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 the environment after the Fukushima accident. From 2013 – 2016 they visited 8 different beaches within 100 km of the accident site, took sand and water samples and measured its radioactivity.
They found that at the bottom of their sand samples, up to 2 m deep into the beach, the 137Cs concentrations were incredibly high, up to 480,000 Bq per square meter in their deepest samples. The soil in the restricted zone of the Fukushima site, up to 100 km away, measured ~100,000 Bq per square meter.
This means even tens of kilometers away, the radiation can actually be higher than near the disaster. (Because, huh?, 137Cs sticks to the sand grains).
https://oceanbites.org/going-nuclear-radioisotopes-from-fuku...
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 use really cheap beach sand to filter the discharge water from a nuclear reactor and collect 99% of the Cs137 in the water which will stick to the sand. The sand in your filter can be replaced and the cesium rich sand can be sequestered for the Cs137 to decay over time.
This is an excellent finding that suggests reactors have a reservoir of sand for pumping cooling water through especially during reactor compromise. Knowing this a future even would release significantly less Cs into the ocean, collecting it instead in the sand filter.
[1] The experiments showed that beach sands have an adequate ion exchange capacity for this level of 137Cs, with an average adsorption fraction of 99% regardless of the salinity, sediment grain size, or mineralogy (Table S3). ---https://www.pnas.org/content/early/2017/09/26/1708659114
See also: https://www.fortum.com/products-and-services/power-plant-ser...
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 measurable limit. There is no reason to try to remove more Cs from that water :)
> 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. Then put the package in some kind of coating and bury it in a safe vault. Water instead has the bad habit to leak, run away, and enter in the life chain when bad weather, monsoon or accidents happen. A huge concrete block is also less vulnerable to terrorism than a water tank. Is not so easy to steal a jar of it, for example. Even if you could make a hole in the coating, the product will not just flow out.
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.
Yes, I though also about it, but I will add something to the idea of a sand filter. This is not our average dead sand, is marine sand, cleaned and oxigenated constantly by the tides. If we discard an effect of grain size, and sand composition, the really interesting hot-stuff is IMHO probably in what remains, the bacterial biofilm coating the sand.
Would it be feasible to stack filters? (E.g., 0.01 * 0.01 * 0.01...)
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.org/wiki/Granite
> Some granites contain around 10 to 20 parts per million (ppm) of uranium. By contrast, more mafic rocks, such as tonalite, gabbro and diorite, have 1 to 5 ppm uranium, and limestones and sedimentary rocks usually have equally low amounts.
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.
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.
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.
You know, the really nice thing about this part of your statement is that there's no way to tell which side you're standing...
This whole thread started with Bq/m^2 (i.e., "gross disintegrations per second" per square meter), after all. Of course you can accept some numbers and reject others as invalid/irrelevant, but when your whole argument looks like "I reject this number because nuclear is dangerous", it starts to look awfully like circular reasoning, or propaganda, if you prefer.
Two points that inform my position. There is no civilian nuclear industry. Military and civilian are two sides to the same coin. Due to it's black budget military origin, that industry lies about risks out of habit. None of the public debate deals with the complex risks, dubious economics, and long tail waste issues.
I actually know almost nothing and I can see the public debate is just a bunch of deeply ignorant people spouting off. So my position, given the industry lies, the risks, and the existence of alternatives, the sooner we stop mucking around with radio-isotopes and sequester the stuff we've made the better.
And we should remember that unless x-chest rays, thousands of people lay practically naked in the same beach and favourite spots for entire weeks, ten hours a day. Being exposed to the UV rays of the sun also, that is another important source of cancer. In this cases, even relatively low dosis could be of concern.
People at the beach eats a lot of local sea foods also.
Radiation is a funky and tricky topic and frequently results in confusing cases like this. Let me try to explain (trying to keep things simple, so there's more nuance than what I'm writing).
Bq is a measurement of activity. That means the number of decays per second. That actually doesn't tell you the strength of that decay, the particle type, or the effective dosage one would receive. BUT it is still an incredibly important number. It will give you an indication of the half-life of the material and how much there is. A high Bq suggests low half life while a low Bq means a long half-life. OR a high Bq can tell you that there's A LOT of a material. This should make logical sense because Bq is telling you how fast it is decaying, and the more of a material there is the longer it takes to decay. Frequently if a material is known people will refer to its Bq as a way to tell someone else how much of the material there is. (yes, this can get confusing and there are two things it can be used to tell you. You have to pay careful attention. Context matters. In our case of the link you provided it tells you how much of the material there is.)
You'll also see Sieverts[0] listed commonly. This is a SI unit that tells you the effective dosage (REM is the equivalent). That means it considers the weighting that happens because of different particle types as well as where it impacts the body (you're in more danger if you swallow radioactive material than if you touch it with your hand). Which is important for maps like this one [1]. This is easier to understand.
On the other hand, there is grays (rads) is pretty similar to Sv but does not include particle weighting. In fact Sv is derived from Grays. They call this absorbed dosage.
So knowing this you should be able to conclude that the most dangerous material is something that has a high activity and has a high particle weighting.
