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Metal-surface-sputtering regularities under the influence of charged particles are of interest for various branches of science and technology; they were considered in [1][2][3]. However, little research has been done on sputtering of uranium and other fissionable-material surfaces during nuclear fission and fragment yield into the surroundings. Knowing the laws of this phenomenon can be important, for example, in radiation chemistry when realizing radiation-chemical processes using fission-fragment kinetic energy [4,5] and in some other branches, where thin layers of uranium-containing materials are used or where nuclear fuel is not enclosed in a special envelope.There is still no perfected and rigorous theory concerning surface sputtering under the influence of fission fragments, but it has been established that the sputtering or ejection ratio K, which is defined as the number of fissionahle-material atoms carried away by one fission fragment leaving the surface, is related to several experimental parameters. The present paper briefly considers the sputtering ratio's dependence on the emitter (fission fragment source) surface state. It is also shown how crystal structure and emitter-material properties influence the ratio K and how the sputtering ratio and integral neutronirradiation dose are interrelated. An~attempt is made to analyze the state of sputtered-material nuclei gathered at the collector and to delimit the probable ejection mechanism from these data.F. S. Lapteva and B. V. Ershler [6] were the first to confirm experimentally the fissionable-material ejection phenomenon. They showed that on the order of a thousand uranium atoms may leave a pure polished 233U or 239pu surface with one fission fragment. If the simple surface is covered with an oxide film, this value is on the average 24 atoms per fragment. B. Lastman [7], referring to [8], names a similar figure -45 molecules of uranium dioxide per fission event in a surface layer with thickness equal to the recoil-atom mean free path.The concepts of radiation-damage theory [9,10] are used to explain surface-sputtering effects under the influence of fission fragments. Fissionable-material surface-layer sputtering can be explained by using the .thermal-peak. hypothesis [9][10][11][12] or the .displacement-peak" theory proposed b~ Brinkman [13][14][15]. Another explanation for ejection (sputtering) is based on the theory of atomic expulsion at the expense of recoil-atom energy; these atoms produce displacement cascades [9,10]. Whaphan and Makin [16] believe damage may occur to a surface from which high-energy charged ions emerge at the expense of expelling larger particles. If we accept the proposition that there exists a high-temperature region along the fission-fragment motion trajectory, then in the .peak. region there arises instantaneously an explosive pressure. This may give rise to motion in the solid-state layers surrounding the track and lead to particle expulsion from the material surface layer. When the temperature in the .thermal-peak. regio...

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