Development of multi-dimensional analysis code (MSG) for steam generators. Transient response analysis by multi-shell model

Temperature profile in a steam generator is effected by location and shape of tubes and the structures in the steam generator. The multi-dimensional analysis code MSG has been developed for the detail evaluation of the thermal-hydraulic design in the steam generator. The downcomer type steam generator has three cylindrical center pipe region, helical coil region, downcomer region connected by a lower plenum region. Sodium flow area of these regions are modeled by the multi-shell in this code. Transient analysis has been performed to confirm the transient response of MSG code by using the experimental data which had been measured in the 50 MWSG test facility. From the analysis, the following results have been obtained: The outlet steam temperature is evaluated within ±15degC for each helical coil layer. The sodium temperature is evaluated within ±20degC for almost all of the temperature data in helical coil tube region. The steam temperature response of the steam generator outlet pipe which considered the time constant of 40 seconds as reference value shows good agreement with experimental data. The sodium temperature response of the steam generator outlet shows good agreement with experimental data. Applicability of the code by the multi-shell model has been confirmed for the transient conditions. (author)