Behavior of the HTR module on hypothetical event flows

Automatic translation: The HTR module (Fig. 1.1) is technically and nuclear-physically constructed designed so that a limitation of the fuel element temperature around 1600 °C is always guaranteed, even if all active devices for shutdown and residual heat removal fail should. This is achieved by the following design that characterizes the module: - Choosing a low mean power density of the reactor core of 3 MW/m3 (Fig. 1.4). - Choosing a suitable geometry of the reactor core and the surrounding ones Core installations and the use of appropriate materials such that the residual heat is solely due to physical processes such as Conduction, radiation and convection from the reactor core can flow to the surrounding structures. - Utilization of the temperature range of approx. 750 K between the maximum permissible fuel element temperature and the maximum operating temperature such that the reactor core is above the negative Temperature coefficients of reactivity (Fig. 1.5) also after Accident-related introduction of the existing excess reactivity switches off by itself before the above limit temperature of approx. 1600 °C is reached. - Limitation of the possible excess reactivity by limitation of the drivable load change range and by choosing a sufficient low heavy metal loading of the fuel assembly 7 g to valuesthat result in incorrect introduction of the reactivity into the Core no unmanageable power transients and temperature developments have as a consequence. - Choice of the arrangement of reactor core and steam generator such that the intrusion of large amounts of water into the core with the potential water gas formation and fuel element corrosion is made more difficult will.