A program analyzing long-term transients after abnormal incidents, excluding loss-of-coolant accidents, has been developed to assess emergency operation procedures for cold shutdown of reactors. The main program features are:1. The thermal hydraulics in both the reactor pressure vessel (RPV) and the primary containment vessel (PCV) are treated.2. Analytical models of the cooling system are included for not only the emergency core cooling system but other cooling systems that are effective for RPV and PCV cooling.3. The on /off switching of cooling systems by plant interlocks, component failures, and operator actions is simulated.The applicability of this program has been evaluated by simulation of long-term thermal-hydraulic behavior of the boiling water reactor transients initiated by loss of feedwater. From the evaluation results, it has been confirmed that the main program models can assess emergency operation procedures.