IR 05000424/1987038
| ML20236M009 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/31/1987 |
| From: | Burnett P, Jape F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20236L995 | List: |
| References | |
| 50-424-87-38, NUDOCS 8708100444 | |
| Download: ML20236M009 (11) | |
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I UNITED STATES jo y Rtcoq
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fo NUCLEAR REGULATORY COMMISSION
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REGION 11 h
101 M ARIETTA STRE ET, N.W.
'2 ATL ANTA, GEORGI A 30323
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Report No..
50-424/87-38 Licensee:
Georgia Power Company
P. O. Box 4545 Atlanta, GA 30302 Docket No.-
50-424 License No.:
NPF-68 Facility Narie:
Vogtle 1 Inspection Conducted:
June 8-10, and June 22-25, 1987 Team Members:
R. S. Baldwin, RII/DRS B. R. Bonser, RII/DRP W. L. Jensen, NRR B. Little, RIII/DRP
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L. P. Modenos, RII/DRP l
A..Ramsey-Smith, NRR/DLPQ R. J. Schepens, RII/DRP
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Inspecto':
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/4 7/8/ [O7 P. T. Burnett, Team Leader g
Date Signed Approved by:
Y8/M9 F. Jape, ' Chief, Test Programsg$betion Date Signed Engineering Branch Division of Reactor Safety SUMMARY Scope:
This special, am.cunced inspection was conducted to assess the causes of reactor trips since lice, sing, and the licensee's efforts to evaluate the trips and reduce the frequer.cy of such events.
Results:
No violations or devietions were identified.
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l 8708100444 8705P90, PDR ADOCK 05000424 i
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REPORT DETAILS 1.
Persons Ccntacted Licensee Employees
- G. Bockhold, General-Manager, Vogtle Nuclear Operations
- C. E. Belflower, Quality Assurance Site Manager
- P. R. Bemis, Plant Support Manager M. Briney, Instrumentation and Controls Supervisor
C. L. Cross, Senior Regulatory Specialist
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- J. F. D'Amico, Manager, Nuclear Safety and Compliance
- E. M. Dannemiller, Technical Assistant to the General Manager j
- C. C. Eckert, Technical Assistant to the Plant Manager R. J. Florian, Reactor Engineering Supervisor G. R. Frederick, Quality Assurance Engineering Supervisor
- W. C. Gabbard, Senior Regulatory Specialist M. Gibson, Simulator Supervisor
- B. Gover, Engineering Supervisor
- T. V. Greene, Plant Manager M. A. Griffis, Maintenance Manager j
- M. L. Hobbs, Instrumentation and Controls Superintendent W. F. Kitchens, Operations Manager
- E. Kozinsky, Human Performance Evaluation Specialist R. L. LeGrand, Shift Supervisor
- R. E. Lide, Engineering Support Superintendent
- W. E. Mundy, Quality Assurance Supervisor
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C. Myer, Operations Administrative Superintendent M. J. Rowe, Operations Superintendent
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- P. Rushton, Plant Training Manager D. Scukanec, Training Supervisor
- D. Smith, Superintendent of Nuclear Operations R. E. Spinnato, Independent Safety Engineering Group Supervisor
Other licensee employees contacted included senior reactor operators reactor operators, engineers, and office personnel.
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Other Organizations i
W. Phoenix, Consul Tec l
l NRC Resident Inspectors H. H. Livermore, Senior Resident Inspector, Construction J. F. Rogge, Senior Resident Inspector, Operations
- R. J. Schepens, Resident Inspector
- Attended exit interview
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l 2.
Exit Interview The inspection scope and findings were summarized on June 25, 1987, with those persons indicated in paragraph 1 above. The inspector described the
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areas inspected and discussed in detail the inspection findings.
No dissenting comments were received from the licensee.
Proprietary material was reviewed during the inspection, but is not included in this report.
3.
Licensee Action on Previous Enforcement Matters l
This subject was not addressed in the inspection.
4.
Unresolved Items Unresolved items were not identified during this inspection.
5.
Introduction Vogtle Unit I was licensed for low-power operation on January 16, 1987 and for full power operation on March 16, 1987.
The 100-hour warranty demonstration run at full power was completed on May 31, 1987. Commercial operation began on June 1, 1987. By June 7, 1987, the unit had suffered
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23 reactor trips.
Five were planned trips as purt of the startup test
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program. Although the initiating events were not all tb9 same, eleven of
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the remaining eighteen were from 10-10 level in one or more steam generators.
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Most of the rest resulted from equipment failure, except for trip 21, on high source range flux, which resulted from the f ailure of an operator trainee at the controls to recognize criticality.
