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  • 1.
    Bjerkén, Christina
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Kinetics of orientational phase ordering near line defects in crystals2015In: International Conference on Solid-Solid Phase Transformation in Inorganic Materials (PTM 2015), TMS PTM-2015: A combination print-CD volume , 2015, p. 36-36Conference paper (Other academic)
    Abstract [en]

    General properties of directed ordering near line defects in elastic crystals undergoing phase transition are studied using the two-component time-dependent Ginzburg-Landau equation. Upon quenching the system below its transition point, the temporal evolution of the order parameter in the vicinity of the defect is evaluated. The development of vortices is explored and their interaction with the structural defect is examined. Finally, phase transitions in improper ferroelectrics in the context of the model are discussed.

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  • 2.
    Bjerkén, Christina
    et al.
    Malmö högskola, School of Technology (TS).
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Nucleation of second-phase near elastic defects in crystalline solids2011In: Proceedings of MS&T'11, TMS , 2011Conference paper (Other academic)
    Abstract [en]

    The problem of heterogeneous nucleation of second-phase in alloys in the vicinity of elastic defects is considered. The defect can be a dislocation line or a crack tip residing in a crystalline solid. We use a compressible Ising-like model, represented by the Ginzburg-Landau equation, to describe the spatiotemporal evolution of the order parameter in the environs of the defect. The model accounts for the elasticity of the solid and the interaction of order parameter field with the elastic field of the defect. A finite volume numerical method is used to solve the governing partial differential equation for the order parameter. We examine the nature of the phase transition and discuss the phase diagram topology near and away from the defect. We discuss our calculations in light of observations of formation of hydrides in zirconium and titanium alloys.

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  • 3.
    Bjerkén, Christina
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Oriented ordering near line defects in crystals2017In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 97, no 27, p. 2437-2467Article in journal (Refereed)
    Abstract [en]

    General properties of directed ordering near line defects, in particular an edge dislocation, in elastic crystals undergoing phase transition are studied using the two-component time-dependent Ginzburg-Landau equation in two dimensions or 2D-XY model. The associated Landau potential comprises a sixth-order term, cubic anisotropy terms and the field of the dislocation. In thermodynamic equilibrium, the phase diagram for the model is delineated. Upon quenching the system below its transition point, the temporal evolution of the order parameter components in the vicinity of the defect is numerically evaluated. The development of vortices, emanated from the model, is explored and their interaction with the dislocation is examined. The dislocation produced a vortex free circular region whose diameter grew almost linearly with time. The time-dependence of vortex density for various settings of the Landau potential coefficients are evaluated. The vortex density ( in 2D) decreased inversely with time, albeit faster in the absence of dislocation. By computing the two-point correlation function, we established that the dynamic scaling law is satisfied for the considered model if the distance is scaled by L = t(1/2) or by its half-width L-1/2 for a dislocation free crystal. Finally, phase transitions in improper ferroelectrics in the context of the model are discussed.

  • 4.
    Bjerkén, Christina
    et al.
    Malmö högskola, School of Technology (TS).
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Phase ordering kinetics of second-phase formation near an edge dislocation2014In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 94, no 6, p. 569-593Article in journal (Refereed)
    Abstract [en]

    The time-dependent Ginzburg-Landau (TDGL) equation for a single component non-conservative structural order parameter is used to study the spatio-temporal evolution of a second phase in the vicinity of an edge dislocation in an elastic crystalline solid. A symmetric Landau potential of sixth-order is employed. Dislocation field and elasticity modify the second-order and fourth-order coefficients of the Landau polynomial, respectively, where the former makes the coefficient singular at the origin. The TDGL equation is solved numerically using a finite volume method, where a wide range of parameter sets is explored. Computations are made for temperatures both above and below the transition temperature of a defect-free crystal Tc0. In both cases, the effects of the elastic properties of the solid and the strength of interaction between the order parameter and the displacement field are examined. If the system is quenched below Tc0, a steady state is first reached on the compressive side of the dislocation. On the tensile side, the growth is held back. The effect of thermal noise term in the TDGL equation is studied. We find that if the dislocation is introduced above Tc0, thermal noise supports the nucleation of the second phase, and a steady state will be attained earlier than if the thermal noise was absent. For a dislocation-free solid, we have compared our numerical computations for a mean-field (spatially averaged) order parameter versus time with the late time growth of the ensemble-averaged order parameter, calculated analytically, and find that both results follow upper asymptotes of sigmoid curves.

  • 5. Blomqvist, Jacob
    et al.
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Bjerkén, Christina
    Malmö högskola, School of Technology (TS).
    A First Principle Atomistic Pre-study of a Multiscale Model of Hydride Induced Embrittlement in Zirconium2010Conference paper (Other academic)
    Abstract [en]

