It works by sparking the center point, which detonates C4. After the smoke clears in a couple seconds, it opens up a place for the BCLN to deposit THDR. The THDR makes a huge pressure blast which destroys the BCLN, and trigger's fission in the PLUT. The heat from the fission melts the barrier between the DEUT and the PLUT, allowing a flood of fission created neutrons to enter the DEUT. The DEUT is glowing because I used the console command "!set life deut 1000". This state also means it's super susceptible to neutrons, and will imediately undergo a massive fission explosion, even upon contact with a single NEUT. And indeed at this point it does so, releasing a huge number of hot neutrons. The BCLN doesn't instantly disapear, so in this massive explosion, the BCLN still giving off THDR for about another second, gets shot out of the bomb, just slower than the molten metal shockwave.

First thing to hit whatever is in the scene when this sucker goes off is ejected molten metal. Then comes the pressure wave and molten metal riding the pressure wave. After that comes that BCLN (ejected by the force of the explosion) still giving off THDR for about another second. And lastly, the wave of super-hot neutrons arrives. This whole explosion is very devastating, and its damage can be increased by turning on heated air, so that it heats air near the hot particles which can then pass the heat to nearby heat-damageable objects, even when the hot particles themselves don't make contact.