Double-supply-frequency pressure pulsation in annular linear induction pump, part II: reduction of pulsation by linear winding grading at both stator ends

In the previous work, the authors showed that the double-supply-frequency pressure pulsation comes from a disturbance of the electromagnetic force occurring near the stator ends, and hence the pressure pulsation may be reduced by some way that suppresses this disturbance, e.g. by a winding grading at the stator ends. In the present work, an experiment and a numerical analysis are carried out to verify the effect of linear winding grading. The experimental data and the numerical results show that this type of grading is an effective way to reduce the pressure pulsation. In addition, the experimental data reveals that the linear winding grading improves the pump efficiency.     

Magnetohydrodynamic instability in annular linear induction pump: Part I. Experiment and numerical analysis

The present paper describes an experimental and analytical study of the magnetohydrodynamic instability arising in an annular linear induction pump. In the experiment, the instability was investigated in detail using an electromagnetic pump of flow rate 7 m³/min. The experimental results show that the instability occurs when the magnetic Reynolds number is larger than unity and the instability becomes more intensive as the slip increases. The instability is characterized by low frequency pressure pulsation, non-uniform magnetic field along the azimuth, wide-frequency vibration of the pump and pipe, fluctuation of winding voltage and current. The numerical analysis reveals that when the magnetic Reynolds number is larger than unity, an azimuthal non-uniformity of the applied magnetic field or of the sodium inlet velocity brings about sodium vortices and hence a low frequency pressure pulsation occurs. In addition, the non-uniformity causes a decrease of the developed pressure and sometimes a dip on the P–Q curve.     

Magnetohydrodynamic instability in annular linear induction pump: Part II. Suppression of instability by phase shift

In the previous work, the authors showed some detailed aspects of the magnetohydrodynamic instability arising in an annular linear induction pump: the instability is accompanied with a low frequency pressure pulsation in the range of 0–10 Hz when the magnetic Reynolds number is larger than unity; the low frequency pressure pulsation is produced by the sodium vortices that come from some azimuthal non-uniformity of the applied magnetic field or of the sodium inlet velocity. In the present work, an experiment and a numerical analysis are carried out to verify the pump winding phase shift that is expected as an effective way to suppress the instability. The experimental data shows that the phase shift suppresses the instability unless the slip value is so high, but brings about a decrease of the developed pressure. The numerical results indicate that the phase shift causes a local decrease of the electromagnetic force, which results in the suppression of the instability and the decrease of the developed pressure. In addition, it is exhibited that the intensity of the double-supply-frequency pressure pulsation is in nearly the same level in the case with and without the phase shift.     

A design and characteristic experiment of the small annular linear induction electromagnetic pump

A small-scale annular linear induction electromagnetic pump (ALIP) of the externally-supported-in-pipe type with a flowrate of 60 L/min and a developed pressure of 1.3 bar was developed for the circulation of sodium liquid metal. The developed pressure and the efficiency of the pump were analyzed on the change of the pump-design variables by using an equivalent circuit method. The pump designed was manufactured with the consideration to the material and functional requirements of a chemically-active sodium environment. The silicon–iron steel plates with high magnetic permeability and alumina-dispersion-strengthened-copper bands were used as cores and coils of the pump electromagnet for operating in a high temperature. Each turn of the coil was insulated by an asbestos band to protect against an electrical short at a high temperature. Stainless steel compatible with sodium was selected as a structural material. The completed pump was installed in the sodium experimental loop system. At temperatures of 150 °C and 350 °C, the performance of the ALIP (including the P–Q characteristic) was tested by changing the electrical input. The measurements showed that the pumping flowrate and the developed pressure were increased as the input current, voltage and power increased. On the other hand, the developed pressure was decreased with the increase of the flowrate. At the nominal input current and voltage, the developed pressure was 1.25 bar with the relative error of 3.8% compared with the prediction of 1.3 bar at 150 °C, where the flowrate was 54 L/min. The test on the pump showed good agreement with the theoretical calculation with some experimental errors.     

