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?
At this point, the mother will chase away the older foal and take care of the younger one. Domesticated horses will sometimes wean their own horses, but often, humans separate mother and baby at 4-8 months of age. After this, the foal is often on his/her own.