Research on Shutdown Protection of Sodium-cooled Fast Reactor for Reactivity Accident Introduction

In the reactor system, when the reactor is in abnormal condition, if the operation parameters exceed the protection limit, the relevant protection actions will be triggered by protection system to ensure that the state of the reactor meets the requirements of the accident acceptance criteria. The main system model of sodium-cooled fast reactor was established by Simulink in the paper. For reactivity accident introduction, the protection parameters and their setting values of the primary loop of the reactor were studied based on the measurement error and data processing of corresponding protection parameters, in the same manner as anticipated transient without scram (ATWS) for fast reactor analysis, and the state of the sodium-cooled fast reactor met the accident acceptance criteria for sodium-cooled fast reactor during the entire reactivity accident introduction. The results show that the current setting values of protection parameters, such as sodium temperature at core outlet, power and power-flow ratio as well as the signal measurement delay and the falling time of the rod can be taken from other values, when the shim rod is accidentally lifted for 5 s or 10 s. While for 15 s, as long as the setting value of the protection parameter, the signal measurement delay of the corresponding parameter and the falling time of the rod can make the reactor enter the depth subcritical before 36.45 s, the state of the reactor will still meet the requirement of the accident acceptance criteria.