Analysis on Water Ingress Volume Effect of The RDE Core to Criticality (Hery Adriala), Suwotob), Pande Made Udiyanic), Amir Hamzahd), Zuhaire)

Abstract. The accident of water ingress is a form of accident that only occurs in HTGR where the fluid of secondary
cooling enters the core due to cracking or rupture at the Steam Generator (SG). This condition will make the RDE core
unsafely. Quite a lot of research is related to the neutronics of reactors regarding water ingress accidents. These studies
generally revolve around relationship on the critical and reactivity to water ingress density. Because this study was
made aiming to analyze the effect of water ingress volume on the criticality of RDE core for various temperatures at
a 4.5 MPa pressure core. The method used is to assume that water ingress accidents occur along the cold leg pipe to
the hot leg pipe on SG. The pressure core after the water ingress is assumed to be the mean pressure between the core
and SG while the temperature core after the water ingress is assumed to range from 105 oC to 450 oC. The results
obtained showed that for temperatures core of 105 oC to 250 oC, the fluid that entered to the core in the form of water
and had a curved curve with the maximum multiplication factor value occurring at a volume water ingress of 20%
then the multiplication factor continued to decline until the reactor became sub-critical as the volume water ingress
increased that goes to the core. Whereas for temperatures of 275 oC to 450 oC, the fluid entering the RDE core is in
the form of vapor (void) which keeps the multiplication factor going up to supercritical state, thus making the reactor
core unsafe as the volume of water ingress enters the core
Keywords: Water ingress volume, RDE, Criticality, MCNP6.1, Pressure core, Temperature various