    Hydrogen induced embrittlement and associated cracking effects in Zirconium alloys impose a serious problem, for example, within the nuclear industry where these materials are used in a range of applications, including fuel claddings. To get a fuller understanding of the hydrogen diffusion, hydride formation and phase transformations taking place at conditions of external stress and at elevated temperature it is crucial to augment experimental measurements with multi-level modelling. It is, for example, possible to simulate hydride phase-transformation trough phase-field calculations[1]. In order to get accurate results from these calculations, however, it is important to have basic physical information, such as interfacial energies and elastic constants. The latter were obtained completely from first principle calculations of density functional theory. In pure zirconium, at low hydrogen concentrations and at low temperatures, hydrogen atoms are dissolved into the matrix and preferentially occupy tetrahedral sites within the thermodynamically stable aZr hexagonal closed packed unit cell. At higher concentrations the various face centred cubic and tetragonal hydride phases start to form. Using the plane-wave code DACAPO, within the generalized gradient approximation, the lattice parameters and the ionic positions of bulk aZr, dZrHx and gZrHx were relaxed with respect to total energies. The formation energies as well as bulk moduli were then obtained by fitting total energies as a function of lattice parameters with a 3rd or 4th order polynomial. By comparing the present results with previous calculations and experiments it was possible to validate the methods for further use. The results, thus, comprise a foundation and serves to verify methods and codes. The next step is to compute more complex properties such as surface free energies, or interfacial energies, of bi-phase Zr-H systems, so that the full multiscale model can be implemented. 1. V. Vaithyanathan et al., Acta Materialia 52 (2004) p. 2973

  • 6.
    Blomqvist, Jakob
    et al.
    Malmö högskola, School of Technology (TS).
    Olsson, Pär
    Malmö högskola, School of Technology (TS).
    Steuwer, Axel
    Maimaitiyili, Tuerdi
    Malmö högskola, School of Technology (TS).
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Bjerkén, Christina
    Malmö högskola, School of Technology (TS).
    Towards a multiscale understanding of hydride induced embrittlement in zirconium and titanium: theory and experiments2013In: Thermec' 2013 Rio Hotel Las Vegas USA, Abstract book, 2013, article id 140Conference paper (Other academic)
  • 7.
    Jernkvist, Lars Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Multi-field modelling of hydride forming metals: part I: model formulation and validation2014In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 85, p. 363-382Article in journal (Refereed)
    Abstract [en]

    A computational model for hydrogen transport, hydrogen induced deformation and fracture in metals that form binary hydrides, such as Zr and Ti alloys, is presented. The model uses a continuum description of the two-phase (metal + hydride) material, and solves the multi-field partial differential equations for temperature and stress-directed hydrogen diffusion together with mechanical equilibrium in a three-dimensional finite element setting. Point-kinetics models are used for metal-hydride phase transformation and stress-directed orientation of hydride precipitates, while a cohesive zone fracture model caters for initiation and propagation of cracks. The local fracture properties of the hydrided material are correlated to the calculated local concentration and orientation of the hydride precipitates, which have a strong embrittling effect on the material. In Part I of this two-part paper, we present sub-models applied for the aforementioned phenomena together with a detailed description of their numerical implementation. The applicability of the model is then demonstrated by simulating five independent experiments on hydrogen transport, metal-hydride phase transformation and stress-directed hydride orientation in zirconium alloys. Based on the results, we conclude that the model captures these phenomena over a wide range of thermo-mechanical loading conditions, including thermal cycling. Part II of the paper is focussed on fracture, and includes details on the fracture model and its validation against tests and experiments on initiation and propagation of hydride induced cracks.

  • 8. Jernkvist, Lars Olof
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    A Numerical Model for Delayed Hydride Cracking of Zirconium Alloy Cladding Tubes2007In: SMiRT 19 Transactions;C01/3, International Association for Structural Mechanics in Reactor Technology , 2007, article id C01/3Conference paper (Other academic)
    Abstract [en]

    An integrated numerical model for hydride-induced failure of zirconium alloys is presented. The model solves the time-dependent and interconnected problems of temperature- and stress-directed diffusion of hydrogen, metal-hydride phase transformation, stress-directed hydride orientation, hydrogen-induced expansion and fracture within a two- dimensional finite element framework. The finite element method allows representation of arbitrary two-dimensional geometries and thermo-mechanical loading conditions. The model has a wide range of application, but is intended primarily for analyses of delayed hydride cracking in cladding tubes of light water reactor nuclear fuel rods.

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  • 9.
    Jernkvist, Lars Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali R
    Malmö högskola, School of Technology (TS). Malmö högskola, Faculty of Technology and Society (TS).
    Modeling stress and temperature history effects on the initiation of hydride cracks at blunt flaws in Zr-2.5%Nb pressure tubes2013Conference paper (Other academic)
    Abstract [en]

    We study initiation of hydride induced cracks in Zr-2.5%Nb CANDU reactor pressure tubes, containing blunt notches and exposed to temperature cycles by use of a novel computational model. The model uses a continuum description of the two-phase (alpha-phase metal plus delta-phase hydride) material, and solves the multi-field partial differential equations for temperature- and stress-directed hydrogen diffusion together with mechanical equilibrium in a finite element setting. Point-kinetics models are used for metal-hydride phase transformation and stress-directed orientation of hydrides, while a cohesive zone fracture model caters for initiation and propagation of cracks. Our calculations show that the propensity for crack initiation through hydride fracture at the notch during an overload event depends on the preceding histories of stress and temperature, and in particular, on the number of ratcheting thermal cycles experienced by the hydrided material. The calculated results agree favorably with experiments reported in open literature.

