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Journal Articles

IAEA benchmark calculations on control rod withdrawal test performed during Phenix End-of-Life experiments; Benchmark results and comparisons

Pascal, V.*; Prulhi$`e$re, G.*; Vanier, M.*; Fontaine, B.*; Devan, K.*; Chellapandi, P.*; Kriventsev, V.*; Monti, S.*; Mikityuk, K.*; Chenu, A.*; et al.

Proceedings of International Conference on the Physics of Reactors; The Role of Reactor Physics toward a Sustainable Future (PHYSOR 2014) (CD-ROM), 16 Pages, 2014/09

no abstracts in English

Journal Articles

Journal Articles

Benchmark calculations on control rod withdrawal tests performed during Phenix End-of-Life experiments

Pascal, V.*; Prulhi$`e$re, G.*; Fontaine, B.*; Devan, K.*; Chellapandi, P.*; Kriventsev, V.*; Monti, S.*; Mikityuk, K.*; Semenov, M.*; Taiwo, T.*; et al.

Proceedings of 2013 International Congress on Advances in Nuclear Power Plants (ICAPP 2013) (USB Flash Drive), 11 Pages, 2013/04

The control rod withdrawal test was one of the various Phenix End-of-Life tests performed in 2009. The main goal was to determine the impact of a rod insertion and/or extraction on the radial power distribution in the fissile core at nominal power. The framework of the Technical Working Group on Fast Reactors (TWG-FR) activities in IAEA, decided to launch a Coordinated Research Project (CRP), devoted to benchmarking analyses on the test. The CRP was performed by experts coming from CEA, ANL, IGCAR, IPPE, IRSN, JAEA, KIT and PSI. After a short description of the test conducted in the Phenix reactor, this paper presents some results obtained in the course of the CRP with special emphasis on control rod efficiencies and power deformation by subassemblies. The paper also discusses the discrepancies found when comparing calculated results with experimental data as well as some preliminary conclusions on the source of these discrepancies.

Journal Articles

A model of turbulence based on a new formulation of the turbulent Reynolds number

Kriventsev, V.; Ninokata, Hisashi; Yamaguchi, Akira; Ohshima, Hiroyuki

Journal of Fluid Mechanics, 0 Pages, 2003/12

A new model of turbulence is proposed for solving of Reynolds equations for fully-developed flow in a wall-bounded straight channelof arbitrary shape. The main idea of Multi-Scale Viscosity(MSV)model can be expressed in the followingphenomenological rule:A local deformation of axial velocity can generate the turbulence with theintensity that keeps the value of local turbulent Reynoldsnumber below some critical one. Therefore,in MSV,the only empirical parameter is the critical Reynolds number. The turbulent Revnolds numberis defined as Re=K/W,where K is kinetic energy and W is the work of friction/dissipation forces. MSV has been applied to the basic channel flows such as a circulartube,an infinitive plane chanael and an annulus. Calculated velocity profiles are in a good agreementwith expe

JAEA Reports

Gas entrainment in sodium cooled FBR: preliminary simulation for 1:1.8 scale water upper plenum experiment by AQUA-VOF

Kriventsev, V.; Ohshima, Hiroyuki

JNC TN9400 2003-085, 55 Pages, 2003/03

JNC-TN9400-2003-085.pdf:3.8MB

Prevention of gas entrainment from the free surface of sodium pool is one of the important problems to solve during feasibility study of commercial fast breeder reactor (FBR). Numerical calculation and experiment should clear clarify conditions when gas entrainment is likely to occur and help in developing the reactor design that can prevent it. In this report, we present the results of AQUA-VOF program that simulated 1:1.8 scale experimental model with water as working fluid. The main question to be answered is whether the effect of free surface is important for gas-entrainment occurrence prediction and whether it must be included in accurate, boundary-fit codes like SPIRAL. In addition, we present here preliminary considerations of gas entrainment phenomena and most important factors to study in experiment.

Journal Articles

Numerical Prediction of Secondary Flows in Complex Areas Using Concept of Local Turbulent Reynolds Number

Ohshima, Hiroyuki; Kriventsev, V.; Yamaguchi, Akira; Ninokata, Hisashi

Journal of Nuclear Science and Technology, 40(9), p.655 - 663, 2003/00

 Times Cited Count:4 Percentile:32.68(Nuclear Science & Technology)

A new model of turbulence is proposed for the estimation of Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape. The main idea of a Multi-Scale Viscosity (MSV) model can be expressed in the following phenomenological rule: A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of the local turbulent Reynolds number below some critical one. Therefore, in MSV, the only empirical parameter is the critical Reynolds number. MSV has been verified on the pipe flow and applied to simulation of turbulence-driven secondary flow in elementary cell of the infinitive hexagonal rod array. Since MSV can predict turbulent viscosity anisotropy in directions normal and parallel to the wall, it is capable to calculate secondary flows in the cross-section of the rod bundle. Calculations have shown that maximal intensity of secondary flow is about 1% of the mean axial velocity for the low-Re flo

Journal Articles

Numerical prediction of secondary flows in complex areas using concept of local turbulent Reynolds number

Kriventsev, V.; Ninokata, Hisashi; Yamaguchi, Akira; Ohshima, Hiroyuki

Proceedings of 10th International Conference on Nuclear Engineering (ICONE-10), 0 Pages, 2002/04

A new model of turbulence is proposed for the estimation of Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape. The main idea of a Multi-Scale Viscosity(MSV) model can be expressed in the following phenomenological rule:A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of the localturbulent Reynolds number below some critical one. Therefore,in MSV,the only empirical parameter is the critical Reynolds number. Since MSV can naturally predict turbulent viscosity anisotropy in directions normal and parallel to the wall,it is capable to calculate secondary flows in thecross-section of the rod bundle.

