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Maximum core height of BN-type reactors is limited by safety considerations. If the core height exceeds 85-90 cm, ULOF-type accident leads to the heavy core damage. Hence, increase of reactor power leads to increase of core diameter and D/H ratio. Neutron field stability in the large diameter cores should be considered. Ratio of the two first eigenvalues of static reactor balance equation (dominance ratio) widely used as neutron field stability criterion. The results of dominance ratio evaluation for large BN-type reactor are considered in the article. Dominance ratio of BN-type reactor compared with dominance ratios for several high power thermal reactors. It is shown that dominance ratio of BN-type high power reactor is still lower, than that of thermal reactors. Hence, instability of neutron field in BN-type reactors due to high dominance ratio seems to be unlikely.

Screening of Orchidaceae on virus diseases in the collection of Fomin's Botanical garden of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine has been conducted. The symptoms of infected plants are described. The presence of mixed infections caused by viral and bacterial agents are defined