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The water rich in heavy volatile metals form the Cheleken Penninsula hot springs was passed through a column containing 850kg of anion exchange resin. The spontaneous fission activity (SF) of the samples was measured by neutron multiplicity detectors. The counting rate of spontaneous fission events was 0.5 per day for 9 kg of saturated resin. After 170kg of the resin had been treated with acid solutions and hydroxides had been precipitated from the eluate with alkali, the counting rate for the precipitate was about five per day. From measurements of the ~/SF ratio it is concluded that the activity cannot be traced back to a contamination by actinides, except to a contamination by pure 25zCf, which, however, seems to be unlikely. Thus the explanation of the observed effect as being due to the spontaneous fission of a new naturally occurring isotope of a superheavy element is considered to be the most probable one.

In bombarding 2~ and 2~176 targets by 55Mn and SaFe ions the yields of "cold fusion" reactions have been determined using a sensitive technique for detecting T~> 1 ms spontaneous fission and the e-decay of heavy actinide elements. It has been shown that the A=263-265 isotopes of element 108, including the even-even isotope 264108, undergo mainly e-decay. The obtained results, together with the known data on the properties of the isotopes of elements 104 and 106, provide evidence for the enhanced stability of the Z = 108 nuclei against spontaneous fission.

The emission of Ne and Mg nuclei was detected in the spontaneous decay of 234U with probabilities of, respectively, (3.9+1.0)• 10 -13 and (2.3_+0.7)• 10 -13 relative to a-decay. The upper limits of this kind of decay for 235U and 236U have been established. Systematics of half-lives for cluster emission are found to be similar to the Geiger-Nuttall dependence for a-decay. Some evidence for the presence of hindrance to cluster emission from the odd-mass nuclei 233U and 235U is obtained.