The Code of Federal Regulations (C.F.R.) is the codification of rules created by the departments and agencies of the Federal Government. It is divided into 50 titles that represent broad areas subject to federal regulation. The 50 subject titles of the regulations in the C.F.R. are similar but not identical to the titles of the federal statutes in the U.S. Code.
There is no one system or set of procedures by which agencies investigate or adjudicate claims. The Administrative Procedures Act (APA) contains some very basic guidelines regarding adjudications, but the format and protocol for such hearings varies from agency to agency. The terminology used to refer to decisions in adjudications may be referred to as decisions or opinions, but they may also be called orders or releases. Bluebook Table T1.2 includes a non-exclusive list of administrative agency and executive materials that can be helpful in determining what an agency calls its decisions and where they may be published.
West's Federal Administrative Practice is a treatise that provides guidance regarding handling matters before Federal departments and administrative agencies. It provides a nice overview of an agency's structure and their adjudication process.
There is no singular publication for administrative decisions and they may be available in one or more several electronic sources.