Given the high number oi trips per hour critical, Region II and NRR directed that a team inspection be perfor med to assess the quality of the licensee's trip reviews, trip reduction efforts and management of resources to those ends. The team leader was on site June 8-10, and the entire team was onsite June 22-25, 1987.
6.
Secondary System Design and Operation a.
Design and Operation Features The original plant design included an electric startup feedwater pump, the purpose of which was to improve control of steam generator level at low power.
This pump was deleted from the design approx-imately four years ago.
The Westinghouse Owners Group made a number of recommendations regarding reactor trip reduction in the sur.mer of 1986.
These included the need to improve steam generator level control systems, feedwater regulator valve response and simulator modeling of steam generator level.
These recommendations were not implemented at
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Vogtle until the number of reactor trips became of concern to management.
Additional factors contributing to the number of low level trips were as follows:
Before initial power ascensions, operators were not forewarned that the plant steam generator level control system would not behave like the simulator and that the system would require considerable control adjustments and manual manipulations.
Assistance was, therefore, not requested from other utilities and Westinghouse until a number of low level trips occurred.
The Westinghouse Plant Limitations and Setpoints document did not provide the optimum control settings for the level control system. The best values were obtained from other utilities. No
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settings appear to be adequate over the entire power range and,
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therefore, considerable manual manipulation is required at low j
power.
Control is made more difficult by the lack of adequate i
steam and feedwater flow indication at low power.
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indication is affected by shrink and swell of the narrow range l
indicators which make control more difficult.
l During initial startup, less than optimum cooperation appears to have existed between the engineering, training, operations, and maintenance divisions. Following certification of the plant as commercial, reactor trips have received increased upper management attention which should improve divisional cooperation.
b.
Summary of Licensee's Corrective Actions to Reduce Number of Low Level Trips
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(1) The utility has made a number of modifications to reduce low level trips.
These include the following:
The steam generator level is programmed at 50% NR at all
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power levels to provide the maximum distance between feedwater isolation at high level and reactor trip on low level.
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The automatic main feedwater pump controller was found to not perform adequately at low power. Thus, speed is set in manual at low power.
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The neutron power level input to the bypass feedwater l
regulator valve controller was found not to be effective and was removed following the first steam generator reactor trip, based on experience at other plants.
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The I/P controllers on the main and bypass regulator valve'
were found not to maintain setpoint and are now tested to full open and close before each startup.
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An additional operator is located in the control room with
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the sole function to control steam generator level.
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An incorrect jumper wire was discovered on main feed Reg valve #2.
It caused two trips before being corrected.
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An inadequate main feedwater discharge check valve design was discovered and corrected af ter causing two reactor I
trips.
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Reactor trips have obtained increased management attention since
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the plant went commercial.
A committee has been formed including the maintenance, operations and engineering divisions to invest-
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igate changes in feedwater control to reduce reactor trips.
l These activities include the following:
(Hi-Hi S/G)
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Evaluating raising upper feedwater isolation avel setpoint including the effect of instrument error to the maximum which will still prevent excessive moisture carryover.
(Lo-Lo S/G)
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Evaluating lowering lower reactor trip level setpoint l
including the effect of instrument error and environmental i
qualification to the minimum which will still provide adequate steam line break protection. A time delay is also being considered.
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Evaluating means of providing adequate steam and feedwater
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flow information to the operator and to the level control system at low power levels.
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Evaluating feasibility of lowering the narrow range low l
level steam generator tap to provide reactor trip at a lower level. This would require the steam generator to be rehydrotested.
Improving the reactor simulator by increasing computer core
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capacity and improving software to better model the actual plant steam generator level during transients.
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Providing operator training on the picnt in controlling steam generator level during low power operations.
The dedicated steam generator-level operator controls three generators and the operator-in-training controls one under supervision of the dedicated operator.
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c.
Operational and Maintenance Experience The operation and performance of the secondary plant and related reactor trips ware discussed with GPC Operations, engineering and I&C personnel.
Major areas discussed with each of the groups were:
Transfer of feedwater from Auxiliary Feedwater (AFW) to feeding the S/Gs on the Bypass Feed Regulator Valve (BFRV) to feeding on the Main Feedwater Regulator Valve (MFRV).
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i Each groups involvement in solving secondary 80P system problems.
Use of other utilities and vendors experience and use of vendor technical representatives in tuning steam generator water level control (SGWLC) system, steam dump, and feedwater pump controllers.
Changes in procedures, guidance and operating practices to reduce reactor trips.
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l Limitations imposed on operation by the narrow range S/G level
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instrumentation and avenues pursued to alleviate this problem.
