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First contact made with melted nuclear fuel at Fukushima plant

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

#171

Post by jplayer01 »

petschge wrote: post #84
lucb1e wrote: post #73

Earlier quoted context omitted.

And another logical argument could be that this causes us to delay cutting emissions enough to prevent massive ecosystem changes resulting in humanity's death in the next few hundred years. It's just not that simple. We need to look at both sides, weigh the options, and find a solution which probably involves a mix where we compromise on having X m³ of earth dedicated for a long time to nuclear waste to save us in th…

The thing is that there is a rather pro-nuclear crowd on HN here that does not understand enough of the physics and the systems engineering of the large scale electrical grid that goes into making this trade-off in a rational way.

Are you suggesting that the anti-nuclear crowd does? What I've seen is that most anti-nuclear people are mostly driven by emotion in a one-sided way (such as not accounting for the environmental and real human cost of oil, gas, coal).

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

#173

Post by hexane360 »

pfdietz wrote: post #99
petschge wrote: post #45

Earlier quoted context omitted.

Boron actually mostly acts as a neutron poison, i.e. it absorbs neutrons. That way further (stimulated) decay of other nucleii that were hit by a neutron is eliminated and the chain reaction stops, reducing the production of thermal energy. A moderator on the other hand inelastically scatters neutrons, converting some of the kinetic energy of the neutrons to heat and leaving a slower neutron. Moderators are used in r…

> A moderator on the other hand inelastically scatters neutrons, Most moderators elastically scatter neutrons. What other kind of collision could there be with a hydrogen nucleus?

When discussing scattering of particles, "elastic" usually refers to electrostatic slingshots where almost the entire kinetic energy of the particle is conserved. Inelastic, however, refers to a direct collision where there is a significant energy loss of the particle. Obviously the former doesn't happen with neutrons, but I believe it's still a typical convention in particle physics.

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

#174

Post by kortilla »

afterburner wrote: post #141
eXpl0it3r wrote: post #115

Earlier quoted context omitted.

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 exis…

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

Those costs are entirely political. Fear mongers have made it extremely difficult to get a nuclear project to completion (see the whole NRC approval process). Solar panels would be super expensive as well if each one had to go through a giant 30 year planning process that NIMBYs could easily disrupt.

>They also weren't built when renewable energy was developed into the very cost-effective solution it is today.

Renewable isn’t cost effective. That’s a lie told to placate people. In reality, renewable currently has no feasible way to replace enough fossil fuels to matter for global warming. Energy storage solutions to bring it into candidacy for base load are so far off the mark that they aren’t even deployed.

Until we have a storage solution that doesn’t 10x+ the cost of renewables, which there is no promise of, we are signing up wholeheartedly for fossil fuels as our electricity backbone (and that doesn’t even address transportation energy where the picture is even more bleak).

Reminder for anyone thinking renewables are so cost effective, here is the energy source breakdown in the US: https://www.eia.gov/energyexplained/images/charts/consumptio...

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

#176

Post by Haga »

pvaldes wrote: post #138
yongjik wrote: post #134

Earlier quoted context omitted.

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…

But sand is not normally made of eroded granite, or it does not contains only granite. A lot of sand is made of shells or coral. Most beaches should have much lower levels of radioactivity.

Behold the prolonger of discussion and destroyer of easy decideability : It deepends

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

#177

Post by underwater »

aaronmdjones wrote: post #154
randomsearch wrote: post #136

Earlier quoted context omitted.

> 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.

And people. Neither of which new plant designs will address.

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

#178

Post by logifail »

petschge wrote: post #74
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…

Part of that problem is that water is actually a decent moderator and neutron reflector, so it helps a lot in keeping a chain reaction with lots of energy output going. Some of the energy also goes into splitting water into hydrogen and oxygen. The hydrogen can then collect in some corner of the building until it reaches an concentration where it explodes rather easily. The explosion can then damage the building, rui…

> Moral of the story? Keep your box of boronic sand nice and dry.

See also:

"For every three units of energy produced by the reactor core of a U.S. nuclear power plants, two units are discharged to the environment as waste heat. Nuclear plants are built on the shores of lakes, rivers, and oceans because these bodies provide the large quantities of cooling water needed to handle the waste heat discharge."[0]

[0] https://www.ucsusa.org/nuclear_power/nuclear_power_technolog...

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

#179

Post by Gibbon1 »

blattimwind wrote: post #150
yongjik wrote: post #134

Earlier quoted context omitted.

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 s…

Yeah this is just a version of the 'chest x-ray' fallacy/lie/propaganda.

You just simply cannot compare radiation hazzards based on gross disintegration's per second. Anyone doing that is either lying because they know better or ignorant.

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

#180

Post by hrktb »

jessriedel wrote: post #129
acidburnNSA wrote: post #49

Earlier quoted context omitted.

Absolutely yes. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) does reports every year or so on the status. Here's the 2017 one [1]. [1] http://www.unscear.org/docs/publications/2017/UNSCEAR_WP_201...

From the executive summary (for others): > ...its assessment of the exposures and effects due to the nuclear accident after the 2011 great east Japan earthquake and tsunami... It had concluded in that report that, in general, doses were low and that therefore associated risks were also expected to be low. A discernible increase in cancer incidence in the adult population of Fukushima Prefecture that could be attribut…

I’m a bit frustrated by some of these arguments. In particular there is all this “expected” part about low level of radiation that _should_ lead to low effects.

That all fine, until we get the numbers of actual cases, which are higher than expected.

But then we have something looking like backpedaling, a lot of “yeah it’s higher, but it’s not what you think. Because it should be low”, wich I’d take as a partly circular argument.

An extract from this study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5770131/#!po=41...

> According to the studies reported until now, it is difficult at this point to attribute thyroid cancers in Fukushima to the direct effects of radiation exposure. The reasons are as follows. Exposure doses in Fukushima are significantly lower than those in Chernobyl (65).

There are other arguments details further down these lines, but the lower exposure shouldn’t be used to argue the effects of radiation when the whole point of the studies are to mesure these effects. It taints the whole conclusion in a veil of “we don’t want to disown or past predictions”

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