[en] The permeation rate of D₂ through 304 and 304L stainless steel for driving pressures 10^-5 to 10^-1 Pa (10^-7 to 10^-3 torr) were measured over the temperature range 650 to 1050⁰K. Two 51 mu m and one 127 mu m, 304 samples and one 127 mu m, electropolished 304L sample were studied. The steady-state permeation rate varied linearly with p/sup ¹/₂/ in the 10^-2 to 10^-1 Pa range but had a higher dependence below 10^-3 Pa. The steady-state and transient data at 10^-1 Pa were used to calculate the permeability phi = 1.9 x 10¹⁵ exp (-6300 T^-10K) molecules D₂ cm^-1 sec^-1 Pa/-¹/₂/ and the diffusion coefficient D = 3.5 x 10^-4 exp (-5100 T^-10K) cm² sec^-1. The processes involved in permeation are discussed and time-dependent formulae for the permeation rate are given for a number of simple cases. Following thermal permeation experiments, permeation rates resulting from bombardment with a 10 mu amp, 15 keV deuteron beam were measured. A high transient permeation rate was observed which is attributed to a surface impedance to reemission which decreases under bombardment

[en] The Fe-Cr-Mn austenitic alloy system is being studied as a replacemnet of the Fe-Cr-Ni system for fusion applications in which reduced long-term radioactivation is an important consideration. This paper describes two aspects of the respone of this alloy system to material and environmental variables. First, the neutron-induced void swelling of simple binary and ternary alloys is investigated as a function of composition, thermal-mechanical treatment, temperature (693 to 873K) and displacement level (9 to 76 dpa). The swelling rate of this alloy system approaches 1%/dpa for those conditions which do not favor formation of large levels of ferrite phases. Second, the tendency of the potentially detrimental sigma phase to form during thermal aging is explored at high manganese levels. Variables such as carbon concentration, cold-work level and aging time are shown to influence the distribution and rate of sigma formation. 18 refs., 10 figs., 1 tab

[en] Two investigations are described that are pertinent to hydrogen hold-up and re-emission in the first wall of fusion reactors. The first employs existing theory to calculate the range distributions for light ions normally incident on metallic targets at energies of one to 20 keV. Three different statistical atomic potentials were used to approximate the interaction between a swift atom and a target atom. A surface correction to the theory of ion penetration was developed to account for the presence of a free surface in the target. The second study employed the diffusion equation to calculate the time dependent fluxes and concentration profiles of a gas originating at a planar source within a finite slab. The purpose of this procedure was to model the transport of gas implanted beneath a metal surface by the impingement of energetic, gaseous ions. Some studies on radiolytic fuel production are briefly reviewed

[en] The effects of fusion neutron spectrum and fluence on the evaluation of transmutation and induced radioactivity of candidate reduced and/or low activation materials such as 9Cr-2W ferritic steel, V-5Cr-5Ti and SiC_f/SiC composite have been examined by simulation calculations using structural models based on ITER design. The transmutations from W to Re and Os in the ferritic steel and from V to Cr in the V alloy were predicted to considerably occur depending on thermal neutron fluxes mainly determined by the composition of blanket/shields while induced radioactivity decay behaviours are not appreciably affected by the spectrum change of fusion neutrons. The acceptable concentrations of impurities such as Mo, Nb and Tb for waste disposal and hands-on recycling have been more restricted with increasing fluence because of the accumulation of nuclides controlling the radioactivity. In the effort of manufacturing high-purity materials, fused-salt electrolysis for vanadium and chemical vapor infiltration for SiC_f/SiC composite have been shown to be potential processes to obtain purified materials satisfying the low activation criteria. (orig.)

[en] Published in summary form only

No abstract available

[en] The effects of exposure to helium containing oxygen of 0.1-115 vpm at 1000⁰C on the mechanical properties of molybdenum and TZM-Mo alloy at room temperature were studied. The stress-relieved molybdenum specimen which was not recrystallized at test temperature showed the ductility after exposure to helium containing oxygen. The recrystallized molybdenum and TZM lost ductility after exposure to helium containing oxygen of 0.1-13 vpm in a few hours. The embrittlement of molybdenum was considered to be due to the grain boundary weakening. Molybdenum to which carbon was added seemed to hinder the grain boundary weakening by the oxygen contamination. Both stress-relieved and recrystallized TZM specimens picked up oxygen linearly with time of exposure to helium. The increase in oxygen content of TZM, which was considered to be caused by the internal oxidation of titanium and zirconium, results in the embrittlement of TZM. (orig.)

[en] The induced activity and compositional change of several superconducting materials such as Nb-based alloys, V-based alloys and MgB₂ have been evaluated with a numerical calculation. We assume that the materials are irradiated for 10 MW a/m² at the magnet of the inboard position of a tokamak-type fusion reactor with a neutron wall loading of 1 MW/m². The materials are Nb₃Sn, Nb₃Al, NbTi, NbZr, V₂Zr, V₂(Zr,Hf), V₃Ga, V₃Si and MgB₂. Most of the induced activity of V-based alloys and MgB₂ after the shutdown of the reactor is controlled by the ⁶⁰Co formed from Cu. After the irradiation, the dose rate decreases to a safe level of 10 μSv/h within 30 years. However, Nb-based alloys are predicted to emit gamma rays for tens of thousands years. The compositional changes and irradiation damage of V-based alloys and MgB₂ are minimal

No abstract available

[en] Analysis of permeation rates of D₂ gas at 10^-4 to 10^-1 Pa through 304 and 304L stainless steel membranes (51 μm and 127 μm thick) at 650 to 1050 K revealed that the chemisorption rate constant, k₁, permeability and diffusion coefficient were 5.0 X 10¹⁵ + 2.2 X 10²⁶ exp(-2.1 X 10⁴T^-1K) molecules D₂.cm^-2.sec^-1.Pa^-1, 1.4 X 10¹⁶ exp(-7700T^-1K) molecules D₂.cm^-2.sec^-1.Pasup(-1/2), and 3.5 X 10^-4 exp(-5100T^-1K) cm² s^-1, respectively. The value of k₁ indicates two chemisorption sites (one unactivated). The scaling laws and the transition between the high and low pressure asymptotes were clarified by developing a dimensionless form of permeation equation applicable for low D₂ activities. Following gas permeation experiments, permeation rates resulting from bombardment with 10 μA, 15 keV deuteron beams were measured. A high transient permeation rate was observed which was attributed to a surface impedance to reemission which decreased under bombardment. (Auth.)