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Fukushima Daiichi nuclear disaster

The robots sent into Fukushima keep dying

the strapline in the article is a little misleading:

Experts baffled as robots sent to clean up Fukushima nuclear site keep dying

as it later goes on to say:

The radiation levels on the site are far higher than any human could possibly survive, so engineers are using purpose-built “scorpion” robots with cameras attached to survey the scale of the damage.

The latest attempt to harvest data on Fukushima failed after a robot designed by Toshiba to withstand high radiation levels died five times faster than expected.

The robot was supposed to be able to cope with 73 sieverts of radiation, but the radiation level inside the reactor was recently recorded at 530 sieverts....
 
I havent done my homework on this properly yet but it looks like they've found clear and obvious nuclear fuel bundle debris in the pedestal area under reactor 2.

http://www.tepco.co.jp/nu/fukushima-np/handouts/2018/images1/handouts_180119_08-j.pdf

The most 'obvious' bit being the handle seen in one of those photos, looks like a fuel bundle handle but I havent actually tried to translate this document myself or go looking fo this story in the news yet.

There have been other 'corium' photos and videos in recent months or years but none of them were particularly photogenic or offered enough interesting features to dwell on. If that handle is a fuel bundle handle then this is just the sort of image I've been waiting nearly 7 years to see!
 
Ah yes it was what I thought, and its been in the news. eg:

Tepco spots Fukushima fuel debris in reactor 2, says fuel rod assembly 'fell out of reactor' | The Japan Times

The image with the handle and other fuel bundle debris visible.

n-tepcoprobe-a-20180120.jpg
 
Scuse my ignorance.

What’s the significance of this please elbows .

It applies to one of the three melted reactors. It provides visual confirmation that at least some of the nuclear fuel bundles fell out of the main reactor vessel, fell apart and melted, and where this debris is located beneath the reactor.

Its the sort of stuff they need to establish in detail in order to work out what kind of clean-up operation may be possible one day. They like to talk somewhat optimistically about this stuff in the medium-long term, but everyone knows that there are loads of really severe challenges that make it hard to envisage how they could actually remove all the core debris from the reactors. There is usually a requirement for optimistic thinking about what technologies might be available in the decades to come. Disasters like this one do add fresh impetus to a range of technological developments, but the degree of radioactivity of this material is quite ridiculous challenge to deal with properly. In my opinion they are just as likely to give up on those plans one day and rely on something far cruder instead.
 
So it demonstrates that things are at the worse-case end of the spectrum of possibilities rather than the best-case end?

Sort of, yes. But I think it was already expected, some of the best case scenarios have not been credible since a few days after the original disaster. Various real data and various accident models have shown pretty consistently that the fuel would have melted inside all 3 reactors, damaged the primary reactor vessels, and some or all of it would have fallen down below. All optimists really had on this front was some hopes about whether all the fuel had melted in each reactor, whether some may be left intact, stuff like that.

In terms of absolute worst case scenarios, the main bullet that was dodged at Fukushima is that things didnt get so bad that they had to permanently evacuate the site and not be able to work on vital areas such as the spent fuel pools and providing cooling water to the shattered reactors.

As for ever cleaning up the mess inside the reactors, again I dont think there has ever been too much genuine optimism, but they should keep studying and trying things for as long as possible. And there are various other factors that may make a difference - eg using water as a shield is often part of future plans, and I believe one of the reactor secondary containment vessels is holding water very much better than one or two of the other reactors. So a different technique may be required at the different reactors, if things ever get that far. They've already been talking about this and much more detail in plans, but the timescale for this stuff is so far off into the future that I dont pay all that much attention yet.
 
...the data hes referencing is from 2013

Yes I got a lot of deja vu reading it, a rehash of the sort of article that was common some years back.

Whether Fukushima is the worst depends on what measure you use. It has always obviously been worst in terms of number of reactors that melted, and worst for PR because these were a common western-designed reactor, so excuses about crap Russian designs lacking 'proper containment' could not be applied. Worst in terms of ocean contamination. Worst in terms of the number of prior errors that combined with the devastation of the tsunami and various mistakes made in the response to create a very tense situation where they could not respond properly for days. Worst in terms of the number of other things that they had to try to manage after the initial meltdowns, ie keeping multiple reactors and fuel pools cool.

Chernobyl was worst in terms of the number of people killed by radiation when responding to the accident. Worst in terms of initial coverup, worst in terms of number of other countries affected by levels of radioactive contamination that required a meaningful response.

Many other things we could measure by other than those I've just mentioned too, but I think I've gone on enough already!
 
Tourists told to stop taking selfies in Fukushima nuclear disaster zone
Authorities in Fukushima are installing warning signs in English telling thrill-seeking tourists not to stop their cars or pose for selfies in areas that still have dangerously high levels of radiation.

Seven years after the disaster at the prefecture's nuclear plant, the government’s nuclear emergency response office has placed 26 signs along a 45-mile stretch of National Road 114 and a number of smaller roads in areas designated as “difficult-to-return” for local residents, the Asahi newspaper reported.

