Configuration Management Benchmarking Group Conference

June 6 – 9, 2004 Kansas City, MO © 2004 CMBG

PAKS EVENT LESSONS LEARNED

Presented By:

Chuck CastoU.S. Nuclear Regulatory

Commission

AgendaAgenda

• BackgroundBackground

• Description of the eventDescription of the event

• Investigation of the eventInvestigation of the event

• Mission InsightsMission Insights

• Pictures of the damaged fuelPictures of the damaged fuel

BackgroundBackground

• PAKS, 4-unit VVER-440 supplies 40% PAKS, 4-unit VVER-440 supplies 40% of Hungary’s electricityof Hungary’s electricity

• Neglected VVER-440 aging SG feed Neglected VVER-440 aging SG feed water sparger operating experience water sparger operating experience

• By 2000, four of six SGs for U-2 could By 2000, four of six SGs for U-2 could not be ignored (had to replace all 4 in not be ignored (had to replace all 4 in one outage)one outage)

• Replacement activities hampered by Replacement activities hampered by high radiationhigh radiation

BackgroundBackground (cont’d) (cont’d)

• SG chemical decon introduced crud SG chemical decon introduced crud deposits into RCSdeposits into RCS

• Eventually three units derated (84-98%)Eventually three units derated (84-98%)

• Core replacement did not helpCore replacement did not help

• Regulator wanted problem solvedRegulator wanted problem solved

2001

1999

2000

UnitUnit 1 1

Magnetite Magnetite deposits in the deposits in the primary circuitprimary circuit

Background Background (cont’d)(cont’d)

Power loss caused by Power loss caused by MagnetiteMagnetite deposition in deposition in the primary circuitthe primary circuit

100

95

85

80

90

2. blokki villamos teljesítmény menet az elvileg vihető teljesítmény százalékában

90%

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

05.24.

06.03.

06.13.

06.23.

07.03.

07.13.

07.23.

08.02.

08.12.

08.22.

09.01.

09.11.

09.21.

10.01.

10.11.

10.21.

10.31.

11.10.

11.20.

11.30.

12.10.

12.20.

12.30.

01.09.

01.19.

1. blokki villamos teljesítmény menet az elvileg vihető teljesítmény százalékában

90%

91%

92%

93%

94%

95%

96%

97%

98%

99%

100%

08.12. 08.22. 09.01. 09.11. 09.21. 10.01. 10.11. 10.21. 10.31. 11.10. 11.20. 11.30. 12.10. 12.20. 12.30. 01.09. 01.19. 01.29.

Unit 1 Unit 2

3. blokki villamos teljesítmény menet az elvileg vihető teljesítmény százalékában

76%

77%

78%

79%

80%

81%

82%

83%

84%

85%

86%

87%

88%

89%

90%

91%

92%

93%

10.01. 10.08. 10.15. 10.22. 10.29. 11.05. 11.12. 11.19. 11.26. 12.03. 12.10. 12.17. 12.24. 12.31. 01.07. 01.14. 01.21. 01.28.

Unit 3

p2

új paraméterek

új paraméterekp2

p2

new parameters

new parametersp2

Reactor scram in December

January 2003.: Reactor shutdown(economic reason)power

scale

92%

94%94%

BackgroundBackground (cont’d)(cont’d)

• ““Fuel Deposit Team” created to look for Fuel Deposit Team” created to look for solutionssolutions

• Two options – internal and external fuel Two options – internal and external fuel cleaningcleaning

• Vendor worked on internal cleaning SE Vendor worked on internal cleaning SE for months prior to the Unit 2 outagefor months prior to the Unit 2 outage

• At last minute changed option to At last minute changed option to externalexternal cleaningcleaning

BackgroundBackground (cont’d)(cont’d)

• Previous experience of external Previous experience of external cleaning seven “cool” assemblies at a cleaning seven “cool” assemblies at a time (total 150 assemblies)time (total 150 assemblies)

• Design expanded to 30 assemblies “hot”Design expanded to 30 assemblies “hot”

• The design as considered as “like-for-The design as considered as “like-for-like”like”

• License application submitted to License application submitted to regulator for “license in principle”regulator for “license in principle”

System ConfigurationSystem Configuration

Unit 2Unit 2: : LLocation of ocation of CCleaning leaning SSystemystem

cleaningtank

reactor cleaning equipmentRefueling machine

Interimcover

Pool No. 1.

The EventThe Event

• Unit 2 outage - April 4 - 10, 2003, 5 Unit 2 outage - April 4 - 10, 2003, 5 loads of fuel cleaned (some hot, loads of fuel cleaned (some hot, some cool)some cool)

• Sixth load was cleaned April 10, Sixth load was cleaned April 10, completed at 4:00p.m. but crane not completed at 4:00p.m. but crane not availableavailable

• Shut down of cleaning system and Shut down of cleaning system and tank remained sealedtank remained sealed

The EventThe Event (cont’d)

• 10p.m. reactor building high radiation10p.m. reactor building high radiation

• 2:00a.m. hydraulic lock opened and lid 2:00a.m. hydraulic lock opened and lid releasedreleased

