Nuclear Production of Hydrogen, Fourth Information Exchange ...

TRANSIENT MODELLING OF S-I CYCLE THERMOCHEMICAL HYDROGEN GENERATION COUPLED TO PEBBLE BED MODULAR REACTOR
In a coupled nuclear hydrogen production system, a transient is initiated on either the nuclear
reactor side or the chemical side of the plant. There are many potential transients that occur in a
nuclear reactor system. Some examples are (Reitsma 2004):
• depressurised loss of forced cooling with or without SCRAM;
• pressurised loss of forced cooling with or without SCRAM;
• load following accidents;
• control rod withdrawal;
• control rod ejection.
Model integration and coupling
The hydrogen and THERMIX-DIREKT codes have three points of interaction:
1. initial steady-state solution;
2. initiating event coupling;
3. in-transient feedback.
First, a steady-state solution is attained in both the THERMIX model and hydrogen model. Second,
a transient is initiated, either in the chemical plant model or in the point kinetics model. Finally, the
THERMIX, point kinetics and hydrogen generation models all interact in each time step. The integration
scheme is shown in Figure 4.
Figure 4: Coupling flowchart
Coupling of the codes is performed through the IHX. The data exchanged between the codes
consists of the flow rate and temperature of helium through both hot and cold legs of the IHX. The
hydrogen model calls THERMIX and the point kinetics model every time step and then new temperature
and flow rate values are returned. This process is repeated each time step.
NUCLEAR PRODUCTION OF HYDROGEN – © OECD/NEA 2010 369