IR 05000528/1999014
| ML17313B054 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 08/09/1999 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML17313B053 | List: |
| References | |
| 50-528-99-14, 50-529-99-14, 50-530-99-14, NUDOCS 9908130030 | |
| Download: ML17313B054 (24) | |
Text
ENCLOSURE U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
Docket Nos.:
License Nos.:
Report No.:
Licensee:
'acility:
Location:
Dates:
Inspectors:
50-528 50-529 50-530 NPF-41 NPF-51 NPF-74 50-528/99-14 50-529/99-14 50-530/99-14 Arizona Public Service Company Palo Verde Nuclear Generating Station, Units 1, 2, and 3 5951 S. Wintersburg Road Tonopah, Arizona June 13 through July 24, 1999 J. H. Moorman, III, Senior Resident Inspector D. R. Carter, Resident Inspector D E. Corporandy, Resident Inspector N. L. Salgado, Resident Inspector K. M. Kennedy, Senior Project Engineer Approved By:
P. Harrell, Chief, Project Branch D, Division of Reactor Projects ATIACHMENT:
Supplemental Information 9908130030 990809 PDR ADOCK 05000528
EXECUTIVE SUMMARY Palo Verde Nuclear Generating Station, Units 1, 2, and 3 NRC Inspection Report No. 50-528/99-14; 50-529/99-14; 50-530/99-14
~Oerations
~
Operator performance during the Unit 2 reactor trip caused by failure of Control Element Assembly Calculator 2 was good. The Management Response Team meeting and subsequent Plant Review Board meeting that authorized restart of the unit covered the required areas with the appropriate emphasis on plant safety (Section 01.1).
Maintenance Knowledgeable technicians used approved procedures to perform routine maintenance activities in an effective manner.
Good work and foreign material control practices were observed (Section M1.1).
Knowledgeable technicians and operators used approved procedures to conduct surveillance activities in a satisfactory manner (Section M1.2).
I Material condition of the three units was good (Section M2.1).
Equipment obsolescence and limited availability of spare parts negatively impacted the licensee's efforts to repair the Unit 2 Core Element Assembly Calculator 2 in that it limited the number of parts that were replaced after a failure of indeterminate cause.
A subsequent similar failure of Core Element Assembly Calculator 2 resulted in the control room operators removing it from service to prevent another reactor trip. A strategic plan for replacement of this equipment has been developed by the licensee, but no firm milestones have been established (Section M2.2).
~En ineerin The engineering evaluation used to determine freeze protection requirements for essential spray pond header risers and spray nozzles was thorough (Section E1.1).
Plant Su ort The licensee effectively demonstrated that the staffing changes to the Emergency Plan would not adversely affect response of radiological protection personnel.
The radiological protection manager effectively managed available personnel to address radiological conditions presented by the drill scenario.
The drill critique was effective in identifying areas for improvement (Section P1.1).
I t
Re ort Details Summa of Plant Status Units 1 operated at essentially 100 percent power for the duration of this inspection period.
Unit 2 began this inspection period at 100 percent power.
On June 18, 1999, the unit experienced an automatic reactor trip due to a failure in Control Element Assembly Calculator (CEAC) 2. See Section 01.1 for details.
The unit was returned to 100 percent power on June 21 and remained at that power level for the duration of this inspection period.
Unit 3 operated at essentially 100 percent power until July 22, when power was reduced to 83 percent for approximately 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to repair a feedwater heater level control valve. The failure of this valve caused a high-high level in the Low Pressure Feedwater Heater 3C and subsequent isolation of the heater string. The unit returned to 100 percent power on July 23 and remained there for the duration of this inspection period.
I. 0 erations
Conduct of Operations 01.1 Reactor Tri Resultin From Failure of CEAC 2 Unit 2 a.
Ins ection Sco e 7170793702 On June 18, 1999, at 10:29 p.m., the Unit 2 reactor tripped due to a failure in CEAC 2.
The inspectors reviewed the sequence of events printout, control room logs, and conducted interviews with personnel.
b.
Observations and Findin s From a review of logs, plant performance data, and reports required by Procedure 90DP-OIP06, "Reactor Trip Investigation," Revision 6, the inspectors determined that operators responded appropriately to the reactor trip and that plant equipment performed as expected.