JAEA Reports

MSV:Multi-Scaler Viscosity Model of Turbulence

Kriventsev, V.

JNC TN9400 2001-053, 38 Pages, 2001/04

JNC-TN9400-2001-053.pdf:1.31MB

Multi-Scale Viscosity (MSV) model is proposed for estimation of the Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape. We assume that flow in an "ideal" channel is always stable, i.e.laminar, but turbulence is developing process of external perturbations cased by wall roughness and other factors. We also assume that real flows are always affected by perturbations of any scale lower than the size of the channel. The turbulence can be modeled in form of internal or "turbulent" viscosity increase. The main idea of MSV can be expressed in the following phenomenological rule: A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of local turbulent Reynolds number below some critical value. Here, local turbulent Reynolds number can be defined in two different ways: (1)as a product of value of axial velocity deformation for a given scale and generic length of this scale divided by accumulated value of laminar and turbulent viscosity of lower scales (2)as a ratio of the difference between total kinetic energy and "flat-profile" kinetic energy to the work of friction forces In MSV, the only empirical parameter is the critical Reynolds number that is estimated to be around 100 in the former case and about 8.33 in the later. MSV model has been applied to the fully-developed turbulent flows in straight channels such as a circular tube and annular channel. Friction factor and velocity profiles predicted with MSV are in a good agreement with numerous experimental data. The MSV model can be classified as "zero-order" integral model of turbulence. Because of simplicity, MSV can be easily implemented for calculation of fuIly-developed turbulent flows in straight channels of arbitrary shapes including fuel assemblies of nuclear reactors. The intent of this report is to summarize the progress made in the development of the model of turbulence. Since the final ...

Journal Articles

Numerical Accuracy of Temperature,Velocity and Pressure Distributions Predicted with Efficient Finite-Differencing(EFD) SCHEME

Kriventsev, V.; Yamaguchi, Akira

CHT'01 : Advances in Computational Heat Transfer II, p.469 - 476, 2001/00

A new Efficient Finite-Differencing(EFD)scheme has been applied to the sample problems of heat transfer and fluid flow.EFD is a "locally-exact" finite-difference scheme that uses one-dimensional analytical solution of convection-diffusion equation with linearized diffusion coefficient and source term. Fully-developed turbulent flow in a plane channel has been chosen as a sample. Energy, momentum and mass conservation equations have been solved in two-dimension rectangular calculation area positioned at the angle of45$$^{circ}$$ to the main flow direction. Results of numerical simulations are compared with the exact solution as well as with other popular finite-difference discretizations. This comparison has shown that EFD can significantly improve the accuracy of simulation or

JAEA Reports

Discretization of Convection-Diffusion Equations With Finite; Difference Scheme Derived From Simplified Analytical Solutions

Kriventsev, V.

JNC TN9400 2000-094, 35 Pages, 2000/09

JNC-TN9400-2000-094.pdf:1.1MB

Most of thermal hydraulic processes in nuclear engineering can be described by general convection-diffusion equations that are often can be simulated numerically with finite-difference method(FDM). An effective scheme for finite-difference discretization of such equations is presented in this report. The derivation of this scheme is based on analytical solutions of a simplified one-dimensional equation written for every control volume of the finite-difference mesh. These analytical solutions are constructed using linearized representations of both diffusion coefficient and source ter. As a result, the Efficient Finite-Differencing (EFD) scheme makes it possible to significantly improve the accuracy of numerical method even using mesh systems with fewer grid nodes that, in turn, allows to speed-up numerical simulation. EFD has been carefully verified on the series of sample problems for which either analytical or very precise numerical solutions can be found. EFD has been compared with other popular FDM schemes including novel, accurate (as well as sophisticated) methods. Among the methods compared were well-known central difference scheme, upwind scheme, exponential differencing and hybrid schemes of Spalding. Also, newly developed finite-difference schemes, such as the quadratic upstream (QUICK) scheme of Leonard, the locally analytic differencing(LOAD) scheme of Wong and Raithby, the flux-spline scheme proposed by Varejago and Patankar as well as the latest LENS discretization of Sakai have been compared. Detailed results of this comparison are given in this report. These tests have shown a high efficiency of the EFD scheme. For most of sample problems considered EFD has demonstrated the numerical error that appeared to be in orders of magnitude lower than that of other discretization methods. 0r, in other words, EFD has predicted numerical solution with the same given numerical error but using much fewer grid nodes. In this report, the detailed ....

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