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V UNITED STATES 8
NUCLEAR REGULATORY COMMISSION a
p wAssincron, o. c. zosss M Ei 1964 MEMORANDUM FOR:
Thomas Novak, Assist' ant Director for Licensing Division of Licensing FROM:
Frank"J. Miraglia, Assistant Director for Safety Assessment Division of Licensing-SUBJECTr GRAND GULF ~ OPERATING EXPERIENCE In response to your request (memorandum of October 6,1983) the Operating Reactors Assessment Branch (0RAB) has reviewed operating experience during the past year at the Grand Gulf facility and prepared the attached report.
The ORAB review included a survey of reported events at Grand Gulf during the past 15 months (i.e the low power license period) and a comparison of the event reports with reports from two other recently licensed BWRs (LaSalle and Susquehanna) fiTed during their low power license periods. The sources of event reports included prompt (telephone) notifications filed per 10 CFR 50.72 as well as Licensee Event. Reports (LER) required by the Technical Specifications. Operating reactor events briefing sumaries were also examined to identify the more significant events. AEOD provided us with substantial support in obtaining event reports.
In general the review reveaTed that high number of prompt reportable events (10 CFR 50~.72) have occurred at Grand Gulf in the past year. The rate of occurrence of these events has been at least three times greater than that of the two other recently licensed BWRs used for comparison. The large number of prompt reports are concerned for the most part with inadvertent actuations of engineered safety features. According to the 50.72 reports, equal numbers of these events have been caused by equipment failure and errors on the part of operators and technicians.
Review of operating reactor event briefing summaries indicates that five "significant" events have been reported for Grand Gulf during the year. They include a low temperature vessel pressurization incident, electrical system malfunction causing inadvertent RPS trips, a diesel generator room fire incident, simultaneous malfunction of both Transamerica DeLaval diesel generators, and an operator error which resulted in 10,000 gallons of water being drained from the reactor vessel to the suppression pool. The number of significant events at Grand Gulf during the low power license period is higher than that for the two other recently licensed BWRs considered in the review. LaSalle had only one event significant enough to be reported at a briefing and Susquehanna had none.
It should also be noted that the periods of low power license for LaSalle and Susquehanna were much shorter than Grand Gulf.
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TABLE I RATE OF REPORTED EVENTS AT THREE BWP. PLANTS DURINE LOW POWER LICENSE PERIOD Period of Low Rate of Reported Events Power License (Avg. No reports / month)
Facility (months 50.72 LER Grand Gulf 12*
10 21 LaSalle 1 4
1 19 Susquehanna 1 4
3 12
- The study period consists of the first 12 months of the low power license period. The actual period of the low power license will be longer than 12 months.
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deficie'ncies. Other causes of reported events include equipment problems and planned. entry of technical specification action statements for purposes of testing or construction..
REVIEW OF SIGNIFICANT EVENTS
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y Significant events which have occurred at Grand G Tf during the past year have been identified through a review of issues raised at the regularly scheduled briefings of NRR' management on operating reactor experience. The review consisted of a review of the Operating Reactor Event Briefing meeting minutes.
For purposes of comparison a similar review has been performed for LaSalle and Susquehanna. for the periods they held low power licenses. Events which are discussed at operating reactor event briefings have been subjected to a screening process in which five or six significant events are selected every two weeks for discussion based on the review of 100 to,150 events reports during the twa week period. The purpose of identifying those events here is to provide a measure of the severity and extent of significant operational problems.
During the Grand Gulf low power license period, five significant problems at Grand Gulf were reported. Our revice indicater that only one significant event was reported for LaSalle during the period of its low power license. No events were reported for Susquehanna. The Grand Gulf events are sumarized below.
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g Violation of RTNDT Heating Limits Durine ECCS Injection October 5,1982 During surveillance testing with the plant in cold shutdown a high DC voltage spike occurred which initiated an ECCS-injection. Low pressure core spray injected and caused the reactor vessel to become water solid (extending to theMSIVs). The resulting pressure transient violatedithe Technical Specification on nil-ductility reference temperature,.RTNDT.
e Reactor Protection System (RPS) MG-Set Output Breaker Trips, May 19, 1983 Inadverter.t *-inning of the RPS MG-set output breakers has occurred repetitively resulting in isolath of the instrument air system and a reactor scram signal.
