05000483/LER-2002-003
| Docket Number | |
| Event date: | 2-7-2002 |
|---|---|
| Report date: | 4-2-2002 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4832002003R00 - NRC Website | |
I. � DESCRIPTION OF THE REPORTABLE EVENT prohibited by Technical Specifications (T/S).
EVENT
reactor power.
THAT WERE INOPERABLE AT THE START
EVENT
DATES AND APPROXIMATE TIMES
to reduce the maximum flow on the MDAFW pumps by 7, 9, and 11, to 142,500 Lbm/hr. During a retest, +/- 10,000 Lbm/hr when flow was secured MDAFW pump. Troubleshooting revealed a a faulty electronic circuit board, ALHVO011 was control problem first occurred on 5/15/01 during flow data was first recorded for just ALHV0009 analyzed, this combined flow data revealed that Since ALHVO011 was not being retested, the data rendered ALHVO011 inoperable, and thus Callaway Plant entered Mode 4 and the T/S 3.7.5 flow, the "A" train of Auxiliary Feedwater was still pump run-out on the "A" MDAFP in the most limiting case (Feed Water Line Break on the flow to the "B" steam generator.
still capable of performing its intended safety
A. REPORTABLE EVENT CLASSIFICATION
This event is reportable under 10CFR50.73(a)(2)(i)(B), a condition
B. PLANT OPERATING CONDITIONS PRIOR TO THE
On 2/7/02, Callaway Plant was shutdown in Mode 4 at 0 percent
C. STATUS OF STRUCTURES, SYSTEMS OR COMPONENTS
OF THE EVENT AND THAT CONTRIBUTED TO THE
None.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING
On 2/6/02, Modification Package 02-1003 was implemented reducing the setpoint for the AFW flow control valves ALHV0005, ALHVO011 ramped up to 163,000 Lbm/hr and then began hunting through ALHV0009, a similar valve which is supplied by a common problem in the electronic flow control circuitry. By replacing restored to proper operation on 2/8/02.
A past operability review revealed that the ALHVO01 I flow ALHV0009 maintenance testing. During the test on ALHV0009, and then the combination of ALHV0009 and ALHVO011. When ALHVO011 was not controlling flow at the desired setpoint.
unsatisfactory flow data was not recognized. This unsatisfactory "A" train of AFW, inoperable from 5/15/01 until 2/1/02 when requirement for Auxiliary Feedwater, was no longer applicable.
Although ALHVO011 did not meet the T/S limit for maximum capable of performing its safety function. This is based on:
1) ALHVO011 was still able to throttle flow enough to prevent limiting NPSH conditions.
2) ALHVO011 was still able to throttle flow enough in the most "C" steam generator) to allow at least the minimum required Therefore, the "A" train of the Auxiliary Feedwater system was function.
The Tech Spec Bases for the Auxiliary Feedwater System states:
a) "The motor driven pumps supply flow to the steam generators through a normally open motor operated valve that automatically throttles flow to prevent pump run-out conditions under all steam generator pressure conditions.
b) "The AFW System design is such that it can perform its function following an FWLB between the MFW (Main Feedwater) isolation valves and containment, combined with a loss of offsite power following turbine trip, and a single active failure of one motor driven AFW pump. This results in minimum assumed flow to the intact steam generators.
One motor driven AFW pump would deliver to the broken MFW header at a flow rate throttled by the motor operated "smart" discharge valve until the problem was detected, and flow terminated by the operator. Sufficient flow would be delivered to the intact steam generators by the residual flow from the affected pump plus the turbine driven AFW (TDAFW) pump.
c) "This SR (Surveillance Requirement 3.7.5.3) verifies that AFW can be delivered to the appropriate steam generator in the event of any accident or transient that generates an ESFAS (Engineered Safety Features Actuation System), by demonstrating that each automatic valve in the flow path actuates to its correct position on an actual or simulated actuation signal. This SR includes the requirement to verify that each AFW motor-operated discharge valve, ALHV0005, 7, 9 and 11, limits the flow from the motor-driven pump to each steam generator to 300 gpm (300 gpm was 320 gpm prior to MP 02-1003).
