ML20168A742
| ML20168A742 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1974-LTR-00 | |
| Download: ML20168A742 (5) | |
Text
1, 1974 Unit Trip at Turkey Point 3-and 4 , Loss of Offsite Power at Turkey Point 4 sequence was:
& 4 were at full power, with unit 4 startup transformer electrically for functional testing of protection system relays and for periodic ce on associated equipment.
transformer protective relays were tested, the transformer lockout reset and current flowed through an unanticipated path (a "sneak and energized unit 4 generator breaker protection system relays, ened the generator breakers for units 3 and *4.
3 & 4 reactors automatically tripped when their turbine-generators The instantaneous grid loss was 1443 MWe.
e unit 4 startup transformer was isolated, off-site power was lost to seadtoapg) ction;(seadtolpg) ions were recommended to the startup transformer protective system e more complete isolation of the protection system relays during sts.
k-open safety valve was closed by removing its manual lifting-device.
se of failed system or component:
electric power provides an alternative source of power to plant es in the event the unit generator is inoperable.
steam safety valves provide over-pressure protection for the steam s and main-steam piping.
ty of system per WASH 140G:
- Offsite power: 10-3 following trip ty of component per WASH 1400:
- Relief valves, failure to close: 10-2 /D 1
ilabilities are in units of per demand D- . Failure rates are in hour HR gin for the additional cooldown, resulting from the stuck-open alve.
system relays, opening offsite power open safety the generator breakers available) valve for units 3 and 4 4 No - additional boron injection available via safety injec-tion system if required
______________________________No No - turbine driven ANW pumps available for R. cooling No No ctual Occurrence for Two-Unit Trip at Turkey Point 3 & 4
House Loads
-No 2
No 3
Yes 4
Yes 5
Nes 6
No 7
Yeo 8
Yes 9
10 11 12 13 C 93702 - Sequence of Interest for Two Unit Trip at Turkey Point 3 & 4 e of HPI following AFW failure not included in mitigation procedures.
ION NUMBER: 93702 May 31, 1974 NT: April 25, 1974 LVED: Electric power system, main steam NVOLVED: Startup transformer protective relays,- main steam safety valve rent flow in a sneak circuit during protective relay testing resulted in the Unit 3 & 4 generator breakers. After reactor trip, a Unit 4 main of offsite power RRENCE: Reactor trip with loss of of~fsite power (Unit 4 only)
E: Turkey Point 4 ER: 50-251 E: PWR TRICAL RATING: 693 INe
- .9 yr stinghouse LGINEERS: Bechtel Florida Power & Light Co.
.25.miles-south.of Miami, Fla.
N/A TING CONDITION: Both units at full power.
URE TYPE OF FAILURE: (a) inadequate performance; (b) failed to start; (c) made inoperable; (0inadvertant-opprat-inn ETHOD: During operation This event and a previous event on March 1, 1974 resulted in the separation of both Turkey Point Units from the grid. However, only Unit #4 and only during this event lost of fsite power.