The high temperature gas-cooled reactor (HTGR) is a promising concept for inherently safe nuclear power generation. This paper deals with dynamic modeling of both the nuclear and the conventional part of a combined heat and power plant coproducing steam for industrial use, based on a HTGR and a closed cycle gas turbine system. A one-dimensional flow model describing the helium flow and the two-phase water flow is used through the whole plant, with different source terms in different pieces of equipment like the compressor, turbine, reactor, natural convection evaporator, and valves, etc. With the model, a number of possible control options have been assessed and the influence of some design choices on the dynamic behavior is investigated.