Container and method for closing an opening of container

A nuclear fuel cladding tube, comprising:

• a container body that includes a wall portion separating inside and outside and is formed of a long-fiber-reinforced silicon-carbide composite material obtained by combining monofilaments of silicon carbide with a silicon carbide matrix, the wall portion having a thickness equal to a specific dimension;
• and
• a lid configured to close at least one opening of the container body, formed of a material containing at least silicon carbide, and equipped with a wall portion separating inside and outside of the lid that has a thickness within a range of 1.2 to 1.9 times the specific dimension, wherein
• the container body accommodates nuclear fuel of a nuclear reactor,
• the lid is an end plug that closes the at least one opening at an end portion of the container body,
• a shape of the lid is at least one of a shape of an outer stopper covering an outer periphery of the end portion of the container body and a shape of an inner stopper provided inside the at least one opening,
• a bonding portion where the container body and the lid overlap is hermetically sealed,
• a gap between the container body and the lid is sealed with an intermediate material under a state where the at least one opening is closed with the lid, the gap formed by overlapping the container body and the lid, and
• at least the bonding portion is locally heated.