Design and preliminary test of an annular linear induction electromagnetic pump for a sodium-cooled fast reactor thermal hydraulic experiment

An annular linear induction electromagnetic pump (ALIP) with a flow rate of 2265 L/min and a developed pressure of 4 bar was designed and fabricated to test the performance of the components of a sodium-cooled fast reactor (SFR) in a sodium thermal hydraulic experimental loop. The design characteristic of the ALIP was calculated using the electrical equivalent circuit method typically used for analyzing linear induction machines. Preliminary tests, such as verification of the moving function using an annular Al pipe, were carried out. The linearity between the input voltage, current, and magnetic flux density was verified. The developed force demonstrated an increase proportional to the square of the input current, whereas the velocity was linearly proportional to the input current. The main design variables of the pump were calculated theoretically for the SFR thermal hydraulic experimental loop. The pump was optimized for the design variables including input frequency, and the characteristics of the optimized pump were compared with those of the pump at the commercially used frequency of 60 Hz.     

CFD analysis of a regular sector of the ITER vacuum vessel. Part I: Flow distribution and pressure drop

The 3D steady-state Computational Fluid Dynamics (CFD) analysis of the ITER vacuum vessel (VV) regular sector #5 is presented, starting from the CATIA models and using a suite of tools from the commercial software ANSYS FLUENT^®. The peculiarity of the problem is linked to the wide range of spatial scales involved in the analysis, from the millimeter-size gaps between in-wall shielding (IWS) plates to the more than 10 m height of the VV itself. After performing several simplifications in the geometrical details, a computational mesh with ～50 million cells is generated and used to compute the steady-state pressure and flow fields from a Reynolds-Averaged Navier–Stokes model with SST k-ω turbulence closure. The coolant mass flow rate turns out to be distributed 10% through the inboard and the remaining 90% through the outboard. The toroidal and poloidal ribs present in the VV structure constitute significant barriers for the flow, giving rise to large recirculation regions. The pressure drop is mainly localized in the inlet and outlet piping.     

Transient failure analysis of liquid-filled shells Part I: Theory

In this paper, the governing equations which consider dynamic fluid-structure interaction, modal coupling in both axial and circumferential directions, and dynamic buckling are derived. The various pressure components acting on the shell wall due to a seismic event are also analyzed. The matrix equation of motion for liquid-filled shells is obtained through a Galerkin/Finite Element discretization procedure. The modal coupling among the various combinations of axial and circumferential modes are identified with a particular reference to the fluid-structure system under seismic excitation. Finally, the equations for the dynamic stability analysis of liquid-filled shells are presented.     

Pu recycling in a full Th-MOX PWR core. Part I: Steady state analysis

Current practice of Pu recycling in existing Light Water Reactors (LWRs) in the form of U-Pu mixed oxide fuel (MOX) is not efficient due to continuous Pu production from U-238. The use of Th-Pu mixed oxide (TOX) fuel will considerably improve Pu consumption rates because virtually no new Pu is generated from thorium. In this study, the feasibility of Pu recycling in a typical pressurized water reactor (PWR) fully loaded with TOX fuel is investigated.Detailed 3-dimensional 100% TOX and 100% MOX PWR core designs are developed. The full MOX core is considered for comparison purposes. The design stages included determination of Pu loading required to achieve 18-month fuel cycle assuming three-batch fuel management scheme, selection of poison materials, development of the core loading pattern, optimization of burnable poison loadings, evaluation of critical boron concentration requirements, estimation of reactivity coefficients, core kinetic parameters, and shutdown margin.The performance of the MOX and TOX cores under steady-state condition and during selected reactivity initiated accidents (RIAs) is compared with that of the actual uranium oxide (UOX) PWR core.Part I of this paper describes the full TOX and MOX PWR core designs and reports the results of steady state analysis. The TOX core requires a slightly higher initial Pu loading than the MOX core to achieve the target fuel cycle length. However, the TOX core exhibits superior Pu incineration capabilities.The significantly degraded worth of control materials in Pu cores is partially addressed by the use of enriched soluble boron and B₄C as a control rod absorbing material. Wet annular burnable absorber (WABA) rods are used to flatten radial power distribution. The temperature reactivity coefficients of the TOX core were found to be always negative. The TOX core has a slightly reduced, as compared to UOX core, but still sufficient shutdown margin.In the TOX core β_eff is smaller by about a factor of two in comparison to the UOX core and even lower than that of the MOX core. The combination of small β_eff and reduced control materials worth may potentially deteriorate the performance under RIA conditions and requires an additional examination. The behavior of the considered cores during the most limiting RIAs, such as rod ejection, main steam line break, and boron dilution, is further investigated and reported in Part II of the paper.     

