For the most part this Section describes the mechanical aspects of plant features located in the core region or its immediate vicinity. This encompasses the description of the fuel channels, the core block itself, its surrounding structures and shields. Section 4.3 describes the various control and instrumentation channels, the control rod drives and the fuel handling system, Section 4.4 presents the core block draining system. Section 4.5 departs from mechanical aspects and outlines the major operational procedures which directly involve the reactor core.