Paul Rincon
BBC: April 3, 2017

A UK-based team of researchers has created a graphene-based sieve capable of removing salt from seawater.

The sought-after development could aid the millions of people without ready access to clean drinking water.

The promising graphene oxide sieve could be highly efficient at filtering salts, and will now be tested against existing desalination membranes.

It has previously been difficult to manufacture graphene-based barriers on an industrial scale.

Reporting their results in the journal Nature Nanotechnology, scientists from the University of Manchester, led by Dr Rahul Nair, shows how they solved some of the challenges by using a chemical derivative called graphene oxide.

Isolated and characterised by a University of Manchester-led team in 2004, graphene comprises a single layer of carbon atoms arranged in a hexagonal lattice. Its unusual properties, such as extraordinary tensile strength and electrical conductivity, have earmarked it as one of the most promising materials for future applications.

But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapour deposition (CVD). Current production routes are also quite costly.

On the other hand, said Dr Nair, “graphene oxide can be produced by simple oxidation in the lab”.

He told BBC News: “As an ink or solution, we can compose it on a substrate or porous material. Then we can use it as a membrane.

“In terms of scalability and the cost of the material, graphene oxide has a potential advantage over single-layered graphene.”

Of the single-layer graphene he added: “To make it permeable, you need to drill small holes in the membrane. But if the hole size is larger than one nanometre, the salts go through that hole. You have to make a membrane with a very uniform less-than-one-nanometre hole size to make it useful for desalination. It is a really challenging job.”

Graphene oxide membranes have already proven their worth in sieving out small nanoparticles, organic molecules and even large salts. But until now, they couldn’t be used to filter out common salts, which require even smaller sieves.

Previous work had shown that graphene oxide membranes became slightly swollen when immersed in water, allowing smaller salts to flow through the pores along with water molecules.

Now, Dr Nair and colleagues demonstrated that placing walls made of epoxy resin (a substance used in coatings and glues) on either side of the graphene oxide membrane was sufficient to stop the expansion.

Restricting the swelling in this way also allowed the scientists to tune the properties of the membrane, letting through less or more common salt for example.

(read the full article at BBC)

Chairman of Japan’s nuclear regulation authority admits “we are still feeling around in the dark”.

Dying robots and failing hope: Fukushima clean-up falters six years after tsunami

Justin McCurry
The Guardian : March 9, 2016

Exploration work inside the nuclear plant’s failed reactors has barely begun, with the scale of the task described as ‘almost beyond comprehension’

Barely a fifth of the way into their mission, the engineers monitoring the Scorpion’s progress conceded defeat. With a remote-controlled snip of its cable, the latest robot sent into the bowels of one of Fukushima Daiichi’s damaged reactors was cut loose, its progress stalled by lumps of fuel that overheated when the nuclear plant suffered a triple meltdown six years ago this week.

As the 60cm-long Toshiba robot, equipped with a pair of cameras and sensors to gauge radiation levels was left to its fate last month, the plant’s operator, Tokyo Electric Power (Tepco), attempted to play down the failure of yet another reconnaissance mission to determine the exact location and condition of the melted fuel.

Even though its mission had been aborted, the utility said, “valuable information was obtained which will help us determine the methods to eventually remove fuel debris”.

The Scorpion mishap, two hours into an exploration that was supposed to last 10 hours, underlined the scale and difficulty of decommissioning Fukushima Daiichi – an unprecedented undertaking one expert has described as “almost beyond comprehension”.

Cleaning up the plant, scene of the world’s worst nuclear disaster since Chernobyl after it was struck by a magnitude-9 earthquake and tsunami on the afternoon of 11 March 2011, is expected to take 30 to 40 years, at a cost Japan’s trade and industry ministry recently estimated at 21.5tr yen ($189bn).

The figure, which includes compensating tens of thousands of evacuees, is nearly double an estimate released three years ago.

The tsunami killed almost 19,000 people, most of them in areas north of Fukushima, and forced 160,000 people living near the plant to flee their homes. Six years on, only a small number have returned to areas deemed safe by the authorities.

Developing robots capable of penetrating the most dangerous parts of Fukushima Daiichi’s reactors – and spending enough time there to obtain crucial data – is proving a near-impossible challenge for Tepco. The Scorpion – so called because of its camera-mounted folding tail – “died” after stalling along a rail beneath the reactor pressure vessel, its path blocked by lumps of fuel and other debris.

The device, along with other robots, may also have been damaged by an unseen enemy: radiation. Before it was abandoned, its dosimeter indicated that radiation levels inside the No 2 containment vessel were at 250 sieverts an hour. In an earlier probe using a remote-controlled camera, radiation at about the same spot was as high as 650 sieverts an hour – enough to kill a human within a minute.

Shunji Uchida, the Fukushima Daiichi plant manager, concedes that Tepco acquired “limited” knowledge about the state of the melted fuel. “So far we’ve only managed to take a peek, as the last experiment with the robot didn’t go well,” he tells the Guardian and other media on a recent visit to the plant. “But we’re not thinking of another approach at this moment.”

