I've been watching the series - and have found it very entertaining. There was an Engineering Marvel type of show/documentary on the other day about the large structure which they have recently built over the sarcophagus which is designed to last 100 years.
https://en.wikipedia.org/wiki/Chernobyl_New_Safe_Confinement
The New Safe Confinement design is an arch-shaped steel structure with an internal height of 92.5 metres (303.5 ft) and a 12-metre (39.4 ft) distance between the centers of the upper and lower arch chords. The internal length of the arch is 245 metres (803.8 ft), and the external length is 270 metres (885.83 ft). The dimensions of the arch were determined based on the need to operate equipment inside the new shelter and decommission the existing shelter. The overall span of the structure is 150 metres (492.1 ft), consisting of 13 arches assembled 12.5 metres (41 ft) apart to form 12 bays. Vertical walls assembled around, but not supported by the existing structures of the reactor building seal the ends of the structure.