Fusion Materials Development Research Articles

Proton irradiation induced phase transformation in AISI 304L stainless steel

Radiation-enhanced and -induced phases precipitation, radiation-induced solute segregation and radiation-induced preferential sputtering have been observed in the irradiated stainless steels. Austenite([gamma]) to ferrite([alpha]) phase transformation has been reported in austenitic stainless steels following neutron- and ion-irradiation, long-term thermal aging and mechanical deformation. Irradiation-assisted stress corrosion cracking (IASCC) has recently become an important issue related to cracking of in-core components in Light Water Reactors (LWR's). It therefore leads to a possibility that the IASCC susceptibility may be related to the austenite stability of stainless steel. The lacks of neutron irradiation environments, preparation and testing equipment, and sufficient time and expense force the use of ion-irradiating simulation experiments for fission and fusion materials research and development. The purpose of this study is to investigate the proton irradiation-induced phase transformation ([gamma][yields][alpha]) phenomenon in commercial purity AISI 304L austenitic stainless steel and the influences on its intergranular stress corrosion cracking (IGSCC) susceptibility.

High-energy/intensity neutron facilities for testing fusion materials

The current status of technology of neutron irradiation test facilities for the development of fusion materials is described focussing to those with a high feasibility of being constructed and brought into operation within a decade. Regarding the facility concept the system with the deuteron-lithium(d-Li) stripping type source has been considered as the most realistic among the currently conceivable candidates. A series of systematic surveys on facility design and neutron field characteristics made recently by an international working group have reached the same conclusion. The base technology developed earlier by the FMIT Project (Fusion Materials Testing Facility Project, 1978–1985) has recently been advanced in the accelerator technology aspect. In Japan, the ESNIT Program has been promoted since 1988, in which the capability of energy selectivity has drawn special attention in resolving the issues specific to the d-Li system. Considering designing, constructing and applying such a type of facility, a realism for a strategy of a staged upgrading process was proposed, in which the actions are to start from a medium size unit module being followed by increasing the test volume in accordance with the progress of the materials development towards the DEMO reactor.

The status and prospects of high-energy neutron test facilities for fusion materials development

The status and prospects of high-energy neutron test facilities for fusion materials development

Evaluation of reduced-activation options for fusion materials development

The European, American and Japanese R&D programmes on the development of low- or reduced-activation materials (LAMs) for fusion were reviewed at an IEA Workshop held at Culham in April 1991 and are surveyed in this paper. The current status and future directions of the work on the establishment of criteria for LAMs in terms of maintenance, safety, recycling and waste disposal and on the assembly of a complete nuclear data base are summarised. Progress in the development of low-activation steels and non-ferrous (vanadium base) alloys is described, their principal advantages and limitations are illustrated and the prospects for further development are outlined. Approaches required to assess the potential of advanced materials, particularly fibre-reinforced ceramic and metal matrix composites, for application as LAMs in fusion reactors are briefly considered, It is concluded that progress in the development of LAMs could be expedited by improved co-ordination and further international collaboration in the respective programmes.

Evaluation of reduced-activation options for fusion materials development

Evaluation of reduced-activation options for fusion materials development

Electron irradiation experiments in support of fusion materials development

Microstructural evolution in response to 1 MeV electron irradiation has been investigated for three simple ferritic alloys, pure beryllium, pure vanadium, and two simple vanadium alloys over a range of temperatures and doses. Microstructural evolution in Fe3Cr, Fe9Cr and Fe18Cr ferritic alloys is found to consists of crenulated, faulted α〈100〉 loops and circular, unfaulted 1 2 α〈111〉 loops at low temperatures, but with only unfaulted loops of both types at high temperatures. The complex dislocation evolution is attributed to sigma phase precipifaults arising from chromium segregation to point defect sinks. Beryllium is found to be resistant to electron damage: the only effect observed was enhanced dislocation mobility. Pure vanadium, V5Fe, and V1Ni microstructural response was complicated by precipitation on heating to 400°C and above, but dislocation evolution was investigated in the range of room temperature to 300°C and at 600°C. The three materials behaved similarly, except that pure vanadium showed more rapid dislocation evolution. This difference does not explain the enhanced swelling observed in vanadium alloys.