One road through the town of Namie was only reopened in September and is primarily used by construction vehicles and lorries removing contaminated waste and debris to landfill sites.

Motorists are able to access the roads, but authorities have installed signs after tourists were spotted getting out of their cars to take photos. Pedestrians, cyclists and motorcyclists are still banned from entering the restricted zone.

The signs read “No Entry!” for motorcycles, mopeds, light vehicles, bicycles and pedestrians, while others warn of “High-dose radiation area” and advise “Please pass through as quickly as possible”.

Fukushima police said they were forced to appeal to the government for help because of the rising number of incidents involving tourists who were unaware that getting out of a vehicle transiting the zone is still prohibited.

The areas that still have levels of radiation that would be harmful to human health lie to the north-west of the Fukushima nuclear plant and were under the plume of radioactivity released when a series of tsunami destroyed the cooling systems of four reactors in March 2011.

Local residents are permitted to return to their homes for brief, closely supervised visits, but the government admits that despite efforts to decontaminate the region, it will be many years before they are able to return on a permanent basis.

Long considered one of Japan’s most unspoilt and beautiful prefectures, Fukushima is today trying to rebuild a reputation among foreign and domestic tourists. A number of other travel firms are now offering tours to some of the towns most severely damaged as a result of the magnitude-9.1 earthquake, the tsunami it triggered and the nuclear disaster.
 
Yeah no, nobody is going to die from that. They might not even get a slightly elevated risk of cancer.​
If I were to fly to Japan, drive out to the location concerned, step out of the car and wander around for half an hour taking photos, then return home I would be exposed to something like 4 or 5 times the additional dose (over natural background) on the flights** alone than I would loitering in the ‘forbidden zone’.

Some weeks ago I went wandering in a landscape which was over 400 times typical background. This similarly was nothing compared to the exposure on the flights to get there and back and represents a negligible increase in lifetime risk.

Rolling around in the dirt on the ground, eating the local plantlife, snorting the dust out of the gutter and licking the road surfaces would, however, be ill-advised.

** something that is gradually increasing at present as the solar magnetic field is weakening.
 
If I were to fly to Japan, drive out to the location concerned, step out of the car and wander around for half an hour taking photos, then return home I would be exposed to something like 4 or 5 times the additional dose (over natural background) on the flights** alone than I would loitering in the ‘forbidden zone’.

Some weeks ago I went wandering in a landscape which was over 400 times typical background. This similarly was nothing compared to the exposure on the flights to get there and back and represents a negligible increase in lifetime risk.

Rolling around in the dirt on the ground, eating the local plantlife, snorting the dust out of the gutter and licking the road surfaces would, however, be ill-advised.

** something that is gradually increasing at present as the solar magnetic field is weakening.

Also on the list of ill-advised acts would be mucking around near the containment plugs of reactors 2 and 3, where this news I missed the other month suggests raditation levels of, wait for it, 10 sieverts per hour!


Exceedingly high radiation levels found inside crippled reactor buildings at the Fukushima No. 1 nuclear plant were labeled by nuclear regulators as an “extremely serious” challenge to the shutdown process and overall decommissioning of the site.

The Nuclear Regulation Authority (NRA) said a huge amount of radioactive materials apparently had attached to shield plugs of the containment vessels in the No. 2 and No. 3 reactors.

Radiation levels were estimated at 10 sieverts per hour, a lethal dose for anyone who spends even an hour in the vicinity, according to experts.

The finding would make it exceptionally difficult for workers to move the shield plugs, raising the prospect that the plan to decommission the reactors will have to be reassessed.

6b99ab8a64e6a9c3ecede7b02dc30269.jpg
 
How is erosion affecting the recovery of the Fukushima area?
01/03/2021
Meltdown of the reactors caused diffusion of radioactive material around the power plant, and residents to evacuate. Decontamination efforts were carried out from 2013 till 2017. The goal was to allow evacuated citizens to return to their homes and resume their lives. Decontamination was applied mostly on residential areas, arable lands, and roads.

Fukushima has a large, forested area and radioactive Cesium was deposited on forests in Fukushima after the accident of the nuclear power plant. However only the edge of the forests that affects residents was decontaminated. These forests can be a source of eroded soil if not managed properly – and that soil could contaminate other areas of Fukushima.

The man who saves forgotten cats in Fukushima's nuclear zone
03/03/2021
FUKUSHIMA, Japan (Reuters) - A decade ago, Sakae Kato stayed behind to rescue cats abandoned by neighbours who fled the radiation clouds belching from the nearby Fukushima nuclear plant. He won’t leave.

“I want to make sure I am here to take care of the last one,” he said from his home in the contaminated quarantine zone. “After that I want to die, whether that be a day or hour later.”

So far he has buried 23 cats in his garden, the most recent graves disturbed by wild boars that roam the depopulated community. He is looking after 41 others in his home and another empty building on his property.

Kato leaves food for feral cats in a storage shed he heats with a paraffin stove. He has also rescued a dog, Pochi. With no running water, he has to fill bottles from a nearby mountain spring, and drive to public toilets.
 
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