AI News, Nuclear Experts: High Radiation Estimates at Fukushima No Surprise to Us

Nuclear Experts: High Radiation Estimates at Fukushima No Surprise to Us

With two robot-probe operations apparently encountering increasingly high radiation levels inside the crippled Fukushima Daiichi nuclear plant during the past three weeks, some media reports suggested the radiation count was climbing rapidly.

In other words, we cannot say that all of the radiation in the containment vessel is coming from one unified lump of damaged fuel in the reactor vessel, and perhaps from a second unified lump sitting under it.” Davis added that it is only to be expected that the closer the robot probes get to the damaged reactor, the higher the dose rates will be.

And the high recent readings—even with the chance of up to 30 percent error—only confirms what experts already knew.” He pointed out that comparably high radiation levels had been recorded in the aftermath of the Three Mile Island and Chernobyl nuclear accidents.

“They are combining and analyzing everything right now, and this will help them determine whether to use the Scorpion or not, and what the next best step is to be.” The American Nuclear Society’s Davis noted that just getting through the approach and planning stages that will precede the removal of the damaged nuclear fuel inside thereactor vessels and the primary containment vessels“is going to take a very long time, probably many, many years.”

But he also pointed out that while the new estimated radiation levels gleaned from the probes may shock people not following the cleanup closely, “it is important to remember that they are extremely localized and have no impact whatsoever to anyone outside the nuclear plant.”

Robot probes show Japan reactor cleanup worse than expected

TOKYO —Robot probes sent to one of Japan’s wrecked Fukushima nuclear reactors have suggested worse-than-anticipated challenges for the plant’s ongoing cleanup.

robot was sent into the Unit 2 reactor’s containment vessel Thursday to investigate the area around the core that had melted six years ago, but its crawling function failed while climbing over highly radioactive debris.

Preliminary examinations over the past few weeks have detected structural damage to planned robot routes and higher-than-expected radiation inside the Unit 2 containment chamber, suggesting the need to revise robot designs and probes.

probe, had to return midway through because two of its cameras became inoperable after two hours when its total radiation exposure reached a maximum tolerance of 1,000 Sievert - a level that can kill a human within seconds.

Images captured from inside the chamber have showed damage and structures coated with molten material, possibly mixed with melted nuclear fuel, and part of a disc platform hanging below the melted core.

Nuke watchdog critical as robot failures mount at Fukushima plant

Some Nuclear Regulation Authority members are skeptical of continuing to send robots into reactors in the crippled Fukushima No.

These regulators are increasingly calling for a new survey methodology after recent investigations utilizing robots controlled remotely generated few findings and were quickly terminated.

“We should come up with a method that will allow us to investigate in a short period of time and in a more sensible way,” said a senior member of the NRA, the government watchdog.

Tokyo Electric Power Co., the operator of the plant, said on March 23 the robot was unable to deliver a camera to planned spots from where images of nuclear fuel debris could be taken.

The lower part of the reactor’s containment vessel is submerged in water where deposits of fuel debris are believed to reside below the surface after melting through in the 2011 nuclear disaster, triggered by the Great East Japan Earthquake and tsunami.

TEPCO sends underwater robot probe inside disaster-ravaged reactor at Fukushima plant

Following multiple failed attempts, TEPCO is hoping the remote controlled robot will be able to capture images below the reactor pressure vessel and thereafter at the the bottom of the containment vessel, where the deposits of melted fuel debris have likely accumulated.

2 reactors failed, as initially, camera images outside the containment vessel that are used to monitor the robot could not be seen on the control room's screen, and a subsequent attempt saw the robot malfunction, possibly due to extremely high levels of radiation.

The information needed to be collected by the robots from inside the damaged reactors includes the necessary data on the high levels of radiation, the temperature, and the amount and locations of melted fuel and nuclear debris, as this data is essential for the eventual decommissioning plans of the tsunami-ravaged plant.

Underwater robot finds melted fuel inside a second Fukushima reactor seven years after Japan's worst nuclear disaster

More melted fuel has been found at the bottom of the Fukushima power planet, seven years after Japan's worst nuclear disaster.

Penetration at the pedestal area at the base of the reactor has been challenging due to deposits that have blocked the path of robots designed to crawl around it as well as high radiation levels that limit the life of electronic equipment.

These high radiation levels mean that the work must be done remotely to protect workers' safety, and precautions are also taken to protect the environment and make sure that no gases escape from the reactor during the tools' insertion.

At the time, plant operator TEPCO said the robot found large amounts of lava-like debris apparently containing fuel that had flowed out of the core into the primary containment vessel of the Unit 3 reactor at Fukushima.

'Even with the new approach this will be a challenging mission, but we will persevere because obtaining this information is important to developing the ability to eventually remove the fuel debris.' During the 2017 study, cameras mounted on the robot showed extensive damage caused by the core meltdown, with fuel debris mixed with broken reactor parts, suggesting the difficult challenges ahead in the decades-long decommissioning of the destroyed plant.

The 2017 expedition relied on a marine robot the size of a loaf of bread dubbed the 'little sunfish.' It was inserted along a rail and it included a camera, temperature sensors and a dosimeter to measure radiation directly.

Kimoto previously said that the robot probe has captured a great deal of useful information and images showing the damage inside the reactor, which will help experts eventually determine a way to remove the melted fuel, a process expected to begin sometime after the 2020 Tokyo Olympics.

Swimming robot to probe damage at Japan nuclear plant

Remote controlled robots are key to the decades-long decommissioning process for the plant.

But super-high radiation and structural damage inside the reactors hampered earlier attempts to inspect areas close to the reactors' cores.

The developers say they plan to send the probe into the primary containment vessel of Unit 3 at Fukushima in July to study the extent of damage and locate parts of melted fuel thought to have fallen to the bottom of the chamber, submerged by highly radioactive water.

A team operated it remotely, with one guiding the robot while another adjusted a cable that transmits data and serves as its lifeline.

The other, designed for cleaning debris for the 'scorpion' probe, was called back after two hours when two of its cameras stopped working after its total radiation exposure reached 1,000 Sievert—a level that would kill a human within seconds.

Scientists need to know the melted nuclear fuel's exact location and understand structural damage in each of the three wrecked reactors to work out the optimum, safest way to remove the fuel.

The decommissioning technology developers IRID and its partners have designed other basic robots, including a 'muscle' arm robot made by Hitachi-GE Nuclear Energy, and a different arm robot made by Mitsubishi Heavy Industries, that are designed to approach the debris from the sides of the reactors.

TEPCO is struggling with the plant's decommissioning, which is now expected to cost 8 trillion yen ($70 billion), four times an earlier estimate.

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