Intelligence

It's wasted effort if they think they are going to hide there nuclear subs. The traditional nuclear triad is very likely broken. Through muon tomography techniques, hiding nuclear material in tactical weapons may not be possible. The U.K. has been silently building it's Watchmen muon detection system for exactly this purpose. Here are a few links to get you up to speed:

https://svoboda.ucdavis.edu/experiments/watchman

https://arxiv.org/abs/1804.00655

https://www.sciencedirect.com/science/article/abs/pii/S0168900215004258

I suspect that the U.S. and Russia have had this capability for a decade or more. Both have been working on this technology since Fermi lab physicist Bruno Pontecorvo defected to Russia because he was being investigated as a Russian spy. Before his defection he submitted a paper to the DOD showing how muons, a form of neutrino, can be used to detect uranium and plutonium. The DOD immediately classified the research, and shut it down because it was an ideological threat to the U.S. Navy's nuclear sub program. Shortly after this paper was submitted, Kim Philby a USSR mole, 'tipped off USSR', who then told Pontecorvo he was about to be arrested for his Red ties, so he fleed to the USSR. He was kept in hiding in Russian for a decade, while presumably he built this detection system for Russia.

BTW - Muon tomography can be used to detect and map deposits of nearly any heavy element including gold & silver. For instance, it's being used to map underground structures including the Great Pyramid and other ancient wonders.