scholarly journals WHOLE CORE COUPLING METHODOLOGIES WITHIN WIMS

2021 ◽  
Vol 247 ◽  
pp. 06006
Author(s):  
Brendan Tollit ◽  
Alan Charles ◽  
William Poole ◽  
Andrew Cox ◽  
Glynn Hosking ◽  
...  
Keyword(s):  
Fuel Assembly ◽  
Cross Sections ◽  
Diffusion Flux ◽  
Thermal Hydraulics ◽  
Reactor Physics ◽  
Fuel Performance ◽  
The Core ◽  
Small Modular Reactors ◽  
Core Solution ◽  
Multiphysics Modelling

The ANSWERS® WIMS reactor physics code is being developed for whole core multiphysics modelling. The established neutronics capability for lattice calculations has recently been extended to be suitable for whole core modelling of Small Modular Reactors (SMRs). A whole core transport, SP3 or diffusion flux solution is combined with fuel assembly resonance shielding and pin-by-pin differential depletion. An integrated thermal hydraulic solver permits differential temperature and density variations to feedback to the neutronics calculation. This paper presents new methodology developed in WIMS to couple the core neutronics to the integrated core thermal hydraulics solver. Two coupling routes are presented and compared using a challenging PWR SMR benchmark. The first route, called GEOM, dynamically calculates the resonance shielding and homogenisation with the whole core flux solution. The second coupling route, called CAMELOT, separates the resonance shielding and pincell homogenisation from the whole core solution via generating tabulated cross sections. Both routes can use the MERLIN homogenised pin-by-pin whole core flux solver and couple to the same integrated thermal hydraulic solver, called ARTHUR. Heterogeneous differences between the neutronics and thermal hydraulics are mapped via thermal identifiers for neutronics materials and thermal regions. The ability for the integrated thermal hydraulic solver to call an external code via a Fortran-C-Python (FCP) interface is also summarised. This flexible external coupling permits one way coupling to an external fuel performance code or two way coupling to an external thermal hydraulic code.

scholarly journals QUALIFICATION OF ANC9 GENERIC INSERT METHODOLOGY (GIM)

2021 ◽  
Vol 247 ◽  
pp. 02003
Author(s):  
Baocheng Zhang ◽  
Boyan D. Ivanov ◽  
Kevin Hoskins ◽  
Harish Huria ◽  
Andre Luiz Pereira Rebello
Keyword(s):  
Fuel Assembly ◽  
Temperature Coefficient ◽  
Power Distribution ◽  
Code System ◽  
Fuel Performance ◽  
Loading Cycle ◽  
Burnable Poison ◽  
The Core ◽  
Burnable Absorber

Discrete burnable poisons like the Wet Annular Burnable Absorber and Pyrex have been used in PWR core to improve core power distribution and provide more negative moderator temperature coefficient. The burnable absorber in the burnable poison rods burns fast and is completely gone after one cycle exposure in the core. Traditionally, the burnable poison rods are designed to be part of the fuel assembly. They are burned together with the fuel in the first loading cycle and discharged after one cycle. In recent years, different insertion scenarios of the burnable poison rods have been introduced in the PWR plants operation to improve the fuel performance, for instance, fresh burnable poison rods are inserted into a burned assembly; burned burnable poison rods stay in the original assembly or are replaced in a different assembly. A Generic Insert Methodology [1] was developed in Westinghouse and implemented in NEXUS/ANC9 code system. With this new methodology, ANC9 is able to follow the assembly history and model all types of absorber insert components for all kinds of insertion scenarios. An extensive methods validation and qualification effort has been completed by modeling different insertion cases. This paper provides details of the qualification cases along with the analysis of the results.

