[en] Investigations on the safety of Light Water Reactors (LWR) being performed in the framework of the safety program 'Reactor Safety' are sponsored by the Bundesminister fuer Forschung und Technologie (BMFT - Secretary of State for Research and Technology). Objective of this program is to continue improving the safety of LWRs, in order to minimize the risk for the environment. With grant assistance from the Bundesminister des Innern (BMI - Secretary of State for Home Affairs) research contracts in the field of reactor safety are being performed. Results of these projects should contribute to resolving questions arising from nuclear licensing procedures. The Forschungsbetreuung (FB - research supervision department) at the Institute for Reactor Safety (IRS), as consultants to BMFT and BMI, provides information about the progress of investigations. Individual reports will be prepared and put into standard forms by the research contractors. Each report gives information on: 1) the work accomplished, 2) the results obtained, 3) the work planned to be continued. Initial reports of research projects describe in addition the purpose of the work. A BMFT-research program on the safety of Fast Breeders (Schneller Brutreaktor - SBR) is presently under discussion. In order to define several problems, investigations included in the present compilation (RS 139, 140, 143, 162) will be previously performed. (orig./HP)