I made 2 points in my original post:
1. Storing above ground is cheaper than below ground.
2. The concrete casks can 'easily' last several hundred years.

Now yes, if they are to last several hundred years you're going to need to put the engineering in to have them last said time, but as a practical matter you don't want to go with thin metal and cheap concrete for this anyways. But creating structures that can last 200+ years with hopefully only the occasional inspection shouldn't cost even twice as much as ones that would be breaking down after 'only' 50.

True. Perhaps switch to an aluminum or titanium vessel, protected by a very thick layer of waterproof rolled concrete? Lots of material choices out there.

It can also be largely alleviated by proper location selection and design of the vessel to ensure that water generally doesn't stay in contact.

This would be made complicated by staff lawyers - many larger companies have staffs of lawyers in house.

Inexpensive is relative; I figure they still want to use premium materials - fiber reinforcement, non-reactive aggregate, stainless steel rather than cheap rebar, etc...

True, I wasn't suggesting just leaving them completely alone for a century. A paintjob every decade or so is cheaper than drilling several miles below the surface.

From what I remember, while verifying that it was the Roman recipe(which varied over time) was fairly recent, we have dams that were built using formulas very similar to the Roman recipe long before we knew it was close to the Roman formulas.

The Upper Stillwater Dam, for example, built in 1987, uses a lot of Roman techniques.

The Hoover Dam is expected to last a lot longer than 50 years, partially due to it's use of non-reactive aggregate.

Pay extra attention to your materials and construction methods and you can easily create concrete that will exceed 50 years. For example, use stainless steel for the inner container and fiber for the reinforcement to help prevent cracking.

Thing is, storing it above ground is so much cheaper(and the only current option), that it's currently the best option.

Besides, give it a few hundred years and the radiation guards for reprocessing it should be trivial. The above-ground casks can easily last that long.

First, unaccompanied children riding in these cars would wait until the cars have proven themselves. I wouldn't support children until it's reached the point that you're dropping the steering wheel.

As for #2, it's easily solved by placing the car into a mode where it only has limited destinations. Worst case, you should readily have records of where the car went and can use that to find the 'cool adult'.

At least the way the USA does it, for offenders who are 'just that dangerous', it amounts to torture. Also from my studying of the issue, I don't see any real alternatives to keep them from killing guards or other prisoners.

Thus my comments here and elsewhere about how people are actually on record for opposing nitrogen asphyxiation as an execution method because it's 'too good for them'. I'm unusual, I look at the issues differently. On average I want shorter sentences, more concentration on reform and re-integration with society, because our current vengeance system is just too expensive in both terms of money and human life. Our prison system turns a lot of petty criminals into murderers. Most murderers in the USA have 'served time' in prisons. I can't help but think that's linked. It's where somebody with no previous record goes off their rocker and kills that is rare enough to be news. On the other hand, slip over a line, one that I've deliberately tried to avoid defining too tightly, and I'll kill you, or support the state doing the job.

Think of it a bit like triage - go through the line, marking some for immediate surgery, some who can wait, and slipping a hefty dose of morphine to those that can't be saved. I'm unusual - I have no thoughts of vengeance when I call for the death penalty. I view it a lot like putting down a mad dog. Kindest thing for everyone.

I stand by my words in this case. 'Increasingly' is modifying 'limited' in this case, indicating an increase in the limits of the quantities.

Not only are there fewer devices available, of unknown providence, but at some point you start having to go through rather crazy acrobatics to get them. I've heard of NASA going to garage sales hoping to get some older computer parts, for example.

After a certain point it makes sense to upgrade the system just to restore availability because otherwise the option is to engage the services of small quantity manufacturers. With them, a floppy drive running into the tens of thousands wouldn't be out of line. Not because they'd be ripping you off, but because that's what it costs to make a floppy drive if the quantities produced are too low.

I've noticed that floppy drives just don't work as well as they used to. Either the disks aren't built up to snuff or the drives aren't, I don't really know. The failure rate is such that I don't trust them.

There are however problems when your 'simple dedicated system' is based on hardware that is now so obsolete that it's no longer manufactured; meaning that any hardware failures means that you're having to source unproven used hardware in increasingly limited quantities, or go to shady 3rd party manufacturers that don't have the quality control of the original.

You offer it. If they don't want it, so be it. Worst case you flood the room with N2 slowly, such that they faint before realizing what's going on.

I currently live in a state without the Death Penalty as well, and think that Texas(majority of US executions by a good margin) applies it too widely. Personally, I tend to compartmentalize. My personal stance on the legitimacy of the death penalty is a separate issue from how we'd implement it, if it is too be done.

While I support the death penalty, it would be an extremely rare event, confined to only applying to those so dangerous that allowing them to live will, statistically speaking, result in more death. Alternatively, it's 3 or more murders, or deliberate torture in addition to the murder, if you have to base it on what someone did, as opposed to what they are.

Thus the orally administered anti-anxiety medicine. I'd prevent the whole 'holding breath' thing by simply removing all clocks from the room, or better yet have the clock be two minutes slow.

As for 'basically the opposite'. It's still fast, though I'll admit not as fast as a bullet to the head, worst case it's still faster than a botched lethal injection, electric chair and such. It's quite possible to have it be 'faster' in the sense that you don't need the setup time involved in most forms of execution where you have to tie the prisoner down. It's still painless. Peaceful - well, there's a limited amount of fighting possible when all the guards have to do is put you in a room. Any violence the inmate can engage in whether he's in that room or not.

I'm not sure how bad the convulsions would be, so I'll give you that one, and counter with another - nearly foolproof. Can't make anything entirely foolproof, but it's a lot easier to flood a room with N2 than it is for inexperienced people to find veins correctly.

Well, it's a good thing they only specify 'large classes' then, right? They aren't saying it's invulnerable.

Still, something as 'simple' as running a VPN type encryption system would make your system effectively invulnerable to 'large classes' of attacks.

Personally, I see using 2 keys per channel, an encryption and a separate authenticator. Encrypt everything you send the plane and any plaintext transmissions look like nonesense. Sign all your packets and it can reject stuff that doesn't have the proper signature.

The complicated part is ensuring you don't take up too much extra bandwidth with the security while maintaining good connections even through noise/jamming.

It's still more efficient to charge a Tesla Roadster's batteries over the grid than to generate hydrogen. 93% average transmission efficiency, 90% charger efficiency, 90% battery. 75% total efficiency to the motor when you need it.

Generating hydrogen? 50-80%. Then you have to ship it from the production facility to the users, unless you're using a home generator, in which case you need to add the transmission lines back in and probably figure on the low end for efficiency.

Converting the H2 back into electricity via fuel cell maxes out at 60%.

As for storage - one of my ideas is to take EV batteries that are too worn out for use in a car and use them for grid standby power.