  Superheavy isotopes are highly neutron rich nuclei in the vicinity of neutron
drip-line, stabilized by shell effect against the instability due to repulsive
component of nuclear force, analogous to superheavy elements similarly
stabilized against Coulomb instability. Here we discuss the stability and
fission decay properties of such nuclei in the $^{254}$Th region and show that
they are stable against $\alpha$ and fission decay and have $\beta$-decay life
time of several tens of seconds. In particular, the $^{254}$Th nucleus has a
low fission barrier and unusally large barrier width. This makes it an ideal
thermally fissile nucleus, if formed by means of a thermal neutron, like other
known nuclei such as $^{233}$U, $^{235}$U, $^{239}$Pu in this actinide region.
It shows a new mode of fast fission decay, which may be termed as
multifragmentation fission, in which in addition to two heavy fragments large
number of scission neutrons are simultaneously produced. Its likely synthesis
during the r-process nucleosynthesis will have important bearing on steller
evolution, and here in the laboratory, it has great potential in energy
production.
