Abstract
This paper documents the models available in Serpent for
high temperature reactor (HTR) calculations. It is
supplemented by a calculation example of ASTRA critical
pebble bed experiments. In the pebble bed reactor
modeling, different methods have been used to model the
double heterogeneity problem occurring in pebble bed
reactor calculations. A solution was sought to avoid
unphysical simplifications in the pebble bed modeling and
the stochastic geometry modeling features available in
the Monte Carlo code Serpent were applied for exact
placement of pebbles and fuel particles. Randomly packed
pebble beds were produced in discrete element method
(DEM) simulations and fuel particles were positioned
randomly inside the pebbles. Pebbles and particles are
located using a Cartesian search mesh, which provides
necessary computational efficiency. Serpent uses Woodcock
delta-tracking which provides efficient neutron tracking
in the complicated geometries. This detailed pebble bed
modeling approach was tested by calculating the ASTRA
criticality benchmark experiment done at the Kurchatov
Institute in 2004. The calculation results are in line
with the sample calculations provided with the benchmark
documentation. The material library selected for the
calculations has a major effect on the results. The
difference in graphite absorption cross section is
considered the cause of this result. The model added in
Serpent is very efficient with a calculation time
slightly higher than with a regular lattice
approximation. It is demonstrated that Serpent can be
used for pebble bed reactor calculations with minimal
geometric approximations as it allows exact pebble bed
modeling with randomly positioned fuel particles and
locations of pebbles produced by DEM. Due to the added
stochastic geometry features and efficient neutron
tracking, it is concluded that Serpent is well suited for
the calculations of HTRs.
Original language | English |
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Pages (from-to) | 223-230 |
Journal | Annals of Nuclear Energy |
Volume | 77 |
DOIs | |
Publication status | Published - 2015 |
MoE publication type | A1 Journal article-refereed |
Keywords
- high temperature reactor
- pebble bed reactor
- reactor physics
- Monte Carlo
- sicrete element method