Concept of a reactor (300 MW) of high inherent safety for district heating supply

The objective of this work is the description of a suitable nuclear district heating reactor concept, the focus being on the physico-technical design of the heating reactor presented, taking into consideration the high level of safety requirements to be met due to the fact that the safety of such district heating provision becomes particularly important in the stage of projecting, including the following: uncomplicated passive safety systems, quick-reacting automatic reactor control, no active coolant recirculation, low power density (passive behaviour under accident conditions), use of low pressure systems, integrated primary loop, redundant and diversified afterheat dissipation systems, taking into consideration minimization of cost by: use of structural components proved in conventional nuclear reactors, simple pressure vessels with low operational parameters, small size, no fuel element replacement. On the basis of functional and safety considerations, a thermohydraulic and neutron-physics investigation was performed for each of the heating reactor components. This included consideration of control behaviour in the various power levels. As a result, without active control of the reactor at no-load, a quasistatical average primary coolant temperature of 1800C is to be expected. As a special feature, there is a recently developed shutdown system design to ensure a totally passive shutdown of the reactor in the event of inadmissible operational parameters. For the support of the thermohydraulic design, a test bench was built and tested. Results obtained from it confirm the procedure of natural circulation design and show particularities in the startup of such a system. (orig.)