3.1 PARCS codePurdue Advanced Reactor CoreSimulator 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 boilingand pressurized water reactor, pressurized heavy water reactor and pebble bedreactor to reactivity changes such as control rod movement or change intemperature/fluid conditions in the reactor core. This code solves the steadystate, time-dependent, and multigroup neutron diffusion equation and SP3transport equation for predicting the dynamic behaviors.

Coarse mesh nodal methods hasbeen used in PARCS code where the geometry is homogenized at the assemblylevel. The capabilities of PARCS code to move the position of control rodduring transient, scram and also TH block for thermal hydraulic calculations makethis code capable to perform calculations during REA more accurate (Downar et al., 2006).3.

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2 DRAGON codeDRAGON is anopen-source simulation package belongs to of École Polytechnique de Montréalthat allows researchers to study the behavior of neutrons in a nuclear reactor.It allows one to determine the isotopic concentrations of radionuclides duringthe burnup cycle, as well as to perform isotopic depletions. The DRAGON code has a collection of models forsimulating the neutronic behavior of a unit cell or a fuel lattice in a nuclearreactor.This lattice code includes many calculation modules that have been linked together.Some capabilities of DRAGON code are as follows: microscopic crosssections interpolation from standard libraries; resonance self-shielding andmultigroup neutron flux calculations in multidimensional geometries;transport-diffusion and transport-transport equivalence calculations; andmodules for editing condensed and homogenized nuclear properties for reactorcalculations. The macroscopic cross sections resulted from this code are fed tothe PARCS code during transient calculations (Marleauet al.

, 2016). 4. REAscenarioThe RIA is anuclear reactor accident that involves unintentional displacement of controlrods from an operating reactor, which lead to a very fast power excursion inthe nearby fuel rods and temperature. The postulated scenario for RIA areincluded few events, which lead to the large reactivity excursions, andtherefore may exceed the safety margins. In SMART core control rods are placedin 25 fuel assemblies that are included in 3 regulating and 2 shutdown banks.

Fig. 5 shows the control bank arrangementin the SMART core. The position of the control banks during the differentpowers of normal operation, according to the SMART SSAR is shown in Fig.

6. As determined in Fig. 6 only a part of R3 regulating bankis inserted in the core during full power condition (Song et al., 2010).According to the Korean reports for the SMART core, the sequences ofevents and operational parameters during REA scenario are as following: theinitial 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 1985.5kg/sec; R3 regulating bank ejection time is 0 sec ~ 0.05 sec; control rodinsertion 1.83 sec ~ 2.43 sec (SMART Report, 2012;SMART SSAR, 2010).