HONG KONG - China's Daya Bay nuclear plant is different from Japan's Fukushima nuclear plant in terms of location, reactor type and structure, so it is safer, experts said on Saturday.
The 9.0 earthquake hit Japan on March 11 "is the 4th largest earthquake ever recorded by seismic instruments, just after the 9.5 quake in Chile in 1960, the 9.2 quake in Alaska, the United States in 1964, and the 9.1 quake in Sumatra, Indonesia in 2004," according to L.S. Chan, professor of science of Hong Kong University.
It has triggered over 600 aftershocks larger than four magnitude, with the largest 7.9 magnitude, he said Saturday at a seminar on Japan's recent massive earthquake.
The nuclear crisis in Japan's Fukushima nuclear plant following the 9.0 earthquake and ensuing tsunami "is the first time a nuclear crisis was triggered by an earthquake," Chan said.
As the nuclear crisis goes on, governments and people around the world are highly concerned about the safety of nuclear plants.
Switzerland has suspended new nuclear plant construction, Germany shut down all 7 reactors built before 1980, Venezuela froze plan to build its first nuclear power plant, the United States ordered review of nuclear plant safety, and China imposed temporary suspension of nuclear power plant construction.
The Chinese, especially people living in Hong Kong are concerned about the safety of Daya Bay nuclear power plant, which locates in eastern Shenzhen, China, some 60 km from Hong Kong.
However, the experts said the Daya Bay nuclear plant is more modern and safer than the Fukushima nuclear plant.
Chance of being hit by massive quake and tsunami is low
The Fukushima Nuclear Plant locates at Japan's eastern shore, which is on the fault. So the nuclear plant is prone to earthquake and tsunami disasters. However, the Daya Bay nuclear power plant, which is not on the fault, has a very low chance of being hit by a massive earthquake and tsunami.
What's more, seawalls built to cope with tsunami at the Fukushima Nuclear Plant is not high enough.
As the earthquake on March 11 triggered massive tsunami, seawalls built around the Fukushima Nuclear Plant were swept over, and the plant was flooded. The diesel generators which were situated in a low spot were damaged.
"The seawalls around the Fukushima Nuclear Plant should have been built higher, or the generators should have been placed on higher ground to withstand potential flooding," engineering expert Dr. Ray Su of the University of Hong Kong said.
"Intact even hit by a boeing-747"
The Fukushima Nuclear Plant, first commissioned in 1971, has in operation for 40 years. Its construction standard is relatively low. The Daya Bay nuclear power plant, however, was built in the 1990s in line with IAEA's new standard.
The Daya Bay plant, using pressurized water reactors, uses pressurized water to carry away the heat generated from the reactors to the steam generators. In order to cope with the pressure, the reactors' protective layers are at least twice to the thickness of those in the Fukushima plant, which uses boiling water reactors.
The containment of Daya Bay nuclear power plant is much more stronger than the Fukushima Nuclear Plant, "it will remain intact even hit by a Boeing-747 plane," according to Professor C.F. Lee of the University of Hong Kong.
Structure of the two nuclear plants is different
The Fukushima Nuclear Plant has only one cooling system, which makes use of reactor heat to raise steam directly for power generation. "In the case of venting, the steam vented may necessarily release radioactive products," said Professor C.F. Lee, who is also a member of the Chinese Academy of Engineering.
The Daya Bay nuclear power plant has two cooling systems, one cooling system uses water under pressure to transfer reactor heat to an adjoining but separate secondary cooling system to raise steam for power generation. Therefore, the steam generated from the reactor bears no radioactive materials, so even if steam leaks, it will not convey radioactive materials.
The Fukushima Nuclear Plant has no effective deployment of back up equipment. When the tsunami flooded the plant and destroyed diesel generators, there was no power to run the reactor's cooling systems, overheating caused partial fuel meltdowns at the reactors.
"The Daya Bay nuclear power plant has three sets of back-up feedwater pumps to support reactor residual heat removal, with two driven by electricity and the remaining one driven by the steam generated from the secondary cooling system," Professor C.F. Lee said.
"So in case of loss of electrical power, the steam-driven pump is still available to pump the cooling water for residual heat removal," he said.