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.
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...