Characterisation of activity content of 226Ra in spiked metallurgical slag using an interlaboratory comparison

More than half of yearly steel production in EU comes from recycling. The metal foundries pass the metal scrap through radiation portal monitors at the entrance of the foundry; nevertheless an orphan radioactive source may still remain undetected e.g. due to the shielding from the scrap load itself. In such case the source may enter the smelting route ending in contaminated steel products and by-products of the process. The European metal foundries are aware of the problem and increasingly apply radioactivity monitoring of the steel products. It is of outmost importance to perform accurate measurements, in order to prove compliance with respect to legal radioactivity limits, and metrologically challenging to ensure the quality of such measurements. In the light of a global steel market it is obvious that harmonisation of the analytical methodologies is critical. In the EURAMET's EMRP joint research project, 'MetroMetal' (Ionising radiation metrology for the metallurgical industry), existing radioactivity measurement methods were studied and new optimized methods, systems and standards were proposed for the radioactivity control of steel and by-products in steel mills. In this context, reference activity standards, including the most frequently occurring radionuclides in melting incidents in suitable geometries and matrices, have been developed. Amongst these standards were two series of sources of 60Co in cast steel, one of 137Cs in fume dust and one of 226Ra in furnace slag. The common feature in all four standards was that Interlaboratory comparisons (ILCs) were used to characterise the activity concentrations. In the particular case of 226Ra in slag the material was prepared by spiking and an ILC was conducted amongst 9 European National Metrology Laboratories and JRC, with the aim to verify the activity concentration of the spiked material and to validate the calibration and correction methods proposed by MetroMetal. In the present work, the organization and the results of the ILC on 226Ra activity concentration in metallurgical slag standards are presented.

TZIKA Faidra;  GARCIA-TORANO Eduardo;  HULT Mikael;  ARNOLD Dirk;  BURDA O.;  BRANGER T.;  CARCONI P.;  CARO B.;  DRYAK P.;  FAZIO A.;  FERREUX L.;  KLEMOLA S.;  LUCA A.;  PEYRES Virginia;  REIS M.;  SAHAGIA M.;  SANTOS M.;  SOLC J.;  TYMINSKI Z.;  VODENIK Branko; 

2016-12-16

University of Helsinki

JRC104016