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

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

#191

Post by GordonS » Sat, Feb 16, 2019, 12:44 PM 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…

I live near Aberdeen, in Scotland, a city built largely of granite, and somewhat famous for having (relatively) high levels of background radiation as a result. Supposedly, background radiation levels are higher than they are in Fukushima!

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

#192

Post by GordonS » Sat, Feb 16, 2019, 12:47 PM UTC

anigbrowl wrote: post #130

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…

I also find it interesting that the "China Syndrome"[2] speculation is pretty much completely debunked. That term was never meant to be taken literally, in the movie where it originates it is presented as a fanciful exaggeration meant to emphasize the seriousness of the risk. The actual plot concerns the risk of groundwater contamination following a nuclear accident, not a planet-piercing tunnel.

> That term was never meant to be taken literally

As a kid growing up in the 80's, I remember people, even school teachers, did take that term literally!

It was one of those things I kind of forgot about for years and took for granted as being "truth", until I actually read about nuclear power!

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

#193

Post by tarre » Sat, Feb 16, 2019, 1:09 PM UTC

pvaldes wrote: post #181

tarre wrote: post #170

Earlier quoted context omitted.

There are reasons, why not to do that: 1) DF doesn't add up like that at low concentrations. Then it comes down to selectivity of the material. Sodium and cesium have similar chemical characteristics, but CsTreat is very efficient in selecting Cs over Na. 2) Material you are using as filter becomes radioactive waste. You want to keep the volume at minimum. 3) With CsTreat you already reach radioactive Cs levels below…

Honest question. Is is being CsTreated since eight years, why we do have radioactive Caesium still accumulating in the coast? > 2) Material you are using as filter becomes radioactive waste. You want to keep the volume at minimum. This is very reasonable, but storing sand for 50 years somewhere is technically feasible and maybe even cheaper than storing water. You can put the sand in concrete and obtain a solid block…

>Is is being CsTreated since eight years, why we do have radioactive Caesium still accumulating in the coast?

As far as I know, this is because about 10 PBq of Cs-137 was released during the accident and the released material is transferred by ocean currents. CsTreat is being used for purification of the water, which is pumped into and out the containment to keep core remnants cool. Nowadays the releases are very limited if any.

>This is very reasonable, but storing sand for 50 years somewhere is technically feasible...

You're right. Also CsTreat is solid, rock/sand-like material. It can be stored as mixed into concrete and disposed as low/intermediate-level radioactive waste.

Now you probably want to ask: Why there is huge amounts of radioactive water stored at the plant site? Because of tritium, which is chemically equal to hydrogen and is very expensive to separate from water. Under normal operating licenses of NPPs, you could release such water into environment, but at Fukushima standards are nowadays peculiar.

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

#194

Post by pfdietz » Sat, Feb 16, 2019, 1:53 PM UTC

hexane360 wrote: post #173

pfdietz wrote: post #99

Earlier quoted context omitted.

> 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.

No, elastic means an encounter where kinetic energy is conserved, rather than being converted to some other form of energy.

THe neutron/nucleus collisions in a moderator are largely elastic. The total kinetic energy of the neutron and the nucleus is conserved, although kinetic energy is transfered from the neutron to the nucleus.

An inelastic collision would involve (for example) nuclear excitation of the target nucleus, or ejection of particles from the target nucleus. The neutrons from fission are usually too low in energy for this to be very likely, though.

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

#195

Post by Krasnol » Sat, Feb 16, 2019, 1:59 PM 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.

There is nothing sad about it.

It's about time. Especially in countries that do not posses any reasonable ways of discarding the produced waste as well as countries that have other capabilities to generate power.

This tech IS dangerous. There WAS fallout and you can still find 9000Bq wild animals in the middle of Europe. Not even mentioning the cancer rates all over East Europe here.

So please spare us this overhyped new rush for nuclear.

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

#196

Post by pfdietz » Sat, Feb 16, 2019, 2:05 PM UTC

kortilla wrote: post #174

afterburner wrote: post #141

Earlier quoted context omitted.

