Presentation on theme: "BWR Vent Order Implementation Workshop II"— Presentation transcript:
1 BWR Vent Order Implementation Workshop II April 9 -10, 2014 Baltimore
2 Workshop Purpose and Plan Phase 1 (wet well) template for Overall Implementation Plans for NRC Order EAReview order requirements and accepted approach to complying with Phase 1 of the Order being developed in conjunction with the NRC.Focus on the detailed physical and analytic elements of implementation.
3 BWR Mark I/II Severe Accident Vent Order Key Dates Order issued June 6, 2013; two phasesSevere accident wetwell vent by June 30, 2018Severe accident drywell vent by June 30, 2019Option to demonstrate drywell vent not neededGuidance NEI R.0 and JLD-ISG R.0Phase 1 (WW) Guidance issued November 2013Developing template for Overall Integrated Plan for meeting Order.BWROG developing engineering guidance for vent.Phase 2 (DW) Guidance by April 2015
4 Venting and Filtering Strategies BWR Mark I and II Prevent core damage during SBO/ELAPVenting via hardened wetwell ventWater injection via FLEXFollowing core damage during SBO/ELAP, prevent containment failureVenting via hardened wetwell and/or drywell ventWater injection via “beyond FLEX”Filtering releases via containment water injection and pressure control
5 Phase 1 Activities Timeline Post OIP Template Development June 2014July – Aug 2014Oct 2014Dec 2014– Phase 1 OIP due– Develop 6-month status template– Phase 1 pilot plant ISE issued– All Phase 1 plant ISE issued– 1st 6-month status due
6 Estimated Phase 2 Guidance Timeline Mar 2014 – NEI Working Group define goals and approach for Phase 2 Apr – May 2014 – NEI WG draft Phase 2 scope from Industry perspective Jun – Sep 2014 – NRC/NEI Draft Phase 2 scope Oct 2014 – NEI/BWROG Industry Comment and Feedback Nov 2014 – NEI Phase 2 Draft Revision Provided to NRC for reference in ISG Dec 2014 – NRC publish draft ISG for public comment Feb 2015 – NRC Public comment period closed Mar 2015 – NRC Issues approved ISG Mar 2015 – NEI/NRC Workshop on Phase 2 Apr – May 2015 – NRC/NEI OIP Template structure and content without Pilots May – Jul 2015 – NRC/NEI OIP Template Pilots including Option for No DW Vent Pilot Aug 2015 – NEI/BWROG Draft OIP To Industry for Comment for Workshop Sep 2015 – NEI/NRC OIP Workshop on Pilots and Template use Oct 2015 – NEI OIP finalized and included in a revision to Dec 2015 – Stations OIP due to NRC
8 Industry Documents Template timeline FAQ & White Paper Process Selected Template ElementsGenericPlant Hatch PilotNine Mile Point 2 Pilot
9 Template Development Information and Key Dates Pilot plant(s) identified – Hatch as MK I & NMP2 as MK IIDraft template by January 20, 2014 – Presented on Jan 15Final Draft template March 15, 2014 – After PilotsNEI Revision for OIP template and FAQs by April 21, 2014NRC-NEI Joint Template MeetingsJanuary 15, 2014 – Complete (Draft Template & 3 FAQ)January 29, 2014 – (Template Elements & FAQs)February 19, 2014 (Pilot Plant Hatch, FAQs & White Papers)March 5, 2014 (NMP2 Pilot Differences, FAQ & White Paper)March 26, 2014 (NRC Feedback on OIP Pilots/Workshop Prep)Industry Template Workshop, April 9-10 in BaltimoreNRC-NEI Check-up Conference Call Proposed for May 7
10 Frequently Asked Questions Clarification items brought to industry NEI core teamNEI Core Team to provide consensus responseSelect FAQs presented to the NRC staff in draft version (interpretation FAQs)Final FAQ documented on NEI websiteClarification items larger than FAQ will be resolved via other means of NEI revision or white paper endorsementPhase 2 revision of NEI will incorporate appropriate FAQs or white papers
11 Frequently Asked Questions FAQ NumberNEI SectionSubjectHCVS-014.2.2, 4.2.3HCVS Primary Controls and Alternate Controls and Monitoring LocationsHCVS-021.2.6HCVS Dedicated EquipmentHCVS-031.2.5, 1.2.6,4.2.3HCVS Alternate Control Operating MechanismsHCVS-044.1.5HCVS Release PointHCVS-054.1.4, 4.1.6, 6.2HCVS Control and ‘Boundary Valves’HCVS-06Multiple FLEX Assumptions/HCVS Generic AssumptionsHCVS-074.2.5Consideration of Release from Spent Fuel Pool AnomaliesHCVS-084.2.2, 4.2.4HCVS Instrument QualificationsHCVS-09MultipleUse of Toolbox Actions for PersonnelFAQ HCVS-01, 02, 03, 04, 05, 06, 07 and 08 have been submitted for NRC Concurrence
12 White Paper Topics HCVS-WP-01: HCVS Dedicated Motive Force Scope of operator actions for selected HCVS electrical and pneumatic suppliesHCVS-WP-02: HCVS Cyclic Operations ApproachAccident sequenceNumber of vent cyclesRadiological limitations from HCVS operationHCVS-WP-03: Hydrogen/CO Control MeasuresPassive measuresActive measuresHCVS-WP-04: FLEX/HCVS InteractionsPortable equipment use under severe accident and BDBEE conditions
14 Template Elements Template Goals: Directly align to the ISG Use Hybrid 050/049 Template with Order and ISG (NEI 13-02) Cross ReferenceDirectly align to the ISGDescribe the phased approach to implementationBig picture schedule statementWetwell performance objectives Discuss the section 1.1 objectives of attachment 2 in orderDiscuss the requirements in sections 4.1, 4.2 and 6.1 and appendix's F and G of NEI 13-02Drywell performance objectivesQuality standardsProgrammatic requirementsLinkage to ISE or SE
15 Template ElementsProposed Template with Order and ISG (NEI 13-02) Cross Reference:IntroductionPart 1: General Integrated Plan Elements and AssumptionsPart 2: Boundary Conditions for WW Vent with specifics about the compliance actions relative to the ISG and NEI section 2Part 3: Boundary Conditions for DW Vent with specifics about the compliance actions relative to the ISG and NEI section 3Part 4: Programmatic Controls, Training, Drills and Maintenance ElementsPart 5: Milestone table elementsAttachment 1: Portable EquipmentAttachment 2: Sequence of Events TimelineAttachment 3: Conceptual SketchesAttachment 4: Failure Evaluation TableAttachment 5: ReferencesAttachment 6: Changes/Updates to this OIPAttachment 7: Open Items in HCVS OIP
16 Template ElementsPart 1: General Integrated Plan Elements and AssumptionsKey Site assumptions to implement NEI strategiesGrouping of Assumptions as FLEX, Generic and Site Specific.Considering making an FAQ on FLEX assumptions and one on Generic to use as a reference in the template.
