First contact made with melted nuclear fuel at Fukushima plant • Hacker News Board

Re: First contact made with melted nuclear fuel at Fukushima plant

#151

Post by firebones » Sat, Feb 16, 2019, 3:49 AM UTC

ChuckMcM wrote: post #79

pvaldes wrote: post #46

Earlier quoted context omitted.

> the "China Syndrome" speculation is pretty much completely debunked You would be dissapointed. Cou-cou! surprise! The ocean strikes back!. Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan. 2017. Sanial, Buessler, Charette, and Nagao. PNAS. DOI:10.1073/pnas.1708659114 "Sanial, Buessler, Charette and Nagao, scientists from Massachusetts and Japan found a new source of Caesium-137 to th…

That is a great paper[1], thanks for the reference I've added it to my nuclear effects library. It doesn't involve the China Syndrome speculation though, what it does find is much much more interesting. The paper reports that beach sand is capable of 99% adsorption of Cs137. And then goes on to discuss how it gets de-adsorbed (up to 11%) when Cs137 free sea water is mixed with it. What this says to me is that you can…

What volume of sand would you need to make a difference? And at what rate does it collect Cs137 to reach 99%?

Would it be feasible to stack filters? (E.g., 0.01 * 0.01 * 0.01...)

Re: First contact made with melted nuclear fuel at Fukushima plant

#152

Post by dralley » Sat, Feb 16, 2019, 4:18 AM UTC

randomsearch wrote: post #136

ChuckMcM wrote: post #17

While I realize it was likely impractical to meltdown reactors just to develop the technology to clean them up, I find the process here pretty interesting. A lot of good engineering has gone into the effort, and the engineering challenges (and risks) of post runaway reactors has gotten a lot more data. The Chernobyl folks just entombed everything, which is a one approach, even though they can "walk up to"[1] the rema…

> realize it was likely impractical to meltdown reactors just to develop the technology to clean them up That's a great insight. Maybe if some technologist approaches you and says "this is a great tech but we can't possibly recreate the worst case scenario, even in an expensive simulation" then that tells you that this is a straight "no". Fukushima is evidence that the worst case cannot be sufficiently modelled and m…

The Chernobyl reactors were built after Fukushima. It was a really, really old plant, that had already gone 10 years past it's intended lifespan, but they kept it open despite that because they didn't have a viable replacement source of energy.

Re: First contact made with melted nuclear fuel at Fukushima plant

#153

Post by stordoff » Sat, Feb 16, 2019, 4:29 AM UTC

mempko wrote: post #119

What strikes me is just how inept the Japanese are in handling Fukushima compared to the USSR during the much worse Chernobyl disaster. The USSR responded quickly and it took just 8 months to entomb the reactor. Over 600k people worked to handle Chernobyl. Fukushima, on the other hand, is still at risk of another disaster, 10 years later. The Japanese government and power company under-handled the situation and lied…

> The USSR responded quickly and it took just 8 months to entomb the reactor.

At a gross cost to human life[1], and in a way that leaves the problem there - work is _still_ to contain and clean up the reactor. There are good reasons for not doing the same here.

The sarcophagus was never intended to be a permanent solution, and was unsuccessful in completely containing the accident: Sr-90 and Pu-239 were leaching into the surrounding water table, and some have suggested that the rainwater and remaining nuclear fuel posed the risk of restarting the nuclear chain reaction[2].

[1] death figures are controversial, and vary wildly, but 600,000 people were involved in the cleanup, some of whom will have been put at risk.

[2] https://outline.com/fTk4GX

Re: First contact made with melted nuclear fuel at Fukushima plant

#154

Post by aaronmdjones » Sat, Feb 16, 2019, 4:37 AM UTC

randomsearch wrote: post #136

ChuckMcM wrote: post #17

While I realize it was likely impractical to meltdown reactors just to develop the technology to clean them up, I find the process here pretty interesting. A lot of good engineering has gone into the effort, and the engineering challenges (and risks) of post runaway reactors has gotten a lot more data. The Chernobyl folks just entombed everything, which is a one approach, even though they can "walk up to"[1] the rema…

> realize it was likely impractical to meltdown reactors just to develop the technology to clean them up That's a great insight. Maybe if some technologist approaches you and says "this is a great tech but we can't possibly recreate the worst case scenario, even in an expensive simulation" then that tells you that this is a straight "no". Fukushima is evidence that the worst case cannot be sufficiently modelled and m…

The Fukushima situation was predicted, several times, and TEPCO were warned about the dangers of having basement emergency generators at least 6 times. Nothing happened, because fixing that would cost money. The sea wall was artificially lowered from 30 metres to 10 metres, because keeping it at 30 during construction would have cost more money.

At the end of the day it's money.

Re: First contact made with melted nuclear fuel at Fukushima plant

#155

Post by wycx » Sat, Feb 16, 2019, 4:46 AM UTC

yongjik wrote: post #134

pvaldes wrote: post #46

Earlier quoted context omitted.