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l Observations resulting from discussions vith systems engineering personnel were as follows:
The setpoints in the Westinghouse Precautions, Limitations and Setpoints (PLS) document were not useful in setting up the
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controllers for the SGWLC system.
Consultation with other
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licensees and Westinghouse technical representatives proved to be more beneficial in tuning the system.
Avenues are being explored to widen the allowable operating span on the S/G narrow range.
One item specifically mentioned was resolution of a generic drift problem with veritrac transmitters.
The feedwater pumps discharge check valve problem was solved by changing the disc hinge pins.
Prior to each startup, I&C and Operations will work together to
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functionally test the response of the MFRVs and BFRVs.
A committee comprised of engineering, operations, and maintenance is looking in to finding more reliable I/P converters for the f
MFRV and BFRV controllers, i
Observations from the inspector's discussions with operation personnel were as follows:
The plant simulator did not behave as the plant. The operators had to go through a relearning process to control steam generator water level and transfer of feedwater from AFW to the BFRV to the MFRV.
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6 A group of operators expert at steam generator water level control have been spread across the shifts to ensere a smooth transition when transferring sources of feedwater.
Operations supervision felt the advantages of trip reduction outweighed the temporary morale problems.
After trial and error with the steam generator water level control system, operations is manually making the transfers from j
AFW to feeding on the BFRV and from the CFRV to the MFRV. After
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the transfers the SGWLC is left in automatic.
At low power, operations has established specific system controls to make steam generator control more efficient.
They include:
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Keeping the main feedwater pump in manual to maintain l
differential pressure across the steam generators.
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Manually controlling steam dump valves to prevent large swings in steam demard.
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Maintaining steam generator blowdown at a specific rate.
I Prior to every startup, operations works with I&C to functionally i
test the BFRVs and MFRVs.
Operations has looked at and is still pursuing using other means to maintain S/G levels at low powers such as using WR S/G 1evel transmitters.
Discussions with I&C personnel reflected the same observations obtained in discussions with the other groups interviewed, and reinforced the fact that different groups were now working together, d.
Maintenance Records The inspectors reviewed MW0s relating to hardware problems which caused reactor trips for the following:
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Actual work performed to ensure problem identified is corrected.
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Documentation was properly implemented as required.
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Functional test was properly performed to verify operability.
All were completed acceptably.
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7.
Independent Safety Engineering Group (ISEG)
The inspectors reviewed the organizational structure, responsibilities and activities of the independent safety engineering group (ISEG). The name
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of the group has been recently changed from Nuclear Safety and Engineering Group (NSEG) to ISEG and some procedure have not been updated with the new name.
ISEG is an independent organization reporting to the general office. The site supervisor reports to the Manager, Nuclear Performance and Analysis, and has a permanent staff of four engineers that meets the minimum require-I ments of Technical Specification 6.2.3.
Nuclear Operations Policy (N0P)-18-050 Nuclear Safety and Engineering Organization Responsibilities and Training, defines the organization, authority and responsibilities of the group.
The following are some of the function of the group:
I Conducting the independent safety review function that encompasses the review of significant plant changes, tests, and procedures; and verifying reportable occurrences and significant events are promptly investigated and corrected in a manner that reduces the probability of recurrence of such events.
Detecting of trends that may not be apparent to a day-to-day observer.
I Assessing selected plant systems to identify design, maintenance, and
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operational problems involving nuclear safety concerns.
Monitoring generic and specific unresolved safety issues at a level determined appropriate by management.
Reviewing the implementation of the operational assessment program.
Performing independent evaluations of the overall quality and safety of routine plant activities.
Nuclear Operations Instruction (NOI)-18-150, Screening of Operating Experience Information, establishes guidelines for ISEG to Screen Operating Experience Information ISEG tracks (by computer) all of their recommendation given to each department. The monthly report sent to the general office summarizes the
item that are used during the month.
In early 1986, the Westinghouse Owners Group (WOG) provided to the licensee report on Trip Reduction Assessment Progress (TRAP).
ISEG made a comparison of VEGP Reactor Trip Reduction Plan to WOG-TRAP recommendations and provided this to the plant management.
However, plant management elected to delay implementation of these recommendations until the plant
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achieved full power. This decision to delay seemed to defeat the purpose and the intent of the WOG report. Some of the recommendations that were made were:
l Improve skill in feedwater control during startup:
Results of an Expert Panel Session should be reviewed and concepts incorporated
into Operations Department policy and operator training.
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A report, Low Power Steam Generator Water Level Control System Improvement, will be available in June 1986. The report will contain ideas regarding timing of steam generator wat-J level control systems.
