ML20168A448
| ML20168A448 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/16/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1977-020-00 | |
| Download: ML20168A448 (4) | |
Text
PRECURSOR DESCRIPTION AND DATA NSIC Accession Number: 123150 Date:
March 10, 1977
Title:
Excess Cooldown Rate Results from Loss of ICS Power at Crystal River 3 The failure sequence was:
- 1. Inverter B output diode failed in the B s.c. inverter, resulting in loss of vital bus B.
- 2. This resulted in a. loss of power to the ICS and consequent reactor trip, turbine trip, and 50% opening of the atmospheric dump valves.
- 3. Main feedwater was lost due to loss of condenser vacuum.
- 4. Emergency feedwater was used for reactor cooling.
Corrective action;
- 1. The B inverter output diode was replaced and the inverter restored to operation.
Design purpose of failed system or component:
- 1. The inverter provides battery-hacked A.C. power for instrumentation loads.
Unavailability of system per WASH 1400:
- vital bus:
3 x 10-6 /hr.
Unavailability of component per WASH 1400:
- power supplies:
3 x 10-6 /hr.
- Unavailabilities are in units of per demand D-1.
Failure rates are in units of per hour HR-1.
Diode failure in inverter caused loss of vital bus B while at power Loss of power to ICS:
reactor trip, turbine trip, 50%/ open atmospheric dump valves Potential Severe Core Damage No No No Yes No NSIC 123150 -
Actual Occurrence for Excess Cooldown Rate Results from Loss of ICS Power at Crystal River 3.
Steam Reactor Steam Auxiliary High PORV Opened IPORV or Long Line Trip Generator Feedwater and Pressure Due to Con-PORV Isola-Term Break Isolation Secondary Injection tinued HPI tion Valve Core Heat Removal
___________________Closure Cooling Potential Se Severe No Core Damage
-No No
-Yes No Possible (with worst case stuck rod)
-No
-Yes
-Yes
-Yes
-Yes quence 2
3 4
5 6
7 8
9 10 NSIC 123150 -
Sequence of Interest for Excess Cooldown Rate Results from Loss of ICS Power at Crystal River 3 small
CATEGORIZATION OF ACCIDENT SEQUENCE PRECURSORS NSIC ACCESSION NUMBER: 12150 DATE OF LER:
March 10, 1977 DATE OF EVENT:
March 3, 1977 SYSTEM INVOLVED:
Vital power supply, Integrated Control System COMPONENT INVOLVED: Inverter CAUSE:
Failed output diode SEQUENCE OF INTEREST:
Stuck open dump valves (Small steam line break)
ACTUAL OCCURRENCE:
50% open atmospheric dump valves REACTOR NAMNE:
Crystal River 3 DOCKET NUMBER:
50-302 REACTOR TYPE:
PWR DESIGN ELECTRICAL RATING:
825 MWe REACTOR AGE:
- 0. 25 yr VENDOR:
Babcock & Wilcox ARCHITECT-ENGINEERS:
Gilbert Assoc.
OPERATORS:
Florida Power Corp.
LOCATION:
7 miles-W-,.ofCrystal River, Fla.
DURATION:
N/A PLAN~T OPERATING CONDITION:
At 40%/ power.
SAFETY FEATURE TYPE OF FAILURE:
(a) inadequate performance; (b) failed to start; (c) made inoperable; (
aie in nunafe manner DISCOVERY METHOD:
Event while operating COMMENT:
-