Initial reference design of ZrCo hydride beds for ITER

To develop ZrCo hydride bed for the storage and delivery system (SDS) and the long-term storage system (LTS) in the ITER, detail design of the internal structural arrangement and the vessel of SDS and LTS beds was implemented by using the ASME VIII Div. 1 pressure vessel design code. The SDS bed is composed of primary and secondary vessels. The primary vessel contains ∝3.5 kg ZrCo, a centralized heater tube, outer heater on the surface of primary vessel, heat transfer fins, and He loop for in-bed tritium measurement. Space between the two vessels provides a guard vacuum zone, and it contains thermal reflectors to reduce heat transfer to the secondary vessel, and secondary vessel surface temperature. Three independent He gas flow paths are provided for removal of the tritium decay heat, for rapid cooling of the ZrCo powder packed section for in-bed tritium inventory measurement in short time (8-24 h), and for purging of the tritium permeated from the primary vessel into the guard vacuum zone. The general structure of the LTS bed is similar to that of the SDS bed. In order to validate an initial reference of ZrCo hydride beds, the following heat analysis was performed: (i) heating performance of ZrCo hydride packed bed during delivery operation, (ii) cooling performance (decay heat removal, etc) to reduce the ZrCo hydride temperature during recovery and storage operation, (iii) thermal shielding performance for reduction of outer vessel surface temperature. The present paper provides the results of heat analysis and discuss the effects of endothermic and exothermic reaction (ZrCo+1/2T2=ZrCoT+80.495 kJ/mol (T2)), and of cooling using He gas. (orig.)