17 Template ElementsPart 2: Boundary Conditions for WW Vent with specifics about the compliance actions relative to the ISG and NEI section 2Severe AccidentFirst 24Beyond 24 hoursSupport Equipment FunctionsBDBEE VentingSevere Accident Venting
18 Template Elements Attachments Part 4: Programmatic Controls, Training, Drills and Maintenance ElementsPart 5: Milestone table elementsAttachmentsAttachment 1: Portable EquipmentAttachment 2: Sequence of Events TimelineOperator action constraints timeline is determined based on the following sequences:Sequence 1 is a FLEX run with Venting in a BDBEE without core damage.Sequence 2 is based on SECY results for a prolonged SBO (ELAP) with the delayed loss of RCICSequence 3 is based on SOARCA results for an SBO (ELAP) with failure of RCIC to inject.4/14/2017
19 Representative BWR Venting Timelines RCICstartsAnticipatoryVentingSBOCase 1Ref: Plantt=0st ≈.5 mt ≈ 5 hrst ≈ 18 hrsContainment Venting(anticipatory venting not represented in SECY )No InjectionNo InjectionCore DamageVesselBreachPortable generator providing power to Safety Related 480VAC System(Ref Plant OIP)Level atTAFCase 2Ref: SECYt ≈ 23 hrst ≈ 24 hrst ≈ 34 hrsContainment Venting(based on exceeding PCPL)Core DamageVesselBreachCase 3Ref: SOARCAt ≈ 1 hrt≈ 8 hrLegendReferences:Case 1: Reference Plant FLEX Overall Integrated PlanCase 2: SECY – ML12344A030Case 3: SOARCA – ML13150A053Adequate core cooling maintainedInjection LostIncreased shine and leakage of radionuclides primarily from WetwellHCVS Post Core Damage Dose Evaluation RequiredNot to scale
20 Review of Key Elements of Phase 1 Overall Integrated Plan Template
21 Hatch SA HCVS Pilot Template Elements Review of Plant Hatch completion of items in revision C3 of the Severe Accident HCVS OIP Template
22 Nine Mile Point Unit 2 SA HCVS Pilot Template Major Differences Review of Nine Mile Point Unit 2 Major Differences from Mark I pilot for Severe Accident HCVS OIP Template
23 Hatch OIP Major Elements Adding Site Characteristics important to HCVSControl Building and Rx Building LayoutMain Stack and vent pipe locationsTime and Environmental Constraint ItemsRupture discHCVS OperationBattery power actions>24 Hour motive force
24 NMP2 OIP Site Characteristics Important to HCVS The primary location for HCVS operation will be the Main Control RoomThe alternate location for HCVS operation will be the Reactor Building track bay, northeast side of Reactor Building, ground elevationThe HCVS release point will be at least 3 feet above the top of the Reactor Building on the northwest side of the Reactor Building
25 Hatch HCVS Venting Timelines t ≈.5 mRCICstartst = 1 hrELAP Declaredt=0sSBOCase 1FLEX SuccessfulRef: HNP FLEX OIPt ≈ 18 hrsContainment Venting(anticipatory venting not represented in SECY )t ≈ 7 hrsAnticipatoryVentingBlow rupture discNo InjectionNo Injectiont ≈ 10 hrsPortable generator in place for FLEX and HCVS loads.Core DamageVesselBreachLevel atTAFCase 2RCIC Late FailureRef: SECYt ≈ 23 hrst ≈ 24 hrst ≈ 34 hrsContainment Venting(based on preventing exceeding PCPL)t ≈ 11 hrsBegin monitoring at MCR or ROP HCVS pneumatic and battery status. No replenishment expected to be required before t = 24 hourst ≈ 24 hrsReplenishment of HCVS power and pneumatic suppliesLevel atTAFCore DamageVesselBreacht ≈ 12 hrsTransfer to HCVS BatteryCase 3RCIC Early FailureRef: SOARCAt ≈ 1 hrt ≈ 2 hrt≈ 8 hrst ≈ 11 hrst ≈ 24 hrst ≈ 12 hrsLegendReferences:Case 1: HNP FLEX Overall Integrated PlanCase 2: SECY – ML12344A030Case 3: SOARCA – ML13150A053Adequate core cooling maintainedInjection LostIncreased shine and leakage of radionuclides primarily from WetwellHCVS Post Core Damage Dose Evaluation RequiredHCVS Time evaluation requiredNot to scale
27 Hatch OIP Major Elements 7.3 Hours, Initiate use of Hardened Containment Vent System (HCVS) per site procedures to maintain containment parameters below design limits and within the limits that allow continued use of RCIC for mitigation in a BDBEE - HCVS controls and instruments associated with containment will be DC powered and operated from the MCR or a Remote Operating Station on each unit. Thus initiation of the HCVS from the MCR or the Remote Operating Station within 7.3 hours is acceptable because the actions can be performed any time after declaration of an ELAP (1 hour) until the venting is needed. In the event of Severe Accident HCVS initiation all required actions occur at a time further removed from an ELAP declaration than the BDBEE HCVS timeline as shown in Attachment 2.
