ML061790481

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

006 Regulatory Information Conference Session TH5D Digital Instrumentation and Control conee Nuclear Stations Diversity and Defense in Depth Analysis for the Digital RPS / ES Upgrade T. Preston Gillespie, Jr.

Reactor and Electrical Systems Engineering Manager Duke Power Company March 9, 2006

iversity and Defense in Depth Analysis istorical Perspective In 2001, ONS elected to replace its originally installed analog RPS/ES System with a digital based system Framtomes Teleperm XS operating system was chosen as the platform for the new system.

This platform is also utilized for the sites emergency power supplys governor system.

2

TP-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

TP-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.1 3/4 D3 analysis is considered a beyond design basis concern 3/4 Recognizes the likelihood of a common case software failure in a high quality digital system is significantly below that of a single active hardware failure 4

iversity and Defense in Depth Analysis 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 SG pressure Pre-existing SG tube leakage at administrative limit 5

nalyzed UFSAR Transients & Accidents Bank Withdrawal @ Zero Power

• Steam Generator Tube Bank Withdrawal @ Full Power Rupture Boron Dilution @ Full Power

• Rod Ejection Loss of Coolant Flow

• Large Steam Line Break Locked Rotor

• SBLOCA (limiting case)

Dropped Rod

• Small Steam Line Break Turbine Trip

• Loss of MFW FDW Line Break

• LOOP 6

iversity and Defense in Depth Analysis cceptance Criteria Offsite dose limits based on R. G. 1.183 3/4 Large steam line break 25 rem TEDE (EAB & LPZ) 3/4 Loss of flow 2.5 rem TEDE (EAB & LPZ) 3/4 Control Room 5 rem TEDE 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

iversity and Defense in Depth Analysis esults Categories

. RPS and ESPS not actuated / no adverse impact

. Event terminated by DSS actuation / no adverse impact

. Event bounded by another event

. Analysis required and results show acceptance limits are met

. Acceptance limits not met / fail diversity and defense-in-depth 8

iversity and Defense in Depth Analysis nalysis Results ategory 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

iversity and Defense in Depth Analysis nalysis Results (cont.)

ategory 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 when RCS pressure reaches 2450 psig 10

iversity and Defense in Depth Analysis nalysis Results ategory 3 - Event Bounded by Another Event / No Adverse Impact Boron dilution at full power (bounded by control rod bank withdrawal)

Control rod ejection containment response and dose results (bounded by LOCA) 3/4 Manual actuation of HPI at 5 minutes credited 3/4 Manual actuation of RBCS and RBS at 8 minutes credited SBLOCA containment response and doses (bounded by LOCA) 3/4 Manual actuation of RBCS and RBS at 8 minutes credited 11

iversity and Defense in Depth Analysis nalysis Results ategory 4:

nalysis Required and Acceptance Criteria Met Control rod bank withdrawal at full power 3/4 No cladding failures, so offsite doses are not significant 3/4 RCS and Reactor Building pressure limits not challenged Loss of coolant flow (four-pump coastdown) 3/4 26.0% cladding failure and 2.14% fuel melt 3/4 Radiological doses bounded by two-pump coastdown 3/4 RCS and Reactor Building pressure limits not challenged 12

iversity and Defense in Depth Analysis nalysis Results ategory 4:

nalysis Required and Acceptance Criteria Met Loss of coolant flow (two-pump coastdown) 3/4 26.6% cladding failure and 2.46% fuel melt 3/4 RCS and Reactor Building pressure limits not challenged 3/4 Radiological doses

• EAB boundary = 2.0 rem TEDE (2.5 rem is limit)

• LPZ boundary = 0.4 rem TEDE (2.5 rem is limit)

• Control Room = 1.2 rem TEDE (5 rem is limit) 13

iversity and Defense in Depth Analysis nalysis Results ategory 4:

nalysis Required and Acceptance Criteria Met Large steam line break 3/4 34.0% cladding failure and 4.75% fuel melt 3/4 RCS pressure limit is not challenged 3/4 Peak containment pressure is 44 psig 3/4 Radiological doses

• EAB boundary = 4.4 rem TEDE (25 rem is limit)

• LPZ boundary = 0.9 rem TEDE (25 rem is limit)

• Control Room = 3.4 rem TEDE (5 rem is limit) 14

iversity and Defense in Depth Analysis nalysis Results ategory 4:

nalysis Required and Acceptance Criteria Met Locked rotor 3/4 No cladding failures, so offsite doses are not significant 3/4 RCS and Reactor Building pressure limits not challenged Small steam line break 3/4 Peak containment pressure is 45 psig 3/4 Manual actuation of RBCS and RBS credited at 8 minutes 15

iversity and Defense in Depth Analysis nalysis Results ategory 4:

nalysis Required and Acceptance Criteria Met Small-break LOCA 3/4 Reactor manually tripped by the operator at 2 minutes 3/4 Reactor coolant pumps manually tripped by the operator at 2 minutes 3/4 HPI and LPI manually started by the operator at 5 minutes 3/4 Peak cladding temperature is limited to around 1000ºF 3/4 RCS pressure limit not challenged 16

iversity and Defense in Depth Analysis Analysis Results ategory 5 - Acceptance Limits Not Met Large-break LOCA 3/4 Crediting manual start of HPI and LPI at 5 minutes is not early enough to maintain a coolable geometry 3/4 LBLOCA does not meet the diversity and defense-in-depth requirements 3/4 A diverse actuation of LPI is required since LOCA is within the scope of the D3 study 17

iversity and Defense in Depth Analysis onclusions Diversity and defense-in-depth demonstrated for all events except large-break LOCA Existing diverse plant systems credited for automatic mitigation 3/4 Diverse Scram System (DSS) 3/4 AMSAC 3/4 Automatic Feedwater Isolation System 3/4 Integrated Control System 18

iversity and Defense in Depth Analysis Conclusions New manual operator action times credited 3/4 Manual reactor trip at 2 minutes (SBLOCA) 3/4 Manual start of HPI and LPI at 5 minutes (SBLOCA, REA) 3/4 Manual start of RBCS and RBS at 8 minutes (SBLOCA, REA)

Acceptance criteria met (except for LBLOCA) 3/4 Diverse actuation of LPI required for LBLOCA with failure of RPS/ES 19