Shutdown margin for high conversion BWRs operating in Th-233U fuel cycle

In an effort to decarbonize the marine sector, there are growing interests in replacing the contemporary, traditional propulsion systems with nuclear propulsion systems. The latter system allows freight ships to have longer intervals before refueling; subsequently, lower fuel costs, and minimal carbon emissions. Nonetheless, nuclear propulsion systems have remained largely confined to military vessels. It is highly desirable that a civil marine core not to use highly enriched uranium, but it is then a challenge to achieve long core lifetime while maintaining reactivity control and acceptable power distributions in the core. The objective of this study is to design a civil marine core type of single batch small modular reactor (SMR) with low enriched uranium (LEU) (<20% 235 U enrichment), a soluble-boron-free (SBF) and using mixed D 2 O+H 2 O coolant for operation period over a 20 years life at 333 MWth. Changing the coolant properties is the way to alter the neutron energy spectrum in order to achieve a self-sustaining core design of higher burnup. Two types of LEU fuels were used in this study: micro-heterogeneous ThO 2 -UO 2 duplex fuel (18% 235 U enriched) and all-UO 2 fuel (15% 235 U enriched). 2D Assembly designs are developed using WIMS and 3D whole-core model is developed using PANTHER code. The duplex option shows greater promise in the final burnable poison design with high thickness ZrB 2 integral fuel burnable absorber (IFBA) while maintaining low, stable reactivity with minimal burnup penalty. For the final poison design with ZrB 2 , the duplex contributes ∼2.5% more initial

Section: Rod Cluster Control Assembly Worth (Rcca) Evaluationmentioning

confidence: 99%

Neutronic feasibility of civil marine small modular reactor core using mixed D2O+H2O coolant

Alam

Almutairi

Kumar

et al. 2020

“…The capture cross-sections of boron and Hf are large over a considerable range of neutron energies, making them suitable not only as control materials but also for neutron shielding. Each element in the AIC alloy has a significant capture cross-section in a certain energy range and the combination of elements covers the whole energy spectrum (Shaposhnik et al, 2014). In contrast, Gd and Cd exhibit high capture cross-sections only in the thermal energy range (Shaposhnik et al, 2014).…”

Section: Candidate Control Rod Materialsmentioning

confidence: 99%

“…Each element in the AIC alloy has a significant capture cross-section in a certain energy range and the combination of elements covers the whole energy spectrum (Shaposhnik et al, 2014). In contrast, Gd and Cd exhibit high capture cross-sections only in the thermal energy range (Shaposhnik et al, 2014). We therefore examine B C, Hf and AIC as candidate control rod materials for our marine core.…”

Section: Candidate Control Rod Materialsmentioning

confidence: 99%

Small modular reactor core design for civil marine propulsion using micro-heterogeneous duplex fuel. Part II: whole-core analysis

Alam

Ridwan

Kumar

et al. 2019

In an e↵ort to de-carbonise commercial freight shipping, there is growing interest in the possibility of using nuclear propulsion systems. In this reactor physics study, we seek to design a soluble-boron-free (SBF) and low-enriched uranium (LEU) (<20% 235 U enrichment) civil nuclear marine propulsion small modular reactor (SMR) core that provides at least 15 e↵ective full-power-years (EFPY) life at 333 MWth using 18% 235 U enriched micro-heterogeneous ThO 2 -UO 2 duplex fuel and 15% 235 U enriched homogeneously mixed all-UO 2 fuel. We use WIMS to develop subassembly designs and PANTHER to examine whole-core arrangements.The assembly-level behaviours of candidate burnable poison (BP) materials and control rods are investigated. We examine gadolinia (Gd 2 O 3 ), erbia (Er 2 O 3 ) and ZrB 2 integral fuel burnable absorber (IFBA) as BPs. We arrive at a design with the candidate fuels loaded into 13⇥13 assemblies using IFBA pins for reactivity control. Taking advantage of self-shielding e↵ects, this design maintains low and stable assembly reactivity with relatively little burnup penalty. Thorium-based duplex fuel o↵ers better performance than all-UO 2 fuel with all BP options considered. Duplex fuel has ⇠20% lower reactivity swing and, in consequence, lower initial reactivity than all-UO 2 fuel. The lower initial reactivity and smaller reactivity swing make the task of reactivity control through BP design easier in the thorium-rich duplex core. For control rod design, we examine boron carbide (B 4 C), hafnium, and Ag-In-Cd alloy. All the candidate materials exhibit greater rod worth for the duplex design. For both fuels, B 4 C has the highest rod worth. In particular, one of the major objectives of this study is to o↵er/explore a thorium-based candidate alternative fuel platform for the proposed marine core. It is proven by literature reviews that the ability of the duplex fuel was never explored in the context of a single-batch, LEU, SBF, long-life SMR core. In this regard, the motivation of this paper is to observe the neutronic performance of the proposed duplex fuel with respect to the UO 2 fuel and 'open the option' of designing the functional cores with both the duplex and UO 2 fuel cores.A companion paper will examine key physics and core safety analysis parameters in the whole-core environment.

“…However, it is notable that due to the strongly negative void reactivity coefficient, the RBWR-Th with pure thorium resource feed may experience issues with shutdown margin; design studies are presently ongoing to resolve this issue (Zhang et al, 2013;Shaposhnik et al, 2014). The radial and axial geometry of the RBWR-Th modeled by BNL is shown in Fig.…”

Section: Light Water Cooled Bwr Configurationmentioning

confidence: 99%

“…2012). These designs may require innovative approaches, such as those suggested by Shaposhnik et al (2014), to meet shutdown margin constraints. The objective of presenting both of these results is to illustrate the impact of important design considerations on potential fuel cycle parameters.…”

Section: Light Water Cooled Bwr Configurationmentioning

confidence: 99%

Sustainable thorium nuclear fuel cycles: A comparison of intermediate and fast neutron spectrum systems

Brown

Powers

Feng

et al. 2015

h i g h l i g h t s• Comparison of intermediate and fast spectrum thorium-fueled reactors.• Variety of reactor technology options enables self-sustaining thorium fuel cycles. • Fuel cycle analyses indicate similar performance for fast and intermediate systems.• Reproduction factor plays a significant role in breeding and burn-up performance. a b s t r a c t This paper presents analyses of possible reactor representations of a nuclear fuel cycle with continuous recycling of thorium and produced uranium (mostly U-233) with thorium-only feed. The analysis was performed in the context of a U.S. Department of Energy effort to develop a compendium of informative nuclear fuel cycle performance data. The objective of this paper is to determine whether intermediate spectrum systems, having a majority of fission events occurring with incident neutron energies between 1 eV and 10 5 eV, perform as well as fast spectrum systems in this fuel cycle. The intermediate spectrum options analyzed include tight lattice heavy or light water-cooled reactors, continuously refueled molten salt reactors, and a sodium-cooled reactor with hydride fuel. All options were modeled in reactor physics codes to calculate their lattice physics, spectrum characteristics, and fuel compositions over time. Based on these results, detailed metrics were calculated to compare the fuel cycle performance. These metrics include waste management and resource utilization, and are binned to accommodate uncertainties. The performance of the intermediate systems for this self-sustaining thorium fuel cycle was similar to a representative fast spectrum system. However, the number of fission neutrons emitted per neutron absorbed limits performance in intermediate spectrum systems.