28 NMP2 OIP Differences Time and Environment Constraint Items 2 Hours, Initiate use of Hardened Containment Vent System (HCVS) per site procedures to maintain containment parameters within the limits that allow continued use of RCIC. Initiation of the HCVS can be completed with manipulation of only 4 switches located within the MCR. The reliable operation of HCVS will be met because HCVS meets the seismic requirements identified in NEI and will be powered by dedicated HCVS batteries with motive force supplied to HCVS valves from installed nitrogen storage bottles. HCVS controls and HCVS instrumentation will be provided from a dedicated panel in the MCR. Other containment parameter instrumentation associated with operation of the HCVS is available in the MCR. Operation of the system will be available from either the MCR or a ROS. Dedicated HCVS batteries will provide power for greater than 24 hours. Therefore, initiation of the HCVS from the MCR or the ROS within 2 hours is acceptable because of the simplicity and limited number of operator actions. Placing the HCVS in operation to maintain containment parameters within design limits for either BDBEE or SA venting would occur at a time further removed from ELAP declaration as shown on the sequence of events timeline on the previous slide
29 Hatch OIP Major Elements At >24 Hours, portable diesel generators will be installed and connected to the pigtail of the battery chargers to supply power to HCVS components/instruments; time critical at a time greater than 25 hours. Current battery durations are calculated to last greater than 26 hours. The connections, location of the DG and access for refueling will be located in an area that is accessible to operators in the Control Building or in the yard area because the HCVS vent pipe is underground once it leaves the Reactor Building.[OPEN ITEM 3: Evaluate location of Portable DG for accessibility under Severe Accident HCVS use]
30 NMP2 OIP Differences Time and Environment Constraint Items (Cont’d) 24 Hours, Replace/install additional nitrogen bottles or install compressor. The nitrogen station will have extra connections so that new bottles can be added or an air compressor can be connected while existing bottles supply the HCVS. This can be performed at any time prior to 24 hours to ensure adequate capacity is maintained so this time constraint is not limiting
31 NMP2 OIP Differences Time and Environment Constraint Items (Cont’d) 24 Hours, connect back-up power to HCVS battery charger. The HCVS batteries are calculated to last a minimum of 24 hours. The HCVS battery charger will be able to be re-powered either from the 600 VAC bus that will be re-powered from a portable diesel generator (DG) put in place for FLEX or locally (Reactor Building Track Bay) from a small portable generatorThe DG will be staged and placed in service within 8 hours (Reference FLEX OIP) and therefore will be available prior to being required. In the event that the DG is not available, a local connection will allow a small portable generator to be connected to the UPS to provide power
32 Hatch OIP Major Elements Vent characteristicsBoundary valve use and cross flowRemote operating station useFLEX type actionsElectric power detailsMilestone schedule
35 NMP2 OIP DifferencesDrywell piping and valve configuration shown for completeness, not for Phase 1 compliance
36 NMP2 OIP Differences Equipment Usage NMP2 will utilize a mixed system, sharing the following componentsContainment penetrationsInboard and Outboard PCIVsPiping to HCVS vent teeBoundary with interfacing systems limited to20” AOV to Standby Gas Treatment System (GTS)2” SOV bypass around 20” AOV to GTS
37 NMP2 OIP Differences GDC-56 Exemption The inboard primary containment isolation valves (PCIV) to be shared with the HCVS system are located inside the primary containmentMost plants implemented a GDC-56 exemption as part of the plant design basis for an alternate configurationThe inboard PCIV will be located outside the containment and thereby significantly improve the reliability of the HCVS system
38 NMP2 OIP Differences Discharge Point NMP2 will utilize a release point above the Reactor Building roof independent of the metrological stackFollows criteria per FAQ HCVS-04
39 NMP2 OIP Differences Power Supply NMP2 HCVS system will be powered by the Divisional Class 1E 600 volt power through a transformer and 125 volt battery charger during normal operationOn loss of AC power, a battery capable of supplying HCVS loads for at least 24 hours will supply HCVS loads without Operator actionA FLEX portable diesel will be connected to repower the 600 volt power within 8 hours to repower the HCVS battery chargerA small portable 120/240 volt generator provides a backup to the FLEX diesel generator that will provide HCVS loads and battery charger through a manual transfer switchStation batteries will not be utilized for HCVS loads
41 NMP2 OIP Differences Containment Protection Features Inadvertent actuation protection is provided by keylock switches used to power up the HCVS panelAdditional keylock switches will be utilized for control of the shared HCVS/Primary Containment Isolation Valves (PCIVs)The HCVS valve double solenoid valve arrangement eliminates the need for defeating containment isolation signals using electrical jumpers or lifted leadsThere are no rupture discs in the NMP2 HCVS design
42 NMP2 OIP Differences Remote Manual Mechanisms Manual valves in the pneumatic supply lines will provide alternate means for HCVS valve operationElectrical power is not required for this methodA manual override for HCVS valve solenoids is being consideredA handwheel for the PCV is being considered, but will not be credited due to environmental concerns in proximity to the valve
43 Hatch OIP Major Elements Portable equipment useWithout core damageWith core damageExample DrawingsElectricalMechanicalPlant Layout
44 NMP2 OIP DifferencesDrywell piping and valve configuration shown for completeness, not for Phase 1 compliance
46 BWROG Companion Guideline for NEI 13-02 Progress between Workshops Pat Fallon - DTEDennis Henneke - GEHBWR Vent Order Implementation Workshop II4/9/14 • Baltimore, MD
47 IntroductionThe BWROG Implementation Guidelines supporting NEI (referred to as the Companion Document) is developed to:Provide guidance on “how to” meet the “what” requirements in NEI and NRC Order EAInclude discussion previously removed from 13-02, due to level of detail (e.g. Hydrogen Overpressure).