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  • 10.
    Jernkvist, Lars Olof
    et al.
    Malmö högskola, School of Technology (TS).
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Multi-field modeling of hydrogen transport and fracture in group 4 transition metals2012In: Proceedings of the International Hydrogen Conference (IHC 2012): Hydrogen-Materials Interactions, ASME Press, 2012, p. 717-726Conference paper (Other academic)
    Abstract [en]

    This work deals with a computational model for hydrogen transport, hydrogen induced deformation, embrittlement and fracture in hydride forming metals, notably Ti and Zr. The model uses a continuum description of the two-phase (alpha-phase metal plus delta-phase hydride) material, and solves the multi-field partial differential equations for temperature- and stress-directed hydrogen diffusion together with mechanical equilibrium in a three-dimensional finite element setting. Point-kinetics models are used for metal-hydride phase transfor¬mation and stress-directed orientation of hydrides, while a cohesive zone fracture model caters for initiation and propagation of cracks. The model as a whole is versatile and can be used to study a wide range of problems and conditions involving transport of hydrogen by directed diffusion in combination with hydride precipitation and fracture. The applicability of the model is demon-strated by simulations of fracture tests on a hydrogen-charged Zr-Nb alloy.

  • 11. Jernkvist, Lars Olof
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Nuclear Fuel Behaviour under Reactivity-initiated Accident (RIA) Condition: State-of-the-art Report2010Report (Other academic)
  • 12.
    Jernkvist, Lars-Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Modelling axial relocation of fragmented fuel pellets inside ballooned cladding tubes and its effects on LWR fuel rod failure behaviour during LOCA2015In: Transactions of SMiRT-23, SMiRT 23 organization , 2015, article id 186Conference paper (Refereed)
    Abstract [en]

    Downward axial relocation of fuel pellet fragments may occur when overheated and internally overpressurized cladding tubes of light water reactor fuel rods distend due to creep during a loss-of-coolant accident (LOCA). The relocation is of safety concern, since it changes the axial distribution of heat load along the rod and also has the potential to increase the amount of fuel material dispersed into the reactor coolant, should the cladding fail. Here, we present a computational model that calculates the fuel relocation on the basis of estimated fuel fragment size distributions and the calculated cladding distension along the fuel rod. The model has been implemented and fully integrated with the FRAPTRAN-1.5 computer program, such that thermal feedback effects of fuel relocation on the axial redistribution of fuel mass, stored heat and power are accounted for in FRAPTRAN’s calculations of the fuel rod thermo-mechanical behaviour. The model has been validated against the IFA-650.4 integral LOCA test in the Halden reactor, Norway, which was done on a very high burnup UO2 fuel rodlet and resulted in extensive fuel pellet pulverization, axial relocation and dispersal into the coolant. Our simulations of this test suggest that thermal feedback effects from axial fuel relocation are strong enough to significantly affect the dynamics of cladding ballooning and rupture, in spite of the short duration of these processes. Moreover, for the considered LOCA test, the axial relocation has a strong effect on the calculated peak cladding temperature and oxidation after rupture.

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  • 13.
    Jernkvist, Lars-Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Models for axial relocation of fragmented and pulverized fuel pellets in distending fuel rods and its effects on fuel rod heat load2015Report (Other academic)
    Abstract [en]

    Loss-of-coolant accidents (LOCAs) in light water reactors may lead to over- heating of the fuel rods, significant distension of the cladding tubes and axial relo- cation of fuel pellet fragments inside the “ballooned” part of the fuel rods. The fuel relocation may localize the heat load to a particular part of the rod, there- by increasing the risk for cladding failure and aggravating local oxidation of the cladding. It may also increase the amount of fuel dispersed into the coolant, should the cladding fail. Recent LOCA tests have revived interest in the relocation and dispersion phenomena among nuclear regulators, since the test results suggest that high burnup (> 65 MWd/kgU) UO2 fuel pellets may pulverize into very fine (< 0.2 mm) fragments, with a higher potential for axial relocation and subsequent dispersal than observed earlier for low to medium burnup fuel. To analyse these issues, a computational model for axial relocation of fuel frag- ments during LOCA and its effects on the fuel rod heat load and failure processes is developed and introduced in SSM’s version of FRAPTRAN-1.5, a computer program intended for fuel rod thermo-mechanical analyses of transients and acci- dents. The fuel relocation is calculated on the basis of estimated fuel fragment size distributions and the calculated cladding distension along the fuel rod, and its ef- fects on the axial redistribution of stored heat and power are accounted for in thermo-mechanical analyses of the fuel rod. Hence, our model fully considers thermal feedback effects from the fuel relocation, in contrast to existing relocation models. It also provides estimates of the amount of fuel that may potentially be ejected into the coolant upon cladding failure anywhere along the fuel rod. The model is validated by comparisons with measured data and discussed in light of tests and experiments. In particular, we study the IFA-650.4 integral LOCA test in the Halden reactor, Norway. This test was done on a very high burnup (92.3 MWd/kgU) UO2 fuel rodlet and it resulted in extensive fuel pulverization, axial relocation and fuel dispersal into the coolant. Our simulations of this test suggest that thermal feedback effects from axial fuel relocation are strong enough to sig- nificantly affect the dynamics of cladding ballooning and rupture, even though the calculated duration of these processes is no more than 7–8 seconds. Moreover, for the considered LOCA test, the axial relocation has a strong effect on the calculat- ed peak cladding temperature and oxidation after rupture. Finally, our work suggests that the aforementioned pulverization mechanism of high burnup fuel is important to axial fuel relocation during LOCA as it may in- crease the packing fraction of crumbled fuel. The pulverization thereby eases axial movements of the fuel pellet column and raises the local heat load in regions where fuel fragments accumulate. Our calculations indicate that fuel with a pellet average burnup around 70–75 MWd/kgU would be particularly prone to axial relocation, due to its expected fragment size distribution.

