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The influence of the atomic electron cloud on the gamma decay constant 2~ was evaluated in third-order approximation according to the theory of Krutov for some highly converted nuclear transitions (resonance case only). The results are 2~3)= 1.5 x l0 s 2~ 1) for the 73 eV transition of U-235m and 2~,,. 3J= 1.01 j[~l) for the 2.17 keV transition of Tc-99 m. Values calculated for Z= 80, E~ =2 keV are in good agreement with those of Krutov. Experimental evidence of the calculated effects does not seem to be obtainable at present because of the extremely low gamma intensity of the transitions in question.

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The mobilization of dust (i.e., detachment and removal of dust grains from a substrate) and the exfoliation of a film of erosion products in tokamaks have been studied theoretically. The following mecha nisms of dust mobilization have been taken into account: (i) sharp heating (thermal shock) as a result of, e.g., plasma disruption and edge instabilities; (ii) substrate vibrations; and (iii) gas and plasma flow (wind) action. The most effective mobilization takes place under the action of sharp heating. Power fluxes that are charac teristic of edge instabilities can mobilize dust grains with dimensions within or even greater than 0.1-1 µm. The velocities of detached grains reach m/s for heavy grains and up to v ~ 300 m/s for the light ones. Conditions favoring the exfoliation of a film of erosion products are determined. It is shown that exfoliation under the action of edge instabilities can take place at a film thickness of h > 1 µm. Under the action of ther mal shock induced stresses, the exfoliated film flakes with a size ranging from fractions of a millimeter to sev eral centimeters break into pieces.