Paving the way to a nuclear future?

One year on from Japan's Fukushima disaster, Australia has engaged with hard nuclear questions and the case for nuclear energy has been clarified.

A year ago, a catastrophic chain of events was triggered by a powerful magnitude 9 earthquake centred under the seabed about 100 kilometres off the north east coast of Japan. Travelling left and right of the ruptured fault, two wide and high water fronts moved in opposite directions. The eastbound tsunami produced moderate 1-2 metre surges at the coasts of Canada, western US, and Chile as its energy dissipated over the several thousand kilometre journey. Still, millions of dollars of damage was reported to boats, jetties and so on.

The westbound water mass covered the 100 kilometres distance to the Japanese coast in about an hour. As it reached shallow land, the tsunami slowed to 30km an hour and seaside residents had 10 minutes warning of an approaching wall of water ranging from 5-15 metres in height, sufficient to breach the sea wall that protects about 40 per cent of the Japanese eastern coastline.

In places, the surge of water extended 10 kilometres inland. Twenty thousand people died or are unaccounted for. More than 90 per cent of the victims drowned. The lives of 5 million Japanese were directly impacted. The reconstruction bill will exceed $250 billion, making this the most costly natural disaster in history.

At the Fukushima nuclear plant, the three operating reactors shut down as accelerometers detected the shaking of the earth. Three other reactors were offline, undergoing routine maintenance or refuelling. But the arrival of the tsunami flooded the site to a depth of 5 metres and knocked out all power – a catastrophic situation where even spent fuel rods in storage require electricity to continuously circulate cooling water for years. Nuclear cores melted, hydrogen gas explosions breached containment buildings, and uncontrolled releases of radiation were sufficiently great that Fukushima is now rated second only to Chernobyl in severity as a nuclear accident.

A year later, the clean-up task at Fukushima is well underway. Three thousand workers are carefully dismantling the site where all six reactors were irretrievably damaged by the tsunami that washed over the Japanese plant.

This decommissioning process, typically taking up to 40 years for reactors which have reached their use-by date, will include eventually removing several centimetres of topsoil contaminated with radioactive caesium from across the site. There is no reliable figure available but the replacement cost of six reactors, decommissioning and site remediation could amount to $50 billion – even before the cost to the national economy of imported fuels to offset the loss of nuclear electricity generation is included.

Investigations continue to better understand this nuclear accident. A number of findings have emerged and mitigation strategies are being recommended and adopted.

The requirement to have capable, independent and active regulators of a nation’s nuclear system has been emphasised, as has the need for rigorous licensing and relicensing procedures for reactors that can operate for 60 years or more.

Reactor operators around the world and nuclear safety agencies have been required to complete stress testing and make changes to ensure safety in extreme circumstances, including scenarios where multiple hazards occur contemporaneously. (In some ways, this is analogous to the current work of the world’s financial regulators in stress testing banks and other financial institutions and increasing safety margins through mandated strengthening of capital adequacy ratios.)

More rigorous evaluation of power plant sites has been demanded, especially in areas with a history of natural hazards, and criteria developed for better designs to reduce risk from earthquakes, hurricanes and tsunamis. Interestingly, Japan’s near neighbour South Korea has an active geology and 21 largely coast based reactors producing 30 per cent of its electricity. Following careful review, that country has confirmed its plan to increase its nuclear network to 40 units by 2030 to produce nearly 60 per cent of its electricity demand. South Korean reactors are increasingly finding a world market for their designs.

Additional onsite portable equipment will be required. This includes diesel driven pumps and electric generators to provide power and water to three key functions: reactor core cooling, used fuel pool cooling, and containment integrity. The locations would be diverse, protected and accessible when other safety systems are compromised. (In the US, such steps were taken following the 9/11 terrorist attacks to help facilities respond to large fires and explosions.)

Improved and hardened vents are to be installed, to maintain containment but also to enable gas pressure to be relieved even when the reactor control room is disabled and cannot function. Appropriate venting of hydrogen would avoid explosions that release radioactive material to the environment.

Instrumentation is to be upgraded to provide remote monitoring of the condition of storage pools and to coordinate responses especially for multi event/ multiple site emergencies. Some reactors from the 60s and 70s operate with analogue controls and are a generation behind modern wireless communications.

A cooperative international emergency response framework is being developed to assist in the expeditious deployment of experts and resources should another nuclear accident occur. In the aftermath of Fukushima, crisis management processes are being upgraded.

One difficult issue refers to the social consequences connected with the evacuations around the Fukushima site. A total 100,000 people remain displaced, awaiting permission to return to their homes within the 20 kilometre exclusion zone. The Japanese government quite reasonably aims to limit radiation exposure of evacuees returning home but struggles to balance this against the major health and welfare impact of ongoing displacement.


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