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  • 14.
    Jernkvist, Lars-Olof
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Massih, Ali
    Malmö högskola, Faculty of Technology and Society (TS).
    Alvestav, Anna
    Axial relocation of fragmented and pulverized fuel and its effect on fuel rod heat load during locas2015In: Conference Proceeding: Top Fuel 2015 Reactor Fuel Performance;2, European Nuclear Society , 2015, p. 457-480, article id PA0059Conference paper (Other academic)
    Abstract [en]

    Downward axial relocation of fuel fragments within distending fuel rods may occur during loss-of-coolant accidents (LOCAs) in light water reactors. The fuel relocation may localize the heat load to “ballooned” parts of the rod, thereby increasing the risk for cladding failure and aggravating local oxidation. It may also increase the amount of fuel dispersed into the coolant, should the cladding fail. Recent LOCA tests have revived interest in the relocation and dispersion phenomena, since the test results suggest that high burnup UO2 fuel pellets may pulverize into very fine fragments, with a higher potential for axial relocation and subsequent dispersal than observed earlier for low to medium burnup fuel. To improve our understanding of these phenomena, a computational model for axial relocation of fuel fragments during LOCA and its effects on the fuel rod heat load and failure processes has been developed and introduced in the FRAPTRAN-1.5 computer program. The axial fuel relocation is calculated on the basis of estimated fuel fragment size distributions and the calculated cladding distension along the fuel rod, and its effects on the axial redistribution of fuel mass, stored heat and power are accounted for in FRAPTRAN’s calculations of the fuel rod thermo-mechanical behaviour. The model has been validated against the IFA-650.4 integral LOCA test in the Halden reactor, Norway, which was done on a very high burnup UO2 fuel rodlet and resulted in extensive fuel pulverization, axial relocation and fuel dispersal into the coolant. Our simulations of this test suggest that thermal feedback effects from axial fuel relocation are strong enough to significantly affect the dynamics of cladding ballooning and rupture, even though the calculated duration of these processes is no more than 7–8 seconds. Moreover, for the considered LOCA test, the axial relocation has a strong effect on the calculated peak cladding temperature and oxidation after rupture.

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    FULLTEXT01
  • 15. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Analysis of a Loosely Supported Beam Under Harmonic Excitations1999Conference paper (Refereed)
  • 16. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Evaluation of fretting wear with the aid of the mechanisms-maps2005Conference paper (Refereed)
  • 17. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Impact oscillations and wear of loosely supported rod subject to harmonic load2004In: Journal of Sound and Vibration, Vol. 278, no 4-5, p. 1025-1050Article in journal (Refereed)
  • 18. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Impact work-rate and wear of a loosely supported beam subject to harmonic excitation2002In: Proceedings of IMECE2002, 2002Conference paper (Other academic)
  • 19. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Non-linear Dynamics and Fretting2001Report (Other academic)
  • 20. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Nonlinear dynamics of a loosely supported beam subject to harmonic excitation2002In: Proceedings of IMECE2002, 2002Conference paper (Other academic)
  • 21. Knudsen, J.
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Vibro-impact dynamics of a periodically forced beam2000In: ASME Journal of Pressure Vessel Technology, Vol. 122Article in journal (Refereed)
  • 22. Knudsen, J
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Gupta, R
    Analysis of a Loosely Supported Beam Under Random Excitations2000In: Proceedings of 7th International Conference Flow-Induced Vibration (FIV2000), 2000, p. 505-512Conference paper (Other academic)
  • 23. Knudsen, Jakob
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Dynamic stability of weakly damped oscillators with elastic impacts and wear2003In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 263, no 1, p. 175-204Article in journal (Refereed)
    Abstract [en]

    The dynamics of non-linear oscillators comprising of a single-degree-of- freedom system and beams with elastic two-sided amplitude constraints subject to harmonic loads is analyzed. The beams are clamped at one end, and constrained against unilateral contact sites near the other end. The structures are modelled by a Bernoulli-type beam supported by springs using the finite element method. Rayleigh damping is assumed. Symmetric and elastic double-impact motions, both harmonic and sub-harmonic, are studied by way of a Poincaré mapping that relates the states at subsequent impacts. Stability and bifurcation analyses are performed for these motions, and domains of instability are delineated. Impact work rate, which is the rate of energy dissipation to the impacting surfaces, is evaluated and discussed. In addition, an experiment conducted by Moon and Shaw on the vibration of a cantilevered beam with one-sided amplitude constraining stop is modelled. Bifurcation observed in the experiment could be captured.

