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{{#Wiki_filter:May 12, 2011Braidwood, IL Purpose of this meetingTo discuss the results of a recent NRC Special InspectionMay 12, 2011 2The inspection covered circumstances at Braidwood and Byron associated with two technical issues that potentially affected both sites IntroductionsK. Steven WestDirector, Division of Reactor Projects, Region IIIEric DuncanBraidwoodandByronBranchChiefDRPMay 12, 2011 3Braidwood and Byron Branch Chief , DRPAlex GarmoeSpecial Inspection Lead Inspector, DRP Jamie BenjaminBraidwood Senior Resident Inspector, DRP What is a Special Inspection?A non-routine inspection in response to operating events or technical issuesNRC reviews aspects of the event or issue to decide whethertoperformaSpecialInspectionMay 12, 2011 4 whether to perform a Special InspectionIs the issue complex or not easily understood?Does this have the potential to affect other plants?What is the potential impact on plant safety? | |||
This inspection reviewed 2 issues 1.Air voids in the piping of a safety system (auxiliary feedwater) could prevent the system from performing its safety functionSpecial Inspection based on t he potential impa ct of the issueonplantsafetyMay 12, 2011 5 issue on plant safety 2.Braidwood Unit 2 declared an Unusual Event on March 24, 2011 due to control room alarms not workingInitial review identified a similar event in August 2010Special Inspection based on the discovery of previously unknown loss of alarms | |||
Auxiliary Feedwater VoidsAFW is a backup system that removes heat from the reactor coolant system after a reactor shutdownThe water source for AFW is a large tank called the Condensate Storage Tank (CST)May 12, 2011 7If the CST is empty or damaged, the backup water source is lake water (ess ential service water system)The voids were found in the pipes that supply water from the lake to the AFW pumps Reactor Coolant SystemWater flows through reactor fuel keeping it coolFeedwater SystemTransfers heat from Reactor Coolant System to the lake Auxiliary FeedwaterBackup to the normal feedwater system after reactor shutdownMay 12, 2011 8Lake water CST ToAFWFrom CSTMay 12, 2011 9 To AFW pumpFrom LakeVoided Pipe Auxiliary Feedwater VoidsNRC inspectors at Byron questioned whether voids in the AFW pipes could damage the pumpsBraidwood is very similar to Byron so NRC asked the same questions there as wellMay 12, 2011 10The licensee responded to the questions by providing a 1993 letter that stated the voids had been evaluatedNRC inspectors reviewed the 1993 letter and determined that it did not provide a suff icient basis that the voids would not damage the AFW pumps Auxiliary Feedwater VoidsContinued NRC questioning led to additional evaluations by Braidwood and ByronThe new evaluations also concluded that the voids would | |||
not prevent the AFW s ystem from functionin gMay 12, 2011 11pygNRC questioned the new evaluationsBraidwood requested an analysis by an independent contractor Auxiliary Feedwater VoidsBraidwood received results of the analysisAFW pumps might not operate properly with the voids presentBraidwood and Byron filled the piping voidsBdthliltflllttiiMay 12, 2011 12 B ase d on th e ana l ys i s resu lt s, f u ll-sca l e t es ti ng i s plannedTesting plans are under development | |||
Loss of Control Room AlarmsThere are several ways to monitor plant equipment in the control roomAlarms: provide light and sound indication when certain conditions are metMtdGidltiiftifMay 12, 2011 14M e t ers an d G ages: prov id e rea l-ti me i n f orma ti on o f pressures, flows, temperatures, etc.Sequence of Events Recorder: provides computer display of alarms with added detailSafety Parameters Display System: computer output of various plant conditions Alarms Meters and GagesMay 12, 2011 15 Gages SER Loss of Control Room AlarmsOn March 24 the licensee began planned maintenance on part of the control room alarm | |||
systemThatmaintenancecausedanexpectedalarmbutMay 12, 2011 16 That maintenance caused an expected alarm but operators were unable to silence or clear the alarmOperators performed a test of all alarms using test | |||
