Event Notification Report for September 21, 2001
U.S. Nuclear Regulatory Commission
Operations Center
Event Reports For
09/20/2001 - 09/21/2001
** EVENT NUMBERS **
38263 38300
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|Power Reactor |Event Number: 38263 |
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| FACILITY: WATTS BAR REGION: 2 |NOTIFICATION DATE: 09/04/2001|
| UNIT: [1] [] [] STATE: TN |NOTIFICATION TIME: 16:54[EDT]|
| RXTYPE: [1] W-4-LP,[2] W-4-LP |EVENT DATE: 09/04/2001|
+------------------------------------------------+EVENT TIME: 13:04[EDT]|
| NRC NOTIFIED BY: RODEN |LAST UPDATE DATE: 09/20/2001|
| HQ OPS OFFICER: CHAUNCEY GOULD +-----------------------------+
+------------------------------------------------+PERSON ORGANIZATION |
|EMERGENCY CLASS: NON EMERGENCY |JOHN MONNINGER R2 |
|10 CFR SECTION: | |
|ARPS 50.72(b)(2)(iv)(B) RPS ACTUATION - CRITICA| |
|AESF 50.72(b)(3)(iv)(A) VALID SPECIF SYS ACTUAT| |
| | |
| | |
+-----+----------+-------+--------+-----------------+--------+-----------------+
|UNIT |SCRAM CODE|RX CRIT|INIT PWR| INIT RX MODE |CURR PWR| CURR RX MODE |
+-----+----------+-------+--------+-----------------+--------+-----------------+
|1 M/R Y 100 Power Operation |0 Hot Standby |
| | |
| | |
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EVENT TEXT
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| REACTOR MANUALLY TRIPPED FROM 100% POWER DUE TO STEAM GENERATOR LEVEL |
| APPROACHING THE LO-LO LEVEL SETPOINT |
| |
| While operating at 100% power, the Watts Bar Unit 1 reactor was manually |
| tripped at approximately 1304 EDT on September 4, 2001 due to steam |
| generator (SG) level approaching the Lo-Lo level setpoint. Just prior to |
| the manual trip of the reactor, an abnormal voltage alarm was received on |
| 125V Vital Battery Board 1-1. The immediate cause of the trip is considered |
| to be the loss of the 1-1 Vital AC Inverter which caused a feedwater |
| regulating valve to close. Subsequently, the maintenance power supply was |
| used to restore power to the 1-1 vital AC bus. |
| |
| All control rods inserted properly in response to the reactor trip. The |
| Auxiliary Feedwater (AFW) System actuated as expected. However, subsequent |
| to the initial actuation signal, additional operator action was required |
| to[manually] start 1B motor driven pump. After the 1B pump was |
| successfully started, the motor driven AFW pump 1A was secured based on |
| instrument indications available to the operating staff. After power was |
| restored to the vital AC bus, the 1A pump was subsequently started and |
| performed properly. Inspections are currently underway to determine the |
| exact cause of the loss of the 1-1 Vital Inverter and basis for the 1B pump |
| failing to [auto] start. |
| |
| No ECCS injection occurred, but the steam generator atmospheric relief |
| valves lifted and fully reseated. |
| |
| The manual actuation of the Reactor Protection System (RPS) is being |
| reported as a four hour report under 10 CFR 50.72 (b)(2)(iv). The actuation |
| of the Auxiliary Feedwater System (an engineered safety feature) is being |
| reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv). |
| |
| The plant is stable in mode 3. |
| |
| The NRC Resident Inspector was notified. |
| |
| * * * UPDATE 1244EDT ON 9/20/01 FROM CHARLES TOUCHSTONE TO S. SANDIN * * * |
| |
| The following information was received as an update: |
| |
| "This report supplements the report made by TVA at approximately 1654 on |
| September 4, 2001 - NRC Event Report 38263. |
| |
| "Description of Event: |
| |
| "While operating at 100% power, the Watts Bar Unit 1 reactor was manually |
| tripped at approximately 1305 EDT on September 4, 2001, due to the level of |
| Steam Generator (SG) Number 1 approaching the low-low level setpoint. The |
| immediate cause of the trip is considered to be the loss of the 1-I Vital AC |
| Inverter which caused the Number 1 SG feedwater regulating valve to close. |
| Subsequently, the maintenance power supply was used to restore power to the |
| 1-I Vital AC board. |
| |
| "10 CFR 50.72 Notification: |
| |
| "Initial notification to NRC of the reactor trip was made by WBN Operations |
| at 1654 EDT The manual actuation of the Reactor Protection System (RPS) was |
| reported as a four hour report under 10 CFR 50.72 (b)(2)(iv). The actuation |
| of the Auxiliary Feedwater System (an engineered safety feature) was |
