Is there a physical law that indicates it's not feasible? Because if not, this is just like saying multiplying a bunch of matrices is not a feasible way to build a machine that speaks English. These things are unpredictable.
I think it'd simply be the fact that the facility isn't aimed at achieving break even, they're mainly interested in performing tests which validate the viability of the nuclear stockpile without having to test the bombs directly.
For example, there isn't really a means to extract the energy released to generate electricity from it in the facility (as the pellet has to be equally compressed from all sides by lasers).
Similarly, the lasers they're using are pretty old and inefficient by modern standards, they're sticking to them because improving electricity-to-laser efficiency is not the bottleneck to their system, it's laser-to-pellet efficiency (along with the stability and accuracy of their optics etc). But if they were concerned about power generation, electricity-to-laser efficiency is obviously important.
Basically, while the general concept of this kind of fusion reactor might be potentially viable, this specific facility likely is not (with its current mandate).
Laser efficiency is important if you're actually building a power plant, but for an experimental facility, it's easy enough to correct for the inefficiency of your old lasers. That doesn't make your research inapplicable to power plants.
I don't think so. The point of these tests is to maintain the deterrent power of nukes by showing that they are still intact.
The West doing this by putting effort into all sorts of extremely advanced machinery like NIF in contrast to Russia having to resort to setting off nukes would be a convenient situation for propaganda, since it only makes Russia look even more like a warmongerer.
As for the advantage provided, IIRC the US has been performing "dry" tests, where a bomb with no nuclear material is detonated to verify the trigger mechanisms. That, combined with the tests at NIF and other facilties to verify the viability of the nuclear material, should be comparable in terms of verifying functionality.
Point of tests is to verify state of the pits after long storage. Plutonium is a bitch to manage because it is alpha-active and alpha particles are in essence, helium atoms, so over time a piece of plutonium gets full of helium caverns and develops internal tension. It's also very complex in terms of crystallic properties (has several stable crystal forms), which are impacted by temperatures and yes, those internal tensions. While it is modelled as much as possible, no one truly knows how good are the pits that were kept in storage for decades, anymore. They certainly still work, but whether they are good enough to properly initiate a secondary, no one really knows. Testing could be very instrumental in finding that out.
Well, somewhat. The amount of precision that the physical worlds demand in the construction of the fuel pellets, and the amount of energy involved in using them, guarantee that you need an extremely expensive mechanical process for the fuel. So, while physically you probably can extract energy from the pellets, it'd be like a steam train powered by gold bars instead of coal.