The status and prospects of high-energy neutron test facilities for fusion materials development

The status of progress in the development of facility concepts and the relevant technology is summarized, referring to the recent outcomes from the international collaborative activities on reviewing the technical feasibility and the suitability of candidate facilities for testing fusion reactor materials. The discussion is focussed on the way to reach the goal of an international fusion materials irradiation facility (IFMIF), which is capable of testing materials for DEMO reactors and beyond. Based on the state of knowledge reviewed, a staged approach is suggested in phase with the current world strategy for fusion power development.

A perspective on the history, status and future of fusion materials research in the United States

Fusion materials research and development in the United States began in the early 1970s with ad hoc research using a wide variety of experimental approaches to approximate (in part) the effects that might be expected from the unavailable fusion reactor environment. Charged particle irradiation dominated but important 14 MeV neutron irradiation studies were initiated with the RTNS-I and fission reactor irradiation was started in the HFIR. By the mid '70s, major effort was directed to the definition and development of fusion specific irradiation facilities. Conceptual reactor design studies provided a focus on machine parameters and materials property requirements. Those studies shifted interest to materials that represented more current technology from the earlier focus on refractory metal alloys. In the early 1980s, a strongly structured DOE fusion reactor materials program increasingly focused on international cooperation, including development and use of irradiation facilities. At the present time, international program activities constitute virtually the total DOE fusion materials program. The development of low activation materials is now the primary long term goal, but resources are increasingly focused in support of the next immediate generation of fusion machines, including CIT and ITER. The unfulfilled requirement for an irradiation facility that is relevant to fusion reactor parameters remains the key agenda item before the international fusion materials community.

Phase stability of a manganese-stabilized low-activation martensitic steel

The development of alloys with reduced long-life radioactivity has been incorporated into the goals of fusion materials development. One possible candidate alloy is an Fe-12Cr-6.5Mn-lW-0.3V-0.1C stabilized martensitic steel. The phase stability of this steel has been investigated following neutron irradiation over a temperature range of 420 to 600° C to doses as high as 100 dpa. The microstructural response of the irradiated steel has been compared to that of the same alloy aged for 10000 h from 365 to 600°C. M 23C 6 was the only carbide found in both the aged and irradiated structures. In the samples aged at 420 and 520°C, and the samples irradiated at 520°C, an Fe-Cr-Mn-W chi-phase formed. In the samples irradiated at 420°C, alpha prime formed. The presence of chi-phase in both the thermally aged and neutron irradiated steels indicates that the Fe-Cr-Mn system is prone to intermetallic phase formation so that careful study of the effects of alloying are needed.

Review of R&D of intense neutron sources for irradiation studies of fusion reactor materials.

Need for the intense neutron sources for the development of fusion materials has been recognized from the early stage of fusion development. A brief history including recent international collaborative activities is described.The most difficult problem in developing fusion materials is related to radiation damage produced during prolonged irradiation in a fusion energy system. Suitability to study this will define the requirements of the neutron source. Although there have been a number of proposals for the source, there seem to be no intense neutron sources satisfying all the suitability and feasibility requirements. Inherent problems and issues to be solved are summarized for various kinds of the sources. In particular, detailed integral descriptions on a d-Li stripping reaction source facility are given as a reference for considering the irradiation facility. It is emphasized that the intense neutron source facility for materials research is not merely an accelerator or a plasma machine but an integrated one composed of ion source, accelerator, target, irradiation cell, remote maintenance, shielding, hot laboratories and waste disposal.

Nuclear data needs for “low-activation” fusion materials development

So-called “low-activation” materials are presently considered as an important means of improving the safety and environmental characteristics of future DT fusion reactors. Essential benefits are expected in various problem areas ranging from operation considerations to aspects of decommissioning and waste disposal. Present programs on “low-activation” materials development depend strongly on reliable activity calculations for a wide range of technologically important materials. The related nuclear data requirements and important needs for more and improved nuclear data are discussed.

