A method for controlling water quality in a nuclear reactor comprises a first and second steps. The developing unit includes a first supported portion configured to be swingably supported with respect to the image bearing member unit, a second supported portion provided configured to be swingably and slidably supported with respect to the image bearing member unit, and a regulated portion configured to be capable of contacting a regulating portion provided on the image bearing member unit. Each of these unit sections 22, 23 has side faces that are displaced periodically in a disk radial direction. Each assembly has a plurality of pitching blades secured in side-by-side aligned relationship. An example is a material that has a transformable property such that a volume of the first andor second element material may undergo a thermal transformation from one volume to a different volume resulting in the deformation of the interconnection element.