The plutonium shortage in NASA really has nothing to do with technology or science, but just politics. We simply stopped producing the stuff, but we could start again at any time; as the article you linked mentions, we're planning on doing so.

There's enough plutonium to make 10,000 nukes stored in the Sellafield facility in Cumbria, England

http://www.independent.co.uk/news/uk/vaults-will-store-the-n...

So, there is no storage.

It isn't that simple:

http://en.wikipedia.org/wiki/Plutonium-238#Production

Of course a program could be spun up to actually do the separation, but I think it might be sort of expensive.

I've been there as a child, if I'd have known that, I probably wouldn't have gone.

I know I read an article about 2 years ago saying that more was being made. Now I have to find it.

EDIT Got it! http://www.spaceflightnow.com/news/n1303/20pu238/#.U9qX5fldX... The date is six before the other story.

"For the first time in 25 years, the United States is producing plutonium fuel to power spacecraft on missions beyond Earth, replenishing a dwindling stockpile to supply NASA's next Mars rover and other proposed probes."

It's impossible to run out of plutonium so long as uranium fuelled reactors are running. It's a common by-product of the fission process.

It maybe be harder or impractical for them to get it or process it, but saying "no new fuel is produced" is false

That's like saying we won't run out of oil because we are producing carbon and oxygen... if it's not in useful form, it's perfectly sensible to say that no new fuel is being produced.

Normal uranium reactors produce a mix of plutonium isotopes, which are hard to separate and end up as nuclear waste. NASA needs pure Pu-238, which has to be made in specialized reactors.

Iirc, all Canadian CANDU reactors produce large amounts of weapons-grade plutonium.

Which is exactly the problem. RTG needs Pu-238, and can't use weapons-grade plutonium, which is mainly Pu-239.

That design has also been altered by India to consume the plutonium by-product, using it as fuel.