Fuel Assembly Bowing and Core Restraint Design in Fast Reactors

2014 ◽  
Author(s):  
J. J. Grudzinski ◽  
C. Grandy
Keyword(s):  
Fuel Assembly ◽  
Cross Sections ◽  
Fast Reactor ◽  
Nuclear Reactor ◽  
Reactor Core ◽  
Transient Behavior ◽  
Restraint System ◽  
The Core ◽  
Fuel Elements ◽  
Over Time

The reactivity of a fast spectrum nuclear reactor core is sensitive to changes in the fuel position. The core is formed by a hexagonal array of fuel assemblies which contain the fuel elements. The main structural components of the assemblies are thinwall hexagonal ducts. The fuel elements represent negligible stiffness in the fuel assembly compared to the ducts such that the ducts determine the location of the fuel. Thermal gradients across the fuel assembly cross sections create differential thermal expansion which causes the assemblies to bow. This bowing is proportional to the power to flow ratio such that it can become an important part of the reactivity change during reactor transients such as during reactor start-up, transient overpower (TOP), and unprotected loss of flow without scram (ULOF). In addition to these short term transients, thermal and fast neutron flux gradients within the core cause the assembly ducts to swell and bow over time due to irradiation creep and swelling. These latter effects produce permanent bowing of the ducts which change the reactivity over time and more importantly affect the mechanical forces required to refuel the core as the bowing is greater that the duct-to-duct clearance. Understanding these bowing responses is important to the understanding of both the transient behavior of a fast reactor as well as the refueling loads. Through proper design of the core restraint system, the bowing response can be engineered to provide negative feedback during the above mentioned transients such that it becomes part of the inherent safety of a fast reactor. Similarly, the opposing effects of creep and swelling can be manipulated to reduce the permanent core bowing deformations. We provide a discussion of the key features of analyzing and designing a core restraint system and provide a brief survey of the past work.

scholarly journals COUPLED TRANSIENT ANALYSIS OF A CORE WITH FUEL ASSEMBLY BOWING WITH A HYBRID CTF/DYN3D MODEL

2021 ◽  
Vol 247 ◽  
pp. 06036
Author(s):  
Y Périn ◽  
A Travleev ◽  
M Zilly
Keyword(s):  
Fuel Assembly ◽  
Cross Sections ◽  
Extreme Case ◽  
Nucleate Boiling ◽  
Reconstruction Method ◽  
Thermal Hydraulics ◽  
Safety Criterion ◽  
Coolant Pump ◽  
Active Length ◽  
Nodal Diffusion

Fuel assembly bowing is a known phenomenon observed in many PWR reactors all over the world. The phenomenon is relevant to safety as it can lead to increased water gaps between assemblies which results in higher pin peaking factors. The goal of the present study is to assess the effect of assembly bowing not only for stead-state nominal conditions but also during a transient. The selected transient is the loss of one reactor coolant pump as it can be limiting especially regarding the Departure from Nucleate Boiling (DNB) safety criterion. This study focuses on an extreme case where the bowing is simulated in the core hot assembly by keeping the water gap constant over the whole core active length. The resulting cross-sections and form functions obtained from a 2d infinite lattice model are used in the nodal diffusion code DYN3D applying its pin-by-pin reconstruction method. For the transient simulation, DYN3D is coupled with the thermal-hydraulics subchannel code CTF on the SALOME platform. Several modelling options are compared: nominal geometry for neutronics and thermal-hydraulics (TH); mixed: neutronics with increased water gap, TH with nominal geometry; and increased water gap for both neutronics and TH. The results confirm that the increased water gap should be considered in both models in order to reduce the conservatism.

