Quenching and Rewetting of Nuclear Fuel Rods

Abstract

Many postulated nuclear reactor accidents result in dryout or film boiling within the nuclear core. To minimize fuel rod damage and potential rod failure, safe or lower cladding fuel temperatures must be reestablished by encouraging coolant-cladding contact. This process is commonly referred to as quenching or rewetting, and these terms are often incorrectly assumed to be synonymous. Quench and rewet are distinctly different phenomena. Quench is the rapid cooling of a hot solid surface (fuel rod cladding) resulting from enhanced heat transfer conditions and does not necessitate liquid-solid contact. Rewet, however, implies direct liquid-solid contact and the establishment of a liquid-solid-vapor triple interface. The rewet temperature is normally lower than the quench temperature. Estimation of quench and rewet temperatures appears to be possible from first principles.