For some comparisons, 137Cs has a half life of 30 years and decays with a beta- of 0.5Mev and a gamma at 0.7MeV. 235U on the other hand has a half life of 730Myr and decays an alpha particle at 4.8MeV.
[0] https://en.wikipedia.org/wiki/Sievert (There's a break down and link to the other units discussed here at the bottom).
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%2Fm%5E2+*+662... 48uSv per day. [If I didn't make a huge mistake.]
It's like 5 times the normal background radiation, a little more than the radiation you get during a flight in a plane, less than the maximum permitted radiation dose for a worked in a nuclear plant (when there is not an emergency). https://xkcd.com/radiation/
I was expecting a much lower value, but this is still on the side of the safe level (if I didn't make a huge mistake).
The other potentially big problem is that Caesium is bioaccumulative. Clams and other animals could take it from the water again.
> 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.)
What is the Sievert dose one receives from being permanently exposed to such radiation (ideally expressed as bananas eaten per time)? To the lay person such numbers are useless without some comparison.
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 reactors to bring neutrons down from their initial velocity to velocities where they are more likely to stimulate fission in another nucleus.
Most moderators elastically scatter neutrons. What other kind of collision could there be with a hydrogen nucleus?
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.
https://en.wikipedia.org/wiki/Transient_Reactor_Test_Facilit...
Glad to hear they restarted it last year for additional research into these topics.
Wikipedia says it can simulate six different reactor loop types. This is a seriously impressive facility.
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.
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...
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.
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.
The A1B being installed on the newest carriers is a 700 MW unit being installed in a pair, so 1.4 GW total. That number seems comparable to a lot of commercial power generation, e.g. Vermont Yankee is a 620 MW plant.
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.
actually the problem was never the reactor itself. chernobyl never failed because the reactor was totally unsafe. It wasn't the newest, but humans could've prevented anything. fukushima wasn't the unsafest reactor as well. however it got hit by a wave it couldn't stand and after that humans missmanaged everything to safely shut it off.
do you see a common denominator? the problem is that money is always involved even when you can build these things for cheap, however money and humans will make reactors unsafe, not the design of the reactor. at some point somebody wants to save money and most often this money saving practice will then be extremly disastorous.
I'm not saying that nuclear is bad per se, of course the waste is bad, but is it worse than coal? I'm not sure. however as long as humans control or have control over these things they will always be unsafe in a certain way.
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...
Solar panels get hot, gas turbines have hot exhausts, coal plants have cooling towers etc.
They all approximate a heat engine, and they must theoretically give off heat to the cold reservoir
For each of those energy sources mentioned, what would happen if the generating station were to be completely inundated with water?
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.
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!
They walked up to it anyway
https://rarehistoricalphotos.com/the-elephant-foot-of-the-ch...
Funny to see that after years they finally reach the fuel with a big stick :P
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 mitigated, at least in a commercial market.
Not saying "don't build nuclear", just that pro-nuclear lobbies should have been able to predict this situation (with a small chance of occurrence) and model it. If not, don't build. If you can predict it, but govt doesn't care about the risks, publicly document it, and that's OK.
OT, but at this point the nuclear debate looks irrelevant - direction of travel is that renewables win.
[ further OT ...moment of wild speculation: the idea that energy will be scarce will, within the 21st century, become as crazy as the idea that food could be scarce in rich nations right now. The race to renewables will look irrelevant as solar costs hit rock bottom, and no-one will remember why coal/nuclear plants were ever a thing. Within our lifetimes. I genuinely think that scenario is more likely than not. ]
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.
At the end of the day it's money.
aka "China Syndrome", just like the 1979 film:
https://en.wikipedia.org/wiki/Nuclear_meltdown#China_syndrom...
Edit: apparently yes: https://www.ncbi.nlm.nih.gov/pubmed/28189090
Are people seriously considered that's a possibility? Even if the melted core went through the earth unstopped, a little bit of physic would conclude that Earth's gravity would pull the melted core toward the Earth's Core, and passing that, it would just be pulled back in the opposite direction, oscillating back and forth until stopping at the Core.
The Chernobyl folks just entombed everything, which is a one approach, even though they can "walk up to"[1] the remains of the nuclear fuel which they call the "elephant foot."
I also find it interesting that the "China Syndrome"[2] speculation is pretty much completely debunked. Molten/melted fuel diffuses into the material it is melting into until it loses criticality and then freezes where ever it is. All modern reactors have a borosilicate sand pile underneath the reactor. The boron acts as a neutron absorber (poison) which stops the chain reaction once the fuel has been glassified by the silicate.
[1] It is too radioactive for that to be literally true, but it is on a floor with direct access rather than being underwater and only accessible through cracks as the Fukishima fuel is.
[2] Speculation that a blob of melted core material would just keep melting into the ground until it "got to china" (which in fact would be interrupted by getting to the earths core).
[3] EDIT: Corrected for the effects of Boron on the reaction acting as a neutron poison (absorbs neutrons) rather than a moderator (which just bounces them around)