Pre-decommissioning radiological characterization of concrete

The decommissioning of the BR3 (Belgian Reactor 3) approaches its final phase, in which the building structures are being decontaminated and either denuclearized for possible reuse or demolished. Apart from the presence of naturally occurring radionuclides in building materials, other radionuclides might be present due to contamination or activation. The overall process of the BR3 building structure D&D (Decontamination & Decommissioning) consists of the following steps: • make a complete inventory and preliminary categorize all elements based on historical data; • characterize and determine the contamination or activation depth; • determine the decontamination method; • perform the decontamination and clean up; • a possible intermediate characterization followed by an additional decontamination step; and • characterize for clearance. A good knowledge of the contamination and activation depth (second step) is fundamental in view of cost minimization. Currently, the method commonly used for the determination of the depth is based on core drilling and destructive analysis. Recently, we have introduced a complementary non destructive assay based on in-situ gamma spectroscopy. Field tests at BR3, both for contamination and activation, showed promising results.