2014. 9

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목차

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Introduction

다중오동작 관련 요건

다중오동작 분석 Progress

다중오동작 분석 수행현황

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Spurious Operation (오동작)

화재로 인한 회로고장은 hot short, open short, short toground의 형태로 발생을 하며, 이 중 hot short*는케이블간(Inter-cable) 또는 케이블내(intra-cable)에서 발생이가능함.이러한회로고장에의하여오동작이발생함.

Undesired operation of equipment, considering all possiblefunctional states, resulting from a fire that could affect thecapability to achieve and maintain safe shutdown.

Multiple Spurious Operation (다중오동작)

위의오동작들이동시에혹은거의시차없이일어나는경우를말함.

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Types of Spurious Operation

• Electrical breakers : changing position• Pump : spurious starts/stops• MOVs : repositioning open or closed

Possible bypass of torque / limit switches • Three-phase AC hot short :only need to be considered

for high-low pressure interface MOVs

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다중회로고장 및다중오동작

• 단일회로고장 (예. 고온단락)은 다음을유발할수있음.– 단일오동작– 다중오동작 (예. 여러안전방출밸브(SRVs)가개방되는것을유발하는하나의고온단락)

• 단일오동작은하나의회로고장이상의결과일수있음. (즉, 다중의고온단락을요구함.)

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다중오동작분석

• It establishes potential pathways where multiple spurious operations of components could have an adverse effect.

• Plant specific

• Based on existing Safe Shutdown Analysis

• For fluid systems look at both achieving flow path andpreventing divergence from flow path

• Appendix G of NEI 00-01, Revision 2&3 provides a table of BWR and PWR MSO scenarios to be considered in an MSO evaluation.

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다중오동작분석

ØMajor Inputs § FSSA/SSEL§ P&IDs, CBDs, EWDs, C&IDs, CLDs§ Required the precise location of cables for detailed

analysis.

ØTwo or Three phases of analysis are required:§ Phase I analysis using available data § Interim analysis to resolve the open-item from Phase I

analysis result § Phase II analysis using final design or as-built data

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Regulatory Guide 1.189

• Revision 2 issued October 2009• Section 5.3.1.1: “The approach outlined in Chapter 4 of NEI

00-01, which relies on the Expert Panel Process and the Generic List of Multiple Spurious Operations contained in Appendix G to that document, provide an acceptable methodology for the identification of multiple spurious actuations…”

• MSO Categorization- SAFE-SHUTDOWN SUCCESS PATH SSCs- SSCs IMPORTANT TO SAFE SHUTDOWN

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Regulatory Guide 1.189 (계속)

Examples of Safe-Shutdown Success Path Structures Systems and Components (SSCs)

• Reactivity control systems that are required to achieve and maintain cold-shutdown reactivity conditions

• Reactor coolant inventory/makeup control systems that are required to maintain the reactor coolant level above the pressurizer level instrument range

• Reactor coolant pressure control systems that are required to control the reactor coolant pressure

• Reactor heat removal systems that are required to achieve and maintain decay heat removal

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Regulatory Guide 1.189 (계속)

Examples of Safe-Shutdown Success Path SSCs (cont.)• Process monitoring SSCs that are required to provide direct

readings of the process variables necessary to achieve and maintain safe shutdown

• Supporting SSCs that are required to provide the process cooling, lubrication, etc., necessary to permit the operation of the equipment used to achieve and maintain safe shutdown

• Significant diversion paths from flow path that would lead to core damage or cause reactor coolant loss if diverted for 1 hour or less

• Power supplies for safe-shutdown success path components

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Regulatory Guide 1.189 (계속)

Examples of SSCs Important to Safe Shutdown• Success path supply tank spurious drain or bypass• Decay heat removal system valves, when not part of safe-

shutdown success path• HVAC systems and components required to provide cooling

to success path components to the extent that cooling is required for post-fire safe shutdown

• Power-operated relief valves and safety relief valves not part of safe-shutdown success path

• Spurious start of equipment not relied on for a safe-shutdown success path, which could cause overfill conditions

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Regulatory Guide 1.189 (계속)• MSO Resolutions

REQUIRED FOR SAFE SHUTDOWN— DESIGN CHANGE— SEPARATION PER III.G. OR III.G.— NO OPERATOR MANUAL ACTIONS WITHOUT

EXEMPTION

IMPORTANT FOR SAFE SHUTDOWN— SAME AS FOR REQUIRED FOR SAFE SHUTDOWN— PLUS OPERATOR MANUAL ACTIONS— PLUS FIRE MODELING

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NEI 00-01ØDifferences Between Revision 2 and Revision 3§Cable/circuit identification clarified§Generic MSO list updated (Scenario 45)§ “Required” / “Important” classifications added (PWRs)

ØRevision Status§Revision 2 – Endorsed by U.S. NRC with exceptions§Revision 3 – In review by U.S. NRC§SKN 34 MSO analysis performing based on Revision 3

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MSO Evaluation Flow Path (KEPCO-E&C)

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MSO Evaluation Flow Path (KEPCO-E&C)

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■ Generic List of MSO

Ø Owners’ Groups have compiled Generic Lists for their plant type

§ Divided into groups by function:ü Reactivity Controlü RCS Inventory / Makeup Controlü RCS Pressure Controlü Decay Heat Removalü Support Systemsü Other

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Ø Scenario 06 – Letdown Fails to Isolate and Inventory Lost to CVCS§ Inventory may be lost to the Chemical Volume

Control System (CVCS), through letdown, if:ü Spurious opening (or failure to close) of the letdown

isolation valves(s), ANDü Spurious opening (or failure to close) of the letdown orifice

valve(s).

