Results - Dynamic Multiphysics simulation of RIA
This simulation studies a postulated reactivity insertion accident (RIA) in the GC-MR assembly by assuming a rapid partial withdrawal of the control rod that induces 1.03$ positive reactivity insertion at the hot full power condition. A 3-D dynamic Multiphysics simulation was completed by coupling Griffin, BISON, SAM, where the Griffin transport solver DFEM-SN with CMFD acceleration was used. As shown in Figure 1, initially, the power rapidly increases to a high peak while the fuel temperature starts to slowly increase with time as shown in Figure 2. After about 0.65 sec the negative thermal reactivity feedback of the system (mainly Doppler reactivity feedback) becomes dominant and starts to decrease the power. Although after ~0.65 sec the reactor power starts to decrease, the fuel temperature continues to increase because the power level is still above the nominal power. Figure 3 shows the 3-D temperature distribution at time = 0.65 sec where the maximum temperature is 1344 K. The maximum fuel temperature at the end of the simulation is ~1615K.
Figure 1: The variation of the power during the RIA
Figure 2: The variation of the power average fuel temperature during the RIA
Figure 3: 3-D temperature distribution during RIA at time = 0.65 sec
The simulation was done with a constant inlet coolant temperature strategy and the results demonstrate limited variations of outlet temperature and coolant velocity at the outlet in each of the coolant channels. For example, in the coolant channel located at x= -0.034641, y= 0.06 the inlet and outlet coolant temperatures and velocities are plotted in Figure 4 and Figure 5, respectively.
Figure 4: Inlet and outlet coolant temperatures
Figure 5: Inlet and outlet velocities
Run Commands
In this simulation the parent app is Griffin, but the child apps are BISON and SAM, so we run the blue_crab code package:
mpirun -np <number_of_cores> /path/to/blue_crab-opt -i Griffin_steady_state.iThen, the user needs to run the Parent App for transient calculations as follows:
mpirun -np <number_of_cores> </path/to/>blue_crab-opt -i Griffin_transient.i