Taking notes
Herman Tsui says there are safety messages Hong Kong can take away from the Fukushima nuclear accident to bolster the effectiveness of contingency plans for a failure at the Daya Bay power plant
Apr 10, 2012
SCMP, Hong Kong
The major nuclear accident at the Fukushima Daiichi nuclear power plant in March last year raised questions again about the safety of nuclear power and contingency planning. With nuclear power plants nearby, Hong Kong is rightly concerned with the safety of these power plants and the adequacy of our contingency plan.
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The questions include: Was the Fukushima accident preventable? Should a major nuclear accident occur, what are the potential impacts on Hong Kong and what can be done to minimise them?
Recently, the government conducted a comprehensive review of the Daya Bay contingency plan. The key is that there are lessons learnt from the Fukushima accident available to improve contingency planning for Hong Kong.
Triggered by the "once-in-a-thousand-years" natural disaster, the Fukushima accident resulted in seriously damaged reactors, radiation releases and evacuation.
Despite the comments on the less than well-prepared emergency response, the consequences were reasonably controlled. (totally lie) Although some workers and nearby residents received radiation above the usual regulatory limits, the official reports confirmed that:
• No radiation casualties were reported by June 2011;
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• Of the 20,549 people who had worked on the site since March 11 last year, six workers received doses over 250 millisieverts;
•No harmful health effects were found in 9,747 residents near Fukushima by July 2011. Of these residents, 5,636 received within 1 mSv, which is a fraction of the global average radiation dose of 2.4 mSv per year from natural sources, and 10 received over 15 mSv, a level equivalent to six years of global average radiation dose from natural sources but much below the world maximum; (totally lie)
• The evacuation zone was 20 kilometres and some contaminated areas within a range of some 20 to 50 kilometres northwest of the plant were also evacuated.
Thus, despite the severity of the Fukushima accident, the general public's exposure to radiation was within safety limits. A 20-kilometre emergency planning zone appears to be appropriate, in accordance with international best practices and in view of the experience from Fukushima. However, due consideration should also be given to actions to mitigate the impact of an unlikely event of radioactive release extending beyond 20 kilometres.
Japan's Daily Yomiuri newspaper reported on February 5 this year that 573 deaths were classified as "disaster-related" as a result of the Fukushima accident. These deaths were not radiation casualties. They were caused by fatigue or the aggravation of a chronic disease due to evacuation. These added to the over 15,850 deaths caused by the natural disasters of the earthquake and tsunami.
A lesson learnt is that evacuation, particularly for the elderly and those suffering from chronic medical conditions, may present a higher risk.
Could the nuclear accident have been prevented in the first place? The scale of the natural disaster went well beyond what the design of the Fukushima plant had catered for. Although the safety measures worked to minimise the impact of the earthquake and tsunami, the accident could have been avoided if the plant had been upgraded to incorporate the latest understanding of the potential hazard (tsunami) and safety technology.
Over the last decade, evidence of much larger once-in-a-thousand-years tsunamis in the area has emerged. For example, there was the 8.3-magnitude Jogan earthquake in the year 869. A 2008 study revealed the tsunami hazard to the plant had been severely underestimated.
Similarly for the Daya Bay nuclear power station, safety measures should be continually reviewed and upgraded, in line with the world's best practices.
The Daya Bay station is located in a geologically more stable region and is designed to withstand various natural hazards such as the effect of the biggest earthquake in history, plus a margin.
The Daya Bay station's pressurised water reactor is also different from the boiling water reactor of Fukushima. The Daya Bay's type of reactor more effectively contains radioactivity released from the reactor cooling system than the Fukushima type, and the corresponding likelihood of a major-core-damage accident is thought to be 10 times less likely. Daya Bay has passive cooling equipment for the reactor as well as a passive sand filter, which could significantly reduce the amount of radioactivity released into the environment.
A nuclear power station's safety design has a direct effect on the severity of the consequences of an accident. Take exposure to the radioisotope iodine-131 as an example. Of the three severe nuclear accidents, Chernobyl released 10 times more iodine-131 than Fukushima, while Three Mile Island released about 100,000 times less than Fukushima.
The Daya Bay contingency plan should give due consideration to the specific safety characteristics of a plant. Our view is that the government should use whatever means available to support continued safety improvements of the power station. Furthermore, the government should ensure that information about the improvements, implemented and planned, is effectively transmitted to the public.
Despite the continuing effort of the nuclear industry to make nuclear power ever safer, there is still a chance of a nuclear accident. The government should make best use of the contingency plan and exercises to ensure the Hong Kong public understand how to respond in the event of a serious nuclear accident. The government should take any further lessons learnt from the Fukushima accident into consideration in planning as well as its review exercise to make the contingency plan most appropriate for our local situation.
Ir Dr Herman Tsui Yik-wai is senior vice-chairman of the Hong Kong Nuclear Society
