| 1. |
- Ottosen, Niels Saabye
(författare)
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Relaxation of a Rectangular Beam and Circular Shaft
- 1982
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Ingår i: Nuclear Engineering and Design. - : Elsevier BV. - 1872-759X .- 0029-5493. ; 75:1, s. 67-72
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Tidskriftsartikel (refereegranskat)abstract
- The paper provides exact and approximate solutions to the title problems. Time-hardening creep is adopted and the stress dependence is assumed to follow the exponential expression proposed by Soderberg. Even though the exact solutions are easy to work with, some approximate solutions are discussed. These approximate solutions are obtained from the exact ones by simply ignoring certain terms; errors bounds are then directly available. The exact and approximate solutions are applied to specific problems and compared with the predictions following the exact, numerical or approximate solution of Norton's power law.
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| 2. |
- Bechta, Sevostian, et al.
(författare)
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Experimental studies of oxidic molten corium-vessel steel interaction
- 2001
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 210:1-3, s. 193-224
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Tidskriftsartikel (refereegranskat)abstract
- The experimental results of molten corium-steel specimen interaction with molten corium on the 'Rasplav-2' test facility are presented. In the experiments, cooled vessel steel specimens positioned on the molten pool bottom and uncooled ones lowered into the molten pool were tested. Interaction processes were studied for different corium compositions, melt superheating and in alternative (inert and air) overlying atmosphere. Hypotheses were put forward explaining the observed phenomena and interaction mechanisms. The studies presented in the paper were aimed at the detection of different corium-steel interaction mechanisms. Therefore certain identified phenomena are more typical of the ex-vessel localization conditions than of the in-vessel corium retention. Primarily, this can be referred to the phenomena of low-temperature molten corium-vessel steel interaction in oxidizing atmosphere.
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| 3. |
- Bechta, Sevostian, et al.
(författare)
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Water boiling on the corium melt surface under VVER severe accident conditions
- 2000
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 195:1, s. 45-56
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results are presented on the interaction of corium melt with water supplied on its surface. The tests were conducted in the `Rasplav-2' experimental facility. Corium melt was generated by induction melting in the cold crucible. The following data were obtained: heat transfer at boiling water-melt surface interaction, gas and aerosol release, post-interaction solidified corium structure. The corium melt charge had the following composition, mass%: 60% UO2+x-16% ZRO2-15% Fe2O3-6% Cr2O3-3% Ni2O3. The melt surface temperature ranged within 1920-1970 K.
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| 4. |
- Eriksson, Kjell
(författare)
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The effective fracture toughness of structural components obtained with the blend rule
- 1998
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 182:2, s. 123-129
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Tidskriftsartikel (refereegranskat)abstract
- The blend rule for the effective fracture toughness of a layered material was originally derived from the special case of a through crack in a globally elastic material and later extended to accomodate non-linear behaviour. It is now derived from a general case by considering material elements of finite size and of different toughness along and around the tip of a crack. Experimental results obtained with an inhomogeneous ordinary structural steel which support the blend rule are presented. It is shown that the effective fracture toughness governs the load-bearing capacity of a cracked full-scale structure. Some further results found in the literature for the heat-affected zone material of a high-strength microalloyed quenched and tempered structural steel and computational results for a structural steel typical of a nuclear pressure vessel are shown to support the blend rule.
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| 5. |
- Lindgren, Lars-Erik, et al.
(författare)
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Thermo-mechanical FE-analysis of residual stresses and stress redistribution in butt welding of a copper canister for spent nuclear fuel
- 2002
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 212:1-3, s. 401-408
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Tidskriftsartikel (refereegranskat)abstract
- The transient and residual temperature, stress and strain field present during electron beam welding of a plane copper end to a canister for spent nuclear fuel is calculated by the use of FEM. The subsequent stress redistribution is calculated up to 10,000 years. The canister consists of two concentric cylinders, an inner steel cylinder containing the spent nuclear fuel and an outer copper cylinder. It was found that the maximum plastic strain (plastic+creep) accumulated in the (possibly brittle) heat affected zone is ≈7%, which seems to be well below the reported ductility for the copper used.
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| 6. |
- Nilsson, Fred L.
(författare)
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Risk-based approach to plant life management
- 2003
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 221:03-jan, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- The growing interest in risk-based management is driven by the need of developing strategies that lead to an optimal safety versus cost balance. The general philosophy behind risk-based management is briefly described here and discussed. It is formally shown that the core damage frequency can be factored into a system (PSA) part and component failure frequency part. Some of the procedures, currently applied in risk-based inspection, are discussed. The basic elements for failure frequency calculations are presented and discussed. A quantitative risk-based inspection study performed for the Oskarshamn 1 unit is briefly presented as an example of how risk-based procedures can be applied.
