Naval Postgraduate School
Finite element solution of the nonlinear coupled neutronic-energy equations for a fast reactor fuel cell.
finiteelementsol00kasd.pdf (8.807Mb)Abstract
A transient overpower (TOP) accident in a Liquid Metal
Fast Breeder Reactor (LMFBR) is considered. The analysis
is formulated to model the dynamic response of the reactor
fuel subassembly during the initial period of the postulated
overpower transient. An equivalent cylindrical cell is used
to model the fuel subassembly. The governing neutronic and
heat transport equations for each region (fuel, clad, and
coolant) of the equivalent cylindrical cell are developed.
Nuclear Doppler broadening feedback is included in the dynamic
model making the coupled equations non-linear. The resulting
non-linear partial differential field equations are
transformed into a system of ordinary differential equations
by the finite element method. An isoparametric, quadratic,
rectangular element is used for the discretization of the
spatial domain. When using the finite element method, large
system matrices may result. To facilitate solution of these
large systems, an optimum compacting scheme is utilized.
The implicit Gear's method is used for the solution of the
system of ordinary differential equations. The results for
a sample problem are presented.
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