"When people injure you, ask yourself what good or harm they thought would come of it. If you understand that, you'll feel sympathy rather than outrage or anger.
Your sense of good and evil may be the same as theirs, or near it, in which case you have to excuse them.
Or your sense of good and evil may differ from theirs, in which case they're misguided and deserve your compassion.
Is that so hard?" - Marcus Aurelius
It occurred to me that now might be a good time to briefly comment on the water release that has begun at the stricken four-unit Fukushima Daiichi nuclear power plant.
For starters, releasing this water into the environment has always been inevitable. Groundwater is continuously leaking into the reactor buildings. Once this groundwater comes into contact with nuclear fuel, melted core debris, or reactor vessel corrosion, it becomes contaminated with radioactive particles. Since shortly after the multiple core melt-downs, this water has been pumped into hastily-built tank farms.
In the immediate aftermath of the meltdowns at Fukushima, 300,000 tons of *untreated* water was released to the environment, in addition to the airborne plumes of radioactive particles from the initial explosions.
Above image courtesy Roulex_45 at wikimedia commons.
It's apparently not possible to prevent groundwater from entering the damaged buildings. It's also not possible to continue eternally building enough tanks to capture all that water until the radioactivity has subsided. That's the reality of the situation, and nothing will change that. Any hand-wringing over the release of this water into the environment is silly. The tank farm would cover all of the island of Honshu before the radioactivity has decayed.
That said, the release is being done as responsibly as possible, with the oversight of the IAEA - the International Atomic Energy Agency. The IAEA is the UN's nuclear watchdog, which monitors such things as nuclear reactor safety, and keeps tabs on nuclear fuel enrichment facilities, to determine if countries are attempting to build nuclear weapons.
The contaminated water that has been held in the tanks will be treated and released. The treatment is being done by three parallel "Advanced Liquid Processing Systems", or ALPS. It took a quite bit of research to learn more or less what technology this ALPS system uses to remove the radioactive contamination from the water. Most of the web pages showed a cartoon diagram showing tanks full of dirty water, a processing box, and a tank full of clean water being pumped into the ocean. See below.
I was interested in how the ALPS process works, and it took some digging to find that out.
The first step is iron co-precipitation. Iron III Chloride solution is injected into the water, while the pH is controlled using an acid, typically sulfuric acid. The iron Fe+++ ion is highly charged and tends to attract dissolved and suspended substances. This allows suspended contaminants in water to agglomerate, grow large, and precipitate.
This process will very likely be done in large clarifiers. See cutaway below:
The clarifier provides a water inlet and chemical mixing section in the very center, a low flow region for the Fe+++ ions to work their magic (grow and precipitate contaminants to the bottom), then allow the clear water to overflow into a catch ring at the top - the "effluent trough".
Meanwhile at the bottom, a precipitated sludge accumulates, and is very slowly scraped into a discharge where it can be pumped out as a sludge, de-watered in a press, and disposed of as solid radwaste.
The treated water from this process is then passed through 16 absorbent columns (I'm assuming activated charcoal) to remove any remaining impurities. The entire process is claimed to remove 62 different radioactive contaminants. The remaining water should be very pure, and mostly stripped of contamination.
However... some of that water will have at one time been reactor coolant, and exposed to neutrons inside the reactor core. This water will sometimes have a hydrogen atom that has two neutrons in the nucleus - just because hydrogen sometimes captures a neutron in the reactor. This isotope of hydrogen is called Tritium, and it is mildly radioactive. This Tritiated water is chemically identical to normal water and cannot be filtered out. Below: Isotopes of hydrogen, including radioactive tritium, and water molecules containing a tritium hydrogen atom.
So the remaining issue is radioactive Tritium, which is part of the water molecule, and thus cannot be filtered or separated from the non radioactive water.
The good news is that Tritium isn't particularly dangerous. It's part of a water molecule, so unfortunately there will be biological uptake. However, unlike strontium or cesium, it won't get built into your bones, or the bones of marine life. Instead it will be moved along and flushed out, as is all water eventually. It has a middling half-life, at 12.3 years, which is not good.
However, possibly the best news is the nature of Tritium's radioactive decay. It emits a very weak beta particle (electron). Most radioactive decays are in the range of 1-5 Million Electron Volts. Tritium's electron has just 0.0186 Million Electron Volts (18.6 KeV). This low energy makes the radiation from Tritium difficult to even detect. It requires a scintillation detector in very close proximity to the Tritium.
The low energy of this beta particle makes its flight path very short, and thus greatly reduce its ability to damage DNA. In air the flight path of this beta particle is jut 1/4 inch, or 6 mm. In ocean water, or in tissue, the flight path should be a great deal less than that - perhaps only a few nanometers, due to the increased density of the surrounding material.
The ocean's current estimated inventory of Tritium is 27kg plus or minus 14 kg. Japan's TEPCO, owner of the melted reactors and thousands of gallons of contaminated water, will be adding to that inventory. Discharges began 24 August 2023, and that will be ongoing.
For comparison, France's La Hague nuclear fuel reprocessing facility discharged 11,460 TeraBequerels of Tritium in 2018, which is 13 times more Tritium than is stored in all the tanks at Fukushima. If there is wailing about Fukushima, there should be 13 times more wailing about La Hague, which ought to have better control over their radioactive releases than a disaster site with three melted down reactors.
Below: Spent fuel pool at the La Hague reprocessing facility.
One other contaminant that the process does not remove effectively is good old Carbon-14, the radioactive carbon dating isotope. There should not be a great deal of this in the water, so I won't discuss it further other than to mention it will be going along for the ride into the open ocean. Both Tritium and Carbon-14 are generated naturally by cosmic ray interactions in the upper atmosphere, but in very minute trace quantities.
Anyway, my final thought on this that while it's never a good thing to release radioactive substances into the environment, this particular release isn't bad, as these things go. Moreover, it's about the best that can be done given the situation, and there aren't really any other options.
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