48 BWROG Companion Document Beginnings:Started as discussion point during formulation of NEI-13-02NEI was created to work with EA to fully define acceptable equipment and man-machine interface to make a successful Severe Accident Capable Hardened Vent.NEI did NOT contain any “how to” elements for implementation.NEI was endorsed (largely) by the NRC due to multiple interface sessions with a small industry team and NEI.NEI needed to have additional industry input to create a workable method for HCVS implementation that would allow use of work conducted for EA and still meet the intents of NEI
49 BWROG Companion Document Thanks to the Authors:Pat Fallon - DTEShayne Tenace - ExelonBob Cowen - GEHDavid Burch - EntergyDeep Ghosh - SNCBob Ginsberg – Duke EnergyFrank Loscalzo - TVADennis Henneke - GEHScott Wood - Energy NWHarold Trenka - ExelonPhil Amway - ExelonKeith Ward – Duke EnergyGlen Seeman – GEHRich Centenaro - PPLAlso THANKS to the large group of reviewers and commenters.
50 BWROG Companion Document First PassIntroduced the concept at first HCVS Workshop in BaltimoreSlides showed more of a wish list than any concrete method of creation of “how to” elements.A few Items were not developed (Appendix J on Reliable Operator Actions)A few new items were added (e.g. interface with FLEX)Example slide on Section 5.0 follows.
51 BWROG Companion Document Outline (11-13-13 Version) 5.0PROGRAMMATIC CONTROLS5.1Environmental conditions & Methods to Confirm for Each Site TBD5.2Seismic and External Hazard Conditions & Relation to Seismic/Flood Reanalysis5.3Quality Requirements & Interface with other Standards5.4Maintenance Requirements & Interface with Maintenance Rule/INPO Standards
52 BWROG Companion Document Outline (4/6/14 version) 5.0PROGRAMMATIC CONTROLS5.1Environmental conditions & Methods to Confirm for Each SiteKeith WardScott WoodGuidance added on environmental conditions and HCVS-FAQ-045.2Seismic and External Hazard Conditions & Relation to Seismic/Flood ReanalysisScott Wood, Jesse LucasGuidance added on Seismic, wind loading and other items5.3Quality Requirements & Interface with other StandardsPat/Phil AmwayFrank LoscalzoGuidance added on instrument quality and HCVS-FAQ-08/OIP Template5.4Maintenance Requirements & Interface with Maintenance Rule/INPO StandardsGuidance added on programmatic requirement and interface with OIP Template
53 BWROG Companion Document Any “How-To” or additional guidance that was identified during the writing of the companion document that potentially required NRC review was separated out into either an FAQ or White Paper:Much of the wording in the companion document was removed, and the FAQ/WP is now referenced in the Companion Document.Some of the developed wording was placed back in the companion document if NRC review was not needed:For example, methods not recommended for H2 control (Flame Arrestors).Interface with the FAQs/WPs has added additional effort to ensure the companion document matches the current version of the FAQs/WPs.
54 BWROG Companion Document Evolution:February, 2014:Document Pages: from 96 to 127Sections with guidance: 69New Appendices: 4Contributors: 18March, 2014Document pages: from 127 to 138Sections with guidance: 77New Appendices: 5Contributors: 16Interfaces with 9 HCVS-FAQs, 3 HCVS-WPs, and OIP Template (alignment)
55 BWROG Companion Document Content (April 2014) Section 4.1Vent Capacity determination methods and criteria to allow < 1% Steam dischargeMulti-purpose penetrations (HCVS-FAQ-02, -05) to discuss requirements for use and testing of PCIVsRouting of piping (Rad and thermal impacts) method and design impacts captured in this section and Appendix G (HCVS-WP-03).Multi-unit interfaces (FAQ not yet written on Hydrogen/cross flow)Release point (See HCVS-FAQ-04)Also discusses releases when lowering containment pressure for FLEX injection.
56 BWROG Companion Document Content (April 2014) Section 4.1 (Continued):Leakage criteria (See HCVS-FAQ-05)Flammable Gas protection (See HCVS-FAQ-05)Design for Hydrogen/combustible gasCombined WW/DW pipingFault/Failure evaluationsEvaluation should include any systems or operations used for Hydrogen Control.
57 BWROG Companion Document Content (April 2014) Section 4.2Inadvertent actuation preventionPrimary/Alternate Controls areas (See HCVS-FAQ-01, -02)Vent Monitoring (See HCVS-FAQ-02, -08)Operational Hazards (See HCVS-FAQ-01, -02, -03)Design to Minimize Operator actions (See HCVS-FAQ-02)
58 BWROG Companion Document Content (April 2014) Section 5Environmental conditionsSeismic and external conditionsQuality (See HCVS-FAQ-08)Maintenance (Tie to Template Part 4)
59 BWROG Companion Document Content (April 2014) Sections 6 (Operational Considerations), 7 (Reporting Requirements) and Appendix B (Roadmap) include discussion on the OIP template, including a summary of where the template interfaces with the Companion document.Section 6Accessibility and feasibilityProcedures (Tie to Template Part 4)Training (Tie to Template Part 4)AppendicesRoadmap (shows FAQ Ties)Source Term and Dose method definedCombustible and Flammable gases methodsPipe sizing methodologies (NEW)Load combination methodologies (NEW)Use of MAAP for timing, Dose Estimate, or estimating number of cycles (NEW).
60 BWROG Companion Document Where to from here?DRAFT Document is Complete, other than possible edits and changes to the FAQs, White Papers and OIP Template.Continue to modify BWROG Companion Document based on OIP Template Workshop Comments, BWROG Fukushima Committee Comments.Continue to capture the “how to” elements from the HCVS-FAQs, HCVS-WPs, and OIP Template items.Begin to formulate similar role with HCVS-Phase 2 creation.
