Abstract
Loss of coolant accidents (LOCA) are a serious type of accidents for nuclear reactors, when the integrity of the liquid-loop breaks. While in traditional pressurized water reactors, pressure drop can cause flash boiling, in Supercritical-Water Cooled reactors, the pressure drop can be terminated by processes with fast phase transition (flash boiling or steam collapse) causing pressure surge or the expansion can go smoothly to the dry steam region. Modelling the pressure drop of big and small LOCAs as isentropic and isenthalpic processes and replacing the existing reactor designs with a simplified supercritical loop, limiting temperatures for various outcomes will be given for 24.5 and 25 MPa initial pressure. Using the proposed method, similar accidents for chemical reactors and other equipment using supercritical fluids can be also analyzed, using only physical-chemical properties of the given supercritical fluid.
Highlights
Loss of coolant accidents (LOCA) are a serious type of accidents for nuclear reactors [1]
While in traditional pressurized water reactors, pressure drop can cause flash boiling, in Supercritical-Water Cooled reactors, the pressure drop can be terminated by processes with fast phase transition causing pressure surge or the expansion can go smoothly to the dry steam region
One of the groups for the Generation IV. reactors are the supercritical water cooled models, where slightly different designs are often referred as Super LWR, HPLWR, etc. [4, 5], but in general, all of these types can be referred as SCWR
Summary
Loss of coolant accidents (LOCA) are a serious type of accidents for nuclear reactors [1]. One of the advantages is that the supercritical fluid is in permanent onephase stage, i.e. there is no separate liquid and steam, at least not in normal working conditions As it has already been discussed [6], during accidents associated with fast pressure drop, phase transitions might happen even in supercritical loops. While in pressurized water reactors (PWR), accidents with pressure drops can cause only fast liquid-to-vapour phase transition (flashing), in SCWRs the reverse might be possible (fast vapourto-liquid transition). For the latter, a similar phenomenon can be observed – at least in theory – for PWRs, but only under special conditions. It is the so-called condensation-induced water hammer (CIWH), which can be occasionally observed in the thermal loop of PWRs or in other
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