Plutonium is much rarer in nature than uranium and is more commonly used for bombs rather than as reactor fuel. Like uranium, it comes in various isotope forms, with plutonium 239 the most commonly used. It is mixed with the much more unstable plutonium 240 to generate power.
It's my understanding that a horse's knees close around age 2- 2 1/2. My gelding JUST turned 3. A couple days ago in fact. Will a horse's knees almost certainly be closed by that age?
The forelegs carry as much as 60 percent of the weight of the horse. Clearly the process of conversion of growth plates to bone takes time; at the age of two the plates in the knees for many of these horses will still not be fully fused, nor will any of the skeletal structure above this location.