LONDON (AP) — A book about the causes and consequences of the Chernobyl nuclear disaster has won Britain's leading nonfiction literary award.

Serhii Plokhy was awarded the 30,000-pound ($39,000) Baillie Gifford Prize at a ceremony in London on Wednesday for "Chernobyl: History of a Tragedy."

Plokhy, a professor of Ukrainian history at Harvard University, explores the way the Soviet political system, a flawed industry and human error triggered an accident that sent radioactive fallout over half of Europe.

He said the lesson he had learned from Chernobyl was that nuclear power "was the cleanest energy as long as nothing happens. Once it happens it is the dirtiest energy in the world."

The award recognizes nonfiction English-language books in the areas of current affairs, history, politics, science, sport, travel, biography, autobiography and the arts.