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■ Plant Specific List of MSO Ø Expert Panel Review

§ Key element in operating plant process§ Review Generic Lists for applicabilityü Review site specific examples from P&ID / PRA reviewü Review site specific examples from fire safe shutdown analysis

§ Review the generic listü Including site-specific examples from other inputs

§ Brainstorm on new combinationsü Inter-system combinations

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■ MSO Scenario LogicØDefine the set of Equipment whose failure would cause

the MSO to occur or whose prevent the MSO

ØEvaluate Scenario Logics§ Determine Success Paths§ Choose Simplest Path to Recoverü Based on complexity, analyst may be required to evaluate all

failed Equipment/Cable(s)§ Detailed Circuit Analysis (DCA)§ Cable Routing Verificationü Layout Drawingsü Raceway, Room, Fire Areaü Unassigned Rooms to Raceways

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■ MSO Scenario LogicØ Scenario 06 – Letdown Fails to Isolate and Inventory

Lost to CVCS§ Orifice Valves : Non-Safety§ Valve 515 or 516 is required CLOSED§ Valves 522 and 523 included to

provide additional success paths. (Pink)

ü 451-V-0515 ORü 451-V-0516 ORü 451-V-0522 ORü 451-V-0523

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■ MSO Scenario Logic - Detailed Circuit AnalysisØ Drawings:

§ Elementary Wire Diagram (EWD)§ Cable Block Diagram (CBD)§ Control Logic Diagram (CLD)§ Control and Instrumentation Diagram (C&ID)

Ø Function of Cable Damaged?§ Control? Power?§ How does it affect the Equipment of interest?ü Annunciation? Space Heater? Related to Equip. of interest?

§ Causes Undesired Position of the Equipment?

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■ Detailed Analysis by Fire AreaØ Fire areas are used as the basis for evaluation

§ No cable or equipment of interest : Excluded

Ø Initial Evaluation of scenarios by fire area§ No fire-induced failure are seen for that scenario in that area§ There are fire-induced failures but these failures do not cause

an MSO scenario failure in that area; or§ There are fire-induced failures and these failures could cause

the MSO scenarios occur; additional analysis and/or a designchange is necessary.

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■ Detailed Analysis by Fire AreaØ Refine the Analysis

§ Review the equipment logic to determine if there arealternatives or if the logic can be supplemented with additionalequipment to help the scenario survive.

§ Review the safe shutdown analysis to determine whether theequipment failing in the fire area is critical to the creditedshutdown path for the fire area.

§ Review the failing cables to determine if they are critical todesired operation or maloperation of the equipment.

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■ ResolutionØ OK-AS-IS

§ Based on Detailed Circuit Analysis, although the cable(s)are associated with the equipment, the failure(s) do notplace the equipment in the undesired position

§ Based on System Design, failure of cable(s) and/or equipment in a MSO scenario do not adversely impact safe shutdown

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■ ResolutionØ Technical Evaluation

§ Manual Action Feasibility assessment on a proposed action outsideof the Main Control Room

§ Only Recommended for “Important” for safe shutdown Equipment§ Not Allowed for “Required” for safe shutdown Equipment

Ø Main Control Room (MCR) Action§ A Main Control Room Action to mitigate a MSO scenario from

occurring§ Allowed without requiring an exemption

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■ ResolutionØ Design Changes

§ Recommendation to modify the existing plant to mitigate a MSOscenario from occurring

ü Wrapping Cable(s)ü Rerouting Cable(s)ü Construction of Radiant Heatshields

§ Possible Alternative Solution to Recommendations of “Fire-Wrap” and “Reroute”:ü Cable is in a dedicated conduit : Mitigates External Hot Shortsü Cable routes in an enclosed(Top/Bottom) tray : Mitigates External

Hot Shortsü Cable routed with no other energized Wires and/or Cables :

Mitigates Any Hot Short

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국내건설원전수행현황

건설원전 적용요건 다중오동작분석

신고리 3,4 RG 1.189 Rev.0 수행중

신고리 5,6 RG 1.189 Rev.2 수행예정

신한울 3,4 RG 1.189 Rev.2 수행예정

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미국원전수행현황2012 Fire Protection Forum 자료2012년 8월조사 /총 54개발전소참여

조사날짜 2012년 8월 비고

참여발전소 총 54개 805 Plant 제외PWR 27개

평균선정시나리오 평균 65개의시나리오 최고 227개최저 4개대부분 50개이상

시나리오타입 65% Orange35% Green

MSO Circuit change 수

평균 29개 MOV Rewires :44%Cable Change :22%

12년 2월 11일이후완료예정발전소

14개발전소 순차적으로 2015년가능까지완료예상