ML061790481

03/09/2006 - RIC 2006 Presentation - Th5D - T. Preston Gillespie, Jr - Digital Instrumentation and Control-Diversity and Defense-in-Depth for Digital Systems

ML061790481
Person / Time
Site:	Oconee
Issue date:	03/09/2006
From:	Gillespie T Duke Power Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML061790481 (19)

Text

2006 Regulatory Information Conference Session TH5DDigital Instrumentation and Control Oconee Nuclear Station's Diver sity and Defense in Depth Analysis for the Digital RPS / ES Upgrade T. Preston Gillespie, Jr.

Reactor and Electrical Syst ems Engineering Manager Duke Power Company March 9, 2006 Diversity and Defense in Depth Analysis Historical Perspective*In 2001, ONS elected to replace its originally installed analog RPS/ES System with a digital based system*Framtome's Teleperm XS operating system was chosen as the platform for the new system.*This platform is also utilized for the site's emergency power supply's governor system.

2 Diversity and Defense in Depth Analysis BTP-19 Requirements*Analyze UFSAR Transients & Accidents and Demonstrate Acceptability of a SWCMF in RPS&ES*Recognizes SWCMF is Beyond Design Basis

• Realistic Demonstration of Unit Capability to Accommodate SWCMF with No Unacceptable Consequences 3

Diversity and Defense in Depth Analysis BTP-19 Requirements*SWCMF is not considered single failure based on NRC endorsed guidelines for licensing digital upgrades.*NRC RIS 2002-22 endorsed EPRI TR-102348 Rev.1D 3 analysis is considered a beyond design basis concernRecognizes the likelihood of a co mmon case software failure in a high quality digital system is significantly below that of a single active hardware failure 4

Diversity and Defense in Depth Analysis D 3 Assumptions *Typical conservative initial conditions*No loss of offsite power*No single failures*Integrated Control System (ICS) in automatic

• Realistic core power distribution (SBLOCA only)

• Realistic core flood tank initial conditions (SBLOCA only)*Realistic operator actions and times*Credit for AMSAC (trip turbine and start EFW on loss of main feedwater)

• Credit for existing Diverse Scram System (DSS) at 2450 psig RCS pressure

• Credit for Automatic Feedwater Isolation System (AFIS) on low SGpressure*Pre-existing SG tube leakage at administrative limit 5

Diversity and Defense in Depth Analysis Analyzed UFSAR Transients & Accidents*Bank Withdrawal @ Zero Power*Bank Withdrawal @ Full Power*Boron Dilution @ Full Power*Loss of Coolant Flow*Locked Rotor*Dropped Rod*Turbine Trip

• FDW Line Break*Steam Generator Tube Rupture*Rod Ejection*Large Steam Line Break*SBLOCA (limiting case)*Small Steam Line Break*Loss of MFW*LOOP 6 Diversity and Defense in Depth Analysis Acceptance Criteria*Offsite dose limits based on R. G. 1.183Large steam line break 25 remTEDE (EAB & LPZ)Loss of flow 2.5 remTEDE (EAB & LPZ)Control Room 5 remTEDE*RCS overpressure limit is 3250 psia (ASME Service Level C), same as ATWS acceptance criterion for B&W plants*Reactor Building overpressure limit is 125 psi based on 98% of ultimate strength (design pressure is 59 psig) 7 Diversity and Defense in Depth Analysis Results Categories1.RPS and ESPS not actuated / no adverse impact2.Event terminated by DSS actuation / no adverse impact 3.Event bounded by another event4.Analysis required and results show acceptance limits are met5.Acceptance limits not met / fail diversity and defense-in-depth 8 Diversity and Defense in Depth Analysis Analysis ResultsCategory 1 -RPS and ESPS Not Actuated / No Adverse Impact*Dropped control rod*Steam generator tube rupture

• Small steam line break (for RCS pressure response and offsite doses)Note: The UFSAR analysis does not credit automatic RPS or ESPS actuation 9

