Information Notice 2004-01, Auxiliary Feedwater Pump Recirculation Line Orifice Fouling - Potential Common Cause Failure: Difference between revisions
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| issue date = 01/21/2004 | | issue date = 01/21/2004 | ||
| title = Auxiliary Feedwater Pump Recirculation Line Orifice Fouling - Potential Common Cause Failure | | title = Auxiliary Feedwater Pump Recirculation Line Orifice Fouling - Potential Common Cause Failure | ||
| author name = Beckner W | | author name = Beckner W | ||
| author affiliation = NRC/NRR/DIPM | | author affiliation = NRC/NRR/DIPM | ||
| addressee name = | | addressee name = | ||
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| docket = 05000266, 05000301 | | docket = 05000266, 05000301 | ||
| license number = DPR-024 | | license number = DPR-024 | ||
| contact person = Dozier J | | contact person = Dozier J, NRR/IROB 415-1014 | ||
| document report number = IN-04-001 | | document report number = IN-04-001 | ||
| document type = NRC Information Notice | | document type = NRC Information Notice |
Revision as of 04:52, 14 July 2019
ML040140460 | |
Person / Time | |
---|---|
Site: | Point Beach |
Issue date: | 01/21/2004 |
From: | Beckner W NRC/NRR/DIPM |
To: | |
Dozier J, NRR/IROB 415-1014 | |
References | |
IN-04-001 | |
Download: ML040140460 (9) | |
UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555January 21, 2004NRC INFORMATION NOTICE 2004-01:AUXILIARY FEEDWATER PUMPRECIRCULATION LINE ORIFICE FOULING -
POTENTIAL COMMON CAUSE FAILURE
Addressees
- All holders of operating licenses or construction permits for nuclear power reactors, exceptthose that have permanently ceased operations and have certified that fuel has been
permanently removed from the reactor.
Purpose
- The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to informaddressees of the potential common cause failure of auxiliary feedwater pumps because of
fouling of pump recirculation line flow orifices. It is expected that recipients will review the
information for applicability to their facilities and consider actions, as appropriate, to avoid
similar problems. However, suggestions in this information notice are not NRC requirements;
therefore no specific action or written response is required.Background
- Point Beach Nuclear Plant (PBNP) is a two unit site. Each unit has a turbine-driven AFW pump(pumps 1P29 and 2P29) which can supply water to both steam generators. Additionally, the
plant has two motor-driven AFW pumps (pumps P38A and P38B) each of which can be aligned
to a steam generator in each unit. Each pump has a recirculation line back to the condensate
storage tanks (CSTs) to ensure minimum flow to prevent hydraulic instabilities and dissipate
pump heat. The recirculation line contained a pressure reducing, flow restricting orifice. An
arrow is pointing to the recirculation flow restricting orifice (RO) in the major flow path AFW
diagram provided in Figure 1 and a picture of the RO is provided in Figure 2. The RO used a multi-stage, anti-cavitation trim package installed in the body of a globe valve tolimit flow. This style of orifice or flow restrictor was installed in the AFW recirculation lines at
PBNP in the past few years to eliminate cavitation caused by the old orifices. This type of flow
restrictor used very small channels and holes in each stage combined with a tortuous path to
limit flow and prevent cavitation. Figure 1. AFW System - Major Flow PathsFigure 2. Recirculation Flow Restricting Orifice
Description of Circumstances
- On October 24, 2002, during post-maintenance surveillance testing of the P38A motor-drivenAFW pump at PBNP, the licensee observed AFW recirculation line flow to be 64.5 gpm, which
was less than the 70 gpm acceptance criterion. Normal flow through the recirculation line was
75 gpm. Suspecting instrument error, plant personnel vented and recalibrated the flow
instrument. The P38A AFW pump was then started and tested again; however, the observed
recirculation flow was essentially unchanged. Following that test run, the recirculation flow
orifice was removed and inspected. After removal of the orifice internals, partial blockage was observed in 24 of the 54 holes in theoutermost sleeve. No particles were found on any of the inner sleeves. Samples of the
particles removed from the orifice were retained for analysis. A boroscope inspection of the
recirculation piping at the orifice location revealed no evidence of debris. Following cleaning
and reassembly, the orifice was reinstalled and the P38A AFW pump was successfully retested.
