An email from a Tokyo Electric Power Co. employee working at one of the Fukushima nuclear power plants gives a rare look at how employees are grappling with personal loss even while working around the clock to respond to the March 11 quake.

"My parents were washed away by the tsunami and I still don't know where they are. Normally I would rush to their house as soon as I could. But I can't even enter the area because it is under an evacuation order," says the email signed by the author, who works for the plant manager at the...