Comparison between standard solid fuel and a new annular fuel performance in the core of a PWR

Kerntechnik ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. 161-168
Author(s):  
N. El-Sahlamy ◽  
M. Hassan ◽  
A. Khedr
Keyword(s):  
Solid Fuel ◽  
Fuel Performance ◽  
The Core

scholarly journals Nuclear Data for Reactor Physics: Cross sections and level densities in the actinide region

2010 ◽  
Vol 2 ◽  
pp. 12001 ◽  
Author(s):  
J.N. Wilson ◽  
S. Siem ◽  
S.J. Rose ◽  
A. Georgen ◽  
F. Gunsing ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Data ◽  
Reactor Physics ◽  
Level Densities

scholarly journals Morphology and Degradation of Multicompartment Microparticles Based on Semi-Crystalline Polystyrene-block-Polybutadiene-block-Poly(L-lactide) Triblock Terpolymers

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4358
Author(s):  
Nicole Janoszka ◽  
Suna Azhdari ◽  
Christian Hils ◽  
Deniz Coban ◽  
Holger Schmalz ◽  
...  
Keyword(s):  
Cross Sections ◽  
Ring Opening ◽  
Particle Diameter ◽  
Average Particle ◽  
Average Particle Diameter ◽  
Selective Degradation ◽  
The Core ◽  
Transmission Electron ◽  
And Control ◽  
Triblock Terpolymers

The confinement assembly of block copolymers shows great potential regarding the formation of functional microparticles with compartmentalized structure. Although a large variety of block chemistries have already been used, less is known about microdomain degradation, which could lead to mesoporous microparticles with particularly complex morphologies for ABC triblock terpolymers. Here, we report on the formation of triblock terpolymer-based, multicompartment microparticles (MMs) and the selective degradation of domains into mesoporous microparticles. A series of polystyrene-block-polybutadiene-block-poly(L-lactide) (PS-b-PB-b-PLLA, SBL) triblock terpolymers was synthesized by a combination of anionic vinyl and ring-opening polymerization, which were transformed into microparticles through evaporation-induced confinement assembly. Despite different block compositions and the presence of a crystallizable PLLA block, we mainly identified hexagonally packed cylinders with a PLLA core and PB shell embedded in a PS matrix. Emulsions were prepared with Shirasu Porous Glass (SPG) membranes leading to a narrow size distribution of the microparticles and control of the average particle diameter, d ≈ 0.4 µm–1.8 µm. The core–shell cylinders lie parallel to the surface for particle diameters d < 0.5 µm and progressively more perpendicular for larger particles d > 0.8 µm as verified with scanning and transmission electron microscopy and particle cross-sections. Finally, the selective degradation of the PLLA cylinders under basic conditions resulted in mesoporous microparticles with a pronounced surface roughness.

Solvent Assisted Coaxial-Electrospun Poly Methyl Methacrylate Polymer and Study of Resultant Fibers

2020 ◽  
Vol 18 (12) ◽  
pp. 905-909
Author(s):  
Arjun Satheesh ◽  
A. A. Alagiriswamy ◽  
S. Devanand ◽  
S. Nithiyanantham
Keyword(s):  
Methyl Methacrylate ◽  
Sem Analysis ◽  
Fiber Formation ◽  
Dimethyl Formamide ◽  
Poly Methyl Methacrylate ◽  
The Core ◽  
Pure Solvent ◽  
Core Solution ◽  
Polymer Dispersions

Electrospinning of dispersions with higher viscosity and limited flow may be carried out, based on the solvent assisted coaxial technique, where the flow of the core dispersion is supported by a free flowing sheath solvent. In the present work, the sheath solvents used are chloroform, toluene and dimethyl formamide and we discuss the fiber formation of Poly Methyl Methacrylate (PMMA) (dispersion-25 wt%). PMMA dispersed in chloroform is taken as the core solution and the sheath is pure solvent. The In-Situ effect of different sheath solvents in fiber formation at two different tip to collector distances are studied. The fibers formed are subjected to SEM analysis and the characteristics are analysed. The fiber formation of high viscos polymer dispersions makes the same materials subjectable to electrospinning and further applications.

