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

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

#141

Post by afterburner » Sat, Feb 16, 2019, 1:54 AM UTC

eXpl0it3r wrote: post #115

m_mueller wrote: post #71

Earlier quoted context omitted.

Obviously it couldn’t melt through to China but AFAIK the way Czernobyl played out was that they had to somehow stop it from melting down to a flooded basement due to the fear of a long lasting series of hydrogen explosions that could have been truly disastrous for the region, if not Europe. Thus I think that the true worst case has so far never happened: A reactor without any of the modern safeguards (such as boroni…

The sad part is that the whole anti-nuclear politics often prevent building new and way safer reactors, yet they also don't manage to force shutdown all the dangers ones.

Building new reactors costs a massive amount of money, more than pro-nuclear advocates realize or are willing to admit.

Shutting down reactors doesn't save much money; they've already been built. They also weren't built when renewable energy was developed into the very cost-effective solution it is today.

The worst thing about building new reactors using existing technology (which would really no better than the existing ones) is the waste of money compared to alternatives, AND you get all the risk on top of that. Delicious government-subsidized risk.

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

#142

Post by afterburner » Sat, Feb 16, 2019, 1:54 AM UTC

m_mueller wrote: post #71

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…

Obviously it couldn’t melt through to China but AFAIK the way Czernobyl played out was that they had to somehow stop it from melting down to a flooded basement due to the fear of a long lasting series of hydrogen explosions that could have been truly disastrous for the region, if not Europe. Thus I think that the true worst case has so far never happened: A reactor without any of the modern safeguards (such as boroni…

Contaminating the groundwater is also a risk.

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

#143

Post by TheCoreh » Sat, Feb 16, 2019, 1:54 AM UTC

ctoth wrote: post #55

I suspect I am not the only person who saw "First contact made" at the top of HN and for one brief, shining moment lived in a far more interesting Universe.

Yeah, my heart raced for a second before I read the full headline. Happy I'm not the only one. One day, it will be for real. Hope that I'm still alive to witness that.

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

#144

Post by afterburner » Sat, Feb 16, 2019, 2:00 AM UTC

jade12 wrote: post #47

mimixco wrote: post #15

It took 10 years to even get a robot that could get close to the fuel... and people still ask if nuclear might not be as bad as coal! The truth is that accidents like this can never be cleaned up or salvaged. It's time to move away from nuclear, as other countries have already figured out. Fortunately for us in the US, the last nuclear plant under construction today will likely be cancelled, as the last two were. The…

Lest anyone forget, the Centralia (coal) mine fire has been burning since at least 1962 and no one knows how to stop it. The Fukushima Daiichi incident really doesn't seem that bad to me, comparatively speaking. https://en.wikipedia.org/wiki/Centralia_mine_fire

The choice is not between coal and nuclear.

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

#145

Post by afterburner » Sat, Feb 16, 2019, 2:01 AM UTC

cgrand-net wrote: post #22

mimixco wrote: post #15

It took 10 years to even get a robot that could get close to the fuel... and people still ask if nuclear might not be as bad as coal! The truth is that accidents like this can never be cleaned up or salvaged. It's time to move away from nuclear, as other countries have already figured out. Fortunately for us in the US, the last nuclear plant under construction today will likely be cancelled, as the last two were. The…

> The truth is that accidents like this can never be cleaned up or salvaged. While global warming is easily solved. Coal or nuclear are both bad but differently. Which one is less bad depends on your risk model

The choice is not between coal and nuclear.

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

#146

Post by AngryData » Sat, Feb 16, 2019, 2:04 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…

I don't entirely agree with you, based mainly on when these reactors were originally designed. They started building in '67, but the actual construction designs were based on even earlier plans and tests that were conceived of in the 50s. So the original designs of the plant were born only around 15-20 years after we even invented nuclear technology. I find it similar to discussing automobile safety based on a Model-T.

Sure they have upgraded some things over the years, but there are only so much you can do when your modifications are done after it was already built or even in the middle of being built. I just don't see how we can really compare nuclear technology of the 60s, with nuclear technology of the 2019.

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

#147

Post by acidburnNSA » Sat, Feb 16, 2019, 2:25 AM UTC

Asparagirl wrote: post #93

People should check out Safecast, which is a citizen-led open data network for monitoring and publishing radiation readings, including an open API: https://blog.safecast.org/ They're using low-cost open hardware, including Arduino: https://github.com/Safecast/General/wiki/Safecast-Devices Here's their latest heatmap (well, radiation map) for Japan, centered on the Fukushima area: https://safecast.org/tilemap/?y=37.14…

Do you know how they're communicating the expected health effects of dose rates like these? For instance the yellow is 4 uSv/hr, roughly 10x a normal dose rate in the USA.

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

#148

Post by gus_massa » Sat, Feb 16, 2019, 2:25 AM UTC

pvaldes wrote: post #137

gus_massa wrote: post #132

Earlier quoted context omitted.

> the 137Cs concentrations were incredibly high, up to 480,000 Bq per square meter in their deepest samples. But is that high? I don't know. Let's make some uninformed back of the envelope calculations. The energy of the Cs137 radiation is 662keV, let's assume a normal person with 100lb and a surface of 2m^2 (only half get the radiation). In a day this person will get https://www.wolframalpha.com/input/?i=480000Bq%2F…

You are missing there an important factor: Life and dynamics of marine ecosystems. One of the problems is that 137Cs is being accumulated by sea currents, therefore even if we have a safe level in eight years, we could have, lets say, the "double" of the safe level in 16 years, rising to "four" times in the next 30 years (of expected half life of 137Cs). Minus the Cs released again to the water, but... The other pote…

Good points. Bioaccumulation is a real problem. For example from https://en.wikipedia.org/wiki/Caesium-137#Radioactive_caesiu...

> In Scandinavia, some reindeer and sheep exceeded the Norwegian legal limit (3000 Bq/kg) 26 years after Chernobyl.

About the slow accumulation in the sand: If we make some simplifications and assume that without decay the flow rate is constant and the concentration increase linearly and in 32 years the concentration will be 5x the current amount. But when we add the decay the actual concentration will be only 2.5x the current amount.

(With a simple model like this using 30 years for the half life, I get the peak in the year 2043 with a concentration 2.4x of the current value.)

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

#149

Post by acidburnNSA » Sat, Feb 16, 2019, 2:27 AM UTC

acidburnNSA wrote: post #58

lotu wrote: post #48

Earlier quoted context omitted.

Nuclear kills less people than Coal mostly from asthma, but coal even causes more cancer because on a normal day it emits far more radiation in the form of small particles of radioactive dust present in coal. The real danger of Nuclear is it can make land unusable by people for centuries (this actually appears to be good from a biodiversity and ecological heath stand point because people do more damage to that than s…

Centuries? Have you been to the Chernobyl exclusion zone recently? [1] That was the worst accident imaginable. Fukushima is much less bad. Natural background radiation in places like Ramsar, Iran are way higher than what you'd experience at Fukushima even right after it happened. And people have been living healthily there for hundreds of years. Low-dose effects of radiation seem to not be all that bad. [1] https://n…

I'm going to correct myself and say that Ramsar rates are what you'd experience around Fukushima a year out, not right after it happened. Some of those workers got way higher doses than anything natural.

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

#150

Post by blattimwind » Sat, Feb 16, 2019, 2:42 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…

> 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.

I don't think this computation is valid, because you have to consider what and how much radiation makes it out of the solid. So converting from activity per mass to activity per surface area cannot be done, I think, by simply assuming a given depth.