As a device it is even simpler, consisting as it does of nothing more than a lump of fissile material with a hole bored in it, sunk into the ground. The mass and geometry of the lump are carefully calculated with consideration for the neutron-reflecting and -moderating properties of the ground so that it is only just below the point of criticality. (It is best if it is sunk into concrete rather than earth so that the nuclear parameters of the surrounding material do not vary drastically with rainfall.)
Since dogshit consists mainly of carbon, hydrogen and oxygen, it is quite a good neutron-moderating material. So when the dog shit falls into the hole, it provides a degree of additional moderation which is sufficient to send the lump of fissile material into criticality. The energy from the chain reaction then vaporises the dog turd. The vapour is ejected by its own pressure, the additional neutron moderation is no longer present and the chain reaction halts.
The device will continue to vaporise dogshits for as long as there is sufficient fissile material and sufficiently low levels of fission poisons for the addition of a turd to tip it into criticality. When these conditions are no longer met it can simply be reprocessed in the normal way.
It is of course necessary to train the dog to shit down a little hole in a lump of fissile material and then to move away smartly in time to avoid getting a radioactive jet of its own vaporised feces up its arse. However, canine psychology and obedience are not matters within the scope of this document.
Important Note: This article has now achieved international recognition. I am very pleased to be able to report that it is itself the subject of an article on a rather fine website, www.dogshit.eu.