61 BWROG Companion Document Content (April 2014) A Few Final Notes:Additional Guidance is developed to help drive consistency between plants.Should try to start with the approaches listed, if possible.Provide comments or enhancements if you find a better approach, in order to have other plants use a similar approach.Document is not intended to be referenced in your submittals; Rather the methodology should be used, with the references provided referred to directly in your submittals.
63 FAQ 01HCVS-FAQ-01: Primary and Alternate Controls and Monitoring locationsQ: What conditions have to be considered in the design and location of the Primary and Alternate Controls locations?Order Element states, “operations from a control panel located in the main control room or a remote but readily accessible location.”Order Element states, “The HCVS shall, in addition to meeting the requirements of 1.2.4, be capable of manual operation”Primary and/or Alternate Control locations located in the main control room are readily accessible locations with no further evaluation required (conform to GDC 19/Alternate Source Term (AST))Primary and/or Alternate Control locations located outside the main control room must be determined to be readily accessible locations by performing an evaluation that includes:AccessibilityHabitabilityStaffing sufficiencyCommunication capability with vent use decision makers
64 FAQ 02 HCVS-FAQ-02: Dedicated Equipment Q: What is the meaning of “Dedicated” in order element 1.2.6, “Order Reference: – The HCVS shall be capable of operating with dedicated and permanently installed equipment for at least 24 hours following the loss of normal power or loss of normal pneumatic supplies to air operated components during an extended loss of AC power.”?The typical definition of “dedicated” is “used only for one particular purpose [function]”.Using this literal interpretation, the words of Order element means that all equipment associated with the HCVS should be permanently installed and only serve the HCVS function.This is inconsistent with other Order elements that permit shared component functions.The interpretation of the word “dedicated” in the context of the HCVS order is essential for the proper implementation of the order.The intent of “dedicated” as it is used in Order EA is to ensure that the HCVS system will have the necessary installed electrical and pneumatic power sources to be functional, independent of these sources that will be lost during an ELAP.
65 FAQ 02 HCVS-FAQ-02 Dedicated Equipment (Cont’d) HCVS components may serve multiple functions described in the plant Current License Basis (CLB). Examples include:Piping and valves for both Drywell and Wetwell may be used for Drywell/Wetwell vent and purge prior to or following refueling outages or for pressure control during normal plant operation.Containment Isolation valves in the HCVS system may provide a containment isolation function independent of the HCVS function.Containment Isolation valve position indication for valves in the HCVS may be used for post-accident indications.Instrumentation may support HCVS and non HCVS functions.The following components are examples of what does not have to be dedicated to the HCVS function at all times and may be shared with other systems and support functions:Containment penetrationsContainment isolation valvesSystem boundary valvesPipingInstrumentationWiring, conduit and connection points used to service non-dedicated componentsDC battery systemsThe above components need not be dedicated, but they support the HCVS functionality when containment venting using the HCVS system is required. Compliance with NEI guidance will ensure that this condition is met.
66 FAQ 03 HCVS-FAQ-03: Alternate Control Operating Mechanisms Q: What means of alternate manual operation is allowable for use in the HCVS system related to Order ElementThe examples of alternate operating mechanisms provided in Order element (e.g., reach-rod with hand wheel or manual operation of pneumatic supply valves from a shielded location) are only intended to be examples. Other means of alternate manual operation are acceptable including but not limited to:Separate electrical components with diverse and flexible power supplies (such as the normal valve operators with FLEX power)*Solenoid valves with manual overrides that may be used to manually operate vent valves without electrical powerManual valves in pneumatic supply and vent lines that may be used to manually operate vent valves independent of solenoid valves or electrical powerHydraulic operators* NEI Section 6.1 – “…At least one method of operation of the HCVS should be capable of operating with permanently installed equipment for at least 24 hours during the extended loss of AC power. The system should be designed to function in this mode with permanently installed equipment providing electrical power (e.g., DC power batteries or electrical or pneumatic operation) valve motive force (e.g., N2/air cylinders)” The primary or alternate method of HCVS operation may use an alternative method to that described by this requirement.
67 FAQ 04 HCVS-FAQ-04: HCVS Release Point Q: What is the meaning of “release point above main plant structures” in order element 1.2. ?Order Reference: – The HCVS shall discharge the effluent to a release point above main plant structures.”Buildings outside of the site’s main power block should not be considered relative to the above. Administrative buildings, warehouses, and other support buildings would typically not be staffed during a BDBE unless they house an accident mitigation type emergency facility (in which case the aforementioned information should be used as stated).Cooling towers, by nature of their location requirements, are situated well away from the power block such that they are not able to detrimentally affect HCVS effluent flow.The Plant Stack provides an acceptable release pointSites may take exception to this guidance with reasonable basisGuidance addresses plants that have a single independent release pipe/vent per unit. (typically mounted onto (or emanating from) the Reactor Building, the Turbine Building, or other adjacent building convenient for the HCVS routing)
68 FAQ 05 4/14/2017 HCVS-FAQ-05: HCVS Functional Boundary Valves Q: Which valves are considered as control valves and which are boundary valves, and why?Q: What are the testing criteria for the various valves cited?HCVS Functional Boundary Valve– Any valve which serves to isolate the HCVS from another system. Depending on the application these valves may be safety related or (potentially in limited cases) non-safety related. This category also applies to valves which isolate the vent system of one plant from that of another.The most typical instance of a boundary valve such as this would be to isolate the Standby Gas Treatment System (SGTS) from the HCVS vent path (in which case such valves would be safety related).HCVS Functional Control Valve– Any valve used to open the containment to the HCVS vent path such that venting may commence. This valve will also have the function of closing thereby effectively halting the venting process.4/14/2017
69 FAQ 05 HCVS-FAQ-05: HCVS Functional Boundary Valves (Cont’d) The valves should be purchased or modified such that they are or can be qualified to operate and/or remain closed (depending on their function, either control or purely isolation) at HCVS design temperature and pressure. It is understood that this may require evaluation and possible modification of existing site systems besides the HCVS itself (including Boundary Valves associated with those systems). System modifications such as flanged connections (for temporary blind flange installation) or maintenance valves may be required to facilitate leak testing.PCIVs – Testing criteria for PCIVs will not change.Appendix J testing requirements are based on a site-specific calculation for La (or Allowable Leakage) based on a number of site specific factors which include leakage of the other PCIVs associated with the containment atmosphere.Isolation Valves and Control Valves (which are not listed as PCIVs) identified as HCVS Functional Boundary Valves – Testing criteria for these valves will be based on the individual site’s Appendix J test criteria for PCIVs associated with the HCVS.
