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 reason for this is pretty basic. The first year of a horse's life involves a period of very rapid growth. With some, it is so rapid that at 12 months of age, the animal will have reached 90% of its adult height and 75% of its mature weight. For others, those plateaus might not be reached until 18 to 24 months of age.