It’s not just background processes that can produce new SnCs, but SnCs themselves produce new, secondary SnCs too.
Imagine that each new SnC produced 3 new SnCs within a day, and also that SnCs had a 50% chance of being removed each day. In that case, there will be 4*0.5 = 2x as many SnCs tomorrow as there is today, leading to exponential runaway growth, immediately exploding in the number of SnCs and dying.
On the other hand, imagine that they only produce 1 new SnC within a day, and also that they had a 66% chance of being removed each day. In that case there will be 2*0.33 = 0.66x as many SnCs tomorrow, leading to quickly returning to the equillibrium caused by outside production.
You’d need some sort of fine-tuning where the production and removal are extremely close to each other to not either have explosive growth or rapid equillibration.
Imagine that each new SnC produced 3 new SnCs within a day, and also that SnCs had a 50% chance of being removed each day. In that case, there will be 4*0.5 = 2x as many SnCs tomorrow as there is today, leading to exponential runaway growth, immediately exploding in the number of SnCs and dying.
On the other hand, imagine that they only produce 1 new SnC within a day, and also that they had a 66% chance of being removed each day. In that case there will be 2*0.33 = 0.66x as many SnCs tomorrow, leading to quickly returning to the equillibrium caused by outside production.
You’d need some sort of fine-tuning where the production and removal are extremely close to each other to not either have explosive growth or rapid equillibration.