Development of the RETRAN input model for Ulchin 1/2 transient analyzer

As a part of the Long-Term Nuclear R and D program, KAERI has developed the so-called NSSS transient analyzer based on best-estimate codes for Ulchin 1/2 plants. The MARS and RETRAN codes are used as the best-estimate codes for the NSSS transient analyzer. Among these two codes, the RETRAN code is used for realistic analysis of Non-LOCA transients and small-break loss-of-coolant accidents, of which break size is less than 3 inch diameter. So it is necessary to develop the RETRAN input model for Ulchin 1/2 plants. In recognition of this, we have developed the RETRAN input model for Ulchin 1/2 plants. This report includes the input model requirements and the calculation note for the input data generation (see the Appendix). In order to confirm the validity of the input data, we performed the calculations for a steady state at 100 % power operation condition, inadvertent reactor trip, loss of flow accidents and load-rejection operation. The results of the steady-state calculation agree well with the design data. The results of the other transient calculations seem to be reasonable and consistent with those of other best-estimate calculations. Therefore, the RETRAN input data can be used as a base input deck for the RETRAN transient analyzer for Ulchin 1/2