• Sharp increase in radioactivitySharp increase in radioactivity

• Classified INES level 2Classified INES level 2

• April 16, video inspection revealed major April 16, video inspection revealed major damage – re-classified INES damage – re-classified INES level 3level 3

End of cleaning 16:00

Events during the incident

Startup of submersible pump 16:40

Discharge of water 16:56

Spent fuel pool water level increase 19:20

Increase of KR-85 activity in the cleaning system 21:50 Supervisor ordered to leave the R. hall 23:30

Venting fans started: 23:45

Hydraulic lock open, bubble outbursts: 02:15

Cover lifting failed: 04:20

Area of spent f.p.: 12 mSv/h 02:45

Rad Level MBq

Investigation of the eventInvestigation of the event

• The Paks plant submitted The Paks plant submitted anan investigation investigation report on report on May May 10 to the HAEA10 to the HAEA

• The report was published on the plant’s The report was published on the plant’s homepage also in Hungarian and English homepage also in Hungarian and English languages (www.atomeromu.hu) languages (www.atomeromu.hu)

• Framatome completed an investigation reportFramatome completed an investigation report

• The HAEA final investigation report The HAEA final investigation report waswas issued at the end of Mayissued at the end of May

• HAEA requested a review by the IAEAHAEA requested a review by the IAEA

Mission InsightsMission Insights

• Time pressureTime pressure

• Heavy reliance on contractorHeavy reliance on contractor

• Novel technologyNovel technology

• Inadequate safety review Inadequate safety review

Mission InsightsMission Insights (cont’d)(cont’d)

• Inadequate safety reviewInadequate safety review

Inaccurate bypass flow calculationsInaccurate bypass flow calculations

Simple thermodynamic calculationSimple thermodynamic calculation

Outlet connection at tank bottomOutlet connection at tank bottom

Undersized submersible pumpUndersized submersible pump

Relied upon 12 min 9 sec time to boilingRelied upon 12 min 9 sec time to boiling

Single failure criteria not metSingle failure criteria not met

NoNo internal instrumentationinternal instrumentation

Mission InsightsMission Insights (cont’d)(cont’d)

• Fuel deposit teamFuel deposit team Not budgetedNot budgeted Consisted mainly of managersConsisted mainly of managers Solving the problem was the priority not the Solving the problem was the priority not the

technique (subcommittee)technique (subcommittee) Managers from independent groups Managers from independent groups

(QA/NAS)(QA/NAS) During safety reviews, same line managers During safety reviews, same line managers

processed the safety evaluationprocessed the safety evaluation

Mission InsightsMission Insights (cont’d)

• Safety evaluation assumptions not Safety evaluation assumptions not translated into design, operating translated into design, operating procedures and training for workers procedures and training for workers (OJT)(OJT)

• Inadequate independent safety review Inadequate independent safety review by PAKS by PAKS

• Safety Culture assessments by HAEA Safety Culture assessments by HAEA were not adequately addressedwere not adequately addressed

Mission InsightsMission Insights (cont’d)(cont’d)

• Inadequate root cause evaluation by Inadequate root cause evaluation by PAKS/HAEAPAKS/HAEA

• Complex HAEA licensing processComplex HAEA licensing process

• HAEA safety review process did not HAEA safety review process did not meet international standardsmeet international standards

• Failure to verify contractor’s claimsFailure to verify contractor’s claims

• Inadequate technical content of licensing Inadequate technical content of licensing packagepackage

Mission InsightsMission Insights (cont’d)(cont’d)

• Regulator failed to understand Regulator failed to understand relationships between cleaning relationships between cleaning modification and safetymodification and safety

• INES classification changes INES classification changes diminished public confidencediminished public confidence

AdditionalAdditional Configuration Configuration Management IssuesManagement Issues

• Five types of licenses Five types of licenses Principle modificationPrinciple modification

Fabrication and importFabrication and import

InstallationInstallation

Modification (includes fab, import and Modification (includes fab, import and installationinstallation

OperationsOperations

• License type determined by “safety License type determined by “safety significance” and “safety class” significance” and “safety class” (design criteria) in that order(design criteria) in that order

• Reverse logic from the IAEA 1999 Reverse logic from the IAEA 1999 standardstandard

• Considered cleaning tank a “cask” Considered cleaning tank a “cask” but did not follow licensing process but did not follow licensing process for a caskfor a cask

Additional Configuration Additional Configuration Management IssuesManagement Issues (cont’d)

Additional Configuration Additional Configuration Management IssuesManagement Issues (cont’d)

• Content of Licenses not specifiedContent of Licenses not specified

• For the tank modification, regulator For the tank modification, regulator accepted an incomplete license accepted an incomplete license packagepackage

Additional Configuration Additional Configuration Management IssuesManagement Issues (cont’d)

• Specific plant issues:Specific plant issues: Did not process concerns for undersized Did not process concerns for undersized

pumppump Did not use remote verification of fuel Did not use remote verification of fuel

assembly alignmentassembly alignment Did not install dedicated craneDid not install dedicated crane Did not provide redundant power supplies Did not provide redundant power supplies

for cooling pumpfor cooling pump Did not notify of past delays in Did not notify of past delays in

opening the tankopening the tank