> The captain claimed mechanical failure, but hull damage showed signs of an external strike consistent with a supercavitating torpedo.

> The Russian warship Ivan Gren soon arrived, demanded control of the site, and launched flares—likely to disrupt satellite surveillance. Shortly after, the Ursa Major disappeared from the surface. Seismographs recorded underwater explosions, and the ship sank to a depth of 2,500 meters.

whoa so what/who struck it?

What is not being said in the article is if the reactor parts were transferred on the second vessel or if they were sunk with Ursa Major.

Anyway it is too often south of Spain which is getting these freak nuclear catastrophes https://en.wikipedia.org/wiki/1966_Palomares_accident