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:Magnitude 6 earthquake strikes Japan's Kyushu island, Channel Asia News, April 14, 2016, http://www.channelnewsasia.com/news/asiapacific/magnitude-6-2-earthquake/2696370.htmlThe 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….
Tadahiro Katsuta. Why was the Sendai nuclear power plant restarted? Bulletin of Atomic Scientists. August 12, 2015, http://thebulletin.org/why-was-sendai-nuclear-power-plant-restarted8644When 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.
Meanwhile, at Fukushima renewed, visible atmospheric emissions continue despite the absence of precipitation:… 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.