That is the Pu238 isotope that is used in thermoelectric generators.
Most of the plutonium produced in nuclear reactors is Pu239. This is the isotope that is useful as nuclear fuel and for nuclear bombs. As another poster has already written, it has a half-life of 24 thousand years, so there is no chance to get rid of it easily, unless it is recovered and used as fuel.
There exists also the Pu244 isotope, with a half-life of 80 million years.
This isotope is produced only in negligible amounts in nuclear reactors, but it is produced in supernova explosions, so the Solar System and the Earth had contained plutonium besides uranium and thorium in the beginning, during the first few hundred million years of their history, but the plutonium has decayed until now.
The main reason people believe a nuclear waste dump needs to last a stupendously long time is because of the long lifetime of Plutonium 239 and some related actinides.
Reactors with a fast neutron spectrum could consume those actinides, the remaining waste becomes less radioactive than the original uranium in 1000 years which is within the time that we've had buildings last, social structures last, etc. In that scenario you have little fear that carefully buried waste incorporated in glass will leach out.
If you are looking 100,000 years down the road like you are with Yucca Mountain it is likely the facility has long been flooded and soluble Uranium will migrate in the direction of Death Valley whereas the Plutonium will not migrate because it is insoluble in water. I think it is sublime that the Pu239 decay chain goes through U235 which retains the nuclear fuel value.
In the "once-through" fuel cycle almost all of the waste buried is unburned U and Pu fuel, the fast reactor cycle could consume all of that starting with the waste that is cooling out now.
