Abstract: A clearance adjusting member that easily attaches and detaches without risk of falling off a pin is disclosed. A first member and a second member are coupled freely to be rotated in relation to each other by a cylindrical pin. For adjusting an axial clearance between the two members, the clearance adjusting member comprises a shim in a U or C-shape attached to the pin in the axial clearance, and a restricting means for restricting the shim while being freely releasable. A restricted piece protruding radially outward is formed on an outer circumferential edge of the shim. The restricting means includes a pair of restricting pieces spacedly arranged circumferentially on the radially outer side of the pin. When the shim is inserted towards the axial clearance, the restricted piece becomes positioned between the pair of restricting pieces and the shim is attached to the pin.

Abstract: Provided is a method for treating scales (101) that have formed on the outer surface of a heat-conducting tube (111) and in a hole (112a) of a tube support plate (112) etc. of a steam generator of a nuclear power plant. The scales (101) are embrittled and also converted to a porous state by bringing the scales (101) into contact with a treatment solution, which contains 0.5 to 3.5 wt % of an organic acid and is at a pH of 2 to 3.5, for 2 to 30 days at 20° C. to 40° C.