Fire risk in the liquid effluent treatment station (STE3) at La Hague

The challenge faced by the designers of the new liquid effluent treatment station (STE3) at La Hague is the non-negligible risk of fire during the lifetime of the workshop, allied to the potentially considerable consequences for personnel and the environment. In the 'bituminization' section of this workshop, the radioactive sludges generated by the decontamination of liquid effluents from the La Hague plants are dried and hot coated in bitumen. The bitumen waste product (BWP) is then poured into drums and stored after cooling. The only identified cause of a fire is an exothermic reaction during the production and cooling of the BWPs, therefore the two drum filling units were of main concern. Attention was then focused on identifying the parameters which increase the risk and on implementing the appropriate means of control. Independent of these steps, reliable detection and powerful fire fighting resources were installed. The drum filling units comprise several types of detector and temperature and pressure measurement instruments. The fire fighting resources in the drum filling units use halon and water. The latter has proved effective in fighting BWP fires which have broken out in various places around the world. The effectiveness of halon has been demonstrated in a specialized laboratory. Finally, to maintain a pressure in the drum filling units that is lower than that in the adjacent rooms, an extraction system was installed which included the washing and filtering of gases and fumes. This also permits extraction of the contaminant while fighting the fire, using the means already described. Various cases of disturbance were also envisaged (loss of electric power and individual equipment failure). A fire detection and fighting system was installed, even though the risk of fire is considered negligible in storage halls. Because of the research that has been conducted into the origins of a fire and the extremely powerful fire fighting resources made available, one can be reasonably certain that the risk to personnel and the environment is negligible. (author). 3 figs, 1 tab