I haven't seen (translations of) court documents, but back in the day I watched a few documentaries that mentioned how a relevant authority wanted a higher embankment to be built, but TEPCO refused it. Furthermore, the documents mentioned rusted inoperable emergency manual valves because thorough emergency drills had been skipped, so the condition of the valves was never revealed. Diesel backup generators were at ground level, making them useful only in normal situations of power down, but useless if the plant got flooded.
In short, it was all because TEPCO wanted to save some yens, yet in the end this incident has most certainly cost a whole lot more money. Furthermore, how many of Japanese nuclear power plants are online today? Does TEPCO have any running now? I do know other companies were allowed to resume power production in some units, but TEPCO has been refused it due to lacking security/emergency measures (a big surprise). So, nobody was deemed guilty, yet years later TEPCO has still not been deemed worthy to run nuclear power plants. That makes you think a little bit.
Edit: Sorry about this off-topic talk, what comes to Gate.
Feel free to read the technical report on the Fukushima incident; there is no mention of any rusted valves anywhere; in fact, throughout all five volumes, the word "rust" does not come up even once. You may be getting it confused with something you saw or read about Chernobyl, or possibly in reference to Peter Bradford's quote how at high enough temperatures the zirconium cladding on the fuel cells interacts with the water in what is effectively a 'high-speed rusting', converting to zirconium oxide (which is much more liable to rupture and release radioactive iodine-131, which it did; with a half-life of just 8 days it broke down to xenon-131, which is a stable, non-radioactive isotope, long before the accident was even fully sized up). Or, you may have read some propaganda that equated its conditions to shitty maintenance situations found elsewhere, which is also exceptionally possible, because ideologues will latch onto anything they can. The one thing related to valves that is mentioned, and repeatedly, is that there should have been some less-difficult manual measures for if there was complete and total loss of all forms of power (as loss of DC power had some important valves 'fail-close', and loss of AC power resulted in other valves 'failing-as-is'), rather than 'just' rely on the massive amount of redundancies (33 power line, 13 diesel generators) that could fail if there was an accident that was one in a thousand years/one in ten thousand years, as this was.
Similarly, "thorough emergency drills" were not skipped; there simply wasn't any training for a complete and total disaster situation, and there cannot realistically be one for where
everything fails. They were trained for many different emergencies, but all with the assumption there would be some function remaining, given that the earthquake and tsunami it caused were well-anticipated; however, it was anticipated to be only about a 7.5-8.0 magnitude quake, significantly weaker than the 9.1 (39.810 times bigger,
251.188 times stronger than a 7.5) that actually hit and
surprised everybody. It's not realistic nor feasible to train (and make sure they had said training refreshed) all your staff for a freak 1-in-1000/1-in-10000 year scenario, both in terms of monetary cost and in terms of what the workers can realistically remember and prepare for. Similarly, seismic activity was the primary concern for the diesel generators, so they were built sturdily to handle earthquakes, which meant that they were built with strong connections to the ground- one set was built in a basement, and another 10-13 meters above sea level (both technically "at ground level"), which would have been sufficient for any but this freak occurence tsunami.
TEPCO executives may have wanted to save yen, sure, but it's also within reason for them not to expect something like what happened. Any given civil engineering project is built around a certain level of risk management, never to the fullest extent possible, because it's just too prohibitively expensive to do so. That's where the hundred year, thousand year, ten-thousand year disaster scenarios are simulated and factored into projects (if you don't believe me, Grady over at Practical Engineering has talked about this sort of thing at length, repeatedly).
As for TEPCO lacking safety measures, from what I've read, a contractor accidentally damaged intruder-detecting equipment on the 12th of February 2021, they notified the NRA as they were fixing it, and in fixing it and doing an inspection of other systems that may have experienced similar errors, they detected 12 other similar pieces of equipment had minorly malfunctioned (including at other sites) by the 19th, and implemented hasty temporary measures while they repaired them. By the 5th of March 2021, all repairs had been completed and no intrusions had occurred, but several inspections from the NRA between the 21st and the 4th stated that since the detection equipment had malfunctioned in 2020 but was only caught in 2021, more inspections were needed (bruh, as soon as it was noticed, they acted immediately; if the equipment malfunctions such that it doesn't signal that it's not working right and regular inspection doesn't show anything wrong until a malfunction is fixed, how can you blame them?), and forced them to stop moving nuclear fuel at Kashiwazaki-Kariwa by suspending their NRA pre-use inspections; the actual safety of the reactors themselves is not in concern, and they meet the new standards properly.
As for reactors, there are 54, 43 of which were originally deemed operable but has been reduced to 33 following further decommissionings, and only 10 have been given the go-ahead, which all were on the west side of Japan (Kansai, Shikoku, and Kyushu EPCOs); TEPCO is building a new reactor at Higashidori, and aside from that, there's just Kashiwazaki-Kariwa under TEPCO. Chubu, JAPC, Tohoku, Hokuriku, Hokkaido, Chugoku, and J-Power EPCOs all do not have any plants running, as well, with Chugoku, JAPC, and TEPCO all having current-standard reactors available.
You brought this upon yourself and everyone else in the comments section because you had to snark off about something without properly knowing what you were talking about.