pushbuttons and received no response Braidwood Operators determined the alarms were not working and declared an Unusual Event, as requiredUnusual Event is the lowest of four emergency levelsThemaintenanceactivitywassuspendedandtheLoss of Control Room AlarmsMay 12, 2011 17 The maintenance activity was suspended and the system was restored to the original condition Loss of Control Room AlarmsInvestigation into why the alarms stopped working found that part of the alarm circ uitry was wired incorrectlyAs a result, certain maintenance activities resulted in loss of the control room alarmsMay 12, 2011 18Alarms stopped working during maintenance on March 24, 2011, August 10, 2010, and also in 2002 and 2003The alarms functioned properly at all times except during the maintenance activities | |||
Auxiliary Feedwater Voids Potential Finding: Design of a safety-related system included voids that could prevent the system from functioningInitial information indicated that the voids would affect the ability of the AFW pumps to functionMay 12, 2011 20This potential finding affects Braidwood and Byron Finding: Inadequate evaluation of the affect of voids on plant equipmentThe licensee evaluated the voids on several previous occasions and incorrectly concluded that they would not be a problemThis finding affects Braidwood and Byron Loss of Control Room Alarms Finding: Incorrect installation of wiringPart of the alarm system wiring was not installed according to design documents during initial constructionAs a result, a loss of alarms occurred at Braidwood Unit 2 in March 2011, August 2010, and several times in 2002 and 2003May 12, 2011 21 2003This finding affects only Braidwood Finding: Untimely Unusual Event declarationThe Unusual Event was not declared within the time required by the Emergency PlanTimely emergency declarations are important because they initiate the various em ergency response organizationsThis finding affects only Braidwood | |||
ConclusionsThe auxiliary feedwater voids su bject to this inspection at Braidwood and Byron have been filledThe annunciator wiring error at Braidwood has been | |||
correctedMay 12, 2011 23There was no actual safety impact from the AFW voids or loss of control room alarms on workers, the public, or the environmentBraidwood and Byron are operating safely The licensee is preparing for full-scale testing of the AFW pumps and voids, which the NRC will independently observe and evaluateThe NRC is continuin g to evaluate the safet y ConclusionsMay 12, 2011 24 gysignificance of the voids NRC Contact InformationReport an Emergency:(301) 816-5100Report a Safety Concern:(800) 695-7403 Allegation@nrc.govMay 12, 2011 25Region III Public Affairs StaffViktoria Mitlyng: 630-829-9662Prema Chandrathil: 630-829-9663NRC website: www.nrc.govNRC blog located on the NRC website May 12, 2011Braidwood, IL}} | |||
Revision as of 04:55, 8 August 2018
| ML111330674 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 05/12/2011 |
| From: | NRC/RGN-III/DRMA |
| To: | |
| References | |
| Download: ML111330674 (26) | |
Text
May 12, 2011Braidwood, IL Purpose of this meetingTo discuss the results of a recent NRC Special InspectionMay 12, 2011 2The inspection covered circumstances at Braidwood and Byron associated with two technical issues that potentially affected both sites IntroductionsK. Steven WestDirector, Division of Reactor Projects, Region IIIEric DuncanBraidwoodandByronBranchChiefDRPMay 12, 2011 3Braidwood and Byron Branch Chief , DRPAlex GarmoeSpecial Inspection Lead Inspector, DRP Jamie BenjaminBraidwood Senior Resident Inspector, DRP What is a Special Inspection?A non-routine inspection in response to operating events or technical issuesNRC reviews aspects of the event or issue to decide whethertoperformaSpecialInspectionMay 12, 2011 4 whether to perform a Special InspectionIs the issue complex or not easily understood?Does this have the potential to affect other plants?What is the potential impact on plant safety?
