2. The analytical techniques most widespread for certification in the iron and steel industry are X-ray Fluorescence Spectrometry (XRF), Arc/Spark Optical Emission Spectrometry (OES), and Glow Discharge – OE Spectrometry (GDS-OES), which are all Atomic Emission Spectroscopy (AES) techniques relying on the analysis of radiation emitted by atoms from the surface layers of the investigated material. By contrast, nuclear INAA investigates the whole sample as its entire volume is irradiated in the thermal neutron field of a nuclear reactor without any physico-chemical or microstructure alteration. For this reason, and given the performance of INAA, we assumed its application could improve the information on elemental composition usually obtained by AES techniques, especially in the case of minor and trace elements. ……………………………………………………………..…………………………………………………………………………...……..…..………….... International Workshop “IWIRAD 2005” Bucharest, 20-21 June, 2005

3. Objective Checking the above assumption by comparing results obtained within the frame of an international Proficiency Tests (PT) exercise by 19 laboratories (18 of which employed AES techniques, and only the 19th one employed the INAA technique) with results obtained by a network composed of 5 INAA Laboratories on samples from the same material - a special high alloy steel (SS1) produced by the Swedish Institute for Metals Research (SIMR)*. The PT exercise, launched and organized by SIMR/ KIMAB envisaged an accurate characterization of the material composition in order to obtain a Certified Reference Material. ….…………… * Later, SIMR changed its title as follows: the Swedish Institute for Corrosion & Metals Research (KIMAB) ……………………………………………………..………..………………………………………………………………………… International Workshop “IWIRAD 2005” Bucharest, 20-21 June, 2005

4. The ACTIVA-N laboratory (IFIN-HH, Romania), which joined the KIMAB PT exercise in 2004, developed in 2005 a Network collaboration with four other INAA laboratories, namely, with: - Belgium (with the Belgian Nuclear Research Centre, Mol), - Hungary (with INT, Budapest), - Poland (with INCT, Warsaw), - Romania (with INR, Pitesti), aiming at checking within the frame of an Inter-Laboratory Comparison (ILC) exercise the INAA performance on the same material : reproducibility, influence of the various standardization methods, consensus of results obtained by the same technique in different laboratories, and the usefulness of the network for analyzing and certifying stainless steels. The SS1 used for INAA experiments consisted of chips of 2-3 mm each. ……………………………………………..…………………………………………………………………………………...… International Workshop “IWIRAD 2005” Bucharest, 20-21 June, 2005

5. Experimental and evaluation conditions The SS1 samples were irradiated in the nuclear reactor of each participant laboratory in a thermal neutron flux of (10 12 -10 13 ) n  cm -2  s -1 and then analyzed by  -ray spectrometric equipments using high resolution HPGe detectors. The measurements, mainly based on measurements of the delayed  -rays emitted by the activated nuclei, evidenced 11 elements (Cr, Mn, Fe, Ni, Co, Cu, As, Sb, Mo, V, W) in the irradiated samples. The element concentrations were determined by each laboratory using its own standardization procedure: a relative procedure based on CRMs materials ( ACTIVA-N Lab. Romania, Hungary), - a complex procedure involving chemical treatment* (Poland), - an in-house developed standardization method similar to the k 0,Au one, but using Zr instead of Au (INR –Romania), - the Laboratory from Belgium used INAA based on single element solution standards traceable to NIST, and a SMELS sample to check and validate the experimental protocols. …………………………………………………………………………………….…….…. * the elemental standards and spectral purity elements or oxides were dissolved in aqua regia or nitric acid of high purity, and then air-dried in a laminar flow box for obtaining solid standards ………………………………………………………………..………………………………………………………………………….. International Workshop “IWIRAD 2005” Bucharest, 20-21 June, 2005

6. Evaluation and Conclusions The comparative performance of the nuclear and Atomic Emission Spectroscopy techniques was evaluated using the z-score criterion 1-3, calculated for the mean concentration values of each element ; the AES data were taken from the preliminary data presented in the KIMAB Report 4 issued in June 2005. The results proved a new evidence of the INAA performance established within the INAA network, as the standard deviation values corresponding to the mean concentration of each of the 11 elements were reduced, irrespective of the fact that they were obtained in different irradiation / measurement conditions and using various Standardization methods and impose a more deep and detailed study in continuation. In the following, we present - comparatively - the preliminary results obtained within the frame of the INAA - ILC exercise and the preliminary results obtained by the KIMAB Institute from the international PT exercise they had launched in 2004, directly taken from their Report. …………………………………………………………….…..……………………………………….……………………………………. International Workshop “IWIRAD 2005” Bucharest, 20-21 June, 2005