  Scattering of neutron collision inside a reactor depends upon geometry of the
reactor, diffusion coefficient and absorption coefficient etc. In general these
parameters are not crisp and hence we may get uncertain neutron diffusion
equation. In this paper we have investigated the above problem for a bare
triangular homogeneous reactor. Here the uncertain governing differential
equation is modelled by a modified fuzzy finite element method using newly
proposed interval arithmetic. Obtained eigenvalues by the proposed method are
studied in detail. Further the eigenvalues are compared with the classical
finite element method in special cases and various uncertain results have been
discussed.
