Hopefully it lasts longer than the last attempt.
The construction will last approx. 100 years. The Chernobyl's 'Elephant foot' (melted plutonium) has a half-life of 24,000 years which means
comparing to a humans life... is eternity. Probably the homosapiens will extinct before the radiation comes down to safe levels. Besides, during
those 24,000 years, they will have to rebuild this sarcophagus 245 times. Bravo for human stupidity !
245 times and each one bigger to encapsulate the old one unless a new technology is created to clean up the mess. 24,000 years is the half life of the plutonium. It is still lethal long after. This sarcophagus has only bought the former Soviet knuckleheads time to try to come up with a better solution within the next 100 years or so. Concrete decays at a fast rate when bombarded with radioactivity. In 5,000 years people might just forget what lies at Chernobyl.
If you want to see human stupidity demostrated, the movie "Fail Safe" (1963) is worth seeing. It is quite feasible, even today. Especially with Trump having absolute, unquestioned power to launch a nuke within THREE MINUTES of him making the decision. If Trump ever decides to "press the button", the only thing that can stop him is mutiny. Having that sort of power at the hands of someone who is psychologically unstable like Trump is extremely dangerous. Trump will have an aid near him at all times who can assist him in carrying out an order to have nuclear missiles launched. By the way, President does not have a physical button, but a well defined process in which to launch a nuclear attack.
These nine irresponsible countries are not going to give up their nukes without a fight... http://www.icanw.org/the-facts/nuclear-arsenals/
You really want to get educated about this sort of science before making such sweeping statements. The new safe confinement:
https://en.wikipedia.org/wiki/Chernobyl_New_Safe_ConfinementIts an enormous building not to only contain the existing structures but to allow them to be dismantled and decontaminated without further releases of radioactive material. This is a well planned and long term approach allowing the site to be gradually reduced in scope, not building a series of matryoshka dolls as you suggest.
The isotopes released and those retained in the reactor are well known and extensively researched:
http://www-pub.iaea.org/MTCD/publications/PDF/Pub1239_web.pdf (pg 19)
The short lived beta and gamma emitters have largely decayed and as mentioned above the largest dose at the moment is from caesium and strontium, and as those decay over the next decade or so the biggest threat will become the (relatively) short lived alpha emitter Cm244 which is only a threat through contamination if you are on site or taking up material through the foodchain. Only a tiny fraction of activity has been released as Plutonium, and being a long lived isotope means the exposure/dose it can present to people is a further tiny fraction again. The radiation at the site is already low enough to live there:
http://chernobylgallery.com/chernobyl-disaster/radiation-levels/And if they made an effort to identity and dispose of (bury) the easily identifiable hot spots and contaminated material (as they have done in Fukushima) then the area would have lower background radiation than other natural places on earth where people live without problems:
https://en.wikipedia.org/wiki/Background_radiation#Areas_with_high_natural_background_radiationSo the natural processes of decay have already happened and now the focus is on isolating and storing the dangerous long lived material, but its danger is not through exposure but contamination.
If you want to get all technical about it, the releases from intentional testing of nuclear weapons dwarfs all accidents from civilian uses:
http://www.nuclear-risks.org/en/hibakusha-worldwide/nevada-test-site.htmlThink about that for a while. Nuclear power has always been more about politics than anything else, and its never going to change. The entire industry was built on military demand for weapons grade materiel and the investments to pivot to higher burn up or other isotopes with lower waste activity wont come as they don't have a military use.