Cutting operation of simulated fuel assembly heating examination by AWJ

This is a report on Abrasive Water Jet (AWJ) cutting work carried out on specimen, which was used for Simulated Fuel Assembly Heating Examination by Collaborative Laboratories for Advanced Decommissioning Science (CLADS) Molten Core Behavior Analysis Group in February 2016. The simulated fuel assembly is composed of Zirconia (ZrO₂) for the outer crucible/simulated fuel, B₄C/stainless steel for the control blade and Zircaloy (Zr) for the cladding tube/channel box. In order to measure the state and component distribution inside the melted aggregate which affects re-criticality and removal of debris, it is necessary to cut at once substances having a wide range of fracture toughness and hardness. Moreover, it is a large specimen with an approximate size of 300mmφ × 1,000mmH. AWJ was selected from these impacts and past experience of decommissioning technology. The following two points (I. If it was not possible to cut at one time like a molten portion of boride, it was repeatedly cut. II. Abrasive Suspension Jet (ASJ) system with higher cutting ability than Abrasive Injection Jet (AIJ, conventional method) system method was used for places where cutting is difficult even in repeatedly cut.) were devised. This specimen could be cut with AWJ to a size that allows sample processing (cutting and polishing) acceptable by the analyzer. As a result of this work, the cutting method in Simulated Fuel Assembly Heating Examination was established. Incidentally, in the cutting operation, when the cutting ability was lost at the tip of the AWJ, a curved cut surface, which occurs when the jet flowed away from the feeding direction, could be confirmed at the center of the test body. From the next work, to improve the cutting efficiency, we propose adding a mechanism such as turning the cutting member itself for re-cutting from the exit side of the jet and appropriate traverse speed to protect cut surface. (author)