Simulation Exercise Using CONTAIN-LMR Code (Description of Methods and Model)

TerraPower performed both cases in WP-3 as defined in Section 3: • Case 1: sodium spray fire in the reactor containment building • Case 2: sodium pool fire in the small enclosure space Case 1 provided a baseline comparison among the WP-3 participants. Since the ejected sodium was sprayed in a large space with sufficient oxygen, the sodium chemical reaction occurs instantaneously. FIG. 275 shows the CONTAIN-LMR noding scheme including the control volumes, sodium spray fire location, and heat structure options. The containment leak was not assumed so it would result in the limiting containment responses in terms of pressure and temperature. Case 2 was a more realistic simulation as the ejected sodium is initially confined within the small enclosure volume above the reactor roof slab. Additionally, the containment heating, ventilating, and air-conditioning (HVAC) system was also included and was isolated within 10 seconds during the event. As shown, a few more volumes were added in the CONTAIN-LMR model (i.e., volume nos. 4 and 5) in order to simulate proper natural circulation between the enclosure volume (volume no. 1) and the containment volume (volume no. 2).