  • 24. Manngård, Tero
    et al.
    Jernkvist, Lars Olof
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Evaluation of Loss-of-Coolant Accident Simulation Tests with the Fuel Rod Analysis Code FRAPTRAN-1.42011Conference paper (Other academic)
    Abstract [en]

    An integrated computer model for reactor fuel cladding rupture under loss-of-coolant accident (LOCA) conditions has been implemented in the transient fuel rod performance code FRAPTRAN. The model treats the zirconium alloy solid-to-solid phase transformation kinetics, cladding oxidation, cladding deformation, and eventually cladding rupture concurrently. It is for use together with the recently developed finite element based solution module in FRAPTRAN-1.4. The model has been employed to calculate ex-reactor single-rod transient burst tests in which the rod internal pressure and the heating rate were kept constant during the tests. The calculations are compared with experimental data on cladding rupture strain, temperature and pressure. Furthermore this model in FRAPTRAN-1.4 has been used to evaluate a LOCA simulation test within the IFA-650 series performed in the Halden boiling heavy- water reactor. The Halden test was made on a pressurized water reactor fuel rod with Zircaloy-4 cladding. It simulated the blowdown and refill (heatup) phase of a LOCA. The results of the FRAPTRAN-1.4 calculations are compared with experimental data on (i) maximum hoop strain at rupture, (ii) cladding diameter increase versus axial position, (iii) internal rod pressure versus time, (iv) peak cladding temperature at rupture, and (v) post-test cladding outer surface layer thickness. The results are discussed in terms of various uncertainties in the calculations. Nevertheless, the new implementation of the cladding rupture models indicates an overall improvement of the code for fuel rod LOCA analysis.

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  • 25. Manngård, Tero
    et al.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Modelling and Simulation of Reactor Fuel Cladding under Loss-of-Coolant Accident Conditions2011In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. 48, no 1, p. 39-49Article in journal (Refereed)
    Abstract [en]

    We present a unified model for calculation of zirconium alloy fuel cladding rupture during a postulated loss-of-coolant accident in light water reactors. The model treats the Zr alloy solid-to-solid phase transformation kinetics, cladding creep deformation, oxidation, and rupture as functions of temperature and time in an integrated fashion during the transient. The fuel cladding material considered here is Zircaloy-4, for which material property data (model parameters) are taken from the literature. We have modelled and simulated single-rod transient burst tests in which the rod internal pressure and the heating rate were kept constant during each test. The results are compared with experimental data on cladding rupture strain, temperature, and pressure. The agreement between computations and measurements in general is satisfactory. The effects of heating rate and rod internal pressure on the rupture strain are evaluated on the basis of systematic parameter variations of these quantities. In the α-phase of Zr, the burst strain decreases with increasing heating rate, whereas in the two-phase coexistence (α+β) domain and β-phase, the situation is more complex. Also, the mechanism for creep deformation in the (α+β) domain is not well understood; hence, its mechanistic constitutive relation is presently unknown.

  • 26. Manngård, Tero
    et al.
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Stengård, Jan-Olof
    Evaluation of the Halden IFA-650 loss-of-coolant accident experiments 2, 3 and 42014Report (Other academic)
    Abstract [en]

    The Halden reactor fuel rod loss-of-coolant accident (LOCA) tests, IFA-650 series 2, 3, and 4, are evaluated using two versions of the computer code FRAPTRAN-1.4. The test sample IFA-650.2 was a fresh fuel rod, that is unirradiated, with pressurized water reactor (PWR) rod characteristics, while IFA-650.3 and IFA-650.4 sample rods were refabricated from fuel rods irradiated in a PWR to rod burnups of 82 and 92 MWd/kgU, respectively. All the rods failed during the LOCA tests at temperatures around and below 800◦C by fuel cladding burst. The results of our computer calculations are compared with measured data for the following parameters: (i) Cladding temperature as a function of time; (ii) Cladding diameter at rupture versus axial position of the rod; (iii) Fuel rod pressure as a function of time; (iv) Peak cladding temperature at rupture; and (v) Maximum cladding oxide layer thickness after LOCA transient (test 2). The agreement between calculations and measurements and between the two versions of the utilized code are satisfactory. The report offers descriptions of the tests, the computer codes, the computations and a summary of the results.

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  • 27.
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Effects of additives on uranium dioxide fuel behavior2014Report (Other academic)
    Abstract [en]

    The main incentive to dope UO2 fuel with a small amount of metal oxides, such as Cr2O3 is to enlarge fuel grain size, increase fuel density and possibly make softer fuel pellets. Enlarging fuel grain size ( > 30 µm) will extend the diffusion path for fission product gases to grain boundaries, through which most of the gas is released from fuel pellet. Hence, the outcome would be a delay in thermal-activated gas release at a given fuel temperature. Increasing fuel density puts more U-235 mass per fuel assembly, while leading to less fuel densification during irradiation. Softer pellets, i.e. fuel with a higher creep rate and/or lower yield strength can reduce the intensity of pellet-cladding mechanical interaction during reactor power ramps, alleviating the risk of cladding failure. Additives may also affect the thermophysical properties of UO2 fuel, such as heat capacity, thermal expansion and thermal conductivity. However, experimental data and theoretical analysis indicate that if the concentration of the additive is low (e.g. for Cr2O3 dopant < 0.2 wt%), these properties are hardly affected. The aim of this report is to assess data and models for some important properties of UO2- base fuel containing additives. The additives considered are those investigated and reported in the literature. The main additive discussed here is Cr2O3, but also we include Al2O3, MgO and Nb2O5. Appropriate models for thermophysical properties are assessed and recommended for M2O3-type (M: metal) additives and even for MgO-doped UO2. Fission gas diffusivity data and correlations are assessed and used in a standard model for fission gas release and gaseous swelling to evaluate these quantities. Moreover, the effects of grain size on gas release and swelling are assessed. Available data and correlations for thermal creep of Nb2O5- and Cr2O3-doped fuels are evaluated critically, and possible creep mechanisms are delineated. The results of some in-reactor irradiation programs, ramp tests and transients on additive fuel are briefly reviewed. The report also intends to provide a basis for model implementation in a fuel rod performance code.

