Fast Reactor Physics and Computational Methods

Yang, Won Sik

doi:10.5516/net.01.2012.504

Cited by 70 publications

(24 citation statements)

References 39 publications

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“…The core is represented by a simplified "R-Z" model. The results from the R-Z model are in good agreement with those obtained when the core is 1 The TRU conversion ratio is defined as the ratio of the neutron capture rate by 238 modeled as a collection of hexagonal fuel assemblies (Heidet and Greenspan, 2013;Yang, 2012). Due to the limitation of the R-Z model, the control assemblies are not accounted for in this study.…”

Section: Modelingsupporting

confidence: 66%

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

Zhang

Fratoni

Greenspan

2018

Progress in Nuclear Energy

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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...

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Section: Modelingsupporting

confidence: 66%

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

Zhang

Fratoni

Greenspan

2018

Progress in Nuclear Energy

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“…As the neutron mean free path in fast reactors is larger than the lattice pitch, each burnup node for neutronic analysis is homogenized 18 ; the fuel, claddingstructural material, and coolant in the core are mixed preserving their volume fractions. For this feasibility study, the core is represented by a simplified radialsymmetric R-Z model.…”

Section: Breed-and-burn Thorium Blankets · Zhang Et Al 189mentioning

confidence: 99%

“…The results from the R-Z model are in good agreement with those obtained when the core is modeled as a collection of hexagonal fuel assemblies. 9,18 Because of the limitation of the R-Z model, control assemblies are not included in this study; this is expected to somewhat overestimate the core performance. The core is radially divided into three equal-volume concentric burnup zones for the seed and one burnup zone for each blanket batch; each radial zone is further divided into six axial burnup nodes.…”

Section: Breed-and-burn Thorium Blankets · Zhang Et Al 189mentioning

confidence: 99%

“…The value is calculated conservatively without considering an effective insertion of control rods that remain stationary during core expansion. 18 The radial expansion coefficient represents the reactivity change due to the expansion of the reactor supporting structure, which is induced by the grid temperature change when the inlet coolant temperature increases. The assembly pitch increases with temperature according to the thermal expansion coefficient of the structural material whereas the fuel and structure densities decrease to preserve the initial mass.…”

Section: Iiic Reactivity Coefficients and Kinetic Parametersmentioning

confidence: 99%

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

2017

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-This paper assesses the feasibility of designing seed-and-blanket (S&B) sodium-cooled fast reactor (SFR) cores to generate a significant fraction of the core power from radial thorium-fueled blankets that operate 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). The S&B core is designed to have an elongated seed (or driver) to maximize the fraction of neutrons that radially leak into the subcritical B&B blanket and reduce the neutron loss via axial leakage. A specific objective of this study is to maximize the fraction of core power generated by the B&B blanket that is proportional to the neutron leakage rate from the seed to the blanket. Since the blanket feed fuel is very inexpensive and requires no reprocessing and remote fuel fabrication, a larger fraction of power from the blanket will result in a lower fuel cycle cost per unit of electricity generated by the SFR core. It is found possible to design the seed of the S&B core to have a lower transuranics (TRU) conversion ratio (CR) than a conventional advanced burner reactor (ABR) core without deteriorating core safety. This is due to the unique synergism between a low CR seed and the B&B thorium blanket. The benefits of the synergism are maximized when using an annular seed surrounded by inner and outer thorium blankets. Two high-performance S&B cores are designed to benefit from the annular seed concept: (1) an ultra-long-cycle core having a CR = 0.5 seed and a cycle length of~7 effective full-power years (EFPYs) and (2) a high-transmutation core having a TRU CR of 0.0. The TRU transmutation rate of the latter core is comparable to that of the reference ABR with a CR of 0.5, and the thorium blanket can generate close to 60% of the core power. Because of the high blanket power fraction along with the high discharge burnup of the CR = 0 seed, the reprocessing capacity per unit of core power required by this S&B core is only approximately 1/6th that of the reference ABR core with a TRU CR of 0.5. Although the seed fuel CR is nearly zero, the burnup reactivity swing is low enough to enable a cycle length of more than 4 EFPYs. This is attributed to a combination of reactivity gain in the thorium blankets over the cycle and the relatively high heavy metal inventory. Moreover, despite the very low leakage, the S&B cores feature a less positive coolant reactivity coefficient and large enough negative Doppler coefficient even when using nonfertile fuel for the seed, because of the unique physics properties of the 233 U and Th in the thorium blankets. With the long cycles, the S&B SFR is expected to have a higher capacity factor, and therefore a lower cost of electricity, than conventional ABRs. The discharge burnup of the thorium blanket fuel is typically 70 MWd/kg such that the thorium fuel utilization is approximately 12 times that of natural uranium in light water reactors. A sensitivity study is subsequently un...

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“…In particular, liquid metal cooled fast spectrum reactors such as the sodium-cooled fast reactor (SFR) and lead-cooled fast reactor (LFR), coupled with a closed fuel cycle using recycling of actinides, can provide effective burning due to excellent neutronic properties such as a large number of excess neutrons produced by fission and a high fission-to-capture ratio [4][5][6]. With a closed fuel cycle, the nuclear park, which consists of PWRs and liquid metal cooled fast reactors, significantly reduces the required capacity of the final repositories for the nuclear wastes because only a small fraction of TRU nuclides lost during reprocessing and fuel fabrication go to the repositories and the surplus amount of uranium that is produced from the reprocessing of PWR spent fuel can be utilized in the fast reactors.…”

Section: Introductionmentioning

confidence: 99%

An Advanced Sodium-Cooled Fast Reactor Core Concept Using Uranium-Free Metallic Fuels for Maximizing TRU Burning Rate

You

2017

Sustainability

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Abstract:In this paper, we designed and analyzed advanced sodium-cooled fast reactor cores using uranium-free metallic fuels for maximizing burning rate of transuranics (TRU) nuclides from PWR spent fuels. It is well known that the removal of fertile nuclides such as 238 U from fuels in liquid metal cooled fast reactor leads to the degradation of important safety parameters such as the Doppler coefficient, coolant void worth, and delayed neutron fraction. To resolve the degradation of the Doppler coefficient, we considered adding resonant nuclides to the uranium-free metallic fuels. The analysis results showed that the cores using uranium-free fuels loaded with tungsten instead of uranium have a significantly lower burnup reactivity swing and more negative Doppler coefficients than the core using uranium-free fuels without resonant nuclides. In addition, we considered the use of axially central B 4 C absorber region and moderator rods to further improve safety parameters such as sodium void worth, burnup reactivity swing, and the Doppler coefficient. The results of the analysis showed that the final design core can consume~353 kg per cycle and satisfies self-controllability under unprotected accidents. The fuel cycle analysis showed that the PWR-SFR coupling fuel cycle option drastically reduces the amount of waste going to repository and the SFR burner can consume the amount of TRUs discharged from 3.72 PWRs generating the same electricity.

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Fast Reactor Physics and Computational Methods

Cited by 70 publications

References 39 publications

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

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

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

An Advanced Sodium-Cooled Fast Reactor Core Concept Using Uranium-Free Metallic Fuels for Maximizing TRU Burning Rate

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