ML17306B402
| ML17306B402 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 04/19/1993 |
| From: | Rosenthal J NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Ross D NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| Shared Package | |
| ML17306B403 | List: |
| References | |
| NUDOCS 9304210273 | |
| Download: ML17306B402 (6) | |
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MEMORANDUM UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O. C. 20555 APR 1.9 593 FOR:,
Denwood, F."Ross,'cting 'Director Division of Safety Programs Office for Analysis and. Evaluation of Operational Data FROM:
Jack E. Rosenthal, Chief
. Reactor Operations Analysis Branch Division of Safety Programs.
Office for Analysis and'valuation of Operational Data
SUBJECT:
HUMANPERFORMANCE STUDY REPORT-PALO VERDE UNIT 3 (2/4/93)
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At 3:22:52 p.m. on February 4, 1993, with Unit 3 at 100'percent power, the."A",main feedwater pump turbine (MFWPT) high vibration annunciator alarmed when the MFWPT had'ecreased to 1500 rpm from its normal 4500 rpm. Alleight steam bypass control valves had opened and steam generator (SG) levels were decreasing rapidly. 'The priinary side reactor operator (RO), verified a reactor cutback had'not occurred and alerted the Shift Supervisor (SS) and the Control Ro'om Supervisor (CRS). After verifying low steam generator levels and low MFWPT suction pressure,:the.,SS concurred with the secondary side'RO's recommendation to trip the "A"MFWPT. Tripping this pump would initiate a reactor power cutback and potentially avoid a.reactor. trip.
However,. an automatic reactor, trip on low SG P2 level occurred at 3:23:52 p.m. before the MFWPT could be manually tripped. Auxiliaryfeedwater actuation system,(AFAS 1
and 2) followed immediately.
By 3:24:34 p.m., the reactor coolant system temperature and pressure had decreased,.
causing safety injection and containment isolation signal (SI/CIS) actuations.
By the time the secondary side RO checked SG levels and.flow using the safety function.flow.
charts, he found,'no'auxiliary feedwater'(AFW) flow.(because the control system had recovered the SG."levels).. SG 1 level. was slightly higher than SG 2 level. AFW valve HV-30 indication'Ishowed.that it was not in its required position despite a proper control signal.'oth the valve and its associated pump were declared inoperable.
This produced confusion as to the status-of the AFW valves and response of the main feedwater (MFW) downcomer valves.'The CRS and secondary RO'discussed using the operating 8 MFWPT'to feed the SGs, which'-was not included, in the-emergency;procedure,(EP).
The operators took manual'control of the SG 2 downcomer valve arid closed the SG. 1 downcomer isolation valves to stabilize SGlevels.
P10114 93042i0273 9304i9 PDR ADOCK 05000530 S 'DR ol
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Denwood F'. Ross Thie SS declared a NotiGc;<tictn qf Pnijsual Event at 3:46 p.m. anid terminated it at 5:00 p.m. after the SI termination criteria was veriGed satisfactory ajxd the high and low pressure safety injection pumps were secured.
SI/CIS signals were reset at 6:00 p.m. and diesel, generators A and B, w)iicP hyd started on the SI and. never loaded, were stopped
,at 8:05 p,.m. and 8:10 p.m..
As para of the AEOD progratn tp sptQ the human performance aspects of operational qvqnts~ a team was sent to thk site Februaiy 9. The team leader was Jose Ibarra of AEOD; other team members were Robert Spence of AEOD, and WilliamSteinke of the Idaho National Engineering Laboratory (INEL). The team was at the site for 2 days and gathered data from discussions, plant logs, strip chart recordings, and interviews with the plant staff.
EnclqseId i<s'he INTEL IIeport on the results of this human performance study.
Specific human perl'orinaiice aspects of this event are atddressed in this memorandum.
$hift Staffing and Operator Response The shift staffirig was adequate.
Having a third RO as part of the, normal shift crew was.
beneficial sirice it @llowe;d the,otl~er, twq ROs to address their EPs without having to divert their attention to backpanels.
Additional personnel were available due to the time of the event. An administrative aide assisted the einergency coordinator. A dedicated sIiif( technical advisor for eaclII of'hy three unitss also prctvided additional. resources.
L,icensee personnel quickly diagnosed the problem, made a decision to trip the MFWPT,
, apd mini)iated recovery actions.
Whey. control board indication was incorrect or unavailable, operators used backup indiIcation or Geld personnel.
A similar loss of feedwater (FW) without,a MFA~'T )rip occurred on February 17; the same operators were a)le to more quickly diagnose the problem and had authority to trip the "A" hAVFPT which caused an automatic reactor power cutback to lower power instead of a reactor trip.
OperatI'ons Procedures The, operators satisfactorily used safety function flowcharts which were an improvement oiler the past procedures.
They had simulator training on the new EPs, issued 6 months before the event,.and found thI'm mqre comprehensive, but more tiime consuming.
Overriding the HPSI and LI'SI systems was done by procedure and reinitiation criteria was ~opitored closely by the primary RO.
Several difficulties with the EPs occurred during recovery.
Procedures did not quickly restore the electrical system and did not consiider using the FW system to f'eed the SGs.
The procedure directed manual control of the pressurizer spray valve which gould result.in excessive RO task workload in other emergency conditions. The EP prplongi;d the time from automatic initiation to
, shutcwovIjn of the emergency diesel generators.
Denwood F. Ross Command, Control, and Communications Based on post event interviews, operator communications were good during the course of the event.
The SS and CRS worked with operators who had been together as a crew for 1 month. The licensee practice of'keeping SS and CRS teams intact was a positive influence. Within a few seconds, effective teamwork allowed assessment and decision making.
Command and control was effectively shifted from the SS to'CRS, as the situation dictated.
As the number of people increased in the control room (CR), the SS demonstrated proper command and control by moving extra personnel to the satellite technical support facility to lower noise levels and minimize distractions.
The SS stationed himself in the CR in a manner making him readily available to the crew.
Transferring the emergency coordinator duties to an available qualified person enhanced the SS oversight capability.
Training The experience of personnel interviewed was above industry, norm. Although operators had been trained on a loss of a MFW pump, this event required them to diagnosis conditions not previously seen.
Human-Machine Interface The CR SG level. on the CRT was behind actual plant conditions since the current computer system. is not able to adequately display fast transients.
AFW and SI flows do not have a recorder to,readily'identify the amount of water injected.
Overall The response to this event was successful.
Many strengths were identified. The operators responded quickly to assess the situation and recover with minimal problems.
There were some concerns identified in the areas of human-machine interface and EPs.
This report is being sent to the Office of Nuclear Reactor Regulation for appropriate distribution to the licensee and region.
6rTginaf slgne85$ 3ack EHosenthal Jack E. Rosenthal, Chief Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated ROAB RO RSpence:rgz G
4/]$793 4/jg/93 Distribution: See attached list OAB J
osenthal 4//f/93
Denwood F. Ross Distribution:
PDR Central File ROAB R/F RSp ence JIbarra GLanik JRosenthal EJordan DRoss VBenaroya
'Spessard, KBrockman SRubin PBaranowsky ETrager
JKauffman RSavio, ACRS
'MTaylorEDO KRaglin, TTC AChaffee, NRR FCoffm'an, RES WSwenson, NRR "JL'ieberman, OE WSteinke, INEL CTrammel,'RR KPerkins, RV HWong, RV JSloan, SRI/RV PLewis, INFO DQueener, NOAC VChexal, EPRI
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