The causes of the trips have been identified as thermal overload due to insufficient cabinet ventilation, and low voltage due to voltage swings while the RPS bus is fed from the alternate power supply. To reduce the number of output breaker trips the licensee increased cabinet ventilation, installed voltage regulators to smooth out voltage fluctuations, and installed a new station electrical transmission line from off-site.
In addition instrument air system isolation relays have been re-aligned to an interruptable power supply. This problem
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re-occurred in January 1984. Upward voltage spikes remaining above the setpoint longer than.1 second have caused the protective MG-set output breaker to trip, resulting in de-energization of containment isolation system logic circuits followed by isolation of the RHR system. The licensee has been unable to identify the source of the voltage spikes. To correct the problem, the licensee has. increased the output. breaker delay time from.1 second to 1.4 seconds. The new delay time is based on measurements of spike duration and consultation with suppliers of the electrical equipment. The modification assurer that spikes lasting less than 1.4 seconds will not result in a trip of the protective breaker. Additional corrective actions are also under discussion between the licensee and Region II.
Inadvertent Rea,ctor Vessel Drainace Durino Shutdwn April 3,1983 On ' April 3,1983, approximately 10,00CT gallons of water drained from the reactor vessel to the suppression pool through the residual heat removal (RiiR) system. This drainage was caused by two RHR valves (F004 and F006) being open simultaneously. At the time of the event, the reactor was at atmospheric pressure with vessel water temperature approximately 100*F (cold shutdown conditions)_ The vessel water level continued to decrease until the low level isolation: signa 11was received and shutdown cooling isolation valves c.losed to terminate the leakage.:
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Diesel Generator Room Fire September 4,1983 A diesel generator engine fire was caused by a Nptured fuel oil supply line which sprayed oiT on the hot exhaust manifold of the diesel. The diesel which caught fire was. running at 25 percent load for testing at the time.
Two other diesel generators were not affected by the fire. The water deluge systen failed to function automatically,but was manually activated to extinguish the fire _. The diesel generator governor and turbo chargers were damaged.- In addition some electrical equipment in the room suffered water damage.
Inoperability of Delaval Diesel Generators October 28, 1983 On October 28, 1983, a Technical Specification Action Statement was entered when two of the three diesel generators became inoperable. The Division I diesel generator was inoperable due to gasket failure on a lube oil line.
The Division II diesel generator became inoperable due to a loose base plate nut on the turbocharger which resulted in a trip of the vibration sensor which tripped the diesel. Corrective action was taken to repair both diesel generators. Both of the diesel generators were manufactured by Transamerica Delaval Inc. (TDI). TDI diesel generators have recently come under close scrutiny by the staff following a crankshaft failure in a TDI diesel generator at the Shoreham plant. Staff review of the Transamerica Delaval diesel generator problem at Grand Gulf is still ongoing.
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CONCLUSIONS Based on our review, we have concluded that operating experience at Grand Gulf during the low power license period has been atypical. Comparison of Grand Gulf experience with that of other BWRs indicates that the period of operation with the Tow power license at Grand Gulf has been abnormally long (12 months versus 4' months for Susquehanna and LaSalle) and that the rate of prompt reportable events has been much greater than expected. Based on discussions with Region II we believe that the high rate of reported events is related, at least~in part, to the large amount of testing and construction activities which have gone on during the past year. This construction and testing activity is the result of design changes being. implemented at the plant. The fact that many of the events are related to personneT errors may indicate a lack of experience en the' part of plant personnel. The rate at which events have occurred at Grand Gulf has not decreased steadily over the long term as the plant has moved closer ta commerical operation. However, a sudden sharp decrease in the rate did occur in November 1983 which may be attributed to site inactivity following corapletion of the low power testing in October. On this basis, we believe.it is reasonable to expect the incident rate to continue this decreasing trend. as the plant moves closer to commercial operation, and testing and construction activities cease. Should an abnormally high rate of incidents re-appear, appropriate actions such ar initiating a review of personnel training programs and plant procedures. should be initiated to identify the root cause'of the-continuing problem so that necessary corrective measures measuresccan be taken.-
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OPERATING EXPERIENCE REVIEW AT GRAND GULF UNIT #1 INTRODUCTION The staff review of operating experience included a survey of reported events at Grand Gulf durir.g the past 15 months (i.e. the low power license period) and a comparisort of the event reports with reports from two other recently licensed BWRs (LaSalle and.Susquehanna) filed during their low power license periods.
