In case of accident at a nuclear power plant, water sources may not be available for a long period of time and the core heats up due to the residual power. Any attempt to inject water during core degradation can lead ...In case of accident at a nuclear power plant, water sources may not be available for a long period of time and the core heats up due to the residual power. Any attempt to inject water during core degradation can lead to quenching and further fragmentation of core material. The fragmentation of fuel rods and melting of reactor core materials may result in the formation of a ＂debris bed＂. The typical particle size in a debris bed might reach few millimeters （characteristic length-scale： 1-5 mm）. The two-phase flow model for reflood of the degraded core is briefly introduced in this paper. It is implemented into the ICARE-CATHARE code, developed by IRSN （Institut de radioprotection et de surete nucleaire）, to study severe accident scenarios in pressurized water reactors. Currently, the French IRSN sets up two experimental facilities to study debris bed reflooding, PEARL and PRELUDE, and validate safety models. The PRELUDE program studies the complex two phase flow （water/steam）, in a porous medium （diameter 180 mm, height 200 mm）, initially heated to a high temperature （400℃ or 700℃）. On the basis of the experimental results, thermal hydraulic features at the quench front have been analyzed. The two-phase flow model shows a good agreement with PRELUDE experimental results.展开更多
Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during que...Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during quenching and used to estimate surface temperature and surface heat flux by using a developed numerical inverse solution of heat conduction. Heat flux reached its maximum value just after the WF （wetting front） （visible leading edge of boiling region） started moving from stagnation towards the circumferential region. WF moved in a non-uniform manner in angular direction on the hot rotating surface. With the increase of surface velocity, heat flux decreased. Higher surface velocity moved away the produced vapor bubbles and reduced the solid-liquid contact time which made it one-dimensional heat conduction from multi-dimensional, that reduced heat flux. The generated boiling curve from the estimated heat flux showed a reasonable agreement with existing studies. The surface maximum heat flux （maximum value in each cycle） distribution trend with radial position is entirely comparable with the static surface critical heat flux in literature. An explosive to a sheet like flow patterns were observed with the decrease of surface temperature. The flow patterns were followed by the intensity of sound during quenching.展开更多
文摘In case of accident at a nuclear power plant, water sources may not be available for a long period of time and the core heats up due to the residual power. Any attempt to inject water during core degradation can lead to quenching and further fragmentation of core material. The fragmentation of fuel rods and melting of reactor core materials may result in the formation of a ＂debris bed＂. The typical particle size in a debris bed might reach few millimeters （characteristic length-scale： 1-5 mm）. The two-phase flow model for reflood of the degraded core is briefly introduced in this paper. It is implemented into the ICARE-CATHARE code, developed by IRSN （Institut de radioprotection et de surete nucleaire）, to study severe accident scenarios in pressurized water reactors. Currently, the French IRSN sets up two experimental facilities to study debris bed reflooding, PEARL and PRELUDE, and validate safety models. The PRELUDE program studies the complex two phase flow （water/steam）, in a porous medium （diameter 180 mm, height 200 mm）, initially heated to a high temperature （400℃ or 700℃）. On the basis of the experimental results, thermal hydraulic features at the quench front have been analyzed. The two-phase flow model shows a good agreement with PRELUDE experimental results.
文摘Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during quenching and used to estimate surface temperature and surface heat flux by using a developed numerical inverse solution of heat conduction. Heat flux reached its maximum value just after the WF （wetting front） （visible leading edge of boiling region） started moving from stagnation towards the circumferential region. WF moved in a non-uniform manner in angular direction on the hot rotating surface. With the increase of surface velocity, heat flux decreased. Higher surface velocity moved away the produced vapor bubbles and reduced the solid-liquid contact time which made it one-dimensional heat conduction from multi-dimensional, that reduced heat flux. The generated boiling curve from the estimated heat flux showed a reasonable agreement with existing studies. The surface maximum heat flux （maximum value in each cycle） distribution trend with radial position is entirely comparable with the static surface critical heat flux in literature. An explosive to a sheet like flow patterns were observed with the decrease of surface temperature. The flow patterns were followed by the intensity of sound during quenching.
