05000529/LER-1997-006, :on 971020,manual Reactor Trip Occurred Due to Vibration & Bearing Temp Increases in Reactor Coolant Pump. Caused by Failed Lower Journal Bearing.Bearing Assembly Was Disassembled,Inspected & Rebuilt
| ML17313A120 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/12/1997 |
| From: | Marks D ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | |
| Shared Package | |
| ML17313A119 | List: |
| References | |
| LER-97-006, LER-97-6, NUDOCS 9711280051 | |
| Download: ML17313A120 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| 5291997006R00 - NRC Website | |
text
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION I
ACII.ITYNAME Palo Verde Unit 2 DOCKET NUMBER LER NUMBER YEAR g~jI SEOVENTIAI. cN.'EVISION NUMBER
%~i NUMBER PAGE 0
5 0
0 0
5 2
9 9
7 0
0 6
0 0 02of 0 4
1 ~
REPORTING REQUIREMENT:
This LER 529/97-006-00 is being written to report an event that resulted in a manual actuation of the Reactor Protection System (RPS)
(JC) as specified in 10 CFR 50 '3(a)(2)(iv))
~
Specifically, at approximately 1050 MST on October 10,
- 1997, Palo Verde Unit 2 was in Mode 1
(POWER OPERATION) operating at approximately 100 percent power when a manual reactor (AC) trip was initiated by Control Room personnel following vibration and bearing temperature increases in reactor coolant pump (RCP)
(AB) 2B.
No other safety system actuations occurred and none were required.
2.
EVENT DESCRIPTION
Prior to the event, at approximately 1013 MST on October 20, 1997, Control Room personnel received a high temperature alarm for RCP 2B' lower journal bearing.
The temperature exceeded the RCP t ip setpoint as specified in an approved RCP abnormal operating proce" re.
Initially, Control Room personnel could not validate the alarm s'nce no other RCP 2B parameters indicated adverse trends.
At approximately '030 MST, Control Room and Engineering personnel validated the RCP 2B lower journal bearing high temperature anomaly when RCP 2B thrust bearing, upper radial bearing, and RCP oil sump temperatures as well as RCP 2B vibration began to increase.
Following a tailboard, at approximately 1050 MST, Control Room personnel manually tripped the reactor; At approximately 1051
RCP 2B was quarantined in accordance with an approved procedure.
All safety systems functioned as required.
There were no safety system actuations and none were required.
At approximately 1059 MST, the Shift Supervisor classified the event as an uncomplicated reactor trip.
At approximately 1615 MST, Control Room personnel commenced reactor coolant system (AB) cooldown and proceeded with the Mode 3
(HOT STANDBY) to Mode 5
(COLD SHUTDOWN) entry procedure in order to facilitate RCP troubleshooting and repairs.
3.
ASSESSMENT OF THE SAFETY CONSEQUENCES AND IMPLICATIONS OF THIS EVENT:
The manual reactor trip did not result in a transient more severe than those a'eady naly"ed '
the upda"ed "-'al afe"y Eva'"at'n Report Chapters 6 and 15.
- he pr'a y system and se"o..dary pressure boundary limits were not approached and no violations of the specified acceptable fuel design limits (SAFDL) occurred.
LlCENSEE EVENT REPORT (LER) TEXT CONTINUATION ACflllYNAME Palo Verde Unit 2 DOCKET NUMBER YEAR LER NUMBER SEQUENTIAL NUMBER REVISCN NUMBER PAGE EXT 0
5 0
0 0
5 2
9 9
7 0
0 6
0 0
0 3 of 0 4
The event did not esult in any challenges to the f'ss'on product barriers or result in any release of radioactive materials.
Therefore, there were no adverse safe"y consequences or implications as a result of this event.
This event did not adversely affect the safe operation of the plant or health and safety of the public.
CAUSE OF THE EVENT
An independent investigation of this event is being conducted in accordance w'ith the APS Corrective Action Program.
The cause of the reactor trip was due to a manual initiation of the RPS by Control Room personnel following vibration and bearing temperature increases in RCP 2B ~
An engineering evaluation has determined that the apparent root cause is attributed to a failed lower journal bearing (SALP Cause Code E: Component Failure)
The cause of the component failure and the failure mode, mechanism, and effect of the failed component is discussed in Section 5.
No unusual characteristics of the work location (e.g.,
- noise, heat, poor lighting) di rectly contributed to this event.
No personnel or procedural errors contributed to this event.
5.
STRUCTURES,
- SYSTEMS, OR COMPONENTS INFORMATION:
APS Engineering personnel have reviewed the failure of RCP 2B lower journal bearing and have determined that the most probable
cause
was intrusion of debris into the interface between the lower journal bearing pads and the shaft protection sleeve The source and composition of the debris material is unknown.
A preliminary evaluation has determined that the appa ent failure mechanism appears to be a very small particle of hard material which caused increased friction between the bearing pad faces and the shaft protection sleeve.
As the pump shaft rotated, it rolled the material around the shaft, gouging the surface of the shaft protection sleeve and the bearing pads, entraining metal from the shaft protection sleeve and the pads, aggravating the extent of the damage.
The increased friction generated additional heat which ultimately resulted in partial melting of the bearing babbit material as evidenced by the phys'cal inspection of the bearing pads.
There we e no '.".""" ":ons that any structu es, y "ems, or components were inope able at the start of the event wh'h contr'u=ed to this event.
No failures of components with multiple functions were involved.
No failures that rendered a train of a safety system inoperable were involved.
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