AIRTIGHT VESSEL FOR RADIOACTIVE MATERIAL, AIRTIGHT WELDING METHOD FOR THE AIRTIGHT VESSEL AND EXHAUST DEVICE USED FOR THE AIRTIGHT WELDING

摘要

PROBLEM TO BE SOLVED: To provide an airtight metal vessel which prevents generation of welding defect and is superior in airtightness, an airtight welding method for the airtight vessel and an exhaust device used for the airtight welding. SOLUTION: A shield body 44 is installed in the upper end opening of a vessel body 40 containing a radioactive material to seal the upper end opening of the vessel body. At the periphery of the shield plate, an O-ring 46 is provided to seal the gap between the inner surface of the vessel body and the shield body. In the upper end opening of the vessel body, a primary lid 48 is installed overlapping the shield plate of which the periphery is welded to the inner surface of the vessel body. When the primary lid is welded, steam in the vessel body is exhausted out of an exhaust hole 50 formed in the primary lid and the shield plate and shield gas is filled or passed in the space 30 formed in the periphery of the lid to shield inflow of steam into the welding part.