The sources of event reports incTude prompt (telephone) notifications filed per 10 CFR 50.72 as well as Licensee Event Reports (LER) required by the Technical Specifications Operatig reactor events briefing summaries were also examined to identify the mere significent cvants.. These briefings are regularly scheduled meetings among NRC management to discuss recent events at operating reactors.
SURVEY OF EVENT REPORTS In the period betweert mid-August 1982 and September 1, 1983 160 incidents requiring prompt notification were reported as required by 10 CFR part 50.72 One hundred and twenty-two of these events involved plant systems. The remaining 38 events involved the plant physical security system. This review has focused on the non-security.reTated events. The security related events were not considered significant and.were expected based on the testing and construction occurring at the plant. Thirty-five percent (35%) of the non-security related events have root causes related to operator and technician activities (e.g.. M ting, troubleshoorting). Equipment problems (mostly electrical) account for thirty-two (32%) of the events. The direct causes of the remaining one-third of the events are unknown or not apparent from the brief~ 50.72 reports Most of the events involve inadvertent actuations of safety systems with the plant shutdown (e.g., diesel generator start). The standby gas treatment system, control room fresh air system, reactor trip, average monthly rate at which these events have been reported is approximately 10 events / month This rate is compared with rates for LaSalle and Susquehanna in Table 1 and appears to be abnormally high. Region II inspectors attribute the high rate to the large amount of testing and construction going on at the plant. A review of the data by month does not reveal any particular trend in the incident rate. Data for the past three months shows a rate of occurrence close to the average in September and October with a sharp decrease in November to 3 events / month. The sharp decrease is attributed to site inactivity following completion of low power tests. A steady reduction in the rate of occurrence is expected as the plant nears corrinercial operation, since design changes and associated tests are expected to be completed.
In the period beginning August 1, 1982.and ending July 1, 1983 a total of 227 LERs were issued from Grand Gulf. The average monthly rate at which LERs have been issued is shown in table 1 along with comparable rates for LaSalle and Susquehanna. The Grand Gulf rate is similar to the rates for LaSalle and Susquehanna. This is in sharp contrast with the 10 CFR part 50.72 renorts discussed above where the Grand Gulf rate was significantly higher than the other two plants. Review of the Grand Gulf LERs indicates that about one-half of the reports relate to problems with fire protection systems. These problems include many instances of smoke detector alarus caused by dust from construction; and, removal of fire barriers for construction purposes. Only nineteen percent (19%) of the 227 reported events involved personnel errors and/or procedural
TE8 2 71&q Thomas M. Novak Based on our review we have concluded that operating experience at Grand Gulf during the past year has been atypical.
Comparison of Grand Gulf experience with that of other BWPs indicates that the period of operation with the icw power license at Grand Gulf has been abnormally long (greater than 12 months versus 4 months for Susquehanna and LaSalle) and that the rate of prompt reportable events has been much greater than expected. Based on discussions with Region II we believe that the high rate of reported events is at least in part related to the large amount of construction and testing activities which have gone on during the past year. This construction and testing activity is the result of design changes being inplemented at the plant. The fact that many events which have occurred are related to personnel errors may indicate a lack of experience, on the part of plant personnel.
The rate at which events have occurred at Grand Gulf has not decreased steadily over the long term as the plant has moved closer to commercial operation.
However, a sudden sharp decrease in the rate did occur in November 1983 which may be attributed to site inactivity following conpletion of low power testing in October. On this basis it would be reasonable to expect the incident rate to continue this decreasing trend as the plant noves closer to commercial operation, and testing and construction activities are completed.
We have discussed the results of our review with IE Region II, and they have informed us that our conclusions are consistent with their most recent SALP review.
Region II will continue to monitor plant perfornance and take appropriate actions should problems continue to occur at a high rate.
roricinni su ' :
Trnat J Ein l
Frank J. Miraglia, Assistant Director for Safety Assessment Division of Licensing
Enclosure:
As Stated DISTRIBUTION Central Files ORAB r/f FMiraglia GHolahan EButcher MCaruso DHoustan AWagner(RII)
Tippolito PFarron DVerrilli (RII)
- PREVIOUS CONCURRENCE SEE DATE ORAB:DL*
ORAB:DL*
ORAB:DL*
JI DL MCaruso EButcher GHolahan Ffi lia 01/11/84 01/11/84 02/S9f84 02/;$f/84