No abstract available

[en] The first wall surfaces of fusion devices will be exposed to bombardment by inert gaseous projectiles such as helium. The flux, energy and angular distribution of the helium radiation will depend not only on the type of device but also on its design parameters. For near term tokamak devices, the first wall surface phenomena caused by helium bombardment that appear to be quite important are physical sputtering and radiation blistering. Examples of these processes for a number of first wall candidate materials are discussed. While the physical sputtering phenomen is well understood, the mechanism of blister formation is still not fully understood. The various models proposed for radiation blistering of metal during helium bombardment is critically reviewed in the light of most recent experimental results

[en] The fabrication of large and heavy nuclear components like reactor pressure vessels, steam generators and pressurizers needs maximum safety and requires a high degree of know how for the planning, design and production stages, including, quality assurance. Highly skilled and experienced operators are needed for the manifold tasks involved, as well as all the necessary equipment for handling, machining, non-cutting shaping, heat treatment, welding and for a great number of destructive and non-destructive tests. (author). 9 figs

[en] The interaction of plasma radiations with the exposed surfaces of components of plasma devices and future controlled thermonuclear fusion reactors (CTR) can cause a variety of surface effects. In turn, such surface effects can cause (a) the release of plasma contaminants, and (b) the damage and erosion of the irradiated surfaces. The contamination of the plasma can have serious effects on plasma stability and on plasma temperature, and the surface erosion can seriously limit the lifetime of the irradiated components. At present, knowledge of surface erosion rates for the plasma parameters and materials envisioned in CTR applications is only fragmentary. To what extent the erosion rates will be affected by synergistic effects due to the simultaneous bombardment of surfaces by high fluxes of energetic particles of various types and by photons is almost completely unknown. A summary of some of the major surface erosion phenomena which have been identified as being important for CTR applications by using single irradiation sources (e.g., accelerators) will be given. A discussion of some potential solutions to reduce surface erosion will be included. The main features of a recently completed two component irradiation facility at ANL for CTR related surface studies will be described

No abstract available

[en] Experiments were conducted to determine the surface damage of ATJ graphite, V, Cu, and Type 316 stainless steel under 60-keV D⁺ irradiation. The irradiations were conducted in the pulsed mode. For a total accumulated dose of 8.1 x 10¹⁸ ions/cm², blisters were readily seen for Cu surfaces, but no blisters were observed on Type 316 stainless steel and vanadium surfaces. For the case of ATJ graphite, the surface damage was observed in the form of ridges and grooves. In the case of copper, many large blisters with diameters ranging from 3.5 μm to 46 μm are observed in addition to some small ones (average diameter approx. 2 μm. The blister density of the large blisters is the highest in the case of copper (1.1 x 10⁵ blisters/cm²). These observations of blister formation are related to the differences in the premeability of deuterium in these materials. An examination of the cross section of the ridges in fractured samples of graphite indicates that they are not hollow. The mechanisms of formation of these ridges is not clear at present. 1 figure

[en] The surface damage and erosion of chemically vapor deposited TiB₂ coatings and commercial grade Ti, caused by 40-, 60- and 120-keV D⁺ and ⁴He⁺ irradiation, has been studied for the as deposited coatings and for the coating surfaces that were mechanically polished prior to irradiation. SEM analysis of polished TiB₂ samples irradiated with D⁺ and ⁴He⁺ to a dose of 3.1 x 10¹⁸ ions/cm² reveal significant surface damage due to blistering and flaking whereas for identical irradiation conditions, the as deposited TiB₂ coatings show very little damage. For similar irradiation conditions the Ti metal samples showed blistering for the ⁴He⁺ irradiation case but no significant surface damage for the D⁺ case. Estimates of the irosion yields due to blister exfoliation in polished TiB₂ samples show an increase with increasing projectile energy for the total dose studied

[en] Studies have been conducted to find materials with microstructures which minimize the formation of blisters. A promising class of materials appears to be sintered metal powder with small average grain sizes and low atomic number Z. Studies of the surface erosion of sintered aluminum powder (SAP 895) and of aluminum held at 400⁰C due to blistering by 100 keV helium ions have been conducted and the results are compared to those obtained earlier for room temperature irradiation. A significant reduction of the erosion rate in SAP 895 in comparison to annealed aluminum and SAP 930 is observed. In addition results on the blistering of sintered beryllium powder (type I) irradiated at room temperature and 600⁰C by 100 keV helium ions are given. These results will be compared with those reported recently for vacuum cast beryllium foil and a foil of sintered beryllium powder (type II) which was fabricated differently, than type I. For room temperature irradiation only a few blisters could be observed in sintered beryllium powder type I and type II and they are smaller in size and in number than in vacuum cast beryllium. For irradiation at 600⁰C large scale exfoliation of blisters was observed for vacuum cast beryllium but much less exfoliation was seen for sintered beryllium powder, type I, and type II. The results show a reduction in erosion rate cast beryllium, for both room temperature and 600⁰C

[en] Different metals have been proposed for radiation blistering of metals. For example, for the formation of blisters on helium bombarded metal surfaces such models are based on the coalescence of gas bubbles and the build-up of excess gas pressure in the implant region, causing large enough stresses for the occurrence of plastic deformation of the surface regions; or the percolation of helium in the lattice; or the build-up of large, lateral stresses in the implant layer causing buckling. These models are critically reviewed in the light of recent experimental results. A discussion of blistering effects at high doses is included

No abstract available