4. METHOD OF SOLUTION
The code assumes that heat transfer depends entirely on spray mechanisms and radiation. The heat transfer history of an accident is divided into three parts:
- Convective heat transfer, terminated by dryout.
- Low radiative heat transfer.
- Spray cooling of the cluster.
LOCA-MK-2 performs a 1-D transient conduction calculation for a typical pin of each ring; temperature is found as a function of radius from the centre of the fuel.
The solution of the conduction equation is by an implicit method and is therefore stable for all sizes of time steps.
The variation of neutron flux after the accident is determined from the conventional six precursor group single point kinetics equations.