The BR3 Decommissioning project: A Pilot for Submarine Reactors

Abstract

The BR3 PWR is a small nuclear power plant (thermal power 40.9 MWth, net electrical power output 10.5 MWe), designed in the late fifties and started in 1962. Its design was directly deduced from the submarines reactors developed by Westinghouse. Even the implantation of the loops and equipments, enclosed in tight and small areas are directly inherent in submarine designs. For different reasons, the irradiated fuel is still on site and solutions for its evacuation and storage will also be presented. In 1989 the BR3 was selected by the European Union as pilot decommissioning project in the framework of its RTD programme on the decommissioning of nuclear installations. A pre-dismantling decontamination of the reactor primary loop was carried out and allowed to save doses to the operators, estimated to be up to about 5 to 7 man-Sv savings. The pilot project concerned then mainly the dismantling of the highly radioactive reactor internals and the pressure vessel. Different techniques were used and compared on actual pieces : from plasma are torch cutting to mechanical sawing, including also electric discharge machining. Results of these operations will be presented and the lessons drawn for the risk prevention, dose uptake minimization and waste reduction will be highlighted. The size and geometry of the reactor and internals being similar to those of submarines reactors, the results gained on this actual practical experience can be seen as an interesting approach for the prevision of risk prevention and assessment of nuclear submarine decommissioning.