A Japanese power company says it will change its rule of closing tide gates at one of its nuclear plants to prevent flooding by a possible tsunami.
Kansai Electric Power Company reported the rule change to the Nuclear Regulation Authority on Thursday.
The company's Takahama nuclear plant is on the Sea of Japan coast in Fukui Prefecture.
Under the new rule, it will close the tide gates when it detects any abnormal change in the tide level, rather than in response to a tsunami warning issued after an earthquake.
The authority had earlier asked the company to consider the possibility of a tsunami triggered by causes other than earthquakes.
It is said there is no established method in the world for issuing a warning against a tsunami caused by volcanic or underwater landslides.
The Nuclear Regulation Authority cited the possibility of an underwater landslide at the Oki Trough off the Takahama plant site. The authority said no tsunami warning may be issued after such a landslide as it would be technically difficult to do this.
Kansai Electric now says the plant will shut the gates if abnormal changes in tide levels are detected by gauges near the pump rooms for each of its four reactors.
The Tokai No.2 power plant of the Japan Atomic Power Company in Ibaraki Prefecture, north of Tokyo, makes it a rule to close tide gates following a tsunami warning.
The Nuclear Regulation Authority hasn't asked the company to revise the rule. It says there is no risk to the plant of an underwater landslide causing a tsunami.
A major tsunami triggered by a volcanic eruption in Indonesia in December prompted the authority to review the anti-tsunami measures for nuclear plants.