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Evaluation and categorization of feedwater related trips and i
identification of remedial measures to feedwater and other major i
plant systems should be performed, j
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Review and revise, Reactor Trip Review, to ensure the root cause or
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component failure for the reactor trip have been identified, i
documented and repaired.
Condensate and feedwater system should be subject to independent
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verification following calibration checks, during valve and switch lineups, for equipment clearance and tagging etc. This will require
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revisiens to plant administrative, operations and maintenance procedures.
The plant manager will assign a reactor trip reduction team scheduled for
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July 1,1987, to incorporate the WOG-TRAP recommendations and review trips and they occer.
It seems that the plant did not take full advantage of the benefh;, they would have gained by learning from industry experience and their own ISEG group.
Furthermore, ISEG erred in accepting a plant implementation date later than the startup date.
No violations or deviations were identified, t
8.
Human Performance The inspection team interviewed licensee personnel, toured the control room, observed a simulator exercise, and reviewed written documents to investigate the contributors to human performance during reported operating events.
Primary attention was given to the events that demonstrated operator dif ficulties in controlling Steam Generator (SG)
level.
These events represent 23 of the 58 events occurring between February 9, 1987, and June 7, 1987. In the opinion of licensee personnel, i
a number of these events were caused by equipment malfunctions of such a
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nature that the operator could not reasonably have been expected to control steam generator level and, thus, prevent a reactor trip on 10-10 SG level,
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l This portion of the inspection teani's investigation concentrated on
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discovering the factors that contributed to the operator's inability to
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control SG level during the remaining events.
l In the team's opinion, the primary contribution to the 10-10 reactor trip
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involved operator's la-of skill in contrt 11ing SG level was less-than-l adequate training.
The design of the SG system and its associated swell
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and shrink phenomena require intensive skill training to develop the right j
" touch" or " feel" for transferring from auxiliary feedwater (AFW) to l
bypass feed regulating valve to main feedwater regulating valve control.
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Such training was conducted at the licensee's full-scale simulator during j
initial and requalification training and subsequently during special j
simulator training.
However, problems exist with the fidelity of the
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simulator in that, the simulator does not accurately reflect valve and l
indicator response in the plant. Consequently, operators can demonstrate j
mastery of the skill during simulator training, but then be unsuccessful in duplicating SG level control in the control room.
I The licensee is aware of the discrepancies between the simulator and l
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l the plant as related to SG 1evel control. An ISEG document, dated July l
1986 recommended upgrades specifically to the simulation of the SG system.
The Training Department has upgraded its computer capability to permit further upgrades to the plant simulator.
The Operations Department has
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collected plant data to be used by training in continuing to improve the simulator's fidelity.
Procedure changes have been made to enhance SG level control. Efforts are being made to cooperate an ERFS monitor at the j
control board to enhance operator response time to S/G level changes.
I Nevertheless, the team is concerned that the licensee's management is not l
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aggressively pursuing a speedy resolution of the problem. No milestones or schedule were provided to the team that illustrated. management's commitment to addressing the simulator fidelity issue and providing the additional shift training to ensure all operators have the correct touch.
I It is the team's judgment that without scheduled milestones, simulator improvement will not be realized on a relatively near-term basis. On the contrary, the licensee has established an elite corps of operators who, in their judgment, have the right " touch" for controlling SG level.
This corps will be responsible for feedwater control during plant startups.
The team is concerned that this approach, although perhaps expedient in the short-term, is short-sighted.
Again, without established milestones for upgrading the plant simulator or enhanced skill training, the team does not sense an urgency on the part of licensee management to ensure that all its licensed operatnrs have the skill required to successfully control SG level.
The team noted that the licensee's management did not carefully evaluate its response to the operator's difficulties with controlling SG level, that the establishment of specific simulator improvement milestones and schedules sensitive to Operations Department needs was lacking, and that the consequences on both operator morale and skill levels of establishing an elite corp of operators to perform designated plant manipulations was not considere '
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9.
Conclusions The secondary system design at Vogtle is more sensitive than most older plants to secondary system level perturbations because of the design of the Model F steam generators.
The feedwater and steam generator level control systems do not appear to be adequately designed to maintain steam generator level within the required ranges without a significant amount of operator interruption. Other recent Westinghouse plants have similar secondary system designs to Vogtle.
By the time Vogtle was licensed, a considerable amount of experience was available both from the individual owners and from the Westinghouse owners group on trip reduction.
This information was not made available to Vogtle operators or engineers before initial startup.
The licensee has not moved aggressively to ensure that all operators have the skill to operate all of the plant controls.
Within the areas inspected, no violations or deviations were identified.
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