Robotic mishaps aside, exploration work in the two other reactors, where radiation levels are even higher than in reactor No 2, has barely begun. There are plans to send a tiny waterproof robot into reactor No 1 in the next few weeks, but no date has been set for the more seriously damaged reactor No 3.

Naohiro Masuda, the president of Fukushima Daiichi’s decommissioning arm, says he wants another probe sent in before deciding on how to remove the melted fuel.

Despite the setbacks, Tepco insists it will begin extracting the melted fuel in 2021 – a decade after the disaster – after consulting government officials this summer.

But Shaun Burnie, a senior nuclear specialist at Greenpeace Germany who is based in Japan, describes the challenge confronting the utility as “unprecedented and almost beyond comprehension”, adding that the decommissioning schedule was “never realistic or credible”.

The latest aborted exploration of reactor No 2 “only reinforces that reality”, Burnie says. “Without a technical solution for dealing with unit one or three, unit two was seen as less challenging. So much of what is communicated to the public and media is speculation and wishful thinking on the part of industry and government.

“The current schedule for the removal of hundreds of tons of molten nuclear fuel, the location and condition of which they still have no real understanding, was based on the timetable of prime minister [Shinzo] Abe in Tokyo and the nuclear industry – not the reality on the ground and based on sound engineering and science.”

Even Shunichi Tanaka, the chairman of Japan’s nuclear regulation authority, does not appear to share Tepco’s optimism that it will stick to its decommissioning roadmap. “It is still early to talk in such an optimistic way,” he says. “At the moment, we are still feeling around in the dark.”

(read the full article at The Guardian)

Second robot abandoned due to ‘extreme radiation’ in Fukushima nuclear plant

James Gorman
9news: February 20, 2017

Another robot sent to investigate the crippled Fukushima nuclear plant has been abandoned after succumbing to extreme radiation levels.

The “Scorpion” robot, designed by the Tokyo Electric Power company (TEPCO), experienced catastrophic failure as it approached the core of reactor number two due to “unimaginable” radiation levels.

It is the second robot TEPCO has been forced to abandon inside the crippled plant, which suffered a catastrophic meltdown during an earthquake and subsequent tsunami in 2011, phys.org reports.

The advanced robot had been carrying two small cameras and other sensor equipment in an attempt to locate melted fuel cells inside the plant.

As it suffered the failure, it was moved to a position so as not to hinder future expeditions. It was then shut down and abandoned.

Earlier this month, TEPCO revealed the radiation level in the containment vessel of reactor two had reached more than of 530 sieverts per hour.

The “unimaginable” radiation levels were assessed by the National Institute of Radiological Sciences (NIRS).

According to the NIRS, just 4 sieverts of radiation exposure would be enough to kill a handful of people.

Earlier this month, TEPCO sent in its first exploratory robot to clear debris out of the way for future missions. The robot’s cameras shut down when it exceeded its maximum tolerance of 1000 sieverts.

TEPCO has insisted it will continue to push forwards with missions to examine the crippled reactors one at a time, as pressure mounts from the public and government officials to officially decommission the plant – an endeavour the company is still unsure how to accomplish.

(Read the full article at 9news)

Zero Hedge: February 4, 2017

With just 3 years left until the 2020 Olympics, Japan is likely desperate to reassure the world’s athletes that all is well, but an admission from TEPCO – the Fukushima nuclear plant operator – that they discovered a hole at least one square meter in size beneath the reactor’s pressure vessel, and lethal record-high radiation levels have been detected, will not likely reassure anyone.

Radiation levels of up to 530 Sieverts per hour were detected inside an inactive Reactor 2 at the Fukushima Daiichi nuclear complex damaged during the 2011 earthquake and tsunami catastrophe, Japanese media reported on Thursday citing the plant operator, Tokyo Electric Power Company (TEPCO). A dose of about 8 Sieverts is considered incurable and fatal.

As RT reports, a hole of no less than one square meter in size has also been discovered beneath the reactor’s pressure vessel, TEPCO said. According to researchers, the apparent opening in the metal grating of one of three reactors that had melted down in 2011, is believed to be have been caused by melted nuclear fuel that fell through the vessel.

The iron scaffolding has a melting point of 1500 degrees, TEPCO said, explaining that there is a possibility the fuel debris has fallen onto it and burnt the hole. Such fuel debris have been discovered on equipment at the bottom of the pressure vessel just above the hole, it added.

The latest findings were released after a recent camera probe inside the reactor, TEPCO said. Using a remote-controlled camera fitted on a long pipe, scientists managed to get images of hard-to-reach places where residual nuclear material remained. The substance there is so toxic that even specially-made robots designed to probe the underwater depths beneath the power plant have previously crumbled and shut down.

However, TEPCO still plans to launch further more detailed assessments at the damaged nuclear facility with the help of self-propelled robots.

TEPCO confirmed a black lump in the space beneath the pressure vessel. There is a possibility of nuclear fuel melting down (fuel debris).

(read the full article at zero hedge)

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