Lanthanum Staining of Neurotubules in Axons from Cockroach Ganglia

1970 ◽  
Vol 7 (1) ◽  
pp. 217-231
Author(s):  
NANCY J. LANE ◽  
J. E. TREHERNE
Keyword(s):  
Cross Sections ◽  
Periplaneta Americana ◽  
Water Soluble ◽  
Clear Zone ◽  
Lanthanum Hydroxide ◽  
Small Water ◽  
The Core ◽  
Soluble Ions ◽  
Water Soluble Ions ◽  
Form Part

The axoplasm of the neurons of Periplaneta americana contains numerous neurotubules which are morphologically similar to the microtubules found in non-nervous tissues after sectioning or negative staining. In cross-sections of fixed material such tubules usually appear as electron-dense circles containing a less dense core and surrounded by a non-opaque ‘clear zone’. However, when cockroach ganglia are fixed and incubated in lanthanum hydroxide, the lanthanum is taken up intracellularly by the axoplasm of certain of the neurons and in these is found to stain the entire core of the neurotubules, as well as the clear zone. At least part of the wall of the tubules remains unstained and appears as a ring of non-opaque subunits against an electron-dense, lanthanum-stained background. Since lanthanum staining, under the conditions used here, is sometimes considered to demonstrate the presence of acid muco-polysaccharides, its uptake by the neurotubules may indicate that they contain carbohydrate as well as the protein that is generally considered to form part of the microtubular wall. Alternatively, the lanthanum could indicate the location of other anionic molecules, possibly undergoing extra- or intratubular translocation. The extent to which neurotubules could mediate movements of relatively small water-soluble ions and molecules is considered in relation to their diffusion through the polyanion matrix represented by the core of the tubules.

Main Steam Line Break Calculations Using a Coupled RELAP5/PARCS Model for the Ringhals-3 Pressurized Water Reactor

2008 ◽  
Author(s):  
Mathias Sta˚lek ◽  
Jo´zsef Ba´na´ti ◽  
Christophe Demazie`re
Keyword(s):  
Steady State ◽  
Fuel Assembly ◽  
Thermal Power ◽  
Steam Line ◽  
Pressurized Water ◽  
The Core ◽  
Different Types ◽  
Main Steam Line ◽  
Main Steam ◽  
Control Rods

A Main Steam Line Break (MSLB) is an important transient for Pressurized Water Reactors (PWR) due to the strong positive reactivity introduced by the over-cooling of the core. Since this effect is stronger when the Moderator Temperature Coefficient (MTC) has a large amplitude, a conservative result will be obtained for a high burnup of the fuel due to the more negative MTC late in the cycle. The calculations have been performed at a cycle burnup of 12.9742 GWd/tHM. The Swedish Ringhals-3 PWR is a three loop Westinghouse design, currently with a thermal power of 3000 MW. The PARCS model has 157 fuel assemblies of 8 different types. Four different types of reflector are used. The cross sections, and kinetic data were obtained from CASMO-4 calculations, using a cross section interface developed at the department. There are 24 axial nodes, and 2×2 radial nodes for each assembly. The transient option for calculating the effect of poisoning was used. The PARCS model has been validated against steady-state measurements from Ringhals-3 of the Relative Power Fraction (RPF) and of the core criticality. The RELAP5 model has 157 channels for the core which means that there is a one to one correspondence between the thermal hydraulics model and the neutronics model. There is eight axial nodes. Originally, the intention was to have 24 axial nodes but this proved not to work because of some limitation in RELAP5. There is currently no mixing between the different channels in the core. The feedwater, and turbines are modelled as boundary conditions. The stand-alone RELAP5 model has been validated against steady state measurements from Ringhals-3. A number of different cases were considered. In the first case, both the isolation of the feedwater for the broken loop, and all the control rods were assumed to work properly. For the second case one of the control rods was assumed to be stuck. The stuck rod was located in the fuel assembly with the highest power. This rod has also one of the highest rod worths. In the final case, the feedwater control valve for the broken loop was fully open. None of the cases led to any recriticality. The increase in power for each fuel assembly was also investigated. With the control rod located in the assembly with the highest power, the maximum power increase before scram turned out to be about 25% compared to the initial power.

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