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 disrup…

> Those costs are entirely political.

This is simply not true. There has been tremendous ongoing incompetence and mismanagement in the reactor construction process in recent years. You may blame regulation -- that's the goto excuse for pronuclear people to avoid coming to unpleasant conclusions -- but the problem is that reactors are complicated things, and reactors with safety systems are even more complicated things (and reactors without regulation are complicated things that will almost certainly fail in unpleasant ways.) Building complicated things is hard, especially if all the institutional knowledge of how to do it, and the supply chains for the parts, have decayed away.

The huge advantage solar/wind have is they are simple and scalable. Installations consist of thousands, or even millions, of replicated parts. Experience builds up rapidly as the same damned thing is built and installed over and over. Nuclear doesn't have that.

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

#197

Post by mimixco » Sat, Feb 16, 2019, 2:05 PM UTC

tomatotomato37 wrote: post #56

mikro2nd wrote: post #41

Earlier quoted context omitted.

I don't know how nuclear can be considered remotely "carbon free" if you take into account the usually-externalised emissions incurred in mining, refining and processing the uranium ores into fuels. Then, too, I've seen no figures on the carbon costs of nuclear waste-management.

Uranium mining is a tiny operation due to it's absurd energy density. I wouldn't be surprised if the mining cost of rare Earth's used to maintain broken solar units surpasses it it's so insignificant. Besides most countries with a nuclear weapons program end up with a lot of reactor-grade uranium lying about anyway, and those countries also happen to be the biggest polluters in energy

No, it's actually a terribly polluting and inefficient mining process. Only a tiny fraction of what is dug up is usable. It requires many (even more toxic) steps in order to turned into fuel. There's a good documentary about uranium tailings and how they pollute the local water permanently.

Besides, there isn't enough uranium in the world to provide baseload nuclear power that would replace coal.

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

#198

Post by mimixco » Sat, Feb 16, 2019, 2:11 PM UTC

petschge wrote: post #107

saagarjha wrote: post #103

Earlier quoted context omitted.

What parts are we missing?

Regulatory capture and "understandings" between supervising authorities and commercial operators that boarder on corruption, unsolved waste problem, very slow ramp-ups and ramp-downs which are annoying for the grid and a lot of things I don't understand well as an astrophysicist either. But both friends I have in the nuclear energy field have become very anti nuclear power and would rather see it shut down tomorrow i…

I'd add to that the astronomical costs of decommissioning (always passed on to ratepayers) and the fact that nuclear is basically uneconomic. It requires enormous subsidies and always goes over budget. Perhaps most disturbing is the aging fleet of nuclear plants we already have in the country, almost all of them way past their designed lifetimes. This is a recipe for accidents.

I notice that no one brings up that all recent plant construction in the US has been cancelled except one -- which could get killed any day. And no new nuclear plants are planned or proposed for the US.

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

#199

Post by javagram » Sat, Feb 16, 2019, 3:30 PM UTC

pfdietz wrote: post #196

kortilla wrote: post #174

Earlier quoted context omitted.

>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 disrup…

> Those costs are entirely political. This is simply not true. There has been tremendous ongoing incompetence and mismanagement in the reactor construction process in recent years. You may blame regulation -- that's the goto excuse for pronuclear people to avoid coming to unpleasant conclusions -- but the problem is that reactors are complicated things, and reactors with safety systems are even more complicated thing…

> Experience builds up rapidly as the same damned thing is built and installed over and over. Nuclear doesn't have that.

Do you think this is the reason the US Navy doesn’t seem to have major problems getting nuclear power plants built and installed in submarines and aircraft carriers? It’s interesting how civilian power companies have had a bunch of high profile failures in this area but as far as I can tell new warships still seem to be able to get reactors fine.

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

#200

Post by cladari » Sat, Feb 16, 2019, 4:15 PM UTC

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…

In a pressurized water reactor the water is the moderator (bounces and slows the neutrons) and dissolved boron is the poison used to control the reaction.