[en] A ultra-long cycle(5 years) SMART core design is examined using the thorium fuel. Most of design configurations of SMART core such as fuel loading pattern, control rod management strategy, and burnable absorber material remain unchanged but uranium fuel which is replaced with a homogeneous mixture of 20% enriched uranium and thorium. The number of burnable absorber pins of the thorium loaded SMART core was adjusted to control the excess reactivity during the cycle burnup. It was shown that mixing ratio of 40:60 of uranium fuel and thorium fuel is necessary to achieve a 5 year cycle length of SMART core. The results also show that the ultra-longer cycle SMART core satisfying all design constraints such as Fq less than 2.5, axial offset less than 0.3, keff less than 0.95 when refueling shutdown margin of 1% with most reactive control rod stuck, and ejected rod worth less than 250 pcm, are possible by using thorium fuel and absorber materials effectively