The inspectors also determined that the trip was caused by simultaneous high local power density (LPD) and low departure from nucleate boiling ratio (DNBR) reactor trip signals which were generated by all four core protection calculators (CPC). The inspectors attended the Management Response Team meeting and subsequent Plant Review Board meeting that authorized restart of the unit. The meeting included discussions of plant performance with the appropriate emphasis on plant safety.
The licensee determined that the trip signals were generated because a failure in CEAC 2 caused an erroneously high penalty factor to be sent to all four CPCs.
The CPCs use this penalty factor in the calculation of the LPD and DNBR trips. The CPC system consists of four CPCs and two CEACs. The CEACs receive analog input signals representing the position of each control element assembly (CEA) in the reactor core and derive penalty factor data. The CPCs calculate the DNBR and LPD trip values based on various plant inputs, including penalty factor data generated by both CEAC Troubleshooting and repair of the CEAC are discussed in Section M2.2 c.
Conclusions Operator performance during the Unit 2 reactor trip caused by failure of CEAC 2 was good. The Management Response Team meeting'and subsequent Plant Review Board meeting that authorized restart of the unit included reviews of the required topics with the appropriate emphasis on plant safety.
Miscellaneous Operations Issues (92901)
08.1 Closed Licensee Event Re ort LER 50-528/99-001-00:
Reactor Trip On High Pressurizer Pressure Due to a Loss of Heat Removal.
This event was discussed in NRC Inspection Report 50-528,-529,-530/99-04.
No new issues were revealed by this event report or in the associated Condition Report>Disposition Request (CRDR) 1-9-0039. The inspectors found that the cause determinations and corrective action contained in these documents were detailed and commensurate with the safety significance of the event.
08.2 Closed LER 50-529/99-005-00:
Reactor Trip on Low Departure from Nucleate Boiling Ratio.
The event described in this LER is discussed in Section 01.1 of this report.
II. Maintenance M1 Conduct of Maintenance M1.1 General Comments on Maintenance Activities a.
Ins ection Sco e 62707 The inspectors observed all or portions of the following activities performed per the listed work document:
858004
"Inspect/Clean Pump, Perform 6 Month Inspection of Charging Pump E Gear Reducer, Crankcase and Seal Lube System" (Unit 3)
857260
"Sample and Change Oil in the Pump Bearings and Grease Coupling for High Pressure Injection Pump 2MSIBP02" (Unit 2)
b.
Observations and Findin s The inspectors found that these activities were properly performed.
Allwork observed was performed with the work package present and in active use.
Work and foreign
-3-material exclusion practices observed were good. Technicians were experienced and knowledgeable of their assigned tasks.
c.
Conclusions Knowledgeable technicians used approved procedures to perform routine maintenance activities in an effective manner.
Good work and foreign material control practices were observed.
M1.2 General Comments on Surveillance Activities a.
Ins ection Sco e 61726 The inspectors observed all or portions of the following activities performed per the listed surveillance procedures:
36MT-9SF1 5 "CEDMCS CEA Coil Traces At Power Operation," Revision 6 (Unit 1 and 3)
"CEA Operability Checks," Revision 3 (Unit 3)
"Diesel Generator B Test," Revision 11 (Unit 2 and Unit 3)
"Containment Spray Pumps and Check Valves - Inservice Test,"
Revision 6 (Unit 1)
b.
Observations and Findin s The inspectors found that knowledgeable personnel performed these surveillances satisfactorily, as specified by applicable procedures.
c.
Conclusions Knowledgeable technicians used approved procedures to conduct surveillance activities
'in a satisfactory manner.
M2 Maintenance and Material Condition of Facilities and Equipment M2.1 Review of Material Condition Durin Plant Tours a.
Ins ection Sco e 62707 During this inspection period, routine tours of all units were conducted to evaluate plant material conditio Observations and Findin s Observation of plant material condition during this inspection period identified no major material condition deficiencies.
Minor deficiencies brought to the attention of the licensee were documented with work requests.
Conclusions Material condition of the three units was good.
Troubleshootin and Re air of CEAC 2 Unit 2 Ins ection Sco e 62707 The inspectors observed portions of troubleshooting activities conducted on CEAC 2, reviewed CRDR 2-9-202, and conducted interviews with maintenance technicians and supervisors.
