Global Perspectives: Japan quake sounds the alarm for China’s nuclear safety
Will the Japan quake slow China’s nuclear power generating plans for huge growth, 26 units now under construction? Third-generation, passive safety, may help.
The March, 11, 2011, 9.0-magnitude earthquake and tsunami, which killed thousands, damaged the Fukushima Daiichi plant's cooling functions. A subsequent fire at the No.4 reactor was reported after explosions of the number 1, 2, and 3 reactors.
The Japanese media reported that the first nuclear leakage drifted to Tokyo, resulting in radiation levels 20 times higher than usual and rising. Japan faced the world’s worst nuclear security crisis after the 1986 explosion of reactor number 4 at the Ukraine's Chernobyl plant.
Will China stop?
China's nuclear power industry has shown a trend of rapid development in recent years. Compared with thermal power, nuclear power is very clean. Under the pressure of reducing carbon emissions and growing energy demand, the number of nuclear power plants that China plans to build in the next 10 years will be three times higher than the sum of other countries.
According to data recently released by the China Electricity Council, China’s nuclear power installed capacity exceeded 10 million kilowatts [10,000 MW or 10 GW], with 26 units under construction. [Many new nuclear units are designed to generate 1000 MW or more each.] In accordance with China 12th five-year energy plan, the scale of China's nuclear power plant could reach 39 million kilowatts by 2015.
However, the explosions at the Fukushima Daiichi plant may diminish China’s enthusiasm for rapid nuclear power development. Hunan Taohuajiang nuclear plant, one of 26 nuclear plants under construction in China, is a joint project by the China National Nuclear Corporation and other three companies, with an investment of 60 billion RMB [Ren Min Bi, Chinese currency, on Aug. 17 ~$9.4 billion]. The plant is still in the early stages of development. Construction was originally scheduled to begin in 2011 and be completed in 2015, but it now might be delayed for security reasons.
Data from 2008 showed that nuclear power accounted for only 2% of China's total generating capacity. In response to China's energy shortage, a national nuclear energy development plan has been a key issue in China’s 12th five-year energy plan. However, some feel that China should slow down the pace to ensure safe operation. Cai Guoxiong, deputy chief engineer of China Electric Power Research Institute, suggested that nuclear plant safety mechanisms must be reviewed. In addition to technology, population density, resources, and other factors, Cai said locations of coastal nuclear power plants should also take into account the possibility of a tsunami.
Third-generation nuclear power technology
Luqi Zhou, the general manager of China Power Investment Group Corporation, said that China adopted third-generation nuclear technology using a passive safety system, which is safer than second-generation technology used by the Fukushima plant. The new technology does not need to enable backup power for heat elimination with cooling water.
Cao Xuewu, an expert in nuclear reactor engineering and safety research and professor at Shanghai Jiao Tong University, also said that unlike the Fukushima nuclear power plant, China’s plant did not use the same type of boiling water reactors (BWR). That means the possibility of radioactive pollution is much smaller.
Because the Fukushima plant used second-generation nuclear power technology, after an emergency shutdown, it had to use backup power to drive cooling water for heat elimination. This problem doesn’t exist for third-generation AP1000 nuclear power technology, which China used in its nuclear plant along the coast and wants to promote to inland plants. It uses a passive safety system—that is, there are multiple kiloton-level water tanks on the top of the reactor, so when an emergency occurs, it does not need an ac power supply and emergency generator; it uses only gravity and other natural phenomena to drive nuclear power plant safety systems. It could cool the reactor core cleverly, eliminate the afterheat of the core, and spray the exterior for containment, thus restoring the security status of nuclear power plants.
Lessons of the crisis
Plant aging – The Fukushima nuclear power plant had operated for nearly 40 years. The design life span of the reactor at the time of construction was 30 to 40 years. With the current level of industrial technology, equipment reliability and durability of materials are significantly improved.
Anti-seismic grade – Japan’s seismic design standard for nuclear power plants originally accounted for 6.5 magnitude earthquakes. In 2006, Japan revised its nuclear seismic standards to address a maximum of magnitude 7.0. But among the 55 nuclear power plants in Japan, only one nuclear power plant in Shizuoka, Bin Gang, complies with the latest seismic standards. According to Tokyo Electric Power Company documents, the first and second nuclear power plants there are designed to withstand only magnitude 7.9 earthquakes, far from the magnitude 9 earthquake that occurred in March 2011.
Power – The Fukushima nuclear power plant’s safety systems are active safety systems. After the earthquake, the nuclear power plant automatically shut down. But there was after heat from the reactor, which should have been cooling constantly. At that time, the active safety systems needed emergency pumps and valves, but after the disaster, power supply for these devices remains a big problem.
- Aileen Jin is with Control Engineering China, part of the Control Engineering International group of editions, provide Global Perspectives on automation and controls: http://www.controleng.com/index.php?id=1330
- Edited by Mark T. Hoske; posted by Chris Vavra, Control Engineering, www.controleng.com