Spray cooling of a rod bundle with a counter-current steam flow in spent fuel pool conditions
Résumé
Since the Fukushima-Daiichi accident, much attention has been paid to the vulnerability of Spent Fuel Pools (SFP). The DENOPI project conducted by the IRSN is part of this approach with the aim to gain knowledge in SFP under loss of cooling or loss of coolant accident conditions and to better evaluate the safety margins. Within this project, an experimental test series was performed in the MEDEA facility in order to assess the efficiency of a water spray to cool down an uncovered rod bundle in SFP conditions. In this experimental campaign, a superheated steam flow is injected at the bottom of the test section. Then, the steam crosses the central test section with a 17x17 rod bundle from bottom to top. In the opposite way, a water spray falls from the upper head and cools down the assembly as well as the test section walls. In the final paper, the cooling kinetics of the rods and the walls will be presented and discussed. No clear top-down rewetting was observed in this experimental campaign. On the contrary, some stochastic behaviors are noticed regarding the spatial and temporal cooling of each individual rod. However, statistical average evaluation leads to quite smooth trends of the temperature evolution with time and along the height of the assembly. Besides, the impact of the spray temperature and mass flow rate on the rod bundle temperature evolution will be analyzed.