Fukushima Miracle: In a first, tsunami-destroyed nuclear reactor gets inspected using palm-sized drone

The mangled wreckage of Unit 3 is seen at the tsunami-crippled Fukushima Daiichi nuclear power plant in Fukushima prefecture. Source: REUTERS

After a 9.0 magnitude earthquake and tsunami destroyed Japan’s Fukushima Daiichi nuclear plant almost 13 years ago, a drone, tiny enough to fit in one’s hand, flew inside one of the damaged reactors core on Wednesday to examine some of the molten fuel debris.

The drone reached areas where robots have previously failed to go.

Details of drone sent inside Fukushima damaged reactors

The drones were sent on a recon mission to get more data. The recon mission involved a fleet of four drones which were set to fly one at a time into the hardest-hit Reactor No. 1’s primary containment vessel.

The drones, each weighing 185 grams, are highly maneuverable. The propellers of the tiny aerial reconnaissance devices hardly stir up dust.

It has a high definition camera on the front, which will be used to record and transmit a live video feed and a higher-quality pictures to an operating room.

Each drone is shaped like square of about 18 centimeters on each side and is about 5 centimeters (2 inches) thick.

As the drone was designed to be operated inside the highly radioactive environment, it needed special, heavy-duty circuitry. Due to its diminutive size, the designers of the drone could not fit a high-capacity battery in it. Therefore, the drone’s investigation inside the reactor, was limited to a mere 5-minutes of flight time, each.

The drone flight on Wednesday (28 February) comes after months of preparations and training that began in July last year at a nearby mockup facility outside of the plant.

How will data collected by these drones used?

Tokyo Electric Power Company Holdings (TEPCO), the plant’s operator, said the new data will be used to develop technology for future probes and a process to remove the melted fuel from the reactor in the coming years.

The details gathered will also be used in investigating how exactly the 2011 meltdown occurred.

Purpose of four drones

Of the four drones, two will be sent initially to inspect the area around the exterior of the main structural support in the vessel, called the pedestal. After this it will be decided if the remaining two should be sent inside the vessel, an area which previous probes could not reach.

The pedestal is directly under the reactor’s core. The aim is to film the core’s bottom to understand how overheated fuel dripped there in 2011.

About 880 tons of highly radioactive melted nuclear fuel remain inside the three damaged reactors.

The drones are being used after several probes — including one which involved a crawling robot and an underwater vehicle — were sent inside each of the three reactors. The efforts so far have been hindered by debris, high radiation and the inability to navigate the probes through the rubble. They, however, were able to collect some data in recent years.

The first robot to go inside the reactor was in 2015, but it got stuck on a grate. Though, some helpful information was received from the mission, the crawling robot had to be abandoned.

In March 2011, an earthquake and subsequent tsunami destroyed the plant’s power supply and cooling systems, causing the three reactors out of four to melt down.

The discharges from the nuclear reactors have faced strong opposition from fishing groups following a Chinese ban on Japanese seafood.

It is also worth mentioning that on Wednesday (28 February, 2024) TEPCO also has started releasing the fourth batch of the plant’s treated and diluted radioactive wastewater into the sea.

The government of Japan and TEPCO claim that the water is safe and the process is being monitored by the International Atomic Energy Agency.

With inputs from Associated Press