COBRA/RELAP5: A Merged Version of the COBRA-TF and RELAP5/MOD3 Codes

The best-estimate thermal-hydraulic codes RE-LAP5/MOD3 and COBRA-TF were adopted to the Apollo DN 10000 workstation and subsequently merged. This was done to combine the excellent features of the two codes and thus produce a code with much enhanced capability. The resulting code was named COBRA /RELAPS. This code has features in common with COBRA/TRAC or TRAC-PF1: three-dimensional reactor vessel and one-dimensional loop modeling capability. The merging of the two codes is focused on the hydrodynamic model and numerical solution schemes. In COBRA/RELAP5, the system pressure matrices of the two codes are merged and solved simultaneously. The merged COBRA/RELAP5 calculations are done in process-level parallel mode on the Apollo DN10000 computer with two central processing units. Through various test simulations, the merging scheme and its implementation were proven to be valid. Thus, the code predictability is presumed eventually to depend on the generic capabilities of COBRA-TF and RELAP5/MOD3. However, to evaluate the overall code capability of COBRA /RELAP5, a systematic assessment should be done, including multidimensional effect tests.