI 2.5 2.0 Bq kg-1 IAEA 1.5 PO (i) GE (ii) 1.0 239+240 Pu (IAEA-465) 0.5 0.0 26 2 23 9 13 17 12 5 10 6 22 18 22 4 20 1 16 25 27 21 Laboratories Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
Data distribution for Am-241 in IAEA-465 3.0 2.8 241 Am (IAEA-465) 2.6 2.4 2.2 2.0 1.8 Bq kg-1 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 17 1 9 6 12 20 26 17 11 10 12 8 Laboratories Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
Massic activities in the natural uranium and thorium series in IAEA-465 (Reference date is 26 th August 2012) Uranium series 234 U 230 Th 226 Ra 210 Pb/ 210 Po 238 U 88.6 ± 5.7 71.6 ± 9.7 189 ± 8 54.2 ± 3.1 87 ± 6 Bq kg -1 Bq kg -1 Bq kg -1 Bq kg -1 Bq kg -1 Thorium series 228 Ra 228 Th 224 Ra 208 Tl 232 Th 53 ± 8.5 65.7 ± 4.4 67.4 ± 8.7 63.1 ± 7.0 62.4 ± 5.0 Bq kg -1 Bq kg -1 Bq kg -1 Bq kg -1 Bq kg -1 36% Environment Laboratories, Monaco Department of Nuclear Sciences & Applications
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