Some designs currently in use, if catastrophically mismanaged, yes. OTOH, some newer designs (eg LFTR) are walk-away safe: Nuclear explosions/meltdowns are phy

Some designs currently in use, if catastrophically mismanaged, yes. OTOH, some newer designs (eg LFTR) are walk-away safe: Nuclear explosions/meltdowns are physically impossible short of deliberate sabotage.