PWR Integral Gadolinia Burnable Absorber Loading Design In A Once-Through Core Reactivity Swing Minimization Assessment

UO2–Gd2O3 fuel is mostly used as a burnable absorber fuel in the form of a homogenous mixture of Gd2O3 and UO2. More effective reactivity control can be achieved by lumping Gd2O3 within the UO2 because this enhances the spatial self-shielding factor of the burnable absorber fuel. The fabrication of lumped burnable absorber fuel containing lumped Gd2O3 spherical particles or compacts has been experimentally demonstrated using yttrium-stabilized zirconia (YSZ) as a UO2 fuel surrogate. Interfacial cracks or gaps forming under the interfacial stress that develops during the fabrication of the fuel can be eliminated by controlling the initial density of the lumped Gd2O3. In this study, this interfacial stress during the fabrication process was simulated using finite element methods. The effect of the size, shape, and initial density of the lumped Gd2O3 on the distribution and magnitude of the interfacial stress was investigated. The addition of Gd2O3 spherical particles resulted in a lower and more uniform interfacial stress distribution than the addition of cylindrical Gd2O3 compacts. The interfacial stress was increased with increasing Gd2O3 size and initial density. The calculated interfacial stress was compared with experimental results to estimate the threshold stress for crack development in a lumped burnable absorber fuel.

Download Full-text

A Finnish District Heating Reactor: Neutronics Design and Fuel Cycle Simulations

10.1115/icone28-64347 ◽

2021 ◽

Author(s):

Jaakko Leppänen ◽

Ville Valtavirta ◽

Riku Tuominen ◽

Antti Rintala ◽

Unna Lauranto

Keyword(s):

Fuel Cycle ◽

Natural Circulation ◽

Reactor Core ◽

District Heating ◽

Research Centre ◽

Computational Framework ◽

Conceptual Design Phase ◽

Burnable Absorber ◽

Control Rods ◽

Type Fuel

Abstract The development of a small PWR for district heating applications has been started at VTT Technical Research Centre of Finland, and the pre-conceptual design phase was completed by the end of year 2020. The heating plant consists of one or multiple 50 MW reactor modules, operating on natural circulation at around 120°C temperature. This paper presents the neutronics design and fuel cycle simulations carried out using VTT’s Kraken computational framework. The reactor is operated without soluble boron, which together with low operating temperature and pressure brings certain challenges to the use of control rods and burnable absorber. The reactor core is loaded with 37 truncated AP1000-type fuel assemblies with 2.0–3.0% fuel enrichment and erbium burnable absorber. The resulting cycle length is around 900 days. The results show that the criteria set for stability, reactivity control and thermal margins are fulfilled. More importantly, it is concluded that the new Kraken framework is a viable tool for the core design task.

Download Full-text

Microstructure-dependent rate theory model of defect segregation and phase stability in irradiated polycrystalline LiAlO2

Modelling and Simulation in Materials Science and Engineering ◽

10.1088/1361-651x/ac4001 ◽

2021 ◽

Author(s):

Shenyang HU ◽

Yulan Li ◽

Shunli Shang ◽

Zi-Kui Liu ◽

Douglas Burkes ◽

...

Keyword(s):

Phase Stability ◽

Release Kinetics ◽

Field Method ◽

Thermomechanical Properties ◽

Theory Model ◽

Phase Field Method ◽

Rate Theory ◽

Kinetic Properties ◽

Burnable Absorber ◽

Defect Mobility

Abstract Gamma lithium aluminate (LiAlO2) is a breeder material for tritium and is one of key components in a tritium-producing burnable absorber rod (TPBAR). Dissolution and precipitation of second phases such as LiAl5O8 and voids are observed in irradiated LiAlO2. Such microstructure changes cause the degradation of thermomechanical properties of LiAlO2 and affect tritium retention and release kinetics, and hence, the TPBAR performance. In this work, a microstructure-dependent model of radiation-induced segregation (RIS) has been developed for investigating the accumulation of species and phase stability in polycrystalline LiAlO2 structures under irradiation. Three sublattices (i.e., [Li, Al, V]I [O, Vo]II [Lii, Ali, Oi, Vi]III), and concentrations of six diffusive species (i.e., Li; vacancy of Li or Al at [Li, Al, V]I sublattice, O vacancy at [O, Vo]II sublattice, and Li, Al and O interstitials at [Lii, Ali, Oi, Vi]III interstitial sublattices; are used to describe spatial and temporal distributions of defects and chemistry. Microstructure-dependent thermodynamic and kinetic properties including the generation, reaction, and chemical potentials of defects and defect mobility are taken into account in the model. The parametric studies demonstrated the capability of the developed RIS model to assess the effect of thermodynamic and kinetic properties of defects on the segregation and depletion of species in polycrystalline structures and to explain the phase stability observed in irradiated LiAlO2 samples. The developed RIS model will be extended to study the precipitation of LiAl5O8 and voids and tritium retention by integrating the phase-field method.

