I keep seeing this nonsense about "why not dump it into the dirt", as if that ever made any sense. The answer is always simple, there is already a massive amount of Tritium in the ocean.
The water, is also literally sea water. It is salt water taken from the ocean, now with some radioactive isotopes of hydrogen (H20 remember?) which is called tritium. The dilution process literally takes sea water, and mixes it.
Dumping salt water into a local lake or river, or the dirt is literally what starts ecological disasters. But you didn't even do basic research did you?
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>But you didn't even do basic research did you?
It makes sense BECAUSE that's exactly how dilution works. Diluting in Japanese lakes (or just the closest) is still as safe as diluting the fucking ocean because japanese lakes are also fucking massive relative to volume of water to be released. Politicians chose ocean because domestic politics. Use your brain and do some basic math. Dump all 1.25 tons / 1.2B litres / 660T becquerels into Lake Inawashiro @ 5.4km3 / 5.4T litres and it'll work out to ~120 becquerels of tritium per litre, still less than WHO limit of 10,000 per litre for drinking water. Diluting 1/5400 of the one lake with some salt water, +0.01% salienty, which is... drum roll fresh water territory. That's dumping everything at once. Now spread it out over 30 years. Spread that out over even more bodies of water and it's even more trivial. JP gov chose negligible domestic ecologic disaster with terrible domestic optics that will affect domestic sentiment and governance for negligible chance of international disaster with more managable optics. Which is still based on assumption that TEPCO can be trusted for decades and release will indeed be negligible. But we both know that's far from certain given reputation, hence JP gov would rather hedge by offloading potential political fallout into international commons, because they can't trust TEPCO not to fuck around on the time scale involved, so best not even risk something as sensitive as more radiation drama on JP soil. They'd rather risk losing 100s of billions in fishing exports than potential domestic ire. Which is fine. But also recognize this issue has as much if not more politics considerations than science. But you didn't even do basic political/geopolitical thinking relative to science did you?
Problem 1 : Water extraction
Extracting large volumes of water, is naturally not a ecologically friendly practice. It's actually one of the large barriers stopping us from solving water issues via large scale desalination. Ecological damage includes animals being sucked in, to higher water temperatures causing algae blooms. (Moving all that water, does overall increase the water temperature) Furthermore, it may actually case over-oxygenation of the water, which can cause it's own set of problems. But I'm not a specialist so I will leave that topic as "I have heard of this thing".
Problem 2 : Actual dilution
That's not all though. You need to ensure local PH balances are stable. Since we are starting off by using ocean water (it was the closest and most viable option), you now have to do an ecological analysis of the lake, and make the water match the lake's overall water profile. That requires a whole other set of equipment, and imported materials to balance it out. Of course, "it's relatively speaking, a drop in an lake", but that's the thing, it's a lake. It doesn't have ocean currents.
The Lake is overall a enclosed environment, when compared to the ocean. And it is one hell of a lot more expensive than the ocean, which is right next door!
Now lets take your number, 120 becquerels of tritium per liter. Lets ignore the WHO safe level for a moment. Since our goal is diluting it, preferably, we won't appreciably change the per-liter value of tritium in fresh water. But that's not the case is it? The natural background amount of tritium in 1cubic liter in surface water is around 0.4–1.2 Bq/L. So your proposal, increases the amount by 100x. That misses the entire point of "dilution", which is why I said it doesn't count. When you dilute something like this, the whole point is to dilute in a manner that makes environmental effects negligible. Your proposal, misses the entire point.
Further more, they are only releasing ~28becquerels (officially it is 22becquerels) per year into the ocean, to ensure proper dilution. Divide 28 by 365 days, that is 0.077becquerels per cubic liter (rounded up), in an entire 24 hour cycle! Which would bring it very close to the natural background! This is dilution! This is the bloody point of it all!
Dumping it all in a lake, makes this completely pointless!
Problem 3 : Logistics (AKA, why are we even transporting this?)
This one is simple. Why in the actual hell, would you spend time and risk a truck flipping, rather than just use the pipe you already have and release into the ocean? And this ties into the two previous comments. You have to extract water from the lake, bring it to the water storage facility, mix it, then transport it back.
Or take sea water, desalinate it, then get it to the correct profile, then transport... The amount of extra steps, and chances for human error are significantly higher. It's impractical, and a waste of time.
Problem 4 : Local Resistance (Or domestic politics)
Naturally, locals don't like it. It doesn't matter if it's safe, or checked by independent auditors or international organizations. Humans are overall, emotional, social creatures. Not logical ones. Local pressure is naturally easier to evade if you say "It won't be your problem in the future", which is unfortunately how humans work. Hell, if I had the money, I'd buy the lake (which isn't possible), and let them dump it there (Which I cant, because the fresh-water underground water table is legally protected). Of course, I would tell them "It won't be a problem in 14 years, due to the half-life", but they won't care.
Non-salt water is also significantly more valuable than salt water. It's the difference between incredibly energy intensive and expensive desalination and, just not needing it. People care more about non-salt water than salt water.
I'd happily drink it, assuming it's boiled and de-salted. (And I am not being facetious)
Ultimately, regardless of feasibility, it's simply a solution which they didn't even consider, because again, as you recognized why would they. That's politically suicide even if it's deemed ecologically sound plan. Which circles back to your first point, does any country dump tritium in their local lake? Not publically, and Fukushima is notoriously public politics. But you know what most try to do with nuclear waste? They attempt to engineer supremely expensive local storage solutions, and frequently fail only to spend stupid resources to warehouses it domestically, instead of dumping that into the commons. It's 60 olympic swimming pools worth of water. It's trivial storage problem for nation state. Hence problem 1/2/3 isn't even a problem especially if they bothered with local dumping studies which again, is 3 tankers per day for 30 years. It's nothing. Desalinating 1.25m tons is also trivial, and not even that costly. A 10m gallon / day plant cost less than 100M and sort filter that in a month. Which is peanuts versus aggregate clean up cost, and even potential lost fishing revenue. Cost isn't driving this decision to release, politics is. And it's not regional geopolitics because JP isn't releasing this water out of spite for her neighbours. Let's not forget, it's not PRC but most of region as well as countries across the Pacific not pleased with this decision.
Which ultimately circles back to point 4, and my broader point. LOCALs don't like it. LOCALs vote. Can't risk LOCAL votes even if they're irrational, and EVEN worse if their rational distrust of TEPCO becomes reality down the line. IIRC even more containated water already leeched into ground water. Risk of future leaks, however "safe" this water is, and heads will roll. So the politically expedient solution is to dump into ocean and remove any potential risk. The political math is simple, they would never even consider local disposal or long term local storage due to the risks, so into the ocean it goes. Which again, is fine. Fine in the sense that it's a calculated decision. But let's just acknowledge that's whats actually driving decision making. Less science and more domestic JP politics. They didn't have to dump this water. A 5T economy can afford to store it indefintely and ignore geopolitical shit show. But domestic JP politics want that water gone from JP territory, so into the ocean it goes.
