Improved resource utilization by advanced burner reactors with breed-and-burn blankets

Abstract

A B S T R A C TPrevious studies assessed the feasibility of designing Sodium-cooled Fast Reactors (SFR) in a novel Seed-andBlanket (S&B) configuration in which a significant fraction of the core power is generated by a radial metallic thorium-fueled blanket that operates in the Breed-and-Burn (B&B) mode. The radiation damage on the cladding material in both seed and blanket does not exceed the presently acceptable constraint of 200 Displacements per Atom (DPA). This paper investigates a number of blanket fuel options other than metallic thorium fuel, including thorium dioxide fuel, thorium hydride fuel, thorium nitride Fully Ceramic Encapsulated (FCM) fuel, and Pressurized Water Reactor (PWR) Used Nuclear Fuel (UNF) after limited reprocessing. Since the neutron spectrum of the oxide fueled blanket is softer than that of the reference metallic thorium fueled blanket, it can discharge its fuel at an average burnup of around 110 MWd/kg versus 65 MWd/kg of the metallic thorium. The two thorium hydride fueled blankets feature an even softer neutron spectrum than the oxide fueled blanket and, therefore, a higher average discharge burnup -192 MWd/kg and 245 MWd/kg when the H-to-Th ratio is, respectively, 0.5 and 2.0. The FCM fuel is composed of SiC matrix and cladding that is expected to self-anneal the neutrons induced damage. With the assumption that the FCM fuel will indeed be proven not limited by radiation damage, its discharge burnup could be up to 482 MWd/kg. As a result, the corresponding thorium utilization is the highest of all options examined -close to 80 times the utilization of natural uranium in present Light Water Reactors (LWRs). The amount of Trans-Th isotopes accumulated in the thorium blanket per unit of generated electricity decreases as the blanket fuel is discharged at a higher burnup. Therefore, a higher discharge blanket burnup results in lower long-term radioactivity and radiotoxicity. It is also found that the 232 U/ 233 U ratio in the discharged thorium fuel is over 3 times higher in the thorium hydride than in the other blankets thus improving the thorium-hydride blanket's proliferation resistance. Softening of the blanket spectrum leads to softening of the seed spectrum region interfacing with the blanket and this enables to discharge the seed fuel at a higher average burnup. The higher discharge burnup of the seed fuel reduces the required reprocessing and fuel fabrication capacities per unit of generated electricity. The cores having softer neutron spectrum blankets also feature less positive feedback to sodium voiding and much more negative Doppler coefficient. When PWR UNF is used after limited reprocessing to fuel the blanket, the subcritical blanket driven by the excess neutrons from the seed can discharge this fuel at an average burnup of ∼120 MWd/kg. Combined with the burnup in the first stage PWRs, this two-stage energy system can achieve an accumulated uranium burnup of ∼170 MWd/kg. This increases the fuel utilization of natural uranium by a factor of three relative to oncethroug...

The neutronics effect of TRISO duplex fuel packing fractions and their comparison with homogeneous thorium‐uranium fuel

“…This is consistent with the findings in Figure 8C, which show that 235 U consumption can reach 83% for duplex fuel with a 20% packing fraction but only 71% for fuel with a 40% packing fraction. Higher burnup fuel is also advantageous due to lesser long‐term radioactivity and radiotoxicity 36 …”

“…Pin peaking in heterogeneous duplex thorium fuel tends to decrease as burnup increases, but pin peaking in homogeneous fuel tends to increase. 6,36,51 For example, for EFPY equivalent to 5 years, the pin power peaking for duplex fuel with 20% packing fraction would be lower than for all homogeneous fuels. Similarly, after 7 years, the pin power peaking for duplex fuel blocks with a packing fraction of 30% would be lower than for homogeneous fuel blocks with packing fractions of 30% and 40%.…”

Fuel cycle analysis of Advanced Burner Reactor with breed-and-burn thorium blanket

“…It is also possible to increase the 232 U/ 233 U ratio in the discharged fuel by softening the spectrum in the blanket and thereby increasing the blanket fuel proliferation resistance. The spectrum softening can be achieved by using thorium oxide or possibly thorium hydride rather than metallic thorium (Zhang et al, 2017b). Table 6 compares the natural resources required for the PWR-ABR, PWR-S&B and PWR systems per unit of electricity.…”

“…For example, if the blanket fuel cladding could withstand 400 DPA, the thorium utilization could be close to 17% (Zhang et al, 2017a). Alternatively, if the blanket is designed to have a softer spectrum by using thoria or thorium hydride, the thorium utilization of S&B reactors is estimated to increase to 11% and 19%, respectively (Zhang et al, 2017b).…”

Advanced Burner Reactors with Breed-and-Burn Thorium Blankets for Improved Economics and Resource Utilization

“…This high thorium utilization is due to the beneficial use of the excess neutrons from the seed that drive the blanket in a subcritical B&B mode. Significantly higher thorium utilization can be achieved by softening the blanket spectrum 44 and/or by the development of a cladding material capable of withstanding higher radiation damage (Sec. V.D).…”