[en] Automatic translation: 1. Reference design prototype system (HRB): 1.1 Summary: After it was agreed with GAC at the end of 1973 to carry out a concept comparison study in the first half of 74 in order to arrive at a uniform system concept if necessary, work on the previous 700 MWe prototype system began largely postponed. Only work that was critical in terms of deadlines and fundamental investigations were continued. As part of the HRB / GAC study, system designs with a power plant output of 1050 MWe with 3 turbo sets each in a horizontal and vertical construction are made compared to each other. A trend analysis carried out at the end of March showed that the aim of the HRB / GAC concept study to come to a common concept, opportunities for realization especially if the horizontal variant preferred by the HRB does not differ significantly from the vertical variant in terms of cost. The work was carried out on schedule, so that the study expected to be completed by the end of June.