Daily Bulletin


The Conversation

  • Written by Tony Irwin, Visiting Lecturer, Nuclear Reactors and Nuclear Fuel Cycle, Australian National University

We all remember March 11, 2011, when the magnitude-9.0 Great East Japan earthquake triggered a 14-metre tsunami that flooded the Fukushima Daiichi nuclear power plant. Four of the six reactors on site were badly damaged, three suffering core meltdowns.

Also affected by the tsunami, but to a much lesser extent, were the four reactors at the Fukushima Daini nuclear power plant, roughly 11km further south. That site was partially flooded, but sufficient safety systems were still available to shut down and cool the reactors safely.

At 5.59 am local time on Tuesday the tsunami alarms sounded again, as a magnitude-6.9 earthquake 10km off the coast shook the area. Just over half an hour later the resulting tsunami hit the Fukushima coast – but this one was barely a metre high, and well below the height of the 5.7m seawall, meaning that Fukushima’s nuclear plants were spared another flood.

image The earthquake again triggered a tsunami on the Fukushima coast. USGS/AAP Image

However, the earthquake caused a circulation pump in the used fuel cooling pond of Fukushima Daini reactor 3 to shut down. After checking the system, the pump was restarted after 99 minutes, and operator TEPCO said the plant had suffered no lasting damage.

The situation might have been more serious were it not for the fact that Fukushima Daini, like most of Japan’s nuclear power stations, has been out of action ever since the disaster at its neighbouring station prompted Japan to shut down all of its nuclear reactors for safety checking and upgrades.

Although all of Daini’s systems have since been restored, its reactors have not been restarted. All the fuel has been removed from the reactors and is stored in cooling ponds – which is where the circulation pump failed that normally pushes water through a heat exchanger for cooling.

Because of the low residual heat in the used fuel, the reported temperature rise was less than 1℃ during the 99-minute outage. Without cooling, the temperature of the cooling pool would be expected to rise by 0.2℃ per hour. It would therefore take more than a week without cooling before the normal operating range of 65℃ would be exceeded, and this would still be far below the fuel melting point of around 2,800℃.

There has been no reported damage from the latest earthquake at the Fukushima Daiichi plant where decommissioning work continues (although it was briefly stopped in response to the earthquake). As of 11am on Tuesday, plant parameters show reactor cooling systems operating normally with reactor temperatures of 20-25℃, again far below any dangerous levels. Again, the low amount of residual heat in the fuel means that any changes on loss of cooling are slow. This is in stark contrast to the situation in 2011 where loss of cooling to the operating reactors led to fuel melting in less than four hours.

Before the 2011 meltdowns, there were 54 nuclear power reactors operating in Japan. Since then, only three reactors have completed all of the required modifications and safety inspections and returned to operation, and one of these is currently shut down for routine refuelling. Currently 42 reactors will potentially be restarted, 24 of which are slowly going through the restart approval process.

The extent of modifications to avoid possible damage from tsunamis is illustrated by the work that Chubu Electric Power Company is carrying out at its Hamaoka nuclear power plant in Japan’s southeast Shizuoka prefecture. This year Chubu has completed construction of a huge seawall, 22m high and 1.6km long, which together with other safety upgrades will cost about 400 billion yen (A$4.9 billion).

After TEPCO faced accusations that it failed to take full account of the tsunami risk at Fukushima, Japan is clearly taking no chances next time around.

Authors: Tony Irwin, Visiting Lecturer, Nuclear Reactors and Nuclear Fuel Cycle, Australian National University

Read more http://theconversation.com/is-fukushima-still-safe-after-the-latest-earthquake-69213

Writers Wanted

No Barnaby, 2050 isn't far away. Next week's intergenerational report deals with 2061

arrow_forward

Tips For Good SEO In The Law Sector

arrow_forward

The Conversation
INTERWEBS DIGITAL AGENCY

Politics

Prime Minister interview with Karl Stefanovic and Allison Langdon

Karl Stefanovic: PM, good morning to you. Do you have blood on your hands?   PRIME MINISTER: No, it's obviously absurd. What we're doing here is we've got a temporary pause in place because we'v...

Karl Stefanovic and Allison Langdon - avatar Karl Stefanovic and Allison Langdon

Prime Minister Scott Morrison delivered Keynote Address at AFR Business Summit

Well, thank you all for the opportunity to come and be with you here today. Can I also acknowledge the Gadigal people, the Eora Nation, the elders past and present and future. Can I also acknowled...

Scott Morrison - avatar Scott Morrison

Morrison Government commits record $9B to social security safety net

The Morrison Government is enhancing our social security safety net by increasing support for unemployed Australians while strengthening their obligations to search for work.   From March the ...

Scott Morrison - avatar Scott Morrison

Business News

Victorian businesses can claim a rebate on COVID-19 deep cleans until 30 June - but many remain unaware

With exposure sites on the rise and financial stresses already on most Victorian businesses, the recent Business Victoria announcement of a substantial 80% COVIDSafe Deep cleaning rebate is a time...

Article by Damien Smith, CEO of Prime Group - avatar Article by Damien Smith, CEO of Prime Group

Six Tips to Get your Business Known on Social Media

Social media is one of the most effective ways to market your brand to the masses. With the meteoric rise in popularity of various social media platforms over the past decade, millions of brands h...

NewsServices.com - avatar NewsServices.com

Boom in Aussies buying up restaurants, pubs, hotels and bars in regional centres

With international borders closed, regional Australia is seeing a dramatic surge in popularity as people move out of the cities and into their quaint communities. City slickers are looking for new...

Tess Sanders Lazarus - avatar Tess Sanders Lazarus