Calculation AL-24 evaluated the effect of dissolved nitrogen on the available NPSH for the AL pumps. Running the limiting accident scenarios on the Plant Simulator validated the results of this calculation. Case 10 in the calculation determined there was adequate Net Positive Suction Head (NPSH) available from the Condensate Storage Tank (CST) at the T/S minimum level to support running 2 MDAFW pumps at 775 gpm per pump. Other Auxiliary Feedwater pump combinations are less limiting due to the TDAFW pump causing the motor operated Auxiliary Feedwater flow control valves to close which reduces the MDAFW pump flow and required NPSH. Conservatively assuming ALHV0009 limits flow to 320 gpm, ALV0011 limits flow to 328 gpm and mini-flow is 120 gpm, the total flow for the "A" MDAFP would be 768 gpm. Therefore, although ALHVO011 did not limit flow to the required T/S value, it was still capable of limiting flow enough to prevent a pump from operating under run-out conditions.
Accident Analysis evaluated the ability of the "A" train of Auxiliary Feedwater to perform its design function with ALHVO011 unable to limit flow to 320 gpm. The FWLB was the limiting accident. Assuming the "B" MDAFW pump fails and the FWLB occurs on the "C" steam generator, ALHVO011 still limits flow through the break enough to provide at least the minimum assumed flow of 93.3 gpm to the "B" steam generator. Therefore, ALHVO01 1 limited Auxiliary Feedwater flow enough at 328 gpm to allow the "A" train of Auxiliary Feedwater to fulfill its Safety Analysis function.
Conclusion:
Although ALHVO011 did not meet the T/S limit for maximum flow, the "A" train of Auxiliary Feedwater was still capable of performing its intended safety function.
E. METHOD OF DISCOVERY OF EACH COMPONENT, SYSTEM FAILURE, OR PROCEDURAL ERROR
The failure of ALHVO011 to control flow at the T/S limit was discovered on 2/7/02, while performing tests associated with Callaway Modification Package 02-1003.
Subsequent review of historical data for past operability determined that ALHVO011 had been inoperable since 5/15/01.
II. A EVENT DRIVEN INFORMATION
A. SAFETY SYSTEMS THAT RESPONDED
Not applicable.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
The total duration of the time that the "A" train Auxiliary Feedwater system was inoperable was from 1259, 5/15/01 until 0426, 2/1/02 when the Callaway Plant entered Mode 4 and the Auxiliary Feedwater system was no longer required to be Operable per T/S 3.7.5. Callaway Plant was still in Mode 4 when repairs were completed on ALHVO 11 and the valve was declared operable. The total time of Inoperability was 260 days, 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />, 27 minutes.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT.
This event did not represent a significant safety concern. Based upon an evaluation contained within this LER that details how the "A" train of Auxiliary Feedwater remained capable of satisfying its intended safety function, this event did not pose an increase in core damage frequency.
III. A CAUSE OF THE EVENT The primary cause of this event was failure of an electronic circuit board for ALHVO011. A contributing factor was the failure to recognize the unsatisfactory test data recorded for ALHVO011 on 5/15/01.
IV. A CORRECTIVE ACTIONS Corrective actions were to replace the faulty electronic circuit board for ALHVO011 and perform a satisfactory retest on 2/8/02. Additional corrective actions addressing the failure to recognize unsatisfactory test data are being evaluated.
V. A PREVIOUS SIMILAR EVENTS A review was conducted of LERs written within the last 3 years and there were no similar LERs. A review of Callaway Action Request System (CARS) data for the last 3 years revealed 3 CARs related to flow control problems associated with ALHV0005, 7, 9, and/or 11.
VI. A ADDITIONAL INFORMATION They were CARs 199903183, 200103109, and 200200577.
The system and component codes listed below respectively.
are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 System: A BA Component: FCV