Approximate Analysis of the Unavailability of Representative Measurement Channel Groups of the THTR-300 Reactor Protection System

[Automatically extracted and translated] As part of the KFA's contribution to the THTR-300 licensing process, reliability analyses were conducted by the ISF for representative measurement channel groups and emergency cooling initiation signals of the reactor protection system. The measurement channel groups selected as representative were those for monitoring fresh steam pressure, room pressure, hot gas temperature, hot gas temperature gradient, and feedwater mass flow. The average unavailabilities of the individual measurement channel groups for different functional test intervals are summarized in the following table. For the incident 'rupture of a fresh steam line', the unavailability of the emergency cooling initiation signal was determined. The signal is triggered in this incident by the two diverse measurement channel groups for monitoring the fresh steam pressure in the pipeline and the pressure in the room where the pipeline is laid. The average unavailability of the emergency cooling initiation signal was found to be 3.8 x 10^-7 during monthly testing of the measurement channel groups.