3.1 PARCS code

Purdue Advanced Reactor Core
Simulator that known as PARCS code has been developed by Purdue University.
This code has shown a great capability to predict the dynamic response of the boiling
and pressurized water reactor, pressurized heavy water reactor and pebble bed
reactor to reactivity changes such as control rod movement or change in
temperature/fluid conditions in the reactor core. This code solves the steady
state, time-dependent, and multigroup neutron diffusion equation and SP3
transport equation for predicting the dynamic behaviors.

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Coarse mesh nodal methods has
been used in PARCS code where the geometry is homogenized at the assembly
level. The capabilities of PARCS code to move the position of control rod
during transient, scram and also TH block for thermal hydraulic calculations make
this code capable to perform calculations during REA more accurate (Downar et al., 2006).

3.2 DRAGON code

DRAGON is an
open-source simulation package belongs to of École Polytechnique de Montréal
that allows researchers to study the behavior of neutrons in a nuclear reactor.
It allows one to determine the isotopic concentrations of radionuclides during
the burnup cycle, as well as to perform isotopic depletions. The DRAGON code has a collection of models for
simulating the neutronic behavior of a unit cell or a fuel lattice in a nuclear
reactor.

This lattice code includes many calculation modules that have been linked together.
Some capabilities of DRAGON code are as follows: microscopic cross
sections interpolation from standard libraries; resonance self-shielding and
multigroup neutron flux calculations in multidimensional geometries;
transport-diffusion and transport-transport equivalence calculations; and
modules for editing condensed and homogenized nuclear properties for reactor
calculations. The macroscopic cross sections resulted from this code are fed to
the PARCS code during transient calculations (Marleau
et al., 2016).

4. REA
scenario

The RIA is a
nuclear reactor accident that involves unintentional displacement of control
rods from an operating reactor, which lead to a very fast power excursion in
the nearby fuel rods and temperature. The postulated scenario for RIA are
included few events, which lead to the large reactivity excursions, and
therefore may exceed the safety margins. In SMART core control rods are placed
in 25 fuel assemblies that are included in 3 regulating and 2 shutdown banks. Fig. 5 shows the control bank arrangement
in the SMART core. The position of the control banks during the different
powers of normal operation, according to the SMART SSAR is shown in Fig. 6. As determined in Fig. 6 only a part of R3 regulating bank
is inserted in the core during full power condition (Song et al., 2010).

According to the Korean reports for the SMART core, the sequences of
events and operational parameters during REA scenario are as following: the
initial power at the beginning of the REA is 103% normal power (339.9 MWt);
coolant inlet temperature is 290.4 oC; coolant flow rate is 1985.5
kg/sec; R3 regulating bank ejection time is 0 sec ~ 0.05 sec; control rod
insertion 1.83 sec ~ 2.43 sec (SMART Report, 2012;
SMART SSAR, 2010).