[RodgerRoentgen]

See the event notification here:
http://www.nrc.gov/reading-rm/doc-collec...ml#en52191

Off-site power "lost", the only backup is the diesel generators. Infact, it seems off-site powere was not 'lost' rather some relays locked out the 'main generator' which (I'm assuming) decoupled the plant with off-site power. Here is the snippet from the report:

Quote: On August 21, 2016 at 1926 EDT, St. Lucie Unit 1 experienced a reactor trip and a loss of offsite power due to a main generator inadvertent Energization Lockout Relay actuation. The cause of the lockout is currently under investigation. Coincident with the loss of offsite power, the four reactor coolant pumps deenergized.

So under optimal conditions we're relying on the backup diesel generators when something goes wrong. And from the sounds of it, the cause was actually some relays energizing at the wrong time (but unknown WHY?). So if the diesels weren't operational, what is the fall back emergency system?

The final update on this event is:

Quote:On August 21, 2016 at 2330 EDT, St. Lucie Unit 1 started two Reactor Coolant Pumps to establish Forced Circulation in order to enhance Decay Heat removal. Plant conditions remain stable with Auxiliary Feedwater and Atmospheric Dump Valves in service.

I'm guessing they figured out the relay issue, or bypassed it, however it took 4 hours to remedy. Again, I'm assuming this mean off-site power is restored. How much fuel do the diesels have on stand by? 12hrs worth? 24? What if one or both of the diesels died after 1 or 2 hours?

Scott Portzline talked about an incident where employee(s) had sabotaged the diesel generators by putting coolant into the oil or some such thing. Anyway, I'm rambling a little so to my point:
If we're relying on the emergency systems in the best of conditions (IE: no natural or other disasters), what can we expect when conditions aren't so optimal?

[Horse]

(08-23-2016, 05:34 PM)RodgerRoentgen Wrote: If we're relying on the emergency systems in the best of conditions (IE: no natural or other disasters), what can we expect when conditions aren't so optimal?

We can expect a meltdown in a core or spent fuel pool.  Heard something like that happened about five years ago.  It could easily happen again. Technology has its limits and equipment does fail.   Redundant backups are expensive to build and maintain.  Cost cutting to increase profits; aging NPPs; NPPs in not so developed countries; NPPs in war zones; captured, ineffectual regulatory agencies; these are not optimal conditions.  A failure leading to another meltdown will again contaminate large areas for a long time.  We can expect more health problems as radioactive heavy metal poisoning increases and spreads.  It doesn't seem worth the risk unless you want bomb making materials.  A few decided we should take the risk because they enjoy the power that atomic weaponry bestows while everyone else bears the cost.

[Horse]

(08-23-2016, 05:34 PM)RodgerRoentgen Wrote: See the event notification here:
http://www.nrc.gov/reading-rm/doc-collec...ml#en52191

Off-site power "lost", the only backup is the diesel generators. Infact, it seems off-site powere was not 'lost' rather some relays locked out the 'main generator' which (I'm assuming) decoupled the plant with off-site power. Here is the snippet from the report:

Quote: On August 21, 2016 at 1926 EDT, St. Lucie Unit 1 experienced a reactor trip and a loss of offsite power due to a main generator inadvertent Energization Lockout Relay actuation. The cause of the lockout is currently under investigation. Coincident with the loss of offsite power, the four reactor coolant pumps deenergized.

So under optimal conditions we're relying on the backup diesel generators when something goes wrong. And from the sounds of it, the cause was actually some relays energizing at the wrong time (but unknown WHY?). So if the diesels weren't operational, what is the fall back emergency system?

The final update on this event is:

Quote:On August 21, 2016 at 2330 EDT, St. Lucie Unit 1 started two Reactor Coolant Pumps to establish Forced Circulation in order to enhance Decay Heat removal. Plant conditions remain stable with Auxiliary Feedwater and Atmospheric Dump Valves in service.

I'm guessing they figured out the relay issue, or bypassed it, however it took 4 hours to remedy. Again, I'm assuming this mean off-site power is restored. How much fuel do the diesels have on stand by? 12hrs worth? 24? What if one or both of the diesels died after 1 or 2 hours?

Scott Portzline talked about an incident where employee(s) had sabotaged the diesel generators by putting coolant into the oil or some such thing. Anyway, I'm rambling a little so to my point:
If we're relying on the emergency systems in the best of conditions (IE: no natural or other disasters), what can we expect when conditions aren't so optimal?

Hi RR, Combing through the nrc event notifications can be scary. Shows some of the things that can go wrong with a complex machine. Very vulnerable in a disaster. Loss of coolant; meltdowns; and radioactive contamination when the infrastructure supporting a NPP fails. Japan has rebuilt after earthquakes and tsunamis but damaged NPP's can't be fixed. The nuclear industry response is a sorry; clean it up later; deny the health problems; live with it attitude. The nrc event notifications are meant to assure us that everything is under control but when something really goes wrong we get the redacted notes.