Ukraine is marking the 25th anniversary of the world's worst nuclear accident - at the Chernobyl power plant.

乌克兰正在举行切尔诺贝利核电事故25周年纪念活动——这是世界上最糟糕的核事故。

A number of workers died trying to contain the radiation leak after the explosion at Chernobyl
An explosion at one of the plant's reactors² sent a plume³ of radiation across Europe and killed at least 30 people in its immediate⁴ aftermath.

A disputed number of others died later from radiation-related illnesses.

The anniversary comes amid renewed global protest over nuclear power and as Japan struggles to contain radiation leaks at its crippled Fukushima plant.

It was on 26 April 1986 that Number Four reactor¹ at Chernobyl, which was then in the Soviet⁵ Union, exploded.

The accident forced the evacuation of hundreds of thousands of people from their homes in Ukraine, western Russia and Belarus.

There is still a 30km (19 miles) exclusion⁶ zone around the plant.

Soviet engineers encased the damaged reactor in a temporary concrete casing to limit the radiation but a new shield is needed.

A donors⁷ conference in Kiev, Ukraine, last week raised 550m euros (£486m; $798m) of the 740m euros needed to build a new shelter and a storage facility for spent fuel.

Soviet officials held off（拖延） reporting the accident for several days.

The Chernobyl anniversary comes less than two months after the Fukushima nuclear plant in Japan was badly damaged by an earthquake and tsunami⁸, renewing concerns about the safety of nuclear power generation.

The operators of the Fukushima plant, Tokyo Electric Power Co, have also come under fire for not quickly disclosing information on radiation leaks from the plant.

Russian President Dmitry Medvedev said there must be greater transparency（透明度） in nuclear emergencies.

"I think that our modern states must see the main lesson of what happened at Chernobyl and the most recent Japanese tragedy as the necessity to tell people the truth," he told survivors⁹ of the clean-up effort at a meeting in the Kremlin.

He is to visit Chernobyl on Tuesday, as is Ukraine's Prime Minister Viktor Yanukovych.

Mr Yanukovich and Russian Orthodox Patriarch Kirill were attending a candle-lighting ceremony in Kiev on Monday night before travelling to Chernobyl.