NUMERICAL ANALYSIS OF THREE-DIMENSIONAL FLOW FIELD IMPACT UNDER STRONG TRANSIENT CONDITIONS IN ADVANCED REACTORS

As a representative of Generation IV nuclear energy systems, sodium-cooled fast reactors (SFR) may cause the liquid sodium flowing through the core to boil after a Core Disruptive Accident (CDA), which then forms a high-energy vapor cavity expansion to push the liquid sodium above, causing an impact failure to the main vessel structure in a very short period of time, which is a safety hazard. In this study, the computational analysis of the process of high-energy vapor cavity expansion pushing liquid sodium impacting on the top of the reactor vessel was carried out from the full scale to derive the effects of high-energy impact on the inner wall and upper components of the reactor vessel after the accident. The results show that after the CDA, the sodium-cooled fast reactor shielding lid is subjected to a great impact pressure at the center of the cork, while the covering argon gas at the top is compressed, resulting in a rapid increase in the internal pressure of the reactor vessel within a short period of time, and extrusion of the vessel inner wall. Through this study, the flow field distribution characteristics inside the reactor vessel in the late stage of the core disruptive accident are grasped, and the distribution of the impact pressure on the top shielding cover at the full reactor scale in the core disruptive accident is obtained, which can provide technical and result references for the studies related to the CDA of pool-type sodium-cooled fast reactors (PSFR).