70 FAQ 06 HCVS-FAQ-06: HCVS Assumptions Document the FLEX related and Generic EA-109 assumptions in a standard location and reference so that they can be reviewed once by the NRC and will not require extensive preparer or reviewer time for each submittal.Refer to the OIP template for assumptions
71 FAQ 07 HCVS-FAQ-07: Source Term From SFP Q: What impact of the SFP source term is required in the environmental sensitive actions for HCVS operation?SFP Level is maintained above EA Level 2 with either on-site or off-site resources such that no contribution to analyzed source term need be considered
72 FAQ 07 HCVS-FAQ-07: Spent Fuel Pool NRC comment: Item requires further information and clarification.Staff believes that if any HCVS equipment is located in an area that could be impacted by source term from either SFP or reactor severe accident, the governing source term should be the higher of the two.There is no assumption or criteria in the EA Order that relates to a “SFP accident”. The Order only mentions core damage and protection of Mk I & II containments, i.e., “reactor severe accident”. There is no mention of source term in the order.Actions under Order EA provides multiple mitigation actions to protect SFP cooling and Order EA provides redundant instrumentation to plant decision makers to allow correct prioritization of any action needed for the SFP. Every site has to be in compliance with these Orders.If action is required for HCVS in the SFP area then the environment in the vicinity and ingress/egress must be evaluated as identified in FAQ HCVS-01.
73 FAQ 08 HCVS-FAQ-08: HCVS Instrument Qualifications Q: What conditions have to be considered in the design and siting of HCVS Controls and monitoring equipment?Order Element states, “The HCVS shall be designed to be manually operated during sustained operations from a control panel located in the main control room or a remote but readily accessible location.”Order Element states, “The HCVS shall, in addition to meeting the requirements of 1.2.4, be capable of manual operation (e.g., reach-rod with hand wheel or manual operation of pneumatic supply valves from a shielded location), which is accessible to plant operators during sustained operations.”Order Element states, “The HCVS shall be capable of operating with dedicated and permanently installed equipment for at least 24 hours following the loss of normal power or loss of normal pneumatic supplies to air operated components during an extended loss of AC power.”
74 FAQ 08HCVS-FAQ-08: HCVS Instrument Qualifications - Thermal Considerations (Cont’d)Primary or Alternate Control location (if other than MCR temperature and heat load that exist for operation of the HCVS system.If this location is NOT in the Reactor Building or other buildings where HCVS piping is located then the heat load impact is similar to the MCR when the location is in a separate air space.Temperature and heat load that exist due to proximity to the undercooled containment.Temperature and heat load that exists due to the ELAP condition (loss of ventilation).If this location is NOT in the Reactor Building or next to the HCVS piping then the heat load impact is similar to the Control Room since it would be located in a separate air spaceHCVS controls and instrumentation located outside the MCR will be similar to other instrumentation and controls found in plant locations outside the MCR.Unless the licensee uses controls and instrumentation in the HCVS system that are known to be susceptible to failure from elevated temperatures but within habitability limits, no evaluation of temperature effects needs to be performed for HCVS components located outside of the Reactor Building or other buildings where HCVS piping is located.
75 FAQ 09 HCVS-FAQ-09: HCVS Toolbox Use Document the use of Toolbox approach for collateral actions that will be symptom based but are within the skill of the craft or general personnel knowledge.Examples:Opening doors when room temperatures become elevatedUsing flashlights to supplement pathway useExchange of personnel, use of ice vests, etc. when action is in an uncomfortable environment, not life threateningUtilizing small fans for air movement, possibly powered from small portable generators and extension cords
76 BWR Vent Order Implementation Workshop II April 9 -10, 2014 Baltimore
77 White Paper 01 HCVS-WP-01: HCVS Dedicated Motive Force Scope of operator actions for selected HCVS electrical and pneumatic suppliesSome components in the HCVS system are powered electrically or pneumatically by non-dedicated sources as described in the plant CLB documents. Examples include:Inverters that supply AC power to solenoids for Primary Containment Isolation valves may be the same power source used for HCVS solenoids,Station batteries that supply DC power to HCVS solenoids may also supply other containment isolation valves,Station batteries that supply DC power to instrumentation in the main control room may also be used to indicate the need for HCVS operation and the status of the HCVS,Plant safety-related air or nitrogen systems used to operate isolation valves or safety-relief valves may be the same pneumatic supply used to operate HCVS valves.
78 White Paper 01 HCVS-WP-01: HCVS Dedicated Motive Force Conclusion: The use of some plant components to supply HCVS electrical and pneumatic power is acceptable provided these components can supply this power for 24 hours with simple and easily accomplished operator action.After 24 hours, the use of portable equipment to replenish these electrical and pneumatic power supplies per the NRC Order is acceptable provided the planned actions are evaluated under the plant conditions that could be reasonable to expect at the time and in the location the action will take place.
