摘要:

There is currently a great deal of uncertainty about the nature and magnitude of mechanical and thermal wall loading anticipated in future Inertial Confinement Fusion (ICF) Facilities. This uncertainty is aggravated by the fact that laser and heavy ion driven reactors will have a much different heat and shock loading than light ion driven systems. The purpose of this presentation was to quantitatively illustrate the differences that can occur in a laser driven facility versus one in which the targets are compressed by light ion beams.

ISSN:0033-7579    

DOI:10.1080/00337578708224732

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Type 316L austenitic and 1.4914 martensitic steels have been selected as alternative first wall and breeder structural component materials for NET. The constitutions and structures of these steels are surveyed and the effects of neutron irradiation on their bulk properties and behaviour (void swelling, creep and rupture, fatigue, fracture toughness and hydrogen embrittlement) are discussed in terms of the proposed NET operating conditions. The investigations which are being undertaken to provide the additional data required to enable the optimum material to be chosen prior to starting the detailed design of NET are indicated. Surface damage of the first wall may also result from the bombardment by ions and energetic neutral atoms from the plasma and from plasma disruption, run-away electron and arcing effects. Various potential solutions for protecting the first wall from plasma disruptions are considered.

ISSN:0033-7579    

DOI:10.1080/00337578708224733

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The phase microstructure of alloys is frequently severely altered during irradiation. Sluggish precipitation reactions including precipitation coarsening are accelerated by irradiation-enhanced diffusion. Radiation-induced segregation redistributes existing precipitate phases within the microstructure, induces precipitation of nonequilibrium phases and affects the composition of phases in multicomponent alloys. The displacement process causes disordering of ordered alloys and frequently amorphization, especially in intermetallic compounds, at low temperature. Although a good qualitative understanding of the basic process involved, i.e., displacement mixing, radiation-enhanced diffusion and radiation-induced segregation exists, methods for detailed quantitative modeling of the evolution of the microstructure of alloys remain to be developed.

ISSN:0033-7579    

DOI:10.1080/00337578708224734

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A survey is presented of recent developments in the study of radiation-induced changes in the microstructure of austenitic structural alloys that occur in fission reactors. The associated macroscopic consequences of these changes on both mechanical properties and dimensional stability are also reviewed. It is anticipated that some changes will occur in these phenomena as a result of the differences inherent in fission and fusion neutron spectra, but relevant data obtained to date do not indicate that the effects of helium and several other transmutation-related differences will be large.

ISSN:0033-7579    

DOI:10.1080/00337578708224735

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The experimental and theoretical basis for predicting microstructural evolution in structural alloys in fusion reactor environments is reviewed. Semi-empirical models are found to be broadly consistent with observed data trends. However, there is insufficient understanding and independent verification to assign a high reliability to model-based extrapolations; additional progress will require new experimentally-based insights, as well as improved models. Three classes of possible experimental initiatives are described. The first seeks to identify and quantify important mechanisms and model parameters, and the second is intended to test integral models of the interacting evolutions leading to rapid void swelling. Particular emphasis is placed on a third category of experiments based on isotopic and spectral tailoring in high flux fission reactors. It is shown that it is possible to carry out both single variables experiments and high exposure irradiations (≳ l00dpa) of alloys with a combination of most enviromentally mediated variables close to that characteristic of fusion reactors.

ISSN:0033-7579    

DOI:10.1080/00337578708224736

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The effect of changes in helium generation rate on void and bubble nucleation, growth and distribution observed mainly in high-purity aluminium are summarized. It is shown that at a given irradiation temperature, the cavity microstructure may be composed of voids only, voids and bubbles or bubbles only, depending on helium generation rate. The accumulation of helium (generated during irradiation) on grain boundaries is considered; the helium generation rate is found to control the flux of helium to grain boundaries and therefore may also determine the rupture lifetime. The influence of materials variables on the flux to the boundaries is also considered. Changes in recoil energy and/or damage rate may have strong influence on precipitation and precipitate stability — and hence on helium flux to grain boundaries and mechanical properties. The implications of the effects of changes in irradiation parameters and materials variables are discussed.

ISSN:0033-7579    

DOI:10.1080/00337578708224737

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

High temperature embrittlement due to helium is controlled by helium-assisted cavity formation on grain boundaries. The basic mechanisms, underlying this process are discussed: bubble nucleation and growth, bubble-void conversion and void growth, crack formation by void coalescence. Differences between the microstructural evolution associated with different test conditions are emphasized. The lengths of the stages, characterized by the dominance of one of the basic mechanisms at a time, and their contributions to the strain are estimated. Mechanism maps constructed from creep rupture and microstructure data in combination with theoretical models are suggested as guidelines for extrapolating simulation results to fusion reactor conditions

ISSN:0033-7579    

DOI:10.1080/00337578708224738

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Three main classes of stability criteria for phases under irradiation are briefly reviewed. Stored energy arguments seem to account for some cases of irradiation induced amorphization or compound destruction; the coupling between point defect and solute fluxes accounts for irradiation induced precipitation in undersaturated solid solutions; quantitative modelling as well as simple stability criteria are available. The phenomenology of ballistic effects has been reformulated and yields sophisticated tools to cope with observed stability inversions or bistability phenomena. New simple models are proposed for the saturation of coarsening under irradiation or for changes in precipitate morphology when irradiation implies a change for composition. Dose rate effects are strongly emphasized.

ISSN:0033-7579    

DOI:10.1080/00337578708224739

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The development of mechanical property tests based on bending of a 3 mm diameter by (typically) 0.25 mm thick disk is described. Slow strain rate testing of such a disk is used to obtain tensile properties. Finite element computer modeling is used to extract yield stress values with accuracies of at least ± 10% of uniaxial tensile test values for a variety of materials. Analytical estimates of ductility from disk bend test values are possible for low-ductility materials. Work directed toward finite element calculations for ductility and ultimate tensile strength is also discussed.

ISSN:0033-7579    

DOI:10.1080/00337578708224740

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

While the effects of irradiation on the mechanical properties of stainless steels have been extensively investigated, most data have been obtained from relatively large specimens. However, fusion reactor materials development will require the extensive use of miniaturized specimens. Yet the synergisms between the influence of specimen size and irradiation are not well understood. Consequently, the objectives of this study were to identify and clarify the potential roles of irradiation and specimen size in tensile and creep properties of austenitic stainless steels; this is an initial step in developing a complete understanding of irradiation effects in small specimens.

ISSN:0033-7579    

DOI:10.1080/00337578708224741

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor