AGreenRoad did a great debunk of this. Text below, FULL credit to AGreenRoad, link below, visit that site.
Did plutonium exist in Nature in the recent past? The answer is a realistic NO. Are there 'natural' fission reactors on Earth? The answer is a realistic NO. We have to go back 1.7 billion years to find any plutonium or fission reactions on Earth, and then it occurred only in one place on Earth, and no where else, and at no other time.
According to Wikipedia; "Trace amounts of at least three plutonium isotopes (plutonium 239 in a few parts per trillion, and its decay products are 'naturally' found ONLY in some concentrated ores of uranium, at the ancient but dead natural nuclear fission reactor in Oklo, Gabon.
Oklo is the only known location for this in the world and consisted of self-sustaining nuclear fission reactions that took place approximately 1.7 billion years ago, and ran for a few hundred thousand years, averaging 100 kW of thermal power during that time.
This underground nuclear reaction happened 1.7 BILLION years ago, way before there was any human life on Earth. This underground, invisible and undetectable nuclear reaction stopped way before human living beings inhabited the planet, so for all intents and purposes, there has been no 'natural' fission happening, and no plutonium has been around since humans walked the Earth, contrary to what pro nuclear apologists claim. All of the plutonium generated by this underground reaction has decayed away. If any is left, that miniscule amount is still found underground, only in the one location, at Oklo, Africa, where almost no one lives.
Primordial plutonium-244 has a relatively long half-life of about 80 million years. These trace amounts of 239Pu originated in the following fashion: On rare occasions, 238U undergoes spontaneous fission, and in the process, the nucleus emits one or two free neutrons with some kinetic energy. When one of these neutrons strikes the nucleus of another 238U atom, it is absorbed by the atom, which becomes 239U. With a relatively short half-life, U-239 decays to neptunium-239 (239Np), and then 239Np decays into 239Pu.
Since the relatively long-lived isotope plutonium-240 occurs in the decay chain of plutonium-244 it should also be present, albeit 10,000 times rarer still. Finally, exceedingly small amounts of plutonium-238, attributed to the extremely rare double beta decay of uranium-238, have been found in natural uranium samples." http://en.wikipedia.org/wiki/Plutonium
With an 80 million year half life, all of the measurable plutonium that happened from the fission process below ground in Oklo, disappeared in 800 million years. This is still a couple hundred million years before people even walked on the planet. Bottom line, anyone who says that large amounts of plutonium were lying around all over the place naturally before the atomic age covered the Earth with it is either lying, or trying to deceive someone into believing that plutonium is 'safe' or 'natural' somehow.
Some pro nuclear apologists even go so far as to claim that because plutonium is 'primordial', it is safe and 'normal' to be around. The only problem with this theory, is that for all practical purposes and intents, plutonium cannot be found in Nature, because the amounts are so small, so buried, so hard to find, so difficult to get to, that for all realistic and practical medical purposes, plutonium did not exist in the human environment. Whatever 'primordial' plutonium exists in nano particle amounts, is only associated with uranium deposits and is locked into those rocks. No one was stupid enough to dig up these very toxic and deadly elements before the atomic age. That miniscule amount of plutonium found in 'primordial' uranium did not register on any medical tests and no one died from it.
Parts per trillion of plutonium inside uranium rocks are so hard to find, it takes special nuclear physics lab equipment to even detect it. Effectively, before the atomic age, no human exposure to plutonium was possible, and plutonium was not detectable in humans before the atomic age.
In addition to the above, uranium or thorium deposits were widely made taboo by indigenous tribes globally. These 'hot' rocks or sands were called 'bad medicine', to be avoided at all costs. American Indians and indigenous peoples around the globe were told by their shamans and chiefs not to disturb the soil or rocks where uranium was present. People were told to avoid going into these areas. These ancient wise people KNEW 'natural' uranium deposits were dangerous and so they made it taboo, to be around any soil or rocks containing uranium.
Since plutonium was 'discovered' in 1940 through initiating nuclear fission in labs, it has been produced artificially in weapons labs and nuclear reactors by nuclear scientists intent on being masters of the power of the sun.
Due to numerous accidents and releases of plutonium via pyrophoric plutonium fires in atomic bomb weapons labs, as well as the 'testing' of 2,400 atomic bombs globally, plus the 'accidental' dropping and exploding of hydrogen bombs where the high explosives went off, crashing plutonium satellites, plutonium is now present in detectable amounts in the global environment as a man made radioactive pollutant and toxic heavy metals. Plutonium has gone all around the world.
Cesium and strontium are now commonly and usually found in the human body due to the 2,400 atmospheric and underwater nuclear tests that have been carried out, as well as due to a small number of major nuclear accidents, such as Santa Susana, Three Mile Island, Fukushima and Chernobyl. Plutonium may also be found in some locations.
"Most atmospheric and underwater nuclear testing was stopped by the Limited Test Ban Treaty in 1963, which was signed and ratified by the United States, the United Kingdom, theSoviet Union, and other nations. Continued atmospheric nuclear weapons testing since 1963 by non-treaty nations included those by China (atomic bomb test above the Gobi Desert in 1964, hydrogen bomb test in 1967, and follow-on tests), and France (tests as recently as the 1990s). Because it is deliberately manufactured for nuclear weapons and nuclear reactors, plutonium-239 is the most abundant isotope of plutonium by far."
What is the take away? For all practical and medical intents and purposes, plutonium is an known and toxic heavy metal and radioactive cancer initiator in the human body, nothing more. There is no known positive and health giving use for plutonium, uranium, thorium or radon. There is no 'natural fission' (except in the sun), and there is no 'natural plutonium'. Even low doses of radiation from radon cause lung cancer. In the same way, low doses of plutonium cause cancer as well.
Plutonium mimics iron in the body, replacing it, and then doing damage where ever it ends up going. Iron concentrates in the bone marrow and liver, so that is where most of the damage done by plutonium occurs, but cancers of all kinds are possible, including lung, brain, liver, bone, blood, and more.
Is There 'Natural' Plutonium And Are There 'Natural' Fission Reactions? via @AGreenRoad