STATE-OF-THE-ART OF NORM NUCLIDE DETERMINATION IN SAMPLES FROM OIL-AND-GAS-PRODUCTION - VALIDATION OF POTENTIAL STANDARDIZATION METHODS THROUGH AN INTERLABORATORY TEST PROGRAM

Gas and oil companies frequently encounter build-up of Naturally Occur ring Radioactive Material (NORM) in their production and processing fa cilities. In the Netherlands NORM is subject to strict national regula tions and, consequently, installations have to be screened on a regula r basis. The availability of accurate and reliable NORM sampling and a nalysis techniques is therefore essential, A number of years ago, the ''Nederlandse Aardolie Maatschappij B.V.'' (NAM) actively Initiated an investigation on analysis techniques for NORM samples from gas and oi l companies. Within this framework, Shell Research Amsterdam organized a four-stage interlaboratory test programme in which representative s amples of increasing complexity were analyzed by a number of Dutch ins titutes. Whereas a large spread in results was observed in the first s tage, results in the last stage deviated less than +/- 10% from the va lues certified by all independent referee institute, even for complex sludge samples. It was found that in particular tile use of different values for tile gamma-yields and branching ratios amongst the institut es was responsible for the initial spread.