Observations and Findin s Following the Unit 2 trip described in Section 01.1, troubleshooting activities were conducted on CEAC 2 in accordance with Work Order 886745. After the trip, the CEAC functioned normally, and testing was unable to identify the cause of the failure.
Technicians replaced the central processing unit and two memory boards in CEAC 2.
Postmaintenance testing determined that the CEAC was operable, and it was returned to service.
At 3:32 a.m. on June 21, CEAC 2 generated the same alarms that preceded the trip on June 18 and warned the control room operators of an impending failure. Recognizing these alarms as indications of a failing CEAC and observing no other anomalies with the unit, the control room operators removed CEAC 2 from service.
Work Request 961041 and CRDR 2-9-0206 were initiated to address this second failure. The licensee replaced the remaining circuit boards in CEAC 2 that contributed to the calculation of the penalty factor, which included the Automatic Load Option board.
Performance of CEAC 2 was monitored until June 24,'when it was returned to service.
No additional problems with CEAC 2 occurred through the end of this inspection period.
From discussions with licensee personnel, the inspectors determined that equipment obsolescence and limited availability of spare parts affected the decision to initially replace only selected circuit boards in CEAC 2. For example, the licensee did not replace the Automatic Load Option board due to the limited availability of this component onsite. The failure of this board in 1994 resulted in a Unit 2 reactor trip. The inspectors discussed equipment obsolescence and aging with licensee management and determined that the licensee has developed a strategic plan for replacement of obsolete and aging components.
The CEACs and CPCs are included in the strategic plan, however, no firm milestones for replacement have been establishe C.
Conclusions Equipment obsolescence and limited availability of spare parts negatively impacted the licensee's efforts to repair the Unit 2 Core Element Assembly Calculator 2 in that it limited the number of parts that were replaced after a failure of indeterminate cause.
A subsequent similar failure of Core Element Assembly Calculator 2 resulted in the control room operators removing it from service to prevent another reactor trip. A strategic plan for replacement of this equipment has been developed by the licensee, but no firm milestones have been established.
III. En 'ineerin E1 Conduct of Engineering E1.1 Essential S ra Pond Header Riser and S ra Nozzle En ineerin Evaluation a.
Ins ection Sco e 37551 The inspectors reviewed an'engineering evaluation used to determine the freeze protection requirements for the essential spray pond header risers and spray nozzles.
b.
Observation and Findin s As detailed in NRC inspection Report 50-528,-529,-530/98-09, the licensee could not retrieve the engineering document that supported the omission of freeze protection from the essential spray pond header risers and spray nozzles.
The licensee initiated CRDR 1-8-0552 to address this deficiency.
The licensee conducted a study to measure the ice formation rate. The testing simulated actual temperature and wind conditions on the spray pond header risers and nozzles.
The test determined the ice formation rate inside the riser piping and nozzles, the thickness to which the ice formed over time, and the pressure required to break the ice.
The evaluation concluded that ice formation could possibly cause blockage under the worst case subfreezing conditions that would be experienced at the site and recommended that the spray pond risers and nozzles be drained during winter months.
The licensee found that the system operability had never been impacted as a result of cold weather conditions.
At the conclusion of the inspection period, the licensee was evaluating options for draining the spray pond risers and nozzles during cold weather conditions.
c.
Conclusions The engineering evaluation used to determine freeze. protection requirements for essential spray pond header risers and spray nozzles was thoroug lV. Plant Su ort R1 Radiological Protection and Chemistry Controls R1.1 General Comments on Radiolo ical Protection Controls a.
Alns ection Sco e 71750 The inspectors monitored radiological protection activities during routine site tours.
'.
Observations and Findin s The inspectors observed radiation protection personnel, including supervisors, routinely touring the radiologically. controlled areas.
Licensee personnel working in radiologically controlled areas exhibited good radiation work practices.
Contaminated areas and high radiation areas were properly posted.
Area surveys posted outside the room were current. The inspectors checked a sample of doors, required to be locked for the purpose of radiation protection and found that they were all properly controlled.
c.
Conclusions The radiological protection program was effectively implemented in those areas reviewed.