| reported as an eight hour report under 10 CFR 50.72 (b)(3)(iv). This report |
| supplements the initial report and is being reported under the same |
| criteria. |
| |
| "Cause of the Event: |
| |
| "The root cause of the reactor trip was the failure of the sensing/current |
| limiting card installed in vital battery charger 6-S or its associated edge |
| connector. The failure of the component resulted in the DC output of the |
| charger rising to 209V. The high DC output voltage resulted in a high input |
| to inverters 1-I and 2-I. Inverter 1-I input and output fuses were blown, |
| while inverter 2-I continued without failure. This occurred because inverter |
| 1-I is equipped with parallel 5 and 15 KVA constant voltage transformers |
| (CVTs), which are more sensitive to high input voltage than the type used in |
| inverter 2-1 which utilizes a single 20 KVA CVT. The inverters are rated for |
| a maximum input of 140 volts. |
| |
| "Equipment Response: |
| |
| "All control rods inserted properly in response to the reactor trip. For |
| WBN, the AFW system consist of a turbine driven AFW (TDAFW) pump and two |
| trains (Train A and Train B) of motor driven AFW (MDAFW) pumps. The design |
| calls for the MDAFW arid TDAFW pumps to start due to the loss of both Main |
| Feedwater (MFW) pumps or an AMSAC actuation, In addition, the MDAFW pumps |
| will actuate on low-low S/G level in any S/G and the TDAFW pump will actuate |
| on low-low level in any two S/Gs. For this event, actuation of the TDAFW |
| pump resulted from the required logic being met for SGs Number 1 and 4. |
| Based on data obtained subsequent to the reactor trip, an auto start for the |
| TDAFW train was initiated immediately after S/G low-low level setpoints were |
| met. |
| |
| "Subsequent to the initial AFW actuation signal, additional operator action |
| was required to start the 1A-A and 1B-B motor driven pumps. For the Train A |
| MDAFW, the pump did not receive an auto start signal due to the loss of |
| Vital Board 1-I. This resulted from the power for the signal generating |
| circuit being lost with the Vital Board. The evaluation performed to |
| establish the cause for the Train B MDAFW not starting found that the |
| breaker for the pump did not close as a result of the automatic signal |
| initiated by the low SG level. The breaker was subsequently tested and |
| performed as designed and therefore, no conclusive cause was found for the |
| breaker not closing. However, it was established that the most likely cause |
| of the problem was dirty relay contacts on the 1X and 30RX relays." |
| |
| The licensee informed the NRC resident inspector. Notified R2DO(Sparks). |
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|General Information or Other |Event Number: 38300 |
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| REP ORG: CALIFORNIA RADIATION CONTROL PRGM |NOTIFICATION DATE: 09/20/2001|
|LICENSEE: STEVEN RAAS AND ASSOCIATES, INC. |NOTIFICATION TIME: 15:15[EDT]|
| CITY: WATSONVILLE REGION: 4 |EVENT DATE: 09/19/2001|
| COUNTY: STATE: CA |EVENT TIME: 16:30[PDT]|
|LICENSE#: 5214 AGREEMENT: Y |LAST UPDATE DATE: 09/20/2001|
| DOCKET: |+----------------------------+
| |PERSON ORGANIZATION |
| |JOHN PELLET R4 |
| |SUSAN FRANT NMSS |
+------------------------------------------------+ |
| NRC NOTIFIED BY: ROBERT GREGER | |
| HQ OPS OFFICER: STEVE SANDIN | |
+------------------------------------------------+ |
|EMERGENCY CLASS: NON EMERGENCY | |
|10 CFR SECTION: | |
|NAGR AGREEMENT STATE | |
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| | |
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EVENT TEXT
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| AGREEMENT STATE REPORT INVOLVING A DAMAGED TROXLER GAUGE |
| |
| "A Troxler model 3401B moisture density gauge (serial #016692) was run over |
| by earth moving/compacting equipment while the gauge was in use (i.e., the |
| source rod was extended). The source rod was bent such that the source could |
| not be retracted into the shielded position. The unshielded source contained |
| nominally 10 mCi of Cs-137. The source rod was cut by the fire department |
| with the source in a lead 'pig' provided by the UC Santa Cruz health physics |
| program. The source and the gauge housing will be sent to Troxler for |
| repairs." |
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Page Last Reviewed/Updated Wednesday, March 24, 2021
Page Last Reviewed/Updated Wednesday, March 24, 2021