Download Full-text

Feasibility study on burnable absorber for FORSETI to reduce productions of Pu238 and Pu241

Journal of Nuclear Science and Technology ◽

10.1080/00223131.2019.1659876 ◽

2019 ◽

Vol 57 (1) ◽

pp. 57-67

Author(s):

Satoshi Takeda ◽

Takanori Kitada

Keyword(s):

Feasibility Study ◽

Burnable Absorber

Download Full-text

Modeling the Spectral History in the Depletion of a PWR Core

18th International Conference on Nuclear Engineering: Volume 2 ◽

10.1115/icone18-29748 ◽

2010 ◽

Author(s):

I. Bilodid

Keyword(s):

Cross Sections ◽

Uranium Oxide ◽

Reactor Core ◽

Actual Distribution ◽

History Effects ◽

Fuel Assemblies ◽

Burnable Absorber ◽

Uranium Plutonium ◽

Moderator Density ◽

Local Parameters

Codes for reactor core calculations use few-group cross sections (XS) which depend on local burnup, given in terms of the energy produced per fuel mass (MWd/kgHM). However, a certain burnup value can be reached under different spectral conditions depending on moderator density and other local parameters. Neglecting these spectral effects, i.e. applying the summary-burnup value only, can cause considerable errors in the calculated power density. This paper describes a way to take into account spectral-history effects. It is shown that the respective XS correction linearly depends on the actual Pu-239 concentration. The applicability of the method was proved not only for usual uranium oxide fuel, but also for mixed uranium/plutonium oxide (MOX) and fuel assemblies with burnable absorber. The code DYN3D was extended by new subroutines which calculate the actual distribution of Pu-239 in the core and apply a spectral-history correction for the XS.

Download Full-text

Development of Safety-Enhanced Fast Reactor by Using Minor Actinide Bearing Internal Blanket

Volume 2: Nuclear Policy; Nuclear Safety, Security, and Cyber Security; Operating Plant Experience; Probabilistic Risk Assessments; SMR and Advanced Reactors ◽

10.1115/icone2020-16746 ◽

2020 ◽

Author(s):

Sho Fuchita ◽

Satoshi Takeda ◽

Koji Fujimura ◽

Toshikazu Takeda ◽

Kazuhiro Fujimata

Keyword(s):

Fast Reactor ◽

Inner Core ◽

Reactor Core ◽

Minor Actinide ◽

Core Damage ◽

Burnable Absorber ◽

Sensitivity Studies ◽

Core Height ◽

Gas Expansion ◽

Control Rods

Abstract For a 750MWe sodium-cooled fast reactor core using MOX fuel, safety-enhancement measures have been studied to reduce the risk of core damage under unprotected loss of flow (ULOF) and unprotected transient overpower (UTOP) accidents. As passive measures the followings are considered: 1) adoption of the axial heterogeneous core configuration with sodium plenum and Gas Expansion Modules (GEMs) to lower sodium void reactivity for ULOF, and 2) addition of minor actinides (MAs) as burnable absorber and fertile nuclides to the internal blanket in the inner core to reduce burnup reactivity for UTOP. In this study, configurations of the safety-enhanced core were optimized based on sensitivity studies as follows. Firstly, effects of 1) above on the sodium void reactivity were evaluated by changing the inner core height, B-10 content of the upper shield, GEMs, and standby position of the backup control rods, which are the dominant factors of core behavior in the event of ULOF. Secondly, the effects of 2) above on the burnup reactivity were evaluated by changing the MA content in the internal blanket and the burnup period, which are the dominant factors of UTOP. Finally, by utilizing sensitivity analysis results, the safety-enhanced core which satisfies the provisional design goals has been developed. This core has negative sodium void reactivity and burnup reactivity less than 1 $.

Download Full-text