Qualification of a gamma sensitive surface measuring technique for the building clearance in the NPP Stade (KKS) using the contamination monitor S.E.A.PL 525

For the clearance of contaminated buildings during reactor dismantling the evidence proof of surface contamination according StrSchV (radiation protection regulations) is required. Into the depth penetrated contamination has to be projected to the surface. Typical coverage of contamination from operation results from decontamination coatings, plastering or pavements. Using beta sensitive measurements the penetrated activity cannot be identified reliably. Using gamma sensitive measuring techniques the penetrated activity can be detected even in case of covering layers. Actually the techniques in-situ gamma spectrometry and gamma spectrometric analysis of sampling are qualified for clearance measurements. When these techniques cannot be applied is necessary to remove the surface layers. Therefore the NPP Stade developed in cooperation with the measuring device producer S.E.A. a gamma sensitive contamination monitor. The qualification has been performed, the detection limits were reached.