  Comet nuclei in the outer Solar system are constantly irradiated by cosmic
rays at low temperatures. Accumulated high concentrations of radicals can
undergo fast recombination with significant heating of cometary surface layers.
We present the model of comet activity at large heliocentric distances caused
by the recombination of radicals. We found that the considered mechanism can
cause activity of comets in distant regions of the Solar system, even at the
Oort cloud distances. Outbursts in distant comet reservoirs can be a new source
of dust and ice particles contributing to the recently discovered anomalous
diffuse light in the cosmic extragalactic background optic light. The orbits of
small-radii comets in the Oort cloud are highly influenced by cometary
outbursts. This effect may account for the observed decrease in the number of
small-radius long-period comets.
