The concept of integral smallmodular reactor (SMR) isn’t new but it seems that the proper time for usingthis idea has been coming. According to the international atomic energy agency(IAEA), the reactors with electrical power lower than 300 MW have been definedas small reactors, although SMRs are categorized by this fact that moreadvantages and design features are attain when intentionally make reactorssmall.
In fact these reactors use theirsize as advantage to attain more design purposes. Thescalability, modularity (many of major components can be assembledanywhere far from the sites and then shipped to the main sites), improved safety characteristics and more important thanother, lower up-front cost of the SMRs, offer great advantages over large commonnuclear power plants. Also, many countries and regions (like many of Asian andAfrican countries) lack suitable sites for producing electricity and waterdesalination or totally for the countries with small electric grids,less developed infrastructure and limited investment capabilities, SMRscan be the best solution (IAEA, 2016). According to theIAEA reports there are many interests all over the world to move toward usingof these kind of reactors. There are many different type of SMRs underdifferent stages of design, licensingand construction.
Russia (KLT40s), Argentina (CAREM) and china (HTR-PM) havethree type of SMRs under construction now and arescheduled to begin commercial operation between 2018 and 2020. KoreanSystem Integrated Modular Advanced Reactor (SMART) has a certified design andalso Russian VBER-300 is under licensing stage. There are many other SMRdesigns that will be prepared for near term deployment, although realisticallyit seems that the first commercial group of SMRs, start operation near 2025 –2030 (IAEA, 2016).Many researchers andengineers all over the world are trying to assessing and surveying differentaspect of these new reactors like in economical, environmental, nuclear characteristicsand many other fields. Identifying the transientbehavior of the neutron flux in a nuclear reactor in response to either aplanned or unplanned change in the reactor behavior has a great importance onthe safe and reliable operation of the reactor. The most limiting caseover the reactivity initiated accidents (RIA) as a very fast transient is therod ejection accident (REA) that has been categorized as design basis accident(DBA).
Our first objective in thisstudy is to evaluate an integral SMR reactor during a REA. There are researchesthat tried to evaluate REA for different type of pressurized reactors (Selim et al., 2017; Nawaz et al., 2016; Tabadar et al.,2012; Barrachina et al., 2011; Diamond et al.
, 2001) but in this studywe are trying to evaluate this accident for Korean SMART reactor as an SMR thataccording to the IAEA reports has a certified design (IAEA,2016). Many codes and methods havebeen used to simulate the REA (Prévot et al., 2017;Songet al.
, 2016; Lee et al., 2015; Grgic et al, 2013;) but in this study weused a combination of DRAGON as a cellcalculation code (Marleau et al., 2016) andPARCS as dynamic core calculation code (Downar etal.
, 2006). Also another purpose of this study is to evaluate thecapability of DRAGON/PARCS codes for modelling REA for a SMR core by comparisonthe results with the REA results of standard safety analysis report (SSAR) ofSMART core. Noori-kalkhoran et al.
(2014) usedWIMSD-5b/PARCS for evaluating REA in a WWER-1000 type reactor but we want toassess DRAGON/PARCS as modelling tools for evaluating REA in SMRs. PARCS codehas been used as neutronic tool coupled with RELAP as a thermal hydraulic code(Vahman et al., 2016) but in this study wealso used TH block of PARCS code that as an Internal coupling procedure withpowerful spatial kinetics methods of PARCS can simulate the transient behaviorof the reactor (Downar et al., 2006).The remainder ofthe paper is organized as follows. Section 2 presents an overview of the SMARTreactor and its operational parameters.
In Section 3, DRAGON and PARCS codesthat have been used for performing our calculations are introduced. The core modeland a validation for steady state condition of SMART core at the beginning ofcycle (BOC) have been presented in Section 4. Section 5 contains the results ofREA calculation from DRAGON/PARCS that have been compared with SMART SSAR forsome results. Finally, conclusion and remarks are given in Section 6.