Testing was successfully completed on the other three AFW pumps to verify acceptable
recirculation flow by October 25, 2002.During the next several days, PBNP personnel evaluated the implications of the orifice pluggingevent. An apparent cause evaluation was initiated with specific directions to assess and
evaluate the potential extent of condition. An action plan was developed to identify the source
of the debris found in the orifice and to determine what other testing or flushing would be
required to assure that future plugging did not occur. As the investigations continued, questions developed concerning the operability of the AFWsystem while supplied by its safety-related water supply, the service water (SW) system.
Although the service water supply was provided through a basket strainer, it was recognized
that the strainer mesh was larger than the much finer RO channel holes and could allow debris
to pass that could clog the RO. These concerns culminated in a meeting on October 29, 2002, at which PBNP personnel concluded that there was no longer a reasonable assurance that
operation of the AFW system using its safety-related suction source of service water would not
result in potential AFW recirculation line orifice clogging.In a worst case scenario, Point Beach personnel determined that it may be possible, althoughunlikely, for each of the four flow control orifices, each associated with one of the four AFW
pumps, to restrict the flow through the associated recirculation line. Under such conditions, it
was hypothesized that if the discharge valves for the AFW pumps were throttled, adequate flow
might be unavailable through the recirculation line and pump damage could occur due to
overheating.On October 29, 2002, all four AFW pumps were declared inoperable. Both units entered theirtechnical specification action statements and required actions which directs immediate action to
restore an AFW system to operable status. Immediate corrective actions consisted of briefing
the on-shift crew of the potential consequences of restricted recirculation flow and initiating
procedure changes. The operators were also directed to secure a running AFW pump if the
pump discharge flows should be decreased to less than 50 gpm for the motor-driven pumps or
75 gpm for the turbine-driven pumps. These flow rates were substantially above the point at
which pump damage could occur. Information tags were placed at the AFW pump flow
indicators on the main control boards to convey that information. With these administrative
controls in place, operations declared the AFW system operable, about four hours after the pumps had been declared inoperable. An incident investigation was initiated to collect andconfirm the facts of this event description beginning with the discovery of the P-38A AFW pump
degraded recirculation flow during post-maintenance testing and concluding with the decision to
declare the AFW system inoperable.In accordance with 10 CFR 50.72(b)(3)(v), an eight-hour ENS notification (EN #39330) wasmade on October 29, 2002. The LER is available in ADAMS (Accession Number
ML032890115).A PBNP multi-discipline event resolution team was formed to identify and resolve the issuesassociated with the discovery of this condition. Activities included initiation of a root cause
evaluation (RCE) to determine the root and contributing causes for the postulated
common-mode failure that would render all AFW pump recirculation lines with restricted
flow rates. The RCE concluded that this event had a direct root cause and an organizational
root cause. The direct root cause was the failure by design engineering to properly evaluate
the potential for orifice plugging within the design process. Instead of revisiting the design for
adequacy and evaluating the potential for plugging of the proposed orifices within the rigor of
the design process, the 10 CFR 50.59 safety evaluation was revised to justify the proposed
design. The organizational root cause was less than adequate management oversight of the
design modification process. Also, in January and February 2003, a specially fabricated orifice was tested at a contractorlaboratory in an effort to determine a plugging probability with service water. Definitive testing
occurred on February 21 when a debris mixture of sand, silt, and zebra mussel shells, representative of what would exist in the Point Beach SW system, was injected into a closed
loop configuration of piping, an orifice, and a centrifugal pump. The orifice plugged in much
less than one minute after the mixture was injected into the loop. These results were contrary
to those of a previously performed computational particle fouling model analysis that indicated
that plugging was unlikely because of the particle size distribution of debris in SW and the
shear forces in the holes and channels of the orifices developed with the minimum flow required
through the orifice for pump cooling.
