The
quake hit 11km east of Kunamoto in Kyushu at a depth of around 10km….There were no irregularities at the Genkai or Sendai
nuclear plants, which are on the southernmost main island of Kyushu, or at the
Ikata plant on nearby Shikkoku, the Kyodo news agency reported….
So far there are no reports of problems at the nuclear power plants. That is good news because the plants are VULNERABLE. Dr. Katsuta explains why at the Sendai plant:
When it comes to safety, the Sendai nuclear power
plant is definitely not at the head of the class: The utility owning the power
plant was given a pass despite a very problematic history. (At one point, a
regulatory commissioner called the plan to restart Sendai “wishful thinking”.)
Pressurized water reactors are considered inherently safe. Because
strict new standards for the regulation of nuclear power plants were imposed in
July 2012—the result of the belated adoption of a tougher global
standard—Japan’s newly formed Nuclear Regulation Authority deemed that
pressurized water reactors (PWRs) such as those used at Sendai were safer than
the boiling water reactor technology used at the ill-fated Fukushima Daiichi
nuclear plant. Consequently, facilities with PWRs were given a longer time
span—five years—to introduce severe accident countermeasures when the new
regulation standards come into force.
For example, a nuclear power plant using a pressurized water reactor is not
required to immediately install a filtered containment venting system to
prevent large-scale radioactive contamination to the environment if the
containment vessel inside is damaged. The Nuclear Regulation Authority’s
reasoning is that the risk of containment vessel damage is low in a pressurized
water reactor because it is so much larger than in a boiling water reactor,
thus allowing considerably more time before any accident measures must be put
into effect. Building on this logic, the agency then gave a temporary exemption
to the requirement to install the venting system to any facility using PWRs.
… But PWRs are not inherently safe at all; for
example, their steam generators are a serious concern. In 1991, the steam
generator in the pressurized water reactor at Mihama Unit 2 of Kansai Electric
Power in Japan was damaged, and the emergency core cooling system had to
activated.
Meanwhile, at Fukushima renewed, visible atmospheric emissions continue despite the absence of precipitation:
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