Consensus evaluation of radioactivity-in-soil reference materials in the context of an NPL Environmental Radioactivity Proficiency Test Exercise

The development of two radioactivity-in-soil reference materials is described - one for peat and one for soil with high sand content. Each bulk material was processed, subdivided and measured before being sent to participants in an NPL Environmental Radioactivity Proficiency Test Exercise. Activity concentrations of radionuclides in each material were determined by 'consensus' evaluations of participants' results using two weighted mean methods. The project demonstrated the use of such exercises in delivering reference materials to the user community.