Patent ID: 7168744

Claim:
A fastening structure for use at a low temperature comprising: a first flange; a second flange superposed on said first flange; and a bolt fastening said first flange and said second flange with a nut; wherein said fastening structure is used at a temperature lower than an atmospheric temperature at which a fastening operation is performed, a relation of L·α≧L 1·α1 +L 2·α2 is satisfied, where L 1 represents a thickness of said first flange, L 2 represents a thickness of said second flange, L represents a thickness of superposed said first flange and said second flange, α 1 represents a coefficient of linear expansion of said first flange, α 2 represents a coefficient of linear expansion of said second flange, and α represents a coefficient of linear expansion of said bolt, and an amount of heat shrinkage of said bolt is equal to or larger than a total amount of heat shrinkage of said first flange and said second flange, and wherein said second flange is a part of a container storing a cryogenic coolant inside, and said container is sealed by fastening said first flange to said second flange with said bolt, and an outer container defining a vacuum portion is provided outside said container.