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  • 28.
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    High-temperature creep and superplasticity in zirconium alloys2013In: Journal of Nuclear Science and Technology, ISSN 0022-3131, E-ISSN 1881-1248, Vol. 50, no 1, p. 21-34Article in journal (Refereed)
    Abstract [en]

    High-temperature (≈ 900−1400 K) steady-state creep test data on as-received zirconium alloys, Zr-1wt%Nb and Zircaloy-4 used as fuel cladding materials in light water reactors are evaluated by employing two sets of models. In particular, the focus of the paper is on the former alloy and in the two-phase coexistence region, i.e. the (α+β)-domain of the alloy. In one modeling approach, the constitutive relations for the two single phase regions (α and β) are combined through a phase transition kinetic model and a phase mixing rule; in another, a superplasticity model is used directly to calculate the creep deformation rate as a function of stress and temperature in the (α+β)-domain. The results show that the former approach is inadequate in retrodicting the experimental data, while the latter one gives a fair overall agreement. The paper describes the details of the models, the data, and derivations of the constitutive laws.

  • 29.
    Massih, Ali
    Malmö högskola, School of Technology (TS).
    Second-phase nucleation on an edge dislocation2011In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 91, p. 3961-3980Article in journal (Refereed)
    Abstract [en]

    A model for nucleation of second phase at or around dislocation in a crystalline solid is considered. The model employs the Ginzburg-Landau theory of phase transition comprising the sextic term in order parameter in the Landau free energy. The ground state solution of the linearized time-independent Ginzburg-Landau equation has been derived, through which the spatial variation of the order parameter has been delineated. Moreover, a generic phase diagram indicating a tricritical behavior near and away from the dislocation is depicted. The relation between the classical nucleation theory and the Ginzburg-Landau approach has been discussed, for which the critical formation energy of nucleus is related to the maximal of the Landau potential energy. A numerical example illustrating the application of the model to the case of nucleation of hydrides in zirconium alloys is provided.

  • 30.
    Massih, Ali
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Jernkvist, Lars Olof
    Malmö högskola, Faculty of Technology and Society (TS).
    Effect of Additives on Diffusion Processes in UO22013Conference paper (Other academic)
    Abstract [en]

    Metal oxides added to UO2 to improve material performance during irradiation, or as burnable absorbers to control reactor energy output, affect point defect processes in UO2. The oxygen and uranium Frenkel pairs and the uranium-oxygen Schottky defects regulate the O/U ratio, which in turn influence diffusion processes in UO2. The dopants considered here include Cr2O3 and Gd2O3. Using the law of mass action to the Frenkel and Schottky defects in doped UO2, we relate O/U to the dopant concentration. Also, we find relationships between the oxygen and uranium vacancies and dopant concentration. The uranium self-diffusion coefficient is proportional to concentration of uranium vacancies in the hyper-stoichiometric region, whereas to that of uranium interstitials in hypo-stoichiometric region. We relate this to the creep rate and diffusion coefficient of fission gases in UO2. We use the model to evaluate creep rate and gas diffusivity in doped UO2 in light of experimental data.

  • 31.
    Massih, Ali
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Jernkvist, Lars Olof
    Malmö högskola, Faculty of Technology and Society (TS).
    Effect of additives on self-diffusion and creep of UO22015In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 110, p. 152-162Article in journal (Refereed)
    Abstract [en]

    The creep of UO2 doped with Nb2O5 and Cr2O3 has been assessed using a point defect model based on the law of mass action, and the diffusional creep according to the Nabarro-Herring mechanism, which relates the creep rate to the lattice self-diffusivity, the inverse of grain area and the applied stress. The self-diffusion coefficients of cation (U) and anion (O) are directly proportional to the concentrations of ions, which in turn are functions of dopant concentrations. The model has been used to evaluate past creep experiments on UO2 doped with Nb2O5 and Cr2O3 in concentrations up to about 1 mol%, with a varying grain size at different temperatures and applied stresses. The creep rate increases significantly with the dopant concentration and the putative model, after a modification of the creep rate coefficient, retrodict the measured data satisfactorily. A number of factors affecting creep rate and thereby our model computations are discussed.

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  • 32.
    Massih, Ali
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Jernkvist, Lars-Olof
    Malmö högskola, Faculty of Technology and Society (TS).
    Assessment of data and criteria for cladding burst in loss-of-coolant accidents2015Report (Other academic)
    Abstract [en]

    We attempt to systematize the zirconium-base fuel cladding burst data obtained under loss- of-coolant accident (LOCA) conditions that have been reported from various experimental programs since the late 1970’s. Our objective is to assess the usable data and evaluate them with the various burst criteria that are available in the QT/SSM version of the FRAPTRAN computer program. The FRAPTRAN program computes the transient behavior of light-water reactor fuel rods during reactor transients and hypothetical accidents, such as LOCAs. The cladding materials in the data base include Zircaloy-4, ZIRLO and Zr- 1wt%Nb type alloys. The report summarizes the data base, the method of computation, the expressions for the various burst criteria, and the outcome of our assessment in the form of measured versus calculated plots: cladding time-to-burst, cladding burst tempera- ture and cladding burst stress/strain. A summary of the uncertainties in the computations is also provided. We have found that the stress-based Rosinger best-estimate burst criterion, originally developed for Zircaloy-4 cladding, is suitable for applications to Zircaloy and ZIRLO claddings on a best-estimate basis. For the ZIRLO cladding, additional improve- ments of this burst criterion can be made, provided sufficient amount of measured data on burst properties and material characteristics would be available.