P1 Conduct of Emergency Plan Activities F
P1.1 On-Shift Radiolo ical Protection RP Personnel Res onse to Emer enc Plan Drill Unit 3 a.
Ins ection Sco e 71750 On June 14, 1999, the licensee conducted a drill to evaluate the effectiveness of Revision 21 to the Emergency Plan, which reduced the required number of on-shift radiation protection staff. The inspectors reviewed the Emergency Plan revision and observed RP on-shift staff performance during the drill.
b.
Observations and Findin s On September 8, 1998, the licensee submitted a request to the NRC to revise their Emergency Plan to reduce the number of on-shift RP staff positions from 10 to 8 individuals. The request also increased by two the number of RP technicians required to respond to the site within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> of an emergency event. The NRC reviewed the licensee's request and concluded in a safety evaluation, dated February 5, 1999, that the proposed staffing changes were acceptabl The licensee conducted a drill on June 14, 1999, to demonstrate that the on-shift RP staff could adequately respond to an event, during the first 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />, prior to the arrival of off-site response personnel.
The inspectors reviewed the drill scenario and determined that it sufficiently challenged the reduced RP staffing.
During the event, the radiation protection manager (RPM) assessed available staff and made preliminary phone calls to alert potentially affected personnel.
The RPM dispatched personnel to perform tasks required by the drill. When task requests were made and personnel were not available, the RPM effectively redirected personnel as necessary, considering safety significance, to complete the tasks.
The RPM and the emergency coordinator were able to utilize available staff to accomplish all tasks required by the drill.
The licensee conducted an effective drill debrief which included areas for improvement.
The following issues were documented in CRDR 9-9-0860:
Delays in briefing players outside the satellite technical support center.
The RPM did.not update adjacent downwind sectors after the field team identified the plume centerline.
Site announcements were slow and infrequent. Announcements of significant changes in radiological conditions were poor.
Available maps and pictures, which show buildings, do not show Emergency Plan sector or degree markings.
c.
Conclusions The licensee effectively demonstrated that the staffing changes to the Emergency Plan would not adversely affect response of RP personnel.
The RPM effectively managed available personnel to address radiological conditions presented by the drill scenario.
The drill critique was effective in identifying areas for improvement.
V. Mana ement Meetin s X1 Exit Meeting Summary The inspectors presented the inspection results to members of licensee's staff at the conclusion of the inspection on July 28, 1999. The licensee acknowledged the findings presented.
The inspectors asked the licensee whether any material examined during the inspection should be considered proprietary.
No proprietary information was identifie ATTACHMENT PARTIALLIST OF PERSONS CONTACTED Licensee M. Banks, Communications Representative, Strategic Communications C. Bolle, Senior Coordinator, Emergency Planning S. Burns, Department Leader, Maintenance Engineering V. Huntsman, Department Leader, Radiation Protection W. Ide, Vice President, Nuclear Production D. Kanitz, Engineer, Nuclear Regulatory Affairs A. Krainik, Director, Nuclear Regulatory Affairs D. Mauldin, Vice President, Engineering and Support D. Marks, Section Leader, Nuclear Regulatory Affairs G. Overbeck, Senior Vice President, Nuclear T. Radke, Director, Maintenance Director, Outages G. Shanker, Department Leader, System Engineering M. Shea, Director, Training S. Terrigrino, Manager, Strategic Communications
-2-INSPECTION PROCEDURES USED 37551 61726 62707 71707 71750 92901 93702 Onsite Engineering Surveillance Observations Maintenance Observations Plant Operations Plant Support Activities Plant Operations Follow-up Prompt Onsite Response to Events at Operating Reactors ITEMS OPENED AND CLOSED
~oened None Closed 50-528/99-001-00 LER Reactor Trip On High Pressurizer Due to a Loss of Heat Removal (Section 08.1)
50-529/99-005-00 LER Reactor Trip on Low DNBR (Section 08.2 )
I I4
.
ej-3-LIST OF ACRONYMS USED CEA CFR CPC CEAC CRDR DNBR LER LPD NRC PDR RP RPM control element assembly Code of Federal Regulations core protection calculators control element assembly calculator condition report/disposition request departure from nucleate boiling ratio licensee event report local power density Nuclear Regulatory Commission Public Document Room radiological protection radiation protection manager
C
~