79 White Paper 02 HCVS-WP-02: Approach Objectives: Sequence per Diagram Minimize analysis requiredMaintain simplicityMaintain BWR fleet consistencySequence per DiagramHCVS Cycling EvaluationGeneric Radiological AnalysisScaled approach based upon capability to perform actions based on the results from bounding curveVent line dose curves (generated based on 1465 release fractions and timing) use simplified assumptions for “base” curve – 7 day curveSensitivity cases performed to evaluate reasonablenessOperator actions for portable equipment can be evaluated based upon MAAP-informed timing of GAP release and ex-vessel. Evaluated impacts will be driven primarily from containment shine and the location of the HCVS pipingOptional Site Analysis utilizing 1465 and site characteristics
80 White Paper 02 HCVS-WP-02: Cycling Summary In a simplistic view, the number of Wetwell vent cycles within the first 24 hours could be established based on the previous slide.Thus a generic number of 8 cycles is reasonableConsequently, the number of Drywell and Wetwell vent cycles within the first 24 hours could be established based on the previous slide.Thus a generic number of 12 cycles is reasonableThe number of cycles is very dependent on the strategy and scenario selected for the evaluation.Multiple Vent cycling is not a requirement in response to EA and the actual benefits have not yet been fully established as part of the filtering strategies rulemaking.
81 White Paper 02HCVS-WP-02: RadiologicalAppendix G of NEI provides a general description of approach to calculate source term based on RTM-96 and NUREG-1465.Number of variables that potentially impact calculation:Timing of eventSize of core, containment, and vent pipeDecayCore fraction release during phasesDecontamination factor (changes with pool temp & pH, location of discharge)Time of swapover from WW to DWDeposition in containmentDeposition in pipingSuppression pool bypass (Mark II containments)SRV Function
82 As expected, NUREG-1465 appears to be bounding White Paper 02HCVS-WP-02: Generic Radiological AnalysisMAAP runs to calculate fission product distributionTest case assumed 4 hour operation of RCICCore damage at approximately 6 hoursVessel breach at 15 hoursRADTRAD results using NUREG-1465 with limited pool scrubbing and depositionNUREG-1465 releasesPlot shifted by 6 hours to account for 4 hours of RCIC operationAs expected, NUREG-1465 appears to be bounding
83 White Paper 03 HCVS-WP-03: Hydrogen/CO Control Measures Option DescriptionAdvantagesDisadvantages1Design the entire vent piping beyond the primary containment isolation valves to withstand flammable gas detonation.Completely passiveAllows venting start/stop with any valveMay require valve(s) to be upgraded due to loadingMay require upgraded pipingMay require upgraded pipe supportsRequires more rigorous stress and support analysis2Install a purge system to prevent flammable gas detonation. Requires minimal modification to existing or as designed systemEliminates detonation concernActive featureManpower requirementAdditional maintenanceAdditional failure mode3Design the system downstream of the secondary containment isolation valve (or flow control valve) to withstand flammable gas detonation. Once CIVs are opened, subsequent vent start/stop cycles are controlled by the single downstream valveMinimizes piping potentially affected by detonationOverall system failure modes are reduced because of the reduced valve cycles within the system (PCIVs will remain open when vent is lined up)Downstream portion of piping still subject to disadvantages listed for Option 1Adds additional valve to the systemAdditional maintenance and testing of the added valveAdditional failure mode (potential failure of the additional valve)
84 White Paper 03 HCVS-WP-03: Hydrogen/CO Control Measures Option DescriptionAdvantagesDisadvantages4Install a check valve at the exhaust end of the vent stack to eliminate the ingress of air to the vent pipe when venting stops and the steam condenses. No operator action requiredEliminates detonation concernAdditional maintenanceAdditional failure modes (inability of check valve to open or to close once opened)5Install the secondary containment isolation valve (or flow control valve) at the exhaust end of the vent stack to eliminate the ingress of air to the vent pipe when venting stops and the steam condenses. Active featureManpower requirementAdditional maintenance and testingAdditional failure modeAdds challenges to support and maintain a large mass with an offset actuator at the end of the vent.6Design and install expansion chambers/mufflers in the exhaust pipe to reduce the detonation load. Completely passiveMinimizes detonation concernPotentially requires valve(s) to be upgraded due to loadingPotentially requires upgraded pipingPotentially requires upgraded pipe supportsPotentially requires more rigorous stress and support analysisMay impose excessive flow restrictionMay not reduce loading sufficiently
85 White Paper 04 HCVS-WP-04: FLEX/HCVS Interactions The purpose of this paper is to define the relationships between Order EA , Mitigation Strategies (aka FLEX) and Order EA , Severe Accident Hardened Containment Vent System (aka SA HCVS).The evaluation is to limit the unintended complications and potential impacts on the success of the FLEX mitigating strategies when applying the severe accidents conditions from the SA HCVS order.The relationship between FLEX and SA HCVS is clearly defined that FLEX is to mitigate core damage while the SA HCVS is to protect the primary containment for a Beyond Design Basis External Event and a postulated ex-vessel core melt.Thus the SA HCVS is required to be functional for FLEX mitigation actions, but applying any ex-vessel core melt criteria onto FLEX modifications and strategies is not a requirement.Where necessary, interpretations of these relationships are based on the order language and the corresponding NEI guidance documents (NEI and 13-02).
86 HCVS-WP-03 - Hydrogen/Carbon Monoxide Control Measures Bob Cowen, PESenior Engineer – GEHBWR Vent Order Implementation Workshop IIApril 9 – 10, 2014 • Baltimore, MD
87 EA BasicsThe HCVS…– Shall be designed to withstand and remain functional during severe accident conditions, including containment pressure, temperature, and radiation while venting steam, hydrogen and other non-condensable gases and aerosols.– Shall be designed and operated to ensure the flammability limits of gases passing through the system are not reached; otherwise, the system shall be designed to withstand dynamic loading resulting from hydrogen deflagration and detonation.– must assume Carbon Monoxide is in there with other non-condensable gases, …we’ll talk about that a bit laterSee as an EITHER/OR statementShould explain DDT and volume percent requirementsThe requirements cites flammability limit, this is 4% hydrogen by volume in an oxygen rich atmosphere. A DDT (leading to a detonation) will not occur at this concentration. Testing shows more on the order of 11 – 13% hydrogen is required (to support a DDT). However it must be assumed (from the next statement) that a detonation can occur so this is a moot point.
