Low-boron OPR1000 core based on the bigt burnable absorber

Abstract

In a low boron PWR core, the critical boron concentration (CBC) is quite smaller than that of the con-ventional PWR designs. A low CBC offers many economic and safety benefits since the core is less depend-ent on soluble boron, which are troublesome in term of reactor operation and maintenance despite its preva-lent use in many commercial PWRs. The particular concern is in the possibly undesirable ‘less negative’ or even ‘slightly positive’ moderator temperature coefficient (MTC) attained in typical PWR with high CBC. In this regards, a ‘more negative’ MTC at beginning of cycle (BOC) may feasibly extend burnup and life of the core, thereby stretching the economics and assuring safety of the PWR. Recently, a new burnable absorber concept named “Burnable Absorber-Integrated control rod Guide Thimble” (BigT) has been proposed for the pressurized water reactor (PWR). In this work, the BigT BA is ap-plied to the existing OPR1000 core in order to reduce the BOC CBC of the core and to make the MTC more negative at HZP (Hot Zero Power).. In this thesis, actual OPR1000 core design of Hanbit Unit 3 Cycle 6 is used as a reference. All neutronic simulations in this thesis are completed by using the Monte Carlo SERPENT code with ENDF/B-VII.0 library. The BigT-loaded fuel assemblies are characterized in comparison with the conventional $Gd_2O_3$-loaded FAs. A detailed quarter core model is considered for the Monte Carlo core design and analysis and the equilibrium cycle is directly searched through repetitive cycle-wise depletions. For comparison, a conventional core design based on the existing $Gd_2O_3$ burnable absorber is also designed and evaluated in this work. Two low boron OPR1000 cores with BigT absorbers are subsequently modeled and evaluated in details. Preliminary core analyses indicate promising potentials of the BigT absorbers to realize the low boron OPR1000 cores as all vital neutronic parameters are within practical limits, while the BOC MTC can be noti...