CEA experimental feedback on sodium loop decommissioning

The aim of this paper is to present experimental feedback on sodium loop dismantling techniques at the CEA (The French Atomic Energy Commission) and to offer recommendations for the decommissioning of Fast Reactor secondary sodium loops. This study is based on acquired CEA decommissioning experience which primarily concerns the following: the decommissioning of RAPSODIE (France's first Fast Reactor), the PHENIX reactor secondary loop replacement, the sodium loop decommissioning carried out by the Laboratory of Sodium Technologies and Treatment, and several technical documents. This paper deals with the main results of this survey. First, a comparison of 8 pipe-cutting techniques is made, taking into account speed in cutting, reliability, dissemination, fire risk due to the presence of sodium, cutting depth, and different types of waste (empty pipes, sodium-filled pipes, tanks...). This comparison has led us to recommend the use of an alternative saw or a chain saw rather than the use of the plasma torch or grinder. Different techniques are recommended depending on if they are on-site, initial cuttings or if they are to be carried out in a specially-designed facility referred to hereafter as 'the cutting building'. After the cutting stage, the sodium waste must be processed with water to become an ultimate stable waste. Four treatment processes are compared with different standards : speed, cost, low activity adaptability and 'large sodium quantity' adaptability. Recommendations are also made for reliable storage, and for the general dismantling system organization. Last, calculations are presented concerning a complete dismantling facility prototype capable of treating large amounts and volume of sodium wastes. (author)