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Nuke watchdog critical as robot failures mount at Fukushima plant

24 03 2017 reactors probes.jpg

Some Nuclear Regulation Authority members are skeptical of continuing to send robots into reactors in the crippled Fukushima No. 1 nuclear plant to collect vital data on the locations of melted nuclear fuel and radiation levels.

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.

The suggestion followed the failure of the latest probe from March 18 to March 22 in which a robot was sent in the No. 1 reactor to ascertain the location of fuel debris, information crucial to preparing for the decommissioning.

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 utility cited the piping and deposits of what looked like sand accumulating on the piping as impediments that hindered the robot surveyor’s path.

The survey was designed for the robot to reach numerous locations inside the No. 1 reactor to determine the location of nuclear fuel debris and their radiation levels.

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.

At one location, the robot succeeded in placing a camera, which is combined with a dosimeter, to a depth 0.3 meter from the containment vessel floor.

The probe measured underwater radiation levels from 3.0 to 11 sieverts per hour during the five-day survey. But it was unable to take images of the debris in the water.

TEPCO and the government hope to start removing molten nuclear fuel from 2021. But they have yet to collect information on the location, amount and condition of the melted fuel.

In a survey of the No. 2 reactor in February, a robot became stuck in deposits and other debris after traveling only 2 meters inside.

Surveyor robots for the No. 1 through No. 3 reactors have been developed by the International Research Institute for Nuclear Decommissioning since 2014, a project costing 7 billion yen ($62 million) by the end of March 2018.

It takes time to develop such multifunctional robots, but the surveys centering around the robots so far have failed to produce meaningful results.

No survey has been conducted at the No. 3 reactor.

http://www.asahi.com/ajw/articles/AJ201703240064.html

March 26, 2017 Posted by dunrenard | Fukushima 2017 | Fukushima Daiichi, Reactor 1, Robot Probes | Leave a comment

Deadly nuclear radiation levels detected in Fukushima

Extremely high radiation levels were detected using cameras and robots in tainted water inside a reactor containment vessel at the Fukushima No. 1 nuclear power plant, Japan Times reported Tuesday, citing Tokyo Electric Power Company Holdings Inc. (Tepco).

The latest readings, taken six years after the Fukushima nuclear meltdown, showed 11 sieverts per hour, according to Japan Times. It is the highest radiation level detected in water inside the containment vessel and is extremely dangerous. Sievert is a unit measurement for a dose of radiation. One sievert is enough to cause illness if absorbed all at once, and 8 sieverts will result in death despite treatment, according to PBS who relied on data from multiple sources including United States Nuclear Regulatory Commission and MIT’s Nuclear Science and Engineering department.

Following a major earthquake on March 11, 2011, a 15-metre tsunami disabled the power supply and cooling of three Fukushima reactors, causing a nuclear accident. Tepco, who operated the plant and has been tasked with cleaning up the worst nuclear incident, since the 1986 Chernobyl disaster in the former Soviet Union, has been some problems of late in its cleanup operation.

Recently, an exploratory robot malfunctioned and died after being sent inside reactor 2, in mid-February, due to exposure to “unimaginable” levels of radiation, close to 650 sieverts per hour. The previous highest recorded level was 73 sieverts per hour. Following the incident, Naohiro Masuda, president of Tepco’s Fukushima Daiichi Decommissioning project, told reporters the company had to rethink its methods in order to examine and extract the hazardous material stuck in the plant’s second reactor.

“We should think out of the box so we can examine the bottom of the core and how melted fuel debris spread out,” Masuda said, according to the Japan Times.

Tepco has been attempting to locate melted fuel which leaked from the reactor’s pressure vessel and is believed to have settled at the bottom of the containment vessel that holds the contaminated water. So far, no such debris has been found, and Tepco decided to extend the survey by one day through Wednesday.

A robot sent by the company on March 20 reached the bottom but was unable to locate the melted fuel due to some pipes that blocked its view. But it was able to take pictures of what appeared to be sand piling up near the pipes. The radiation readings near them were 6.3 sieverts per hour.

“Judging from the radiation level, there is a high possibility that what is piling up on the pipes is not nuclear fuel,” a Tepco official said, according to the Asahi Shimbun.

Cleaning up the plant may take an estimated 40 years and cost an estimated 21.5 trillion yen ($189 billion), according to the Guardian.

https://www.rawstory.com/2017/03/deadly-nuclear-radiation-levels-detected-in-fukushima/

March 23, 2017 Posted by dunrenard | Fukushima 2017 | Fukushima Daiichi, High Radiation, reactors, Robot Probes | Leave a comment