Chernobyl wildlife research. Biologist holding mice captured from within the Chernobyl exclusion zone, Ukraine, that have been used for genetic research. On 26th April 1986, reactor number 4 of the Chernobyl Nuclear Power Plant went out of control, leading to meltdown and an explosion. Around 1000 square kilometres of land were directly contaminated by radioactive fall-out and a 30km exclusion zone was created. Since people left the area wildlife has flourished, seemingly unaffected by the radioactive contamination. Since 1992, Ukrainian and American researchers have studied 28 generations of mice collected from the forests of the exclusion zone. They have found that genetic mutations do exist but they do not seem to affect the daily life of the mice.