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  • 1 Shell Research B. V. P.O. Box 38000 NL-1030 BN Amsterdam (The Netherlands)
  • | 2 Nederlandse Aardolie Maatschappij B. V. (NAM) P.O. Box 28000 NL-9400 HH Assen (The Netherlands)
  • | 3 TNO Radiological Service P.O. Box 9034 NL-6800 ES Arnhem (The Netherlands)
  • | 4 Rijksuniversiteit Groningen Kernfysisch Versneller Instituut (KVI) Zernikelaan 25 NL-9747 AA Groningen (The Netherlands)
  • | 5 RTD B. V. P.O. Box 10065 NL-3004 AB Rotterdam (The Netherlands)
  • | 6 KEMA Nederland B. V. P.O. Box 9035 NL-6800 ET Arnhem (The Netherlands)
  • | 7 DSM Research B. V. Radioisotope Applications & Support P.O. Box 18 NL-6160 MD Geleen (The Netherlands)
  • | 8 Rijksinstituut voor Volksgezondheid en Milieuhygiëne (RIVM) Laboratorium voor Stralingsonderzoek P.O. Box, 1 NL-3720 BA Bilthoven (The Netherlands)
  • | 9 Delft University of Technology Interfacultair Reactor Instituut (IRI) Mekelweg 15 Nl-2629 JB Delft (The Netherlands)
  • | 10 Netherlands Energy Research Foundation (ECN) P.O. Box 1 NL-1755 ZG Petten (The Netherlands)
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Gas and oil companies frequently encounter build up of Naturally Occurring Radioactive Material (NORM) in their production and processing facilities. In the Netherlands NORM is subject to strict national regulations and, consequently, installations have to be screened on a regular basis. The availability of accurate and reliable NORM sampling and analysis 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 oil companies. Within this framework, Shell Research Amsterdam organized a four-stage interlaboratory test programme in which representative samples of increasing complexity were analyzed by a number of Dutch institutes. Whereas a large spread in results was observed in the first stage, results in the last stage deviated less than ±10% from the values certified by an independent referee institute, even for comple, sludge samples. It was found that in particular the use of different values for the -yields and branching ratios amongst the institutes was responsible for the initial spread.