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 plates belonging to bones that are involved in how tall a horse gets -- such as hocks, tibias and femurs -- have usually fused by around 4 years of age. However, the bones of the vertebral column are the last to fuse and rarely do so before a horse is 5 1/2 years old.