[en] This report presents results from a General Atomic Company alternate design study for the core auxiliary cooling system (CACS) of the 300-MW(e) Gas-Cooled Fast Reactor (GCFR) Demonstration Plant. The purpose of this study was to evaluate CACS design concepts similar to that used in the large High-Temperature Gas-Cooled Reactor (HTGR), which has a non-boiling core auxiliary heat exchanger (CAHE) and CACS startup from rest. The study considers current 1977 safety criteria and requirements and includes design, transient analysis, drive and control trade-off studies, and analysis methods development. Transient analysis of the revised CACS design indicates satisfactory core cooling for all required operating conditions, according to current criteria