Dominion officials said it now appears the reactors shut when the earthquake caused a problem inside the cores at both units rather than from the loss of outside power to the plant as initially reported.
"It looks like the (fuel) rods were going into the core prior to the transformer opening," possibly from a relay problem, a Dominion executive said.
Dominion is still working to understand the "root cause" of the plant shutdown as multiple automatic trip signals from various indicators were received within seconds of the quake.
These old plants aren't computerized, but they have a lot of hair-trigger safety relays, all of which may have gone off in the earthquake. Trying to figure out the sequence may be impossible.