A numerical scheme, named UPDATE (Uniform Pressure Drop Approximation Technique), is developed for the thermal-hydraulic design analysis of the core, which based on the COBRA4-I code. The most of assumptions and models used in COBRA4-I are the same as those of UPDATE. It is additionally assumed that the pressure drop is laterally uniform.
The marching method applied to solve the subchannel equations is modified to reduced the computer running time. And the transport coefficient model is employed in order to improve the capability of a whole core analysis.
Various tests are performed in order to compare results predicted by the present code with those of COBRA4-I. It is convicted that the present scheme has the capability of predicting accurately the thermal margins faster than COBRA4-I.