CFD analysis of the ITER first wall 06 panel. Part I: Model set-up and flow distribution

The first detailed Computational Fluid Dynamics (CFD) analysis of the FW06 panel of the ITER shielding blanket is presented in two companion papers. In this Part I we introduce the problem, define the model together with its input and discuss the results with particular reference to the hydraulics of the water coolant. The pressure drop across the panel is computed, together with the distribution of the flow among the different channels. Different design options are studied, with particular reference to the minimization of stagnation/recirculation regions.     

Measurement and analysis of the elongation of Zircaloy-2 pressure tubes in pickering generating station units 1 and 2

Zirconium alloy components in the core of CANDU ^* reactors change shape as a result of neutron irradiation. Dimensional changes in the pressure tubes of the reactors at the Pickering Generation Station have been measured as part of the general maintenance program carried out by Ontario Hydro. The techniques used to measure pressure tube elongation, and the results obtained for Pickering units 1 and 2 over the past six years, are presented. The data are interpreted using a detailed analysis which accounts for the manner in which the elongating pressure tubes interact with the calandria tubes and end shields of the reactor. The free elongation rate obtained from the analysis has been used, with other pressure tube data, to calculate the material dependent constants in the equations which define irradiation enhanced creep and growth in the cold-worked Zircaloy-2 pressure tubes of the Pickering unit 1 and 2 reactors.     

Vibrations of probe used for the defect detection of helical heating tubes in a fast breeder reactor: Part 2. Vibration analysis and numerical simulations

A detection of a defect of a helical heating tube installed in the fast breeder reactor “Monju” in Japan is done by a feeding of an eddy current testing (ECT) probe with magnetic sensor into the tube. An undesirable vibration of the ECT probe always happens under a certain condition and makes the inspection difficult. Several characteristics of the vibration have been made clear by some experiments using a mock-up, but the essential factor of the vibration is still unclear. In this paper, a numerical simulation of the vibration is implemented on the assumption that the vibration is caused by Coulomb friction. An analytical model, which is obtained as a lumped mass model, is a large-scale non-linear vibration system and many computational costs are ordinarily required to carry out the simulations. The Transfer Influence Coefficient Method is applied so that the simulation is efficiently carried out. The results of simulation qualitatively agree well with the experimental results. It confirms the validity of the assumption that the vibration is caused by Coulomb friction.     

Deformation of bitumen based porous material: Experimental and numerical analysis

This paper presents a theoretical and experimental work aiming at understanding the mechanical behaviour of Bituminized Waste Product (BWP). This material is considered for this purpose as a mixture of bitumen and crystals of sodium nitrate. For BWP, both bitumen and crystals contribute to the creep deformations. In this study, an attempt is made to develop an elasto-viscoplastic model that describes the creep behaviour of BWP considering the constituents’ creep behaviour.An experimental program has been set up to get insight in the material response. The elasto-viscoplastic constitutive model has been implemented into a finite element program. The modelling results have been compared with the experimental data.     

VVER机组松脱部件监测系统设计差异及功能验证

介绍了田湾核电站水-水高能反应堆（VVER）机组松脱部件监测系统（LPMS）的设计和设备结构组成,描述了其设计与美国核管会（NRC）RG1.133相关条款要求的差异。基于这些差异以及VVER机组的特殊性,分析了拟采取的改进措施存在的困难和不利影响。为执行与NRC RG1.133中安全要求相当的功能,在田湾核电站3号机组调试阶段开展了LPMS系统的功能补充试验,获取与压力容器相关的传感器信号的响应,验证了目前的传感器布置方式能满足NRC RG1.133的设计要求。      

Validation of the sub-channel code F-COBRA-TF: Part I. Recalculation of single-phase and two-phase pressure loss measurements

The present paper deals with recalculations of single-phase and two-phase pressure loss measurements with the advanced two-phase, three-field sub-channel code F-COBRA-TF. Thereby, experimental data of both the OECD/NRC BFBT benchmark and in-house tests in AREVA NP's KATHY loop are used. The main goal of this paper is not to focus on a special new model or correlation but to give an overview how a complete pressure loss calculation for practical purposes can be carried out being based on a simplified and straightforward method to estimate sub-channel spacer pressure loss coefficients on the one hand and an advanced sub-channel code on the other hand.The pressure loss coefficients are calculated analytically and calibrated at available measurements of total single-phase bundle pressure loss. Thus, they are not adapted to any two-phase measurement and also do not depend on the sub-channel code they are used in.The results of the recalculations of the measurements especially demonstrate the capability of a three-field code to predict both single-phase and two-phase pressure losses with high accuracy, whereas the code is not based on conventional pressure loss correlations using two-phase multipliers but rather on interfacial friction correlations for each flow regime. Thereby, the F-COBRA-TF standard models - which are usually applied for all sorts of calculations (pressure loss, void distribution, lateral mixing, critical heat flux, etc.) - were used. It was not necessary to do special code tuning with respect to certain experiments.     

