The alert was issued due to loss of external power. That was a fairly obvious problem.
I don’t know exactly how the plant in questions set up is but I can guess based on the plants I’ve been to.
The normal source of power is the grid.
The next source of electrical power would be Diesel generators.
The next would be battery banks with alternators.
Any number of things can trigger an unusual event or alert. If one of the back up generators failed to auto start, that could be reason enough. If one of the back up generators fuel supply was compromised below a prestated amount, that could cause an alert. If a normally opperation breaker, which supplies power from the grid fails to close or open properly, that could cause an alert issue. I’m serious that there could be literally hundreds of possible sinarios in which “Normal operational parameters” were not met and the NRC had to be notified.
Should a person be aware of what’s going on? Absolutely.
Should a person be scared right now? NOT at all.
Let me go back to the Radiation limits as an example. Doctors don’t really see any changes in people until around 25 Rem (some changes in the blood count). It’s not until around 400 Rem that death is possible. So with that as a guide line the NRC (formerly the AEC) said that they didn’t want workers to get anything even close to 25 Rem, so they set 5 Rem as a limit. Plants then set their local limits as less then 5 Rem (usually 4 Rem) so that they didn’t run the risk of even getting close to the NRC’s limit.
The same is true with every other aspect of Nuclear power. If the NRC says you need two backup sources, plants will have 4 or more just to fail on the safe side of things. And it isn’t just making sure they have 4 Emergency Diesel Generators, but enough fuel to run each one for enough time to get more fuel sent from an outside source. Most plants have reserves of fuel to last for days without outside assistance. That also goes for spare parts for Emergency sources. Those things are already bought and stored in warehouses.
I’m not saying that anyone should just automatically trust completely what a plant is putting out, but realize that they too are interested in staying safe for their health and safety as well as the surrounding communities. Besides that there are hefty fines and possible imprisionment for creating or covering up a release of dangerous radioactivity.
I would say trust, but verify, and also realize that the people that work at these plants have the same or greater concerns for their lives as those people who live around the power plants. Panic and unjustified fear is not justified here at this point. IF the plant starts calling for evacuation from around the plants, THEN be concerned, but realize again, if the limit is 500 DAC/hour then the danger is going to be around 1000 DAC/hour and the evacuation will be called at 50 DAC/hour.
(DAC=Derived Air Concentration, which is essentially saying if you breath in 1 DAC of something for 2000 hours {about 1 year of work} you could receive an internal dose of 5 Rem.)