Diversity and Defense in Depth Analysis Analysis Results (cont.)Category 2 -Event Terminated by DSS Actuation / No Adverse Impact*Control rod bank withdrawal at zero power*Turbine trip*Loss of main feedwater

• Loss of offsite power

• Main feedwater line break Note: The DSS mitigates the event w hen RCS pressure reaches 2450 psig 10 Diversity and Defense in Depth Analysis Analysis ResultsCategory 3 -Event Bounded by Another Event / No Adverse Impact*Boron dilution at full power (bounde d by control rod bank withdrawal)*Control rod ejection containm ent response and dose results (bounded by LOCA)Manual actuation of HPI at 5 minutes creditedManual actuation of RBCS and RBS at 8 minutes credited*SBLOCA containment response and doses (bounded by LOCA)Manual actuation of RBCS and RBS at 8 minutes credited 11 Diversity and Defense in Depth Analysis Analysis Results Category 4:

Analysis Required and Acceptance Criteria Met*Control rod bank withdrawal at full powerNo cladding failures, so offsite doses are not significantRCS and Reactor Building pressure limits not challenged*Loss of coolant flow (four-pump coastdown)26.0% cladding failure and 2.14% fuel meltRadiological doses bounded by two-pump coastdownRCS and Reactor Building pressure limits not challenged 12 Diversity and Defense in Depth Analysis Analysis Results Category 4:

Analysis Required and Acceptance Criteria Met*Loss of coolant flow (two-pump coastdown)26.6% cladding failure and 2.46% fuel meltRCS and Reactor Building pre ssure limits not challengedRadiological doses*EAB boundary = 2.0 remTEDE (2.5 remis limit)*LPZ boundary = 0.4 remTEDE (2.5 remis limit)

• Control Room = 1.2 remTEDE (5 remis limit) 13 Diversity and Defense in Depth Analysis Analysis Results Category 4:

Analysis Required and Acceptance Criteria Met*Large steam line break34.0% cladding failure and 4.75% fuel meltRCS pressure limit is not challengedPeak containment pressure is 44 psigRadiological doses*EAB boundary = 4.4 remTEDE (25 remis limit)*LPZ boundary = 0.9 remTEDE (25 remis limit)

• Control Room = 3.4 remTEDE (5 remis limit) 14 Diversity and Defense in Depth Analysis Analysis Results Category 4:

Analysis Required and Acceptance Criteria Met*Locked rotorNo cladding failures, so offsite doses are not significantRCS and Reactor Building pressure limits not challenged*Small steam line breakPeak containment pressure is 45 psigManual actuation of RBCS and RBS credited at 8 minutes 15 Diversity and Defense in Depth Analysis Analysis Results Category 4:

Analysis Required and Acceptance Criteria Met*Small-break LOCAReactor manually tripped by the operator at 2 minutesReactor coolant pumps manually tripped by the operator at 2 minutesHPI and LPI manually started by the operator at 5 minutesPeak cladding temperature is limited to around 1000ºFRCS pressure limit not challenged 16 Diversity and Defense in Depth Analysis Analysis ResultsCategory 5 -Acceptance Limits Not Met*Large-break LOCACrediting manual start of HPI and LPI at 5 minutes is not early enough to maintain a coolable geometryLBLOCA does not meet the divers ity and defense-in-depth requirementsA diverse actuation of LPI is required since LOCA is within the scope of the D 3 study 17 Diversity and Defense in Depth Analysis Conclusions*Diversity and defense-in-depth demonstrated for all events except large-break LOCA*Existing diverse plant systems credited for automatic mitigationDiverse Scram System (DSS)AMSACAutomatic Feedwater Isolation SystemIntegrated Control System 18 Diversity and Defense in Depth Analysis Conclusions*New manual operator action times creditedManual reactor trip at 2 minutes (SBLOCA)Manual start of HPI and LPI at 5 minutes (SBLOCA, REA)Manual start of RBCS and RBS at 8 minutes (SBLOCA, REA)*Acceptance criteria met (except for LBLOCA)Diverse actuation of LPI required for LBLOCA with failure of RPS/ES 19