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 Offs ite Power Turbine Generator Runs Back and Assumes House Loads Emer-gency Power Auxiliary Feedwater and Secondary Heat Removal PORV PORV or High Long Potential 1Demanded PORV Isola-Pressure Term jSevere tion Valve Injection Core Core
]Closure CoolingJDamage Sequence No.
2 3
4 5
6 7
8 9
10 11 12 13
-4 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:
-