Nope, it's literally 25,000 degrees C. The higher the temperature and density, the less mass you need to reach supercritical so to get to the point where 20kg i

Nope, it's literally 25,000 degrees C. The higher the temperature and density, the less mass you need to reach supercritical so to get to the point where 20kg is fissile, you need to really turn it up. Increasing the density of a ball of uranium plasma is far harder than just heating it up some more.