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Fusion Engineering and Design 42 (1998) 281288 The use of MNCP for neutronics calculations within large

Summary: Fusion Engineering and Design 42 (1998) 281288
The use of MNCP for neutronics calculations within large
buildings of fusion facilities
J.E. Eggleston *, M.A. Abdou, M.Z. Youssef
Mechanical and Aerospace Engineering Department, UCLA, Los Angeles, CA 90095, USA
The calculation of nuclear parameters within fusion facilities is complicated by the complex geometry and large size
of the proposed buildings housing the reactors. These complications make it impossible to use a single model, or code,
to calculate the transport of neutrons from the plasma out into the rest of the building. In this paper, coupling two
calculational models is demonstrated in calculating the operational dose rates in ITER building. The neutron and
gamma fluxes during operation are calculated from the plasma region out to the cryostat of the machine using a
two-dimensional discrete ordinates model (the subject of a companion paper) whereas a Monte Carlo MCNP model
is applied in the rest of the building. In using this coupling approach, numerous joint Probability Mass Functions
(PMFs) for the different phase space variables are used and constituted a specially-written source subroutine that is
linked to MCNP. Along with the problem of proper source sampling and characterization, the physical size of the
building, in comparison to the tally region, drastically complicates the calculation. As a result of this, the use of
non-analog techniques are needed to help in the transport of particles in regions far away from the source (which is
the NBI duct in this case). The fact that good results were easily achieved in the NBI room where there is a direct
line of sight to the plasma, but as the detectors are placed further away, the results degenerate, exemplifying the need
to use variance reduction techniques. Various techniques in the MCNP calculations are applied and compared and


Source: Abdou, Mohamed - Fusion Science and Technology Center, University of California at Los Angeles


Collections: Plasma Physics and Fusion