Transient Heat Transfer Characteristics Between Molten Fuel and Steel with Steel Boiling in the CABRI-TPA2 Test

SIMMER-III Analyses of Local Fuel-Coolant Interactions in a Simulated Molten Fuel Pool: Effect of Coolant Quantity

“…To enhance the reliability of SIMMER-III code for reactor safety evaluation, in the past, a comprehensive and systematic assessment program of the code was conducted in two steps [7,17,19]: Phase 1, for fundamental assessment of individual code models, and Phase 2, for integral code assessment. Phase 1 assessment applied the code to single and multiphase flow benchmark problems, small-scale experiments with reactor and simulant materials, and physical problems with known solutions, while Phase 2 assessment involved applications of the code to integral and complex multiphase situations relevant to accident analyses, such as boiling and nonboiling pool dynamics [7,17,25], fuel relocation and freezing [26], fuel-coolant interaction [27,28], core expansion dynamics, and disrupted core neutronics. The above two-step program was successfully conducted in collaboration with the European partners KIT (formerly known as FZK), CEA, and IRSN.…”

“…The disaster in March 2011 at the Fukushima Daiichi Nuclear Power Plant in Japan has caused many people to realize that severe accidents might occur, even if their probability is extremely low [1][2][3]. For sodium-cooled fast reactors (SFR), since the core is not generally designed at the most reactive configurations, in the past, the sequences and consequences of hypothetic severe accidents have been extensively investigated [4][5][6][7]. It is believed that, by assuming pessimistic conditions (e.g., minimal fuel discharge from the core), the accident might proceed into a transition phase where a large whole-core scale pool containing sufficient fuel capable of exceeding the prompt criticality by fuel compaction can be formed (see Figure 1) [8,9].…”

“…To clarify the characteristics of molten fuel pool at various disturbances, in the past years, several series of studies, including specifically designed in-pile and out-of-pile experiments as well as numerical simulations [7], have been initiated at the Japan Atomic Energy Agency (JAEA). Among those studies, for the local FCIs, as reported in a recent publication [16], several tests were conducted by delivering a given quantity of water into a molten pool formed with a lowmelting-point alloy.…”

“…From the experimental analyses [16], it was recognized that, for a given melt and water temperature within the nonfilm boiling range, with the increasing water volume, a limited pressure buildup is achievable for both the melt and cover gas regions. In this study, to further understand the mechanisms underlying this interaction, SIMMER-III, an advanced fast reactor safety analysis code [17][18][19], which is believed to be a unique simulation code currently in the world for event progression analyses in a whole-core scale [7], is used for analyses. In Section 2, the physical models and methods of this code are concisely described with an emphasis on the main features related to FCI analysis, while, in Section 3, after a briefing of the performed experiments, the analytical geometry and conditions are determined.…”

Fuel Pin Behavior up to Cladding Failure under Pulse-Type Transient Overpower in the CABRI-FAST and CABRI-RAFT Experiments

“…Under these circumstances, two new types of low-smear-density fuel pins were introduced in the CABRI-FAST 9) and CABRI-RAFT [10][11][12] programs. They were the Scarabix fuel pins, which had a feature of ''thick annular fuels'' with an intermediate burnup level ($6:4 at%), and the Quasar fuel pins, which had a feature of ''thin annular fuels'' with a high burnup level ($12 at%).…”