Transient Analysis of Net Load Rejection for 700 MWe IPHWRs

Indian pressurizer heavy water reactor (700 MWe) is a horizontal channel-type nuclear reactor with partial boiling at the channel outlet. Heat generated due to fission reaction in the reactor core is transferred to primary coolant through the primary heat transport system. There are two loops in the primary heat transport system, and each loop is in the shape of figure of eight and has two steam generators connected in series. The steam generated in the steam generators through the transfer of energy from the primary side drives the turbine for power generation. There is a generator circuit breaker (GCB), which is between generator and generator transformer and another generator transformer circuit breaker (GTCB) which is in between generator transformer and the grid. In the case of net load rejection (NLR), the GTCB opens to disconnect generator from the grid. GCB remains closed, and the generator continues to supply the buses to which unit transformers (UTs) are connected and continue to feed the house load. Transient analysis to simulate the timeline along with the sequence of events and study various parametric variations of the power plant is performed using in-house developed computer code ATMIKA.T. ATMIKA.T code is a coupled thermal hydraulics and 3D neutron kinetics computer code which captures the plant dynamics.