Japan returns to nuclear after almost two years

12 August 2015

Despite continuing widespread public opposition to nuclear power, 11 August saw the restart of unit 1 of Kyushu Electric Power Co's Sendai nuclear plant in Kagoshima Prefecture.

At 10:30am the 890MWe pressurised water reactor started up, achieving criticality at around 11pm that day. Resumption of power generation is expected on August 14, according to the Japan Atomic Industrial Forum. Operations at Sendai 2 are expected to follow in October.

Sendai 1 had been shut down since May 2011. No reactors have been in service in Japan since September 2013, when Kansai Electric's Ohi 1 in Fukui Prefecture was taken offline.

As Japan commemorated the 70th anniversary of the bombing of Hiroshima and Nagasaki, preparations were underway to restart nuclear plants, closed after the 2011 Fukushima accident.

On 5 August, Kansai Electric applied to the Nuclear Regulation Authority for the final checks on Takahama 3 for possible restart in November. However, this will depend on the Fukui district court repealing a provisional injunction blocking restart.

So far all the reactors that have undergone detailed NRA safety checks are pressurised water reactors - boiling water reactors require more complex upgrades to meet the new post-Fukushima safety standards. Nevertheless, on 6 August, NRA decided to prioritise safety screenings for two units at Tokyo Electric Power Co's Kashiwazaki-Kariwa station in Niigata Prefecture. Kashiwazaki-Kariwa 6&7, both ABWRs, will be reviewed ahead of other BWR units. They have installed new equipment and the results will be used as a reference for other BWRs.

However, Kashiwazaki-Kariwa still faces some safety issues, such as earthquake measures and Tepco will be hard pressed to win approval for restart from the local government. A safety review of the plant by an International Atomic Energy Agency Operational Safety Review Team in July, found that safeguards against tsunami and other measures were improved, but emergency manuals were not up to standard. The team found nine areas that needed improving, including more detailed design information.

Fukushima progress

Meanwhile, work to decommission Fukushima Daiichi is continuing with mixed results. In early August, workers successfully completed removal of the largest and most complex piece of rubble from the severely damaged unit 3 reactor building. The 20t fuel-handling machine was securely lifted using two special 600t cranes. This clears the way for removing the remaining rubble and the rest of the 514 used fuel assemblies still in the pool.

In late July, Tepco began dismantling the temporary shroud covering unit 1. The cover was installed in October 2011 to keep radioactive materials from dispersing. Tepco plans to complete the dismantling in fiscal 2016 and to clear debris in preparation for removing 392 used fuel assemblies from the storage pool in FY 2020.

However, work at unit 2 is facing delays. Tepco was planning to send a robot into the containment vessel in August to capture video images of molten nuclear fuel which is thought to have penetrated the reactor core. Concrete blocks are impeding entry for the robot and need to be removed but the remote-controlled machinery which was to remove the blocks is unable to operate in some areas of the damaged reactor building. Tepco says it is now considering using chemicals to clear the blockage or developing new machinery. As a result, investigations may be postponed until December or later.

The problem is compounded because two new devices costing $4m designed to use elementary particles (muons) to take images inside the reactor are too big to install.The devices will not fit the reactor building site unless other equipment is removed and decontaminated - process which would hinder decommissioning and cost twice as much as the devices. Muon detectors have been used at unit 1 since February, but the devices intended for the No.2 reactor were designed to capture images with higher resolutions. The government and Tepco will divert the machines from unit 1 to unit 2 by the end of the year and may abandon plans to use the new devices.

Some progress has been made in clearing highly radioactive water from underground tunnels utility trenches on the ocean side of units 2 and 3 reactor buildings. Tepco has been filling the tunnels with cement to pump out contaminated water since November after attempts to freeze it failed. Tepco has also resumed building an underground ice wall to contain contaminated groundwater after a a power failure caused the equipment to stop working.

Meanwhile, local fishery cooperatives have finally approved Tepco's "subdrain plan" whereby contaminated groundwater is released to the sea following purification as they have no better options to speed up the recovery of the local fishing industry.

Also in July, Japan approved an increase in compensation payments for the Fukushima crisis to JPY7070bn ($57.18bn), as tens of thousands of evacuees remain in temporary housing more than four years after the disaster. Tepco will receive JPY950bn more in public funds on top of the JPY6125bn agreed earlier.



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