Radiation hormesis proposes that radiation exposure comparable to and just above the natural background level of radiation is not harmful but beneficial, while accepting that much higher levels of radiation are hazardous.

Source Wikipedia

The finding that ionizing radiation can (in some circumstances) be beneficial to health goes back more than 100 years - following experiments with X-rays.

The idea of 'Radiation hormesis' - where the source of the ionizing radiation is from nuclear energy, is more recent.

The World's leading nuclear authorities vary greatly in their attitude to radiation hormesis, some maintaining that there are proven benefits and no known risks from very low-dose irradiation - others claiming that radioactivity is hazardous at any level, or that any beneficial effects are outweighed by the risks involved.

Detailed reading RSO Magazine â–ª Volume 8, Number 4 (archived)