Yes but this missile is intended to be nuclear armed as well. Obviously the test missile won't have a live warhead, but if it makes production these are nuclear weapons.
Even the title says "Russia Says Small Nuclear Reactor Blew Up...".
Because Russia has been so truthful about, well, anything and everything they do? No, it's about a nuclear weapon they've been developing and the "nuclear reactor" bit is just a ruse to confuse people who haven't generally been paying attention to Russia developing new kinds of delivery systems for their nuclear warheads.