...the Stuxnet Virus attacked SIEMENS operated plants. The plant at Fukushima is run on Siemens software. When Stuxnet was released, it went Everywhere, even though it was "allegedly" an attack on Irans Bushhier plant ...
The worm itself now appears to have included two major components. One was designed to send Iran’s nuclear centrifuges spinning wildly out of control.
Another seems right out of the movies:
The computer program also secretly recorded what normal operations at the nuclear plant looked like, then played those readings back to plant operators, like a pre-recorded security tape in a bank heist, so that it would appear that everything was operating normally while the centrifuges were actually tearing themselves apart.
via Japan Nuclear Crisis: A Worm IN The Works
... Stuxnet was in Japan last October, presumably still spreading and intended to wreck nuclear power plants.
... So now the difficulty the Fukushima nuclear plant operators faced in recovering control over their runaway reactors takes on a darker significance. Remember that the first problem following the quake was that the automated shutdown systems failed to operate at some of the reactors, because pumps failed and valves would not open even while running on batteries; the very sorts of mischief Stuxnet supposedly was designed to cause at Iran's power station.
Hypothetical: Stuxnet infects water cooling pump PLC, earthquake strikes and Stuxnet is activated, disabling cooling systems. I can say with near certainty that this plant utilized PLC's that can be infected by the worm.
Interesting conspiracy theory, but it is shot down by this post:
All safety related systems at Fukushima are controlled by relay based logic. In other words, its impossible to modify the programming short of rewiring the relays.