in 1986 , reactor 4 in the chernobyl power plant exploded , sending radioactive particles into the air above the city of pripyat , north of kiev .
at the time , the area was part of the former soviet union , but is now ukraine .
the exclusion zone , a nearly 50kilometre -lrb- 31-mile -rrb- radius of contamination , runs around the power plant , although levels have now returned to those which are safe for brief visits to the area that