Nuke plant operators slow to implement tsunami safeguards

February 22, 2012

Operators of nuclear power plants across Japan are dawdling in efforts to make their facilities safer, despite government calls nearly a year ago to immediately start work on emergency protective measures.

Most plant operators are nowhere near close to installing coastal levees to protect their nuclear facilities from massive tsunami, nor do they have strategies in place to prevent hydrogen explosions at the plants, an Asahi Shimbun survey shows.

In the aftermath of reactor meltdowns at the Fukushima No. 1 nuclear power plant last March, the government called on all plant operators to swiftly take safety measures against earthquakes and tsunami.

Nearly 12 months on, it is envisaged that only three nuclear facilities will have coastal levees completed by the end of the year.

Not one operator has managed to put measures in place to prevent hydrogen explosions. In fact, many have not even started the work to implement the measures.

The findings have emerged amid national debate on the wisdom of restarting nuclear reactors that have gone offline for maintenance checks and other reasons.

Towering tsunami spawned by the magnitude-9.0 Great East Japan Earthquake wrecked emergency power generators and other equipment at the Fukushima No. 1 nuclear power plant. This caused huge amounts of radioactive substances to spew from the nuclear reactors there because they could no longer be cooled down.

Following the disaster, the government instructed all operators of nuclear plants in Japan to take emergency safety measures on the assumption that tsunami and earthquakes of the same scale could strike again.

Among the steps were three mid- to long-term programs that would take a relatively long time to complete: the installation or reinforcement of coastal levees or equivalent facilities; prevention of hydrogen explosions; and the installation of new, air-cooled emergency power generators.

The Asahi Shimbun contacted all nuclear plant operators to inquire about the progress of those measures at 17 nuclear plants across the nation.

The plants include the Monju prototype fast breeder reactor operated by the Japan Atomic Energy Agency, but does not include the crippled Fukushima No. 1 nuclear plant operated by Tokyo Electric Power Co.

Twelve of the 17 plants had plans to install new levees or to add to the height of existing ones. However, three of them--Higashidori, Tokai No. 2 and Tsuruga--have yet to start the work.

The coastal levees would range in height from 8 to 18 meters. The envisaged completion dates ranged between April for the Onagawa plant and fiscal 2015, or four years from now, for the Mihama plant.

Measures to prevent hydrogen explosions require the installation of equipment to vent hydrogen gas from nuclear reactor buildings to the exterior and "hydrogen recombiners" that reduce the amount of accumulated hydrogen. Similar measures were planned at 15 plants, but not at the Monju prototype reactor which has a fundamentally different structure. Ten of them, however, had yet to start the work.

Seven plants--Higashidori, Onagawa, Kashiwazaki-Kariwa, Mihama, Takahama, Oi and Shimane--had finished installing emergency power generators that are essential to cooling down reactors and other operations. Five other plants that have plans to install ones envisaged finishing the work by the end of fiscal 2012.

At TEPCO's Kashiwazaki-Kariwa nuclear plant in Niigata Prefecture, work to install a coastal levee is proceeding at a rapid pace. The levee is expected to be completed in one or two years from now.

Work has started on installing piles measuring between 20 and 30 meters near the No. 1 through No. 4 reactors. The project requires 930 piles to be driven into the ground at intervals of between 3 and 4 meters. Ten-meter-tall reinforced concrete walls will be built on them.

TEPCO's worst-case scenario is that a tsunami of 3.3 meters will hit the plant. In light of the disaster at the Fukushima No. 1 plant, it has decided to prepare for tsunami of 15 meters in height.

According to Yoshihiro Nishida, technical adviser of the engineering department, the protective wall is designed to withstand the impact of a tsunami three times its height. To prepare for a tsunami that swamps the levee, flood barriers are also being created at the nuclear reactor buildings, and their doors are being made waterproof, Nishida added.

TEPCO has submitted stress test reports to the industry ministry on the No. 1 and No. 7 reactors of the Kashiwazaki-Kariwa plant, which have been shut down for regular inspection.

Assessments in those reports did not include the coastal levee, which will only be completed around June 2013. Still, the reports asserted that making reactor building doors waterproof and other measures will enable the reactors to withstand tsunami of 15 meters.

Fourteen trucks were seen side by side on a 35-meter-high hill on the plant's premises. Some of them carried emergency power generators to operate reactor cooling systems and heat exchangers to cool down reactors. Others were fire engines that would inject water into nuclear reactors.

The trucks will be moved closer to the reactor buildings in case of an accident. Heavy machinery to keep roads open in an emergency is also on hand so that tsunami debris would not block traffic, plant officials said.

(This article was written by Jin Nishikawa and Takashi Sugimoto.)

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A coastal levee is under construction at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture on Feb. 21. (Eiji Hori)

A coastal levee is under construction at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture on Feb. 21. (Eiji Hori)

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  • A coastal levee is under construction at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture on Feb. 21. (Eiji Hori)
  • The Asahi Shimbun

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