If the nuclear start-up can pull off a successful prototype, its options could be limitless. But that's a big "if."Shares of nuclear start-up Oklo (OKLO 4.20%) have fallen more than 20% from their highs, but they're still up more than 550% year to date.At these prices, the company is valued at about $20 billion -- and it hasn't even produced a working nuclear reactor yet!Although it's a risky bet, an investment in this speculative company could still set shareholders up for life. Here's how. Oklo is combini ...