High Levels of Natural Radiation and Radon Areas - Radiation Dose and Health Effects: Volume II - Poster presentation - Contamination of the Brook receiving Liquid Effluents from the Olen Radium Facility

Radium was dispersed in the environment at Sint-Jozef-Olen as a result of the operation from 1922 to 1969 of one of the largest radium extraction plants. Liquid effluents from the radium facility were discharged into the brook the Bankloop. The Bankloop is 1800 m long over its course extending from the fence of the plant to the point at which it merges with the river Kleine Nete. The lower reaches of the Bankloop were frequently subject to flooding during the winter period up until the beginning of the 1960s, when as a result of land reclamation work, the last 420 m stretch of the brook was diverted. Historical levels of radium contamination of the brook were measured at points located every 10 m at right angles to the Bankloop using portable gamma detectors. At all points, except for at the displaced mouth, enhanced dose rates were observed. The contamination is mostly confined to a narrow strip 5 to 10 m wide, located on one or both sides of the brook. A total surface area of about 5000 m2 is contaminated to levels of between 0.15 and 0.49 μSv/h, and over an area of about 3750 m2 higher levels of contamination are present. Fifteen depth profiles for the determination of the levels of contamination of the banks and the river bed were taken. The most contaminated layer was frequently to be determined at a depth of between 20 and 40 cm, as most of the contamination occurred more than 50 years ago. The total volume of contaminated ground was estimated at 9700 m3. Enhanced dose rates were observed on the farmland located above the former course of the bed of the brook. A surface area of 5.5 ha was investigated with a measurement being performed every 10 metres. The surface area of the farmland where a dose rate of above 0.2 μSv/h was to be determined, was estimated at 2.5 ha, and that where a dose rate of above 0.4 μSv/h occurred at 1 ha. The frequent flooding of the Bankloop was the cause of the contamination.