JRP EMRP ENV54: MetroDecom - Metrology for decommissioning nuclear facilities: Report for D.1.1.8 - Evaluation of the final result

The BR3 (Belgian Reactor 3) is a relatively small 10 MWe (about 41 MWth) Pressurized Water Reactor (PWR) of the SCK•CEN (Belgian Nuclear Research Centre). BR3, a pilot PWR for the later Belgian nuclear commercial Power Plants, was brought into operation in October 1962 and has been definitively shutdown in 1987, after 25 years of operation and eleven campaigns. Today, all the main installations have been dismantled and the focus lies on the building structure itself, more particular in the various rooms of the Waste & Ventilation (W&V) Building next to the Reactor Building. Decommissioning of nuclear building structures usually leads to large amounts of low level radioactive waste. Using a reliable method to determine the contamination depth is indispensable prior to the start of decontamination works in view of minimizing the radioactive waste volume and the total workload. A non-destructive method that already delivered adequate results has been based on geostatistical modelling of in situ gamma-ray spectroscopy measurements using the multiple photo peak method [4]. The main objective of the current study was to further improve and enhance the method reducing the duration of the characterization process by cutting down the amount of time consumed by in situ gamma-ray spectroscopy measurements and by looking for alternative (more efficient) measurement techniques.