> the "China Syndrome" speculation is pretty much completely debunked You would be dissapointed. Cou-cou! surprise! The ocean strikes back!. Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan. 2017. Sanial, Buessler, Charette, and Nagao. PNAS. DOI:10.1073/pnas.1708659114 "Sanial, Buessler, Charette and Nagao, scientists from Massachusetts and Japan found a new source of Caesium-137 to th…

For comparison: According to Wikipedia, granite contains 1-20 ppm of uranium [1]. One gram of natural uranium is about 25,280 Bq. Hence, one ton of granite is somewhere between 25,280 - 505,600 Bq. In other words, if a beach is made of eroded granite, its radioactivity will be between 25,000-500,000 Bq/t: assuming the sand is more than a feet deep, I think it's safe to assume > 25,000 Bq/m^2. [1] https://en.wikipedia…

Radioactivity of rocks is caused by only a few elements so is useful to consider the minerals in which those elements are hosted. i.e. the radioactivity is not evenly distributed among the minerals that comprise granite. The elements that contribute most to the radioactivity of granite are U, Th and K. The K is mostly contained in alkali feldspar and mica. The U and Th are contained in accessory minerals, such as monazite and zircon. Monazite and zircon are dense, robust minerals, which means they persist after weathering and go on to accumulate in detrital sediments, and we call the sediments in which they are concentrated heavy mineral sands. Alkali feldspar is much less robust and rarely survives in mature sediments (i.e. quartz-rich sands), instead all the K ends up in clays.

When heavy mineral sands are processed to extract the Ti and Zr ( from rutile, illmenite, zircon), the residual concentrate is rich in monazite. This material comprises the bulk of our easily accessible Th reserves. However, you can't just leave this monazite-rich material lying around heaps, as it creates a windborne radioactive dust hazard, so it gets mixed back in with the other light material. This is a bit of a shame. All that energy and effort is expended to extract the heavy minerals, but as there is no immediate market for the monazite, and it is a liability to keep it in the extracted state, all that work hard work is undone to mitigate the dust hazard and it gets mixed back with the quartz etc.

So it is perhaps somewhat ironic that we mine beaches to get the minerals that are the source of the bulk of the radioactivity of granites.

Re: First contact made with melted nuclear fuel at Fukushima plant

#156

Post by ggm » Sat, Feb 16, 2019, 5:54 AM UTC

dmurray wrote: post #126

meenzu wrote: post #64

Earlier quoted context omitted.

Thanks for the answer, just curious would the lead sheet have holes thorough it if you put it up to that radiation? I'm picturing a sheet of paper with bullet holes through it. Or is there a better analogy of what is going on?

More like a sheet of paper held up to the light. Some light gets through, and if you have thicker paper it will allow less light through, but it doesn't noticeably damage the paper.

Depends how long you leave the paper exposed to light. if you have a sheet of paper half exposed and half shielded for a year of sunlight the effect is marked.

The equivalent in lead would probably manifest in some way, perhaps a visible patina on the surface? or, as a differential in decay products. you could call that 'damage' if you wanted to.

Re: First contact made with melted nuclear fuel at Fukushima plant

#157

Post by mempko » Sat, Feb 16, 2019, 6:08 AM UTC

stordoff wrote: post #153

mempko wrote: post #119

What strikes me is just how inept the Japanese are in handling Fukushima compared to the USSR during the much worse Chernobyl disaster. The USSR responded quickly and it took just 8 months to entomb the reactor. Over 600k people worked to handle Chernobyl. Fukushima, on the other hand, is still at risk of another disaster, 10 years later. The Japanese government and power company under-handled the situation and lied…

> The USSR responded quickly and it took just 8 months to entomb the reactor. At a gross cost to human life[1], and in a way that leaves the problem there - work is _still_ to contain and clean up the reactor. There are good reasons for not doing the same here. The sarcophagus was never intended to be a permanent solution, and was unsuccessful in completely containing the accident: Sr-90 and Pu-239 were leaching into…

I'm curious, what would have been a better approach the USSR could have taken. Also, is there a better approach that Japan could have taken?

Re: First contact made with melted nuclear fuel at Fukushima plant

#158

Post by jojocool0501 » Sat, Feb 16, 2019, 6:15 AM UTC

JosephRedfern wrote: post #23

Forgive the macabre question, but if a human (or other living creatue) were to venture in to the plant and collect this fuel by hand, how long would they survive? I'm in no way suggesting that this is an option, of course -- just curious.

This is IMO a must read : https://fr.scribd.com/doc/257062334/Chernobyl-Confessions-of...

Re: First contact made with melted nuclear fuel at Fukushima plant

#159

Post by db48x » Sat, Feb 16, 2019, 6:17 AM UTC

dimensi0nal wrote: post #13

furyofantares wrote: post #12

Earlier quoted context omitted.

All pixels in the picture are caused by radiation hitting the camera sensor

I assume the commenter was referring to ionizing radiation.

In a CCD, even photons of visible light are ionizing radiation. The light causes electrons to pop out of a semiconductor and get caught in a capacitor, where they are stored long enough to be read out as a voltage, and turned into a number.

Re: First contact made with melted nuclear fuel at Fukushima plant

#160

Post by tarre » Sat, Feb 16, 2019, 6:39 AM UTC

ChuckMcM wrote: post #79

pvaldes wrote: post #46

Earlier quoted context omitted.

> the "China Syndrome" speculation is pretty much completely debunked You would be dissapointed. Cou-cou! surprise! The ocean strikes back!. Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan. 2017. Sanial, Buessler, Charette, and Nagao. PNAS. DOI:10.1073/pnas.1708659114 "Sanial, Buessler, Charette and Nagao, scientists from Massachusetts and Japan found a new source of Caesium-137 to th…

That is a great paper[1], thanks for the reference I've added it to my nuclear effects library. It doesn't involve the China Syndrome speculation though, what it does find is much much more interesting. The paper reports that beach sand is capable of 99% adsorption of Cs137. And then goes on to discuss how it gets de-adsorbed (up to 11%) when Cs137 free sea water is mixed with it. What this says to me is that you can…

Decontamination factor of 100 is rather terrible compared to DF of over 8 million of actual filter materials, which are being used at Fukushima: https://www.fortum.com/sites/g/files/rkxjap146/files/documen...