  • 33.
    Massih, Ali
    et al.
    Malmö högskola, Faculty of Technology and Society (TS).
    Jernkvist, Lars-Olof
    Malmö högskola, Faculty of Technology and Society (TS).
    Effect of additives Nb2O5 and Cr2O3 on creep of UO22015In: SMiRT 23 Proceedings, SMiRT organization , 2015, article id 054Conference paper (Other academic)
    Abstract [en]

    The creep of UO2 doped with Nb2O5 or Cr2O3 has been assessed using a point defect model based on the law of mass action, and the diffusional creep according to the Nabarro-Herring mechanism, which relates the creep rate to the lattice self-diffusivity, the inverse of grain area and the applied stress. The self-diffusion coefficients of cation (U) and anion (O) are directly proportional to the ion concentrations, which in turn are functions of dopant concentrations. The model has been used to evaluate past creep experiments on doped UO2 that were made as a function of dopant concentration (up to about 1 mol%) with a varying grain size at different temperatures and applied stresses. The creep rate increases significantly with the dopant concentration and the model, after a modification of the creep rate coefficient, retrodict the measured data satisfactorily.

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  • 34.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    A plasticity model for densification and swelling of porous solids2000In: Advances in Computational Engineering and Sciences, Vol. 1, p. 452-457Article in journal (Refereed)
  • 35.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    An evaluation of high-temperature creep of zirconium alloys: data versus models2014Report (Other academic)
    Abstract [en]

    The steady-state creep data of as-received Zircaloy-4 and Zr-1wt%Nb used as fuel cladding materials in light water reactors, reported in the literature, have been reap- praised. The considered creep tests were conducted in the temperature range from 923 to 1873 K in inert environment covering all the solid-state zirconium alloy stable phase domains: α, (α + β) and β as a function of applied stress. The results of model cal- culations and measured data are compared, where the relative difference between the measured and calculated creep rate values are quantified for a series of tests. The mod- els considered are those used or can be used in predictive computer codes for fuel rod behaviour under loss-of-coolant accident conditions in light water reactors.

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  • 36.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Analysis of pellet-clad interaction of LWR fuel rods during power ramps2005Conference paper (Refereed)
  • 37.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Diffusion-controlled phase growth on dislocations2009In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 89, no 33, p. 3075-3086Article in journal (Refereed)
    Abstract [en]

    We treat the problem of diffusion of solute atoms around screw dislocations. In particular, we express and solve the diffusion equation, in radial symmetry, in an elastic field of a screw dislocation subject to the flux conservation boundary condition at the interface of a new phase. We consider an incoherent second-phase precipitate growing under the action of the stress field of a screw dislocation. The second-phase growth rate as a function of the supersaturation and a strain energy parameter is evaluated in spatial dimensions d=2 and d=3. Our calculations show that an increase in the amplitude of dislocation force, e.g. the magnitude of the Burgers vector, enhances the second-phase growth in an alloy. Moreover, a relationship linking the supersaturation to the precipitate size in the presence of the elastic field of dislocation is calculated.

  • 38.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Effect of hydrogen content on mechanical properties of irradiated Zr-base alloys in PWR fuel assembly2000Report (Other academic)
  • 39.
    Massih, Ali R
    Malmö högskola, Faculty of Technology and Society (TS).
    Electronic transport in pure and doped UO22017In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 497, p. 166-182Article in journal (Refereed)
    Abstract [en]

    The thermoelectric properties of pure and doped UO2, namely the thermal and electrical conductivities and the thermopower, are assessed. We adopt the small polaron theory of the Mott type insulators, wherein the charge carriers, the electron and hole on the U3+ and U5+ ions, are treated as small polarons. For the thermal conductivity, the small polaron theory is applicable at temperatures above 1500 K. A review of the experimental data on the temperature dependence of the aforementioned transport properties is made. The data include UO2 with dopants such as Cr2O3, Gd2O3, Y2O3 and Nb2O5. We compare the applications of the theory with the data. Two limiting regimes, adiabatic and nonadiabatic, with the ensuing expressions for the conductivities and the thermoelectric power are considered. We discuss both the merits and shortcomings of the putative small polaron model and the simplification thereof as applied to pure and doped uranium dioxide. (C) 2017 Elsevier B.V. All rights reserved.

