It's been 35 years since the World's worst nuclear disaster happened at Chernobyl, then in Russia and now in Ukraine, near its capital Kiev. The Soviets did not share too much information to the World till the radiation appeared in Sweden. Eventually people were evaluated. Radiation continued to leak till 2019 when the entire reactor building was covered by an arch shaped shelter.

Hotstar / Disney has an interesting series on this.....

35 years on, Chernobyl warns and inspires
https://apnews.com/article/05cf7f5b9affc0e2e88739f4d070c7fe