Sequence of NRC reports:
NRC Friday Event Notifications
Turkey Point (3,4) 52952
Thursday 23:14 – NWS Hurricane Warning issued
Friday 00:06 – Notification – Emergency Declared/Offsite Notification
Friday (no time specified) 'Updated' – no indication of what was updated
(Convenient notification Friday at 00:06 ensures it won't be seen by public until Monday)
NRC Monday NRC notifications
Turkey Point (3,4) 52952
Identical notification appears again
Turkey Point (4) 52960
Sunday 18:55 Reactor only running at 88% for some unknown reason
- failure of loop 4C Steam Generator main feed regulating valve
- Loop 4C S/G [Steam Generator] water levels drop
- Emergency Operating Procedures initiated
- Manual trip of reactor from 88% PWR (?)
- Auxiliary Feed Water initiated as designed [normal response]
- restored S/G water level
- Emergency Operation Procedures exited
- returned to General Operating Procedures
- Reactor at 0% PWR; in Hot Standby
For the textually challenged (me) here's a diagram:
The blue juice in one of the 4 steam generators go too low, so they pumped more in. The red juice got angry at all the commotion so the operators shut the reactor down. The reactor operators don' t like it when the red juice wants to leave the containment building and comes to visit them.
Unusual that reactor was at 88% – something else was happening that they're not saying.
Either the manual scram (if unplanned, i.e., not part of planned shutdown) or the activation of the steam generator aux. feedwater system would have required reporting.
The steam generator main feedwater valve is stuck/closed/secrewed up, so they can't run steam through the turbines, cool it down and pump it back into the steam generators through that valve like normal. That'e the normal route for the secondary steam loop. Instead, they're pumping auxiliary water into the steam generator thorough a different valve, and then just dumping the steam produced into the air outside the plant. That steam/water *shouldn't* be radioactive like the primary loop steam/water, but isn't completely radiation-free, either.
In any case, the reactor doesn't care as long as the steam generators are removing enough heat from the primary loop reactor water. That's the red loop in the diagram that goes in/out the 4 steam generators' U-tubes.
At Browns Ferry they have 3 reactors, and they lost their cooling towers, not good. But they appear to keep running at 100% even though the operation is a critical portion of the safety system, and if one other component failed, they would have a radiation release.
|MECHANICAL DRAFT COOLING TOWER FANS DECLARED INOPERABLE
"At 1000 EDT on September 9, 2017, the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation into why the Division 2 MDCT fan over speed brake inverter failed is in progress. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident based on a loss of a single train safety system."
The licensee entered two (2) LCO Action Statements (AS); 14-day LCO AS 3.5.1 for ECCS (HPCI Inoperable) and 72-hour AS 3.7.2 for UHS. The licensee has two spare inverters on-site. After replacement and successful post-maintenance testing the licensee expects to exit both AS before 72-hours.
The NRC Resident Inspector has been notified.
|Power Reactor||Event Number: 52959|
|Facility: BROWNS FERRY
Region: 2 State: AL
Unit:   
RX Type:  GE-4, GE-4, GE-4
NRC Notified By: ANTHONY ALSUP
HQ OPS Officer: STEVE SANDIN
|Notification Date: 09/10/2017
Notification Time: 20:45 [ET]
Event Date: 09/10/2017
Event Time: 11:51 [CDT]
Last Update Date: 09/10/2017
|Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(v)(A) - POT UNABLE TO SAFE SD
50.72(b)(3)(v)(B) - POT RHR INOP
50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL
50.72(b)(3)(v)(D) - ACCIDENT MITIGATION
ERIC MICHEL (R2DO)
|Unit||SCRAM Code||RX CRIT||Initial PWR||Initial RX Mode||Current PWR||Current RX Mode|
|1||N||Y||100||Power Operation||100||Power Operation|
|2||N||Y||100||Power Operation||100||Power Operation|
|3||N||Y||100||Power Operation||100||Power Operation|
Two nuclear units at St Lucie were able to continue operating as Hurricane Irma made landfall in Florida. One unit at Turkey Point was shut down as a precaution in advance of the storm as nuclear operators and regulators put storm preparation procedures into action, while the other shut down automatically because of a valve-related issue.
Mining Awareness always does good work. He/She picked up on this story and ran with it.