An accelerator based steady state neutron source

Using high current, cw linear accelerator technology, a spallation neutron source can achieve much higher average intensities than existing or proposed pulsed spallation sources. With about 100 mA of 300 MeV protons or deuterons, the accelerator based neutron research facility (ABNR) would initially achieve the 10 16 n/cm 2 s thermal flux goal of the advanced steady state neutron source, and upgrading could provide higher steady state fluxes. The relatively low ion energy compared to other spallation sources has an important impact on R&D requirements as well as capital cost, for which a range of $ 300–450M is estimated by comparison to other accelerator-based neutron source facilities. The source is similar to a reactor source in most respects. It has some higher energy neutrons but fewer gamma rays, and the moderator region is free of many of the design constraints of a reactor, which helps to implement sources for various neutron energy spectra, many beam tubes, etc. With the development of a multibeam concept and the basis for currents greater than 100 mA that is assumed in the R&D plan, the ABNR would serve many additional uses, such as fusion materials development, production of proton-rich isotopes, and other energy and defense program needs.

Instrumented in-reactor test capabilities in FFTF

Fusion materials research and development requires high neutron fluxes coupled with a large irradiation volume. Both of these needs can be provided by the Fast Flux Test Facility. The Materials Open Test Assembly, the vehicle used for materials irradiations in the FFTF, is described.

The fusion materials irradiation test facility at Hanford

The Fusion Materials Irradiation Test Facility (FMIT) is a high-energy, high-flux neutron source for fusion materials development. The FMIT linear accelerator will produce a 35 MeV beam of deuterons that generates high-energy neutrons by a nuclear stripping reaction with flowing liquid lithium targets. The targets will be located in two identical irradiation test cells, either of which will provide an irradiation volume of 10 cm3 at a neutron flux of 1015 n/cm2-s and 500 cm3 at a flux of 1014 n/cm2-s. FMIT has been authorized by the US Congress and will be constructed and operated by the Hanford Engineering Development Laboratory (HEDL) at Richland, Washington, in collaboration with the Los Alamos Scientific Laboratory (LASL) which is providing the accelerator design. The project is currently entering the detailed design phase, targeting for start of construction in early 1980 and operation in 1983–1984. Research and development programs are underway at both HEDL and LASL to resolve uncertainties in the lithium target and accelerator designs.

Irradiation sources for fusion materials development

Development of irradiation resistant alloys for fusion application must initially proceed using non-fusion irradiation sources. Neutron sources appropriate for fusion research are described and their relative roles are discussed. While no single source is sufficient to conduct the programs required, all components of first wall damage can be represented if the various sources are used judiciously.

The Application of Simulation Experiments to Fusion Materials Development

One of the major problems in the development of structural alloys for use in magnetic fusion reactors (MFRs) is the lack of suitable materials testing facilities. This is because operating fusion r...

Controlled Thermonuclear Reactor Neutron Spectra Simulation at the LAMPF Radiation Effects Facility

An essential element of any fusion or fission reactor materials development effort is the availability of irradiation facilities for conducting radiation effects experiments. A Radiation Effects Facility (REF) was provided for such studies at the Los Alamos Meson Physics Facility. Neutron spectra at the REF can be tailored to approximate those in either a fusion or fission reactor, while providing flux levels of approximately 1.4 x 10/sup 18/ m/sup -2/ s/sup -1/ at design maximum beam currents. An intranuclear-cascade/evaporation model was used for computing neutron production. Detailed Monte Carlo neutron transport calculations were performed, some of which were experimentally verified in a foil dosimetry program. Such calculations provide the radiation effects experimentalist with information on spatial-spectral variations of the neutron flux over much of the easily accessible experimental volume (approximately 19,000 cm/sup 3/), which includes irradiation specimen capsule locations and a rabbit tube. From these data, radiation damage indices such as ratios of parts per million helium to displacements per atom can be calculated and compared to those anticipated in fusion reactor blankets or fast fission reactor cores.