Thermo-hydraulic instabilities in parallel boiling channel systems: Part 1. A non-linear and a linear analytical model

Two analytical models are proposed to analyze density wave instability. One is a non-linear analytical model (PARALLEL) solved for the time elapsed and is applicable to systems with more than three channels with the same flow conditions or different flow conditions between channels. The other is a linear model (PARCOMP) solved on a complex plane and is applicable to two channel systems with or without different flow conditions. The results obtained by these models are compared with the density wave instability occurring in a twin parallel boiling channel system. The PARALLEL is applied to systems with more than three channels with the same flow conditions, and the results are compared with those in a twin channel system. Finally, the effects of the different flow conditions on the stable flow limit in a system with more than three channels are investigated analytically using PARALLEL. The approximation method by a linear model is examined and proposed to evaluate the stable flow limit in this case.     

Flow excursion instability in downward flow systems: Part I. Single-phase instability

A procedure for predicting the onset of flow excursion instability in downward flows at low-pressure and low-flow conditions without boiling is presented. It is generally accepted that the onset of significant void in subcooled boiling precedes, and is a precondition to, the occurrence of static flow instability. A detailed analysis of the pressure drop components for a downward flow in a heated channel reveals the possibility of unstable transition from single-phase flow to high-quality two-phase flow, i.e. flow excursion. Low flow rate and high subcooling are the two important conditions for the occurrence of this type of instability. The unstable transition occurs when the resistance to the downward flow caused by local (orifice), frictional, and thermal expansion pressure drops equalizes the driving force of the gravitational pressure drop. The inclusion of the thermal expansion pressure drop is essential to account for this type of transition. Experimental data have still to be produced to verify the prediction of the present analysis.     

Digital Computers in Candu Safety Systems Part I History and Concepts

For many years, digital computers have been used in CANDU (CANada Deuterium Uranium) reactors for direct digital control as well as control room functions such as alarm annunciation, data logging and the display of operating data on the control panels. However, until recently computers were not used in the special safety systems. This paper examines the increasing role computers are playing in CANDU safety systems, especially the two shutdown systems. The reasons for this strong trend toward increased use of computers are outlined and recent designs are described, with special emphasis on system concepts. A companion paper (Part II) describes implementation details for the safety system computer applications and summarizes the experience gained so far during development and operation of these systems.     

Analysis of tensile deformation and failure in austenitic stainless steels: Part I - Temperature dependence

This paper describes the temperature dependence of deformation and failure behaviors in the austenitic stainless steels (annealed 304, 316, 316LN, and 20% cold-worked 316LN) in terms of equivalent true stress-true strain curves. The true stress-true strain curves up to the final fracture were calculated from tensile test data obtained at −150 to 450 °C using an iterative finite element method. Analysis was largely focused on the necking and fracture: key parameters such as the strain hardening rate, equivalent fracture stress, fracture strain, and tensile fracture energy were evaluated, and their temperature dependencies were investigated. It was shown that a significantly high strain hardening rate was retained during unstable deformation although overall strain hardening rate beyond the onset of necking was lower than that of the uniform deformation. The fracture stress and energy decreased with temperature up to 200 °C and were nearly saturated as the temperature came close to the maximum test temperature 450 °C. The fracture strain had a maximum at −50 to 20 °C before decreasing with temperature. It was explained that these temperature dependencies of fracture properties were associated with a change in the dominant strain hardening mechanism with test temperature. Also, it was seen that the pre-straining of material has little effect on the strain hardening rate during necking deformation and on fracture properties.     

Fatigue cracks in Eurofer 97 steel: Part I. Nucleation and small crack growth kinetics

Fatigue crack nucleation and growth were studied in the Eurofer 97 ferritic-martensitic steel at room temperature. Cylindrical specimens with a shallow notch and no artificial crack starters were used. The constant strain amplitude cycling was adopted. First fatigue cracks nucleate at about 5% of the fatigue life along the surface slip bands. If a crack overcome the barrier of the first high angle boundary, its growth is regular and an exponential growth law is observed. This law may be used for the residual fatigue life prediction based on the small crack growth kinetics.