ML20168A446
| ML20168A446 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1979-031-00 | |
| Download: ML20168A446 (4) | |
Text
B-675 PRECURSOR DESCRIPTION AND DATA NSIC Accession Number: 152835 Date: July 31, 1979
Title:
Engineered Safety Features Actuation System Failed at Calvert Cliffs 1 The failure sequence was:
- 1. With the reactor at power, trouble-shooting was in progress regarding a fault in the ESFAS Under-voltage (UV) "A" logic circuitry.
- 2. Both the ESFAS Channel A and B UV Actuation Cabinet Power Supplies were found dc-energized due to a trip of the power supply overvoltage protection circuitry.
Corrective action:
- 1. The power supplies were reset.
- 2. The over-voltage trip setpoints were raised to prevent future inadvertant trips.
- 3. Testing was in progress to determine if any common-mode interrelationships existed between the two channels.
Design purpose of failed system or component:
- 1. The UV Actuation Circuitry sends start commands to the diesel generator and sequencer in the event of a loss of offsite power.
Unavailability of system per WASH 1400:
- Under voltage trip, not specifically addressed; Safety Injection Control System total failure: 5.4 x 10 5 /D Unavailability of component per WASH 1400:*
Unavailabilities are in units of per demand D_1 . Failure rates are iii Units of per hour HR-1
Reactor at Power ESFAS Actuation Channels Potential and ESFAS Under A and B UV Power Supply Severe Voltage (UIV) Logic Over-voltage Protection Core Circuit Trouble Found Actuated, Rendering Damage Shooting in Progress ESFAS Unable to Actuate on UIV No - no requirement for ESFAS actuation
__-No -4 NSIC 152835 - Actual Occurrence for Engineered Safety Features Actuation System Failed at Calvert Cliffs 1
Loss of1 Turbine Emer- Auxiliary PORV PORV or High Long Potential Sequence Offs ite Generator gency Feedwater and 1Demanded PORV Isola- Pressure Term jSevere No.
Power Runs Back and Assumes House Loads Power Secondary Heat Removal ]Closure tion Valve Injection Core Core CoolingJDamage 2
3 4
5 6 -4 7
8 9
10 11 12 13 NSIC 152835 - Sequence of Interest for Engineered Safety Features Actuation System Failed at Calvert Cliffs 1
B-678 CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER: 152835 DATE OF LER: August 14, 1979 DATE OF EVENT: July 31, 1979 SYSTEM INVOLVED: Engineered Safety Features Actuation System COMPONENT INVOLVED: Under-Voltage Actuation Cabinet Power Supplies CAUSE: De-energized due to trip of over-voltage protection circuitry.
SEQUENCE OF INTEREST: LOOP ACTUAL OCCURRENCE. Over-voltage protection trip detected during trouble-shooting REACTOR NAMEz Calvert Cliffs 1 DOCKET NUbMBER :50-317 REACTOR TYPE: PWR DESIGN ELECTRICAL RATING: 845 MWe REACTOR AGE: 4.8 yr VENDOR. Combustion Engineering ARCHITECT-ENGINEERS: Bechtel OPERATORS: Baltimore Gas & Electric Co.
LOCATION: 40 miles south of Annapolis, MD DURATION: 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> PLANT OPERATING CONDITION: At power SAFETY FEATURE TYPE OF FAILURE: (a) inadequate performance; (b) failed to start; 0 made inoperable; (d)___________
DISCOVERY METHOD: During troubleshooting of UV logic cir~uits COMMENT: -