Concepts and characteristics of a soluble-boron-free small modular reactor with centrally-shielded burnable absorbers

Abstract

This paper investigates the neutronic feasibility of an advanced 450MWth soluble-boron-free (SBF) small modular reactor (SMR) core adapting a newly proposed burnable absorber concept, centrally-shielded burnable absorber (CSBA). An optimal CSBA loading scheme is also proposed based on several assembly sensitivity analyses. Utilizing the unique features of CSBA designs, highly self-shielding effect, the core excess reactivity is significantly reduced and remains between 400pcm and 1200pcm throughout the cycle with comparable cycle length. Both axial and radial power peaking factors are very low, even though single enrichment of uranium, 4.95%, is uniformly used in the core. This demonstrates outstanding performance of CSBA. In addition, a 100%-to-15% power drop transient is simulated, indicating that the core can survive through such transient with the minimal reactivity of about 400pcm. It is also demonstrated that the SBF SMR core has inherent safety features with clearly negative coolant and fuel temperature coefficients at every burnup step. All calculations in this assessment of the advanced SBF SMR core are simulated by using Monte Carlo Serpent 2 code with the ENDF/B-7.1 nuclear library.