It seems like disasters are rolling in one after another in Japan. First, the deadly earthquake, then the tsunami, and now nuclear threats that have yet to be brought under control. The failure of the cooling systems for reactors at the stricken Fukushima nuclear power plant has raised the threat of a serious radiation leak and even an eventual meltdown. Unit three appears to be the most severely damaged; the threat there seems most serious as it is the only one that runs on plutonium as well as uranium. Plutonium fuel is far more deadly than enriched uranium. If radiation were released from unit three, the doses could be as serious as in the 1986 Chernobyl nuclear disaster, the worst nuclear accident in history. The next 48 hours will be crucial. Things have not been helped by the lack of transparency at the Tokyo Electric Power Company, while the Japanese government was slow in its initial response, having underestimated the seriousness of the accident. Experts at the French and US nuclear safety agencies have rated the Fukushima accident at six on the international nuclear event scale from 0 to 7. Only Chernobyl rated higher, at 7. The American aircraft carrier, USS Ronald Reagan, and the Seventh Fleet support ships, dispatched to the scene to help, had to quickly reposition themselves at one point because of a radioactive plume. China was the first to issue a mass evacuation order of all its nationals. Russia and other European nations are also evacuating their nationals from Japan. Some Japanese have been moving westwards, away from the stricken area. The crisis is still unfolding and experts are struggling to contain the situation. The entire world, especially countries in the region, cannot afford to sit on the sidelines. We must be prepared for any emergency situation that may arise. What has happened in Japan once again raises concerns about the safety of nuclear power. Switzerland has halted plans to build more nuclear plants. The European Union has woken up from its slumber and is now assessing its capacity to cope with similar disasters. It has decided to re-evaluate the designs of its nuclear power plants to test their ability to withstand earthquakes and natural disasters. Germany has decided to rethink extending the life of the country's older nuclear plants. China, too, has announced that it is suspending all new nuclear plant construction plans and ordering a nationwide safety review, which is a big deal because of its ambitious nuclear energy programme. The world's nuclear energy policy has been thrown into disarray. According to the International Atomic Energy Agency, there are 442 nuclear power plant units in operation in 30 countries, 65 more are under construction in 16 countries, of which over 40 plants are in Asia. The one that concerns Hong Kong most is the Daya Bay nuclear power plant, just 50 kilometres from the city. One million Hongkongers signed a petition to try to block its construction more than 20 years ago. We can't possibly imagine the consequences of a serious accident at Daya Bay. Last year, the Environment Bureau proposed adjusting our energy mix and increasing nuclear energy to make up half of the total mix by 2020, from the current 23 per cent. That means the addition of one nuclear power plant in Guangdong. We have been reassured that the design of the Daya Bay plant is far more advanced than that at Fukushima and that it is not located in a seismic zone, but, still, we cannot predict or control accidents. Another concern is transparency on the mainland; we can never be sure that all the information would be fully released in the event of an accident. It's the government's job to placate growing public concern regarding nuclear safety. But ensuring nuclear safety, raising public awareness and enhancing our responsiveness in the event of a nuclear emergency should be priorities of the entire community. Albert Cheng King-hon is a political commentator