Consequences of Pressure/Calandria Tube Failure in a 31 CANDU Reactor Core During Full-Power Operation

Abstract

The consequences of a hypothetical rupture of a fuel channel i.e., simultaneous failure of both the pressure and calandria tubes, are described generically for CANDU reactors. The transient hydrodynamic and impact loads, and the steady state jet forces resulting from such an accident are discussed for various rupture geometries. Various possible modes of damage to the in-core structures are evaluated. The possibility of fuel ejection is assessed to quantify the potential mechanical damage to the in-core structures due to projectiles. The pressure loading on the calandria vessel is shown to result only in elastic stresses within the vessel wall. The adjacent fuel channels are shown to be well able to withstand the mechanical loadings imposed on them, so that channel failure propagation is precluded. Some guide tubes of the reactivity devices are likely to be damaged due to a combination of the hydrodynamic loads, impact by fuel projectiles, and pipe whip. The extent of damage to the shut-off rod guide tubes is quantified for various Ontario Hydro reactors. For each reactor, calculations of the reactivity depth of the available shut-off rods show that SDS1 acting alone is still capable of shutting down the reactor, and maintaining subcriticality with sufficient margin.