A simplified fast running PWR transient analysis code is developed with the lumped parameter method and analytic solution techniques. Based on the lumped parameter method, NSSS is modeled as 5 components which are loop, core, pressurizer, steam generator, and pump. The mass and energy balance equations are derived in the loop energy transport model, and solved analytically with the aid of the separation of variable technique. The spatial distribution function, to describe the thermal properties of the control volume accurately, is derived from the energy equation of the loop.
The simulation of the station blackout accident in KNU-1 is performed by this developed code and compared with the prediction of the RELAP5/MOD1 and plant data. Compared with the RELAP5/MOD1, this computer code reduces the computer processing time to about one-thirtieth.