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| 7. |
- Nilsson, P., et al.
(författare)
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On the behavior of crack surface ligaments
- 1998
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 184:1, s. 145-153
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Tidskriftsartikel (refereegranskat)abstract
- Small ligaments connecting the fracture surfaces just behind a moving crack front are assumed to exist under certain conditions. The ligaments are rapidly torn as the crack advances. Inelastic straining of such ligaments influences the energy balance in the fracture process. The rapid tearing of a single ligament is studied both numerically and experimentally. An elastic visco-plastic material model is adopted for finite-element calculations. The results show that relatively large amounts of energy are dissipated during the tearing process. Further, the energy needed to tear a ligament increases rapidly with increasing tearing rate. The computed behavior is partly verified in a few preliminary experiments. The implications for slow stable crack tip speeds during dynamic fracture are discussed.
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| 8. |
- Niwa, Y., et al.
(författare)
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Integrated computerisation of operating procedures
- 2002
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 213:2-3, s. 289-301
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Tidskriftsartikel (refereegranskat)abstract
- The computerisation of procedures can address not only the way procedures are presented or displayed, but also how they are generated and maintained. The computerisation of procedure generation will result in an improved basis for procedure display, and also make it possible to maintain the procedures on the level of internal representation rather than on the level of display. This paper describes a project, which focused on developing a system for computerised procedure generation (CPG) based on the principles of cognitive systems engineering. The CPG system was integrated with an already existing system for computerised procedure presentation, and enhanced with a number of other functions to produce a system for integrated computerisation of operating procedures. © 2002 Elsevier Science B.V. All rights reserved.
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| 9. |
- Nourgaliev, R. R., et al.
(författare)
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On lattice Boltzmann modeling of phase transition in an isothermal non-ideal fluid
- 2002
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 211:2-3, s. 153-171
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Tidskriftsartikel (refereegranskat)abstract
- A new lattice Bolztmann BGK model for isothermal non-ideal fluid is introduced and formulated for an arbitrary lattice, composed of several D-dimensional sublattices. The model is a generalization of the free-energy-based lattice Bolztmann BGK model developed by Swift et al. (1996). We decompose the equilibrium distribution function in the BGK collision operator into ideal and non-ideal parts and employ second-order Chapman-Enskog expansion for treatment of both parts. Expansion coefficients for the non-ideal part are, in general. functions of macroscopic variables, designed to reproduce desired pressure tensor (thermodynamic aspects) and to eliminate the aphysical artifacts in the lattice Bolztmann model. The new model is shown to significantly improve quality of lattice Boltzmann modeling of interfacial phenomena. In the present model. the interface spurious velocity is orders of magnitude lower than that for existing LBE models of non-ideal fluids. A new numerical scheme for treatment of advection and collision operators is proposed to significantly extend stability limits, in comparison to existing solution methods of the 'master' lattice Bolztmann equation. Implementation of a 'multifractional stepping' procedure for advection operator allows to eliminate severe restriction CFL = 1 in traditionally used 'stream-and-collide' scheme. An implicit trapezoidal discretization of the collision operator is shown to enable excellent performance of the present model in stiff high-surface-tension regime. The proposed numerical scheme is second order accurate. both in time and space.
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| 10. |
- Sehgal, B. R., et al.
(författare)
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Assessment of reactor vessel integrity (ARVI)
- 2003
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Ingår i: Nuclear Engineering and Design. - 0029-5493 .- 1872-759X. ; 221:03-jan, s. 23-53
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Tidskriftsartikel (refereegranskat)abstract
- The cost-shared project ARVI (assessment of reactor vessel integrity) involves a total of nine organisations from Europe and USA. The objective of the ARVI Project is to resolve the safety issues that remain unresolved for the melt vessel interaction phase of the in-vessel progression of a severe accident. The work consists of experiments and analysis development. Four tests were performed in the EC-FOREVER Programme, in which failure was achieved in-vessels employing the French pressure vessel steel. The tests were analysed with the commercial code ANSYS-Multiphysics, and the codes SYSTUS+ and PASULA, and quite good agreement was achieved for the failure location. Natural convection experiments in stratified pools have been performed in the SIMECO and the COPO facilities, which showed that much greater heat is transferred downwards for immiscible layers or before layers mix. A model for gap cooling and a set of simplified models for the system codes have been developed. MVITA code calculations have been performed for the Czech and Hungarian VVERs, towards evaluation of the in-vessel melt retention accident management scheme. Tests have been performed at the ULPU facility with organised flow for vessel external cooling. Considerable enhancement of the critical heat flux (CHF) was obtained. The ARVI Project has reached the halfway stage. This paper presents the results obtained thus far from the project.
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