05000266/LER-2005-004, Re Auxiliary Feedwater Recirculation Capability in Local Operating Mode
| ML052630287 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 09/16/2005 |
| From: | Koehl D Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NRC 2005-0120 LER 05-004-00 | |
| Download: ML052630287 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(B) |
| 2662005004R00 - NRC Website | |
text
Committed to Nuclear Excellene Point Beach Nuclear Plant Operated by Nuclear Management Company, LLC September 16, 2005 NRC 2005-0120 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555 Point Beach Nuclear Plant Units 1 and 2 Docket Nos. 50-266 and 50-301 License Nos. DPR-24 and DPR-27 Licensee Event Report 266/301/2005-004-00 Auxiliary Feedwater Recirculation Capability in Local Operating Mode Enclosed is Licensee Event Report (LER) 266/301/2005-004-00 for the Point Beach Nuclear Plant Units 1 and 2. LER 266/301/2005-004-00 describes the discovery that the mini-recirculation valves for the motor-driven auxiliary feedwater (AFW) pumps would not automatically open in the local mode of operation. If the pumps were started in this mode, pump damage could occur due to lack of cooling flow though the pump prior to aligning a flow path to a steam generator. This condition is reportable in accordance with 10 CFR 50.73(a)(2)(ii)(B).
This submittal contains no new or revised regulatory commitments.
Dennis L. Koehl Site Vice-President, Point Beach Nuclear Plant Nuclear Management Company, LLC Enclosure cc:
Administrator, Region l1l, USNRC Project Manager, Point Beach Nuclear Plant, USNRC Resident Inspector, Point Beach Nuclear Plant, USNRC PSCW Sk 6590 Nuclear Road
- Two Rivers, Wisconsin 54241 Telephone: 920.755.2321
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LICENSEE EVENT REPORT (LER)
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FACILITY NAME (1)
DOCKET NUMBER (2)
PAGE (3)
POINT BEACH NUCLEAR PLANT UNIT 1 05000266 1 of 4 TITLE (4)
AUXILIARY FEEDWATER RECIRCULATION CAPABILITY IN LOCAL OPERATING MODE EVENT DATE (5) l LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8) 1AI RC FACILITY NAME DOCKET NUMBER MO DAY YEAR YEAR NUMBER NO MO DAY YEAR PT BEACH UNIT 2 05000301 07 20 2005 2005 -- 004 00 09 16 2005 FACILITY NAME DOCKET NUMBER OPERATING I
THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR U: (Check all that apply) (11)
MODE (9) 20.2201(b) 20.2203(a)(3)(i)
X 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)
POWER 100%
20.2201 (d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)
LEVEL (10) 20.2203(a)(1) 50.36(c)(1)(i)(A) 50.73(a)(2)(iv)(A) 73.71 (a)(4) 202203(a)(2)(i) 50.36(c)(1)(ii)(A) 50.73(a)(2)(v)(A) 73.71 (a)(5) 20.2203(a)(2)(ii)
=
50.36(c)(2) 50.73(a)(2)(v)(B)
OTHER 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C)
Specify in Abstract below or In
_202203(a)(2)(iv) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(D) 20.2203(a)(2)(v) 50.73(a)(2)(i)(B) 50.73(a)(2)(vii) 20.2203(a)(2)(vi) 50.73(a)(2)(i)(C) 50.73(a)(2)(viii)(A) 20.2203(a)(3)(i) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(B) l_-_;__:._c-:_i;___
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (Include Area Code)
Eric A. Schmidt I
920-755-6265 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)
MANU-REPORTABLE MANU-REPORTABLE
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX
CAUSE
SYSTEM COMPONENT FACTURER TO EPIX SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR
____________________________________________________x SUBMISSION YES (If yes, complete EXPECTED SUBMISSION DATE).
X NO DATE (1 5)
I____
ABSTRACT While performing a test to validate proper operation of a local control station for auxiliary feedwater (AFW), a deficiency was discovered in Procedure AOP-10, "Control Room Inaccessibility", which could have potentially led to damage of a motor-driven AFW pump. AOP-1 0 provides direction for evacuation of the control room for reasons other than a fire as postulated in 10 CFR 50, Appendix R. One purpose of the procedure is to maintain the plant in safe shutdown condition by locally controlling the turbine-driven AFW pumps until control room accessibility is restored. In the event that supplemental AFW flow was required, AOP-1O directed the operator to place the motor-driven AFW pump in local control and start the pump. The sequence of procedure steps in AOP-1 0 did not account for the local control station circuitry isolating the control function of the AFW flow recirculation valve. This recirculation flowpath provides minimum required flow for cooling the motor-driven AFW pumps when discharge flow is below the recommended flow rate. Consequently, if a motor-driven AFW pump were to be started from the local control station, a flowpath would not exist until a discharge valve was opened. Once the procedure deficiency was identified, operators were briefed on the condition and the procedure was revised to correct it. This procedure deficiency did not result in any damage to the AFW pumps.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
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YEA SEQUENTIAL I
=REISINI POINT BEACH NUCLEAR PLANT UNIT 1 05000266 l YAR l NNUMBER NUMER 1, 2 of 4 2005 004 00 ff TEXT (If more space Is required, use additional copies of NRC Forn 366A) (17)
Event Description
On July 20, 2005, at 0451 CDT, with both Point Beach Units at normal full power operation, a test start of motor-driven [MO] auxiliary feedwater (AFW) [BA] pumps [P] P-38A and P-38B was being performed from the local control station. During this activity, it was discovered that valve AF-4007, the recirculation valve [FCV] for P-38A, would not automatically open in the local mode of operation. The test was suspended, the pump declared out of service, and the system was put in a safe condition. The recirculation valve provides a minimum flow path for pump cooling to prevent pump damage when forward flow is less than a prescribed value. As this test was being performed to validate steps in Procedure AOP-1 0, "Control Room Inaccessibility', it was recognized that the procedural steps were not adequate. The procedure did not address manually opening the recirculation valve prior to local pump start. This was of concern because the control function circuitry for the AFW flow recirculation valve is isolated when the pump is operated from the local control station. Consequently, pump damage could occur due to lack of cooling flow though the pump prior to aligning a flow path into a steam generator. This condition is also applicable to valve AF-4014, the recirculation valve for P-38B motor-driven AFW pump. Therefore, this condition is being reported under 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition that significantly degraded plant safety. This condition was previously reported via the emergency notification system (Event Number 41885) in accordance with 10 CFR 50.72(b)(3)(v)(D).
Controlling motor-driven AFW pumps P-38A and P-38B from a safe shutdown local control condition would only be performed for conditions where steam generator level could not be normally maintained using turbine-driven [TRB] AFW pumps 1 P-29 and 2P-29 and only during those times when the control room was required to be evacuated for reasons other than a fire postulated 10 CFR 50 Appendix R. The station has taken compensatory actions to brief operators about the condition and AOP-1 0 has been revised. The revised procedure directs operators to open the discharge motor operated valve and the recirculation valve prior to a local start of motor-driven AFW pump P-38A or P-38B.
The associated recirculation valve will automatically operate when motor-driven AFW pumps P-38A or P-38B are started from the control room. Follow up testing has verified P-38A AFW pump operability.
Component and system Description:
The AFW system automatically supplies feedwater to the steam generators to remove decay heat from the reactor coolant system (RCS) upon the loss of normal feedwater supply. The AFW pumps provide cooling water to the steam generator secondary side via connections to the main feedwater (MFW) piping inside containment. The steam generators function as a heat sink for core decay heat.
The AFW system consists of three independent pump systems; two motor-driven AFW pumps which are shared between the two units, and one dedicated steam turbine-driven pump per unit. Each motor-driven pump is capable of providing 100% of the design AFW flow rate, while the turbine-driven pump is capable of providing 200% of the design flowrate. Each pump is provided with a recirculation line to maintain pump discharge flow above the minimum required flow rate for pump cooling. Each AFW pump system can be manually aligned to take suction from the service water system. The normal source of water for the AFW pumps is the condensate storage tank (CST) and the safety related supply is the service water (SW) system.