Discussion
- A special inspection was conducted by the NRC to evaluate the facts, circumstances, andlicensee actions, and documented in NRC Inspection Report 50-266/02-15 and 50-301/02-15 (Accession Number ML030920128). This issue was determined to be of Yellow risk
significance for Unit 1, an issue with substantial importance to safety, and Red risk significance
for Unit 2, an issue of high importance to safety. The difference in significance between the
Units was a result of the longer period of time that the AFW recirculation line pressure reduction
orifices were installed in Unit 2.
(See Final Determination Letter, dated December 11, 2003,Accession Number ML033490022). This information notice requires no specific action or written response. If you have anyquestions regarding the information notice, please contact the technical contacts listed below or
the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./Original signed by: Terrence Reis/William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor RegulationTechnical contacts:Jerry Dozier, NRRPaul Krohn, Region III(301) 415-1014(920) 755-2309 E-mail: jxd@nrc.govE-mail: pgk1@nrc.govAttachment: List of Recently Issued NRC Information Notices This information notice requires no specific action or written response. If you have anyquestions regarding the information notice, please contact the technical contacts listed below or
the appropriate Office of Nuclear Reactor Regulation (NRR) project manager./Original signed by: Terrence Reis/William D. Beckner, Chief
Reactor Operations Branch
Division of Inspection Program Management
Office of Nuclear Reactor RegulationTechnical contacts:Jerry Dozier, NRRPaul Krohn, Region III(301) 415-1014(920) 755-2309 E-mail: jxd@nrc.govE-mail: pgk1@nrc.govAttachment: List of Recently Issued NRC Information NoticesDISTRIBUTION
- ADAMS
IN FileDOCUMENT NAME: G:\RORP\OES\Staff Folders\Dozier\InformationNoticeonPointBeachOrifice.wpdAdams Accession No.:ML040140460OFFICEOES:IROB:DIPMTech EditorDLPMSRI:RIIINAMEIJDozierPKleeneDWSpauldingPKrohnDATE12/03/200312/09/200301/14/200401/13/2004OFFICEBC:RIIISC:OES:IROB:DIPMC:IROB:DIPMNAMEAVegelTReisWDBecknerDATE01/13 /200401/14/200401/21/2004OFFICIAL RECORD COPY
______________________________________________________________________________________OL = Operating License
CP = Construction PermitAttachment LIST OF RECENTLY ISSUEDNRC INFORMATION NOTICES
_____________________________________________________________________________________InformationDate of
Notice No. SubjectIssuanceIssued to
_____________________________________________________________________________________2002-26, Sup 2Additional Failure of SteamDryer After A Recent Power
Uprate01/09/2004All holders of an operating licenseor a construction permit for
nuclear power reactors, except
those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.2003-11, Sup 1Leakage Found on Bottom-Mounted Instrumentation
Nozzles01/08/2004All holders of operating licensesor construction permits for
nuclear power reactors, except
those that have permanently
ceased operations and have
certified that fuel has been
permanently removed from the
reactor.2003-22Heightened Awareness forPatients Containing Detectable
Amounts of Radiation from
Medical Administrations12/09/2003All medical licensees and NRCMaster Materials License medical
use permittees.2003-21High-Dose-Rate-Remote-Afterloader Equipment Failure11/24/2003All medical licensees.2003-20Derating Whiting CranesPurchased Before 198010/22/2003All holders of operating licensesfor nuclear power reactors, except those who have
permanently ceased operations
and have certified that fuel has
been permanently removed from
the reactor vessel; applicable
decommissioning reactors, fuel
facilities, and independent spent
fuel storage installations.Note:NRC generic communications may be received in electronic format shortly after they areissued by subscribing to the NRC listserver as follows:To subscribe send an e-mail to <listproc@nrc.gov >, no subject, and the followingcommand in the message portion:subscribe gc-nrr firstname lastname