I'm sorry, no! Just, NO!
To start, even with relatively minor nuclear 'accidents' involving spacecraft re-entering there have been radioactive releases.
Top 10 incidents
https://listverse.com/2012/01/20/top-10-space-age-radiation-incidents/Kosmos 954
https://en.wikipedia.org/wiki/Kosmos_954April 1964, SNAP-9A
https://en.wikipedia.org/wiki/Plutonium_in_the_environmenthttp://www.space4peace.org/ianus/npsm3.htmSNAP-9A released more curies of plutonium (nearly twice as much) to the atmosphere than did the entire global nuclear weapons testing did. It resulted in an estimated 2,100 man-sieverts of dose. Using the "standard" and highly erroneous and misleading risk estimate of 5 x 10^-4 lifetime fatal cancers/man-rem of exposure, this equates to 105 fatal cancers and circa 105 additional non-fatal cancers requiring immense personal and financial costs to deal with. The actual population risk from all causes of death is about 6.6 times these numbers, so ~700 dead - from one minor space accident. Obviously with 700 dead scattered through millions of cancer deaths, cardiovascular deaths and strokes in that period, it is impossible to identify who these 700 were. That does not mean that they do not count! To the contrary, they count. Randomly killing people isn't better. It is far far worse!
The spent nuclear fuel from reactors has to be loaded in highly shielded casks to allow for reasonable safety for workers measured at the surface of the cask. This then means that every 4.5 tones of nuclear fuel requires a bit over 25 tons of cask material.
Using the space shuttle as an example, it would be able to transport no more than 3 casks to low earth orbit per launch. Add rockets and fuel to send this to the sun, and you now are limited to one cask per launch, and at most two. Even with high density loading, which creates serious heat and cooling issues, the limit is still at most 4.
The 373 GWe of nuclear capacity extant in 2009 and all the predecessors had produced an estimated 240,000 metric tons (as heavy metal) of spent nuclear fuel as of 2009. The launch weight of that mass would be at a minimum 400,000 metric tons, and more likely over 1,600,000 tons. At a maximum launch capacity of about 100 metric tons, with at least half going to rockets and propellent to push this into the sun, this would require at a bare minimum 80,000 event free launches! More likely this would require over 500,000 event free launches.
A single failure of a single launch would have Chernobyl/Fukushima scale potential consequences. At a fantastically successful 1% failure rate, that equates to 800 - 5,000 added massive accidents scattered all over the world.
And that doesn't in any way consider the environmental costs to build and launch that many vehicles. Those are substantial impacts and costs.
Just, NO!
In the 1990s, the US Government embarked on a program to eliminate 50 metric tons of weapons plutonium from each of the US and Russian nuclear weapons arsenals. They looked at space launch as one possible solution and quickly dismissed it for these same reasons. They also actually considered dissolving the plutonium in acid and then spraying it from submarines into the oceans of the world. The consequence to coastal peoples, fishermen, fish eaters and others was terrifying. In the end, they settled on two possibilities. 1) combine the plutonium with highly radioactive waste and burying it deep underground, and 2) converting the plutonium to fuel mixed with uranium and burning it in reactors.
The Russians absolutely would not agree to dispose of the plutonium on three grounds. First and by far foremost, they could not ever consider what they considered "throwing the plutonium away". They felt that would disrespect the memory of those that had died (been killed) in creating it during the Russian weapons development program!! Second, those making the decisions are and where staunch nuclear advocates. They could not in any way bring themselves to the idea of "discarding" the plutonium. Third, they refused to believe that the plutonium would be permanently isolated if it was mixed with nuclear waste and buried. They feared that the US would reverse their decision in the future, exhume the plutonium and put it back into weapons.
And so the Russians decided to put all of their 50 tons into mixed oxide fuel. The Americans chose to dispose of two thirds in so-called "glass in glass" - ceramic pucks of plutonium embedded in classified nuclear waste embedded in heavy containers to be buried deep underground. The remaining one third would be converted to nuclear fuel. That decision was later changed to abandon the glass in glass proposal and shift all of the plutonium to reactor use.
Minor problem there, the gallium used as an alloying agent in the plutonium weapons pits is extremely hard to remove. And the resulting fuel is extremely difficult to fabricate in the quality required for reactor use. Efforts to do this have all failed. Even had they succeeded, the costs of operating reactors on MOx (Mixed Oxide Fuel) are substantially higher than for light water reactors. And those are already non-competitive with other power sources. In a capitalist environment, these reactors are non-viable. And the risks from these reactors, both from the likelihood of accidents, and the severity of those accidents is vastly higher, making them even less viable. All of the fuel must be guarded as if it were nuclear weapons material at all times, further adding to the costs and complexity. In short, the entire program and effort has failed at costs measured in the 20 billion dollar range in the US alone.
Today, there are thousands of tons of separated plutonium in the world from attempts at recycling nuclear fuel. All of this is (contrary to assertions from the nuclear health physics folks) - weapons usable. Plutonium from spent nuclear reactor fuel was successfully fabricated into nuclear devices by both the US and UK governments, and no doubt also by the Russians and Chinese. These detonated easily and with fuel nuclear yield. Arguments to the contrary about premature detonation preventing such use were entirely wrong.
Laser isotope separation or other enrichment techniques also can be employed to turn this material into even higher quality, more usable, weapons material. As the plutonium ages troublesome nuclides decay away. In a hundred thousand years it becomes extremely attractive as weapons material. By then, gun assembly becomes trivial.
We cannot pound this genie back into the bottle. And we cannot truly eliminate it or get rid of the waste products. We also cannot leave them lying around or scatter them into the environment without enormous and horrible consequences. We also cannot in any way safely send these wastes off the earth. In short, we are stuck holding the mess, periodically repackaging it, and guarding it for many hundreds of thousands to millions of years. That is a sunk cost we cannot now eliminate with any known and proven technology.
Sam