Motor operated valves are provided to allow the suction supply for the AFW pumps to be manually transferred to the SW system.U.S. NUCLEAR REGULATORY COMMISSION (1.2001)
LICENSEE EVENT REPORT (LER)
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ISEQUENTIAL I REVISION POINT BEACH NUCLEAR PLANT UNIT 1 05000266 YEAR NUMBER RNUMBER 3 of 4 2005 004 00 TEXT (If more space is required, use additional copies of NRC Foir 366A) (17)
Each motor-driven AFW pump is powered from an independent safeguards power supply and feeds one steam generator in each unit. AFW pump P-38A supplies AFW flow to the Unit I and Unit 2 A steam generators, while AFW pump P-38B supplies the Unit I and Unit 2 B steam generators. Each motor-driven AFW pump's discharge header contains two normally closed automatic motor operated valves. Upon receipt of an AFW actuation signal, the discharge valve associated with the affected unit receives an automatic open signal and the discharge valve associated with the unaffected unit receives an automatic close signal. This feature will ensure that 100% of the motor-driven AFW pump flow will be delivered to the affected unit, thereby, assuring that the accident analysis flowrates are met. Each motor-driven AFW pump is also equipped with a backpressure control valve, which is designed to preclude the motor-driven AFW pump from tripping on an overcurrent condition at low steam generator pressures.
Each unit's turbine-driven AFW pump receives steam from both steam generator main steam lines upstream of the main steam isolation valves. Each of the two steam feed lines can supply 100% of the required steam flow to the turbine-driven AFW pump.
The AFW system actuates automatically in response to specific plant conditions. The AFW system is capable of supplying feedwater to the steam generators during normal unit startup, shutdown, and hot standby conditions.
One pump at full flow is sufficient to remove decay heat and cool the unit to residual heat removal (RHR) entry conditions.
A remote/local switch, start/stop pushbuttons, and power light (breaker or starter closed) are available in the event that local operation of the equipment is desired. PBNP FSAR 7.5-13 states that local stop/start pushbutton motor control stations are provided with a selector switch that will transfer control of the switchgear from the control room to local control and initiate an annunciator in the control room. The control function circuitry for the AFW flow recirculation valve is isolated when the pump is operated from the local control station. Westinghouse letter dated March 15, 1968, specifies the design of the local control stations and the requirement for its close proximity to the pumps.
Safety Significance
The entry conditions for Procedure AOP-10, "Control Room Inaccessibility", are toxic gas in the control room, confirmed bomb threat in or adjacent to the control room, or other life threatening conditions as determined by the Shift Manager necessitating evacuation of the control room. Maintaining the plant in safe shutdown until control room access is restored is accomplished through operation of the turbine-driven AFW pumps.
Procedures direct local starting of a motor-driven AFW pump only in the event that supplemental AFW flow were to be needed. Since such an event is beyond the range of design basis accidents analyzed in the PBNP FSAR, no additional failure is postulated to occur. Therefore, a condition that would necessitate starting of a motor-driven AFW pump is unlikely. This contingency action is provided in procedures as a defense in depth. Consequently, the safety significance of this reported condition is considered to be low.
NMC further concluded that this condition did not constitute a loss of any safety function; therefore, the failure of the recirculation valve to open from the local control station did not constitute a safety system functional failure.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
TEXT CONTINUATION FACILITY NAME (1)
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POINT BEACH NUCLEAR PLANT UNIT 1 05000266 YEAR lUENTRL REVSION 4 of 4 2005 004 00 TEXT (If more space Is required, use additional copies of NRC Form 366A) (17)
Cause
The cause of this condition was a deficient procedure caused by inadequate review of procedure AOP-10 during its development. The sequence of procedure steps in AOP-10 did not account for the fact that the control function circuitry for the AFW flow recirculation valve is isolated when the pump is operated from the local control station. Requirements for verification and validation of AOP-10 development in 2002 failed to include engineering review of the new procedure. Additionally, there was an incorrect statement in the supporting documentation that indicated all of the actions contained in this new procedure were already specified in existing plant procedures.
Corrective Action
AOP 10 was revised to ensure that a flowpath is established for the motor-driven AFW pump prior to starting the pump from the local control station. This was done by directing that the discharge valve and the recirculation valve be opened prior to placing the motor-driven AFW pump in local control. Operators were briefed about this condition.
The AFW test procedure for local control testing was revised to include direction to open the recirculation valve prior to starting the pump from the local control station.
The EOP/AOP Verification and Validation process has been improved since the initial revision of this procedure. Significant relevant changes include the addition of additional engineering reviews during revisions to abnormal operating procedures (AOPs) and emergency operating procedures (EOPs).
Plant procedures and documents were reviewed to document the basis regarding the use of the local control stations for the motor-driven AFW pumps.
Previous Similar Events
A review of recent LERs (past three years) identified one event that involved a potential for failure of AFW associated with operation on minimum recirculation flow:
LER Number Title 266-2002-003-00/01 Possible Common Mode Failure of AFW due to Partial Clogging of Recirculation Orifices