  • 40.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Mechanical property data on hydrided Zircaloy-2 fuel claddings irradiated in BWRs2000Report (Other academic)
  • 41.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Mechanisms for hydrogen embrittlement in titanium-base alloys1999Report (Other academic)
  • 42.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Models for MOX fuel behaviour: a selective review2006Report (Other academic)
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  • 43.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Phase transformations near dislocations and cracks2011In: Solid State Phenomena, ISSN 1012-0394, E-ISSN 1662-9779, Vol. 172-174, p. 384-389Article in journal (Refereed)
    Abstract [en]

    A generic model for nucleation of oriented second-phase in alloys in the vicinity of cracks and dislocations, is considered. The model employs the Ginsburg-Landau approach, which accounts for the elasticity of crystalline solid and the interaction of structure/composition with the elastic field in the vicinity of the defect and in the crystalline bulk. We examine the nature of the structural phase transition and construct its phase diagram.

  • 44.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Review of experimental data for modelling LWR fuel cladding behaviour under loss of coolant accident conditions2007Report (Other academic)
    Abstract [en]

    Extensive range of experiments has been conducted in the past to quantitatively identify and understand the behaviour of fuel rod under loss-of-coolant accident (LOCA) conditions in light water reactors (LWRs). The obtained experimental data provide the basis for the current emergency core cooling system acceptance criteria under LOCA conditions for LWRs. The results of recent experiments indicate that the cladding alloy composition and high burnup effects influence LOCA acceptance criteria margins. In this report, we review some past important and recent experimental results. We first discuss the background to acceptance criteria for LOCA, namely, clad embrittlement phenomenology, clad embrittlement criteria (limitations on maximum clad oxidation and peak clad temperature) and the experimental bases for the criteria. Two broad kinds of test have been carried out under LOCA conditions: (i) Separate effect tests to study clad oxidation, clad deformation and rupture, and zirconium alloy allotropic phase transition during LOCA. (ii) Integral LOCA tests, in which the entire LOCA sequence is simulated on a single rod or a multi-rod array in a fuel bundle, in laboratory or in a test reactor, to study the overall behaviour of fuel rod under LOCA. The separate effect tests and results are discussed and empirical correlations deduced from these tests and quantitative models are conferred. In particular, the impact of niobium in zirconium base clad and hydrogen content of the clad on allotropic phase transformation during LOCA and also the burst stress are discussed. We review some recent LOCA integral test results with emphasis on thermal shock tests. Finally, suggestions for modelling and further evaluation of certain experimental results are made.

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  • 45.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Review of reactivity initiated accident simulation experiments on pre-irradiated light water reactor fuel2002Report (Other academic)
  • 46.
    Massih, Ali R
    Malmö högskola, School of Technology (TS).
    Transformation kinetics of zirconium alloys under non-isothermal conditions2009In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 384, no 3, p. 330-335Article in journal (Refereed)
    Abstract [en]

    The overall solid-to-solid phase transformation kinetics under non-isothermal conditions in Zr alloys has been evaluated using a model presented on our preceding note. It uses as input an applied thermal history and calculates the time/temperature variation of the volume fraction of the new phase in α ↔ β transition in Zr alloys under heating/cooling, in concordance with experiments.

  • 47.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS).
    Andersson, T.
    Witt, P.
    Dahlbäck, M.
    Limbäck, M.
    Effect of quenching rate on the beta-to-alpha phase transformation structure in zirconium alloy2003In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, no 322, p. 138-151Article in journal (Refereed)
  • 48.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS).
    Dahlbäck, M
    The effect of beta quenching in final dimension on the irradiation growth of tubes and channels2005In: Journal of ASTM International, E-ISSN 1546-962X, no 2Article in journal (Refereed)
    Abstract [en]

    The effect of β-quenching performed in the final size of Zircaloy-4 guide tubes and Zircaloy-2 sheets during fabrication process on the products' mechanical properties, crystallographic texture, microstructure, and corrosion behavior has been investigated and presented in this paper. Moreover, the impact of this processing on the irradiation growth of pressurized water reactor Zircaloy-4 guide tubes in a test reactor and Zircaloy-2 fuel channels in boiling water reactors has been evaluated. The results indicate that the irradiation growth rates of the final dimension β-quenched (FDBQ) products are substantially lower than those fabricated by conventional (Standard) techniques. BWR channels irradiated up to a fast neutron fluence of about 9 × 1025 m−2 maintain this low growth behavior. Corrosion properties of FDBQ products have been made similar to that of the Standard material by performing an α-annealing step after the β-quenching. The annealing temperature and annealing time have been optimized in order to obtain good corrosion resistance. In-reactor data on Zircaloy-2 channels irradiated to a fuel assembly exposure of about 50 MWd/kgU indicate similar corrosion performance for the FDBQ and Standard materials. Finally, the in-reactor data on Zircaloy-2 channels show that bowing of the FDBQ and Standard channels is comparable up to a fast neutron fluence of about 7 × 1025 m−2.

  • 49.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS).
    Dahlbäck, M.
    The effect of liner component on cladding corrosion, hydriding and PCI resistance2005In: Journal of ASTM International, E-ISSN 1546-962X, Vol. 2, no 9, article id JAI12444Article in journal (Refereed)
  • 50.
    Massih, Ali R
    et al.
    Malmö högskola, School of Technology (TS).
    Dahlbäck, M.
    Limbäck, M.
    Andersson, T.
    Lehtinen, B.
    Effect of beta-to-alpha phase transition rate on corrosion behaviour of Zircaloy2006In: Corrosion Science, Vol. 48, no 5, p. 1154-1181Article in journal (Refereed)
12 1 - 50 of 78
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