This inspection reviewed 2 issues 1.Air voids in the piping of a safety system (auxiliary feedwater) could prevent the system from performing its safety functionSpecial Inspection based on t he potential impa ct of the issueonplantsafetyMay 12, 2011 5 issue on plant safety 2.Braidwood Unit 2 declared an Unusual Event on March 24, 2011 due to control room alarms not workingInitial review identified a similar event in August 2010Special Inspection based on the discovery of previously unknown loss of alarms
Auxiliary Feedwater VoidsAFW is a backup system that removes heat from the reactor coolant system after a reactor shutdownThe water source for AFW is a large tank called the Condensate Storage Tank (CST)May 12, 2011 7If the CST is empty or damaged, the backup water source is lake water (ess ential service water system)The voids were found in the pipes that supply water from the lake to the AFW pumps Reactor Coolant SystemWater flows through reactor fuel keeping it coolFeedwater SystemTransfers heat from Reactor Coolant System to the lake Auxiliary FeedwaterBackup to the normal feedwater system after reactor shutdownMay 12, 2011 8Lake water CST ToAFWFrom CSTMay 12, 2011 9 To AFW pumpFrom LakeVoided Pipe Auxiliary Feedwater VoidsNRC inspectors at Byron questioned whether voids in the AFW pipes could damage the pumpsBraidwood is very similar to Byron so NRC asked the same questions there as wellMay 12, 2011 10The licensee responded to the questions by providing a 1993 letter that stated the voids had been evaluatedNRC inspectors reviewed the 1993 letter and determined that it did not provide a suff icient basis that the voids would not damage the AFW pumps Auxiliary Feedwater VoidsContinued NRC questioning led to additional evaluations by Braidwood and ByronThe new evaluations also concluded that the voids would
not prevent the AFW s ystem from functionin gMay 12, 2011 11pygNRC questioned the new evaluationsBraidwood requested an analysis by an independent contractor Auxiliary Feedwater VoidsBraidwood received results of the analysisAFW pumps might not operate properly with the voids presentBraidwood and Byron filled the piping voidsBdthliltflllttiiMay 12, 2011 12 B ase d on th e ana l ys i s resu lt s, f u ll-sca l e t es ti ng i s plannedTesting plans are under development
Loss of Control Room AlarmsThere are several ways to monitor plant equipment in the control roomAlarms: provide light and sound indication when certain conditions are metMtdGidltiiftifMay 12, 2011 14M e t ers an d G ages: prov id e rea l-ti me i n f orma ti on o f pressures, flows, temperatures, etc.Sequence of Events Recorder: provides computer display of alarms with added detailSafety Parameters Display System: computer output of various plant conditions Alarms Meters and GagesMay 12, 2011 15 Gages SER Loss of Control Room AlarmsOn March 24 the licensee began planned maintenance on part of the control room alarm
systemThatmaintenancecausedanexpectedalarmbutMay 12, 2011 16 That maintenance caused an expected alarm but operators were unable to silence or clear the alarmOperators performed a test of all alarms using test
pushbuttons and received no response Braidwood Operators determined the alarms were not working and declared an Unusual Event, as requiredUnusual Event is the lowest of four emergency levelsThemaintenanceactivitywassuspendedandtheLoss of Control Room AlarmsMay 12, 2011 17 The maintenance activity was suspended and the system was restored to the original condition Loss of Control Room AlarmsInvestigation into why the alarms stopped working found that part of the alarm circ uitry was wired incorrectlyAs a result, certain maintenance activities resulted in loss of the control room alarmsMay 12, 2011 18Alarms stopped working during maintenance on March 24, 2011, August 10, 2010, and also in 2002 and 2003The alarms functioned properly at all times except during the maintenance activities
Auxiliary Feedwater Voids Potential Finding: Design of a safety-related system included voids that could prevent the system from functioningInitial information indicated that the voids would affect the ability of the AFW pumps to functionMay 12, 2011 20This potential finding affects Braidwood and Byron Finding: Inadequate evaluation of the affect of voids on plant equipmentThe licensee evaluated the voids on several previous occasions and incorrectly concluded that they would not be a problemThis finding affects Braidwood and Byron Loss of Control Room Alarms Finding: Incorrect installation of wiringPart of the alarm system wiring was not installed according to design documents during initial constructionAs a result, a loss of alarms occurred at Braidwood Unit 2 in March 2011, August 2010, and several times in 2002 and 2003May 12, 2011 21 2003This finding affects only Braidwood Finding: Untimely Unusual Event declarationThe Unusual Event was not declared within the time required by the Emergency PlanTimely emergency declarations are important because they initiate the various em ergency response organizationsThis finding affects only Braidwood
ConclusionsThe auxiliary feedwater voids su bject to this inspection at Braidwood and Byron have been filledThe annunciator wiring error at Braidwood has been
correctedMay 12, 2011 23There was no actual safety impact from the AFW voids or loss of control room alarms on workers, the public, or the environmentBraidwood and Byron are operating safely The licensee is preparing for full-scale testing of the AFW pumps and voids, which the NRC will independently observe and evaluateThe NRC is continuin g to evaluate the safet y ConclusionsMay 12, 2011 24 gysignificance of the voids NRC Contact InformationReport an Emergency:(301) 816-5100Report a Safety Concern:(800) 695-7403 Allegation@nrc.govMay 12, 2011 25Region III Public Affairs StaffViktoria Mitlyng: 630-829-9662Prema Chandrathil: 630-829-9663NRC website: www.nrc.govNRC blog located on the NRC website May 12, 2011Braidwood, IL