a) "High level waste" retains 95% of it recoverable energy so misnamed. France has done an excellent job of vitrification. One visiting leader asked what France had done with ....the lead energy person said " you are sitting on it" ..it was the floor of the facility.
The actual scale of rods needing refurbishing is small...a fooball field 3m deep ....which if actually gathered would be a hellish result.
Meanwhite sitting in cooling ponds indefinitely is fine ( except on the upper floors

) until a decision is made to starting a fast breeder program
https://catalyst.independent.org/2021/0 ... lear-fuel/which aside from producing power reduces the scale of the spent material by 95% and the half life dramatically.
Yucca mountain was closed in 2010.
....
b) I'm skeptical compressed nitrogen would be effective storage/transport against the energy density of green hydrogen which has some momentum.
There are already storage for renewables that involved compressed air for after hours use.
There was a good article in Sci-Am on the hydrogen economy a good while back ( 1973 ) . I wrote the authors when I did not hear anything further and they said regretfully it had not moved forward.
https://www.scientificamerican.com/arti ... n-economy/A hunt on "the hydrogen economy" brings up a variety of good articles.
https://www.scientificamerican.com/arti ... s-future1/I always considered it the dark horse in the race for carbon neutral. A hydrogen fuel cell aircraft ( hybrid ) is taking its first tests this year with 700bar tanks.
I've revised my thoughts to .....it's a contender or tag team partner to mix my metaphors.
Solid-State Hydrogen Storage Systems and the Relevance of ...
https://mdpi-res.com/d_attachment/energ ... 158-v2.pdf good read.
Hydrides really are the holy grail but....
https://phys.org/news/2021-10-hydrogen- ... l-gas.htmlIt ain't been grasped yet tho there are serious glimmers.
snip
In the recent research, the scientists found a new way to ease the thermodynamic limitation. The team focused on one typical metastable metal hydride called alane. Alane, or aluminum hydride, has a volumetric hydrogen density twice that of liquid hydrogen. However, converting bulk metallic aluminum into alane was long thought to be impossible except under extreme conditions with more than 6,900 atmospheres of dihydrogen (H2) pressure.
The team developed a nanoconfined material with improved thermodynamics of alane regeneration. They found that alane situated within the nanopores of a highly porous bipyridine-functionalized covalent triazine framework can be regenerated at a H2 pressure of only 700 bar (690 atmospheres), which is tenfold lower than that required for its bulk counterpart. This pressure is readily achievable in commercial hydrogen fueling stations, although further improvements are necessary to achieve rapid fueling.
