Slow and steady wins the race, Grasshopper.
Yongbyon was creating about 6Kg/year in that reactor, and estimated over time to have 40+ Kg of Pu239 available in those spent fuel rods, plus whatever U-235 they could extract.
11 Kg of Pu239 are considered the "norm" for a fission device. The Norks haven't shot their wad yet.
Re: Vibrations & yield estimates - underground nuclear tests propogate
multiple seismic waves, which circle the globe in all directions.
They arrive at the civilian and military seismometers (see what I did there?) planted all around the world, hither and yon.
The S-Waves and P-Waves arrive at the seismometer(s), albeit at different times because they move at different speeds through the earth's crust.
Plant a big enough array of those seismometers deep down a hole close to bedrock, and you can triangulate the location, depth, and magnitude of a given "thump".
View those incoming waveforms at The Center on a scope, develocorder, or computer, and you can immediately see the characteristic double hump of a nuclear device.
Countries like North Korea, China, Pakistan, India, and the Soviet Union have attempted to "decouple" their devices in their tunnels or boreholes to reduce the seismic signature.
It doesn't matter much, because the shock wave still transfers energy to the earth, and 1,000 tons of TNT still produce a noticeably different waveform than a fission or fusion bomb.
Low-yield nukes produce a greater level of uncertainty with respect to nailing down the true yield of the device, but are by no means invisible.
This is just the seismic portion of the equation. The guys in the "Zip Room" will call the Watch Officer, who then starts his alert checklist, and it's off to the races.
My pager goes off, and I'm speeding to the squadron to get my first briefing for what is guaranteed to be a fun-filled several days or weeks.
