[en] RETRAN was developed in recognition of the need for utilities with a small analysis staff to be able to perform best estimate analyses of operational transients. RETRAN provides GPU with a powerful tool for independent analysis of dynamic plant performance. The general nature of RETRAN allowed for analysis of many different events with only minor changes to the model and for the modeling of both PWR and BWR plants with the same code. To date, RETRAN has been successfully used to predict plant performance for the purposes of design optimization, short term operational support, inhouse support of licensing, and operator training activities. Plant procedures and postulated transient scenarios have been verified using RETRAN