From what I read about the disaster, there were a long series of design issues that could not withstand failures. As I recall,
1. hydrogen being vented into an enclosed area
2. no backup method for determining coolant levels
3. backup generators were not protected
4. no backup method for adding coolant (I would have had a gravity fed backup system)
5. critical systems were located too close to the reactor - I would have moved them further away so they could be repaired without the workers being irradiated
1. You cannot prevent that if the reactors cannot be cooled down. Ultimately very high temperatures will break vapor into hydrogen and will cause hydrogen to accumulate on the shell.
3. Backup generators were located in different areas. The only mistake is that they were ALL at ground level. That's unfortunate that they were all wiped out at the same time but one of the largest Tsunami ever, some stuff that almost never happens. They'll learn from that.
> None of these are expensive to do.
Yeah, when you are building the plant, it's not expensive to do. When you have to modify an existing design, it's way more expensive and you'll have to make a good case for why you need it.
1. hydrogen being vented into an enclosed area
2. no backup method for determining coolant levels
3. backup generators were not protected
4. no backup method for adding coolant (I would have had a gravity fed backup system)
5. critical systems were located too close to the reactor - I would have moved them further away so they could be repaired without the workers being irradiated
None of these are expensive to do.