88 Here’s the scenario… Station is in a severe accident with fuel damage Containment has been vented several timesOnce the most recent venting is complete, vent is isolatedRemaining steam begins to condense in vent lineReduction of gas volume in vent causes air to be drawn inMixing has the potential to cause deflagrable/detonable mixture to be created in the vent pipeThere must be enough mixture to support DDT (L/D may be as low as 10)There are catalyst particles or another ignition source available
89 Hydrogen Generation Post-Accident Metal-Water Reaction – Most significant contributor of post-accident hydrogen. Oxidation of zirconium in cladding with any available water. Reaction is exothermic and self-supporting once 1500⁰F is reached so long as water/steam is available.Explosion occurred on March 12 at 15:36, venting had begun an hour earlierVenting had started at around 88 psia, self venting had started some 8 hours prior to the explosionVenting continued for several days based on 1F1 pressure DW traces
90 Carbon Monoxide Generation Post-Accident Primarily due to Core Concrete Interaction (CCI)Similar Chapman-Jouguet Pressure (Pcj) to hydrogen (therefore similar pressure spike to that of hydrogen)Based on NASA’s CEARUN program sensitivity studies, carbon monoxide detonation pressure can be considered as enveloped by that of hydrogen.Unit 3 vented for 26 hours, then the Rx Bldg. explodesUnit 3 continued venting for 19 more hours, then Unit 4 exploded
91 Fundamental Conclusions Relative to Combustible Gas Mixtures It is accepted that a detonation can be achieved based on the amounts of combustible gases produced during the course of a severe accident.Based on those gases produced, the hydrogen detonation peak pressure values are considered as bounding (relative to carbon monoxide).Each site must use this in conjunction with existing site commitmentsProbably the meat and potatoes of what the document provides is design pressure values, service level to drive allowables, and suggested and defendable loading conditions for detonation.
92 To Reiterate – Basic Hydrogen Vent Design Philosophies Either -Design your vent system such that it can accommodate a detonation and continue to effectively operate, …orDesign your vent system such that a flammable mixture cannot be achieved (such that a deflagration cannot occur – deflagration proof).
93 HCVS Design Options for Combustible Gas DescriptionCategory1Design for DetonationAccommodate Detonation2Install Purge System for Entire HCVSDeflagration Proof3Install Downstream Control Valve (or FCV)-Extend Containment/Partial Detonation ProofHybrid4Install Check Valve at Release Point (Extend Containment)5Install Control Valve (or FCV) at Release Point (Extend Containment)6Utilize Expansion Chambers/Mufflers to Reduce Detonation Load
94 Option 1 – Design Entire System for Detonation AdvantagesDisadvantagesCompletely passiveRequires valve(s) to be upgraded due to loadingPotentially requires upgraded pipingRequires upgraded pipe supportsRequires more rigorous stress and support analysis T₀ must be containment design pressure
95 Option 1 – Piping Pipe Size -> 12” 14” 16” 18” Grade A Schedule 40 Grade ASchedule 40Schedule 60Grade BStandardGrade CNotes:Schedule 40 pipe use for Grade A 16” and schedule 40 use for Grade B 18” are considered marginalColor for effect only, indicates departure from Std. scheduleIt is understood that such static loading will mainly manifest in pipe hoop stressCorrosion Allowance of 0.020” is ConsideredAll Piping SA Service Level C Allowables
96 Option 1 – ValvingExisting vent system valves are typically Air- Operated Standard Class 150 butterfly valves.As per ASME B16.34 – 2009, a like valve to account for detonation must be Class 900 or above.This roughly doubles the weight of the valve (depending on manufacturer).
97 Valve Changeout Changeout of a Torus Vent CIV A 900# Valve and actuator will be significantly heavier than the existing CIVConsideration must be given to “Torus Attached Piping”NUREG-0661 (for Mark I), Section 4.1, Subsection 3 cites affected appurtenancesNUREG-0487 (and Supplements) is the applicable document for Mark IIsIf there are interfaces with other systems (e.g., SGTS), the isolation valve(s) for that system will be affected
98 Option 2 – Install a Purge System AdvantagesDisadvantagesRequires minimal modification to existing or as designed systemEliminates detonation concernActive featureManpower requirementAdditional maintenanceAdditional failure modesPotentially difficult to operate manually at the remote panel. May need to be automatic from both locations
100 Option 2 Consider active or passive design Tie purge gas supply close to Control ValveUse Argon gas due to relatively high molecular weight and plentiful supplySite to perform volumetric calc and assure that vent is filled at completion of purgingAssure that ample Argon pre-staged or available for maximum venting cycles
101 Option 2 – Design Considerations Maximum Steam Condensation Rate CalcWorst case (coldest) ambient temperature (outside) must be consideredWorst case building temperature (adjacent to pipe) must be consideredInsulation must be considered
102 Option 3 – Install Downstream Control Valve AdvantagesDisadvantagesMinimizes piping potentially affected by detonationDownstream portion of piping still subject to disadvantages listed for Option 1Adds additional valve to the systemAdditional maintenance and testing of the added valveAdditional failure mode (potential failure of the additional valve)
103 Option 3 Configuration – Interim Control Valve
104 Option 3Extends containment such that upstream piping is inerted (steam, nitrogen) during ‘standby’ periodsDesign of downstream piping has option to consider –Designing shorter section for detonationInstalling minimal capacity purge system
105 Option 3 – Design Considerations If Designing for DetonationIf possible, place control valve at convenient location prior to last vertical leg of pipe to minimize complexity of stress analysisDesign for convenient support/anchor opportunity for control valve (maybe near pier, substantial concrete column or structural steel) to isolate the final run from inerted upstream piping
106 Option 3 – Design Considerations (cont.) If Designing Using PurgeConsider opportunity for easy tie-in to argon tank arrayPotentially consider manual system based on placement of valving and argon tanks (keeping in mind the reduced purge time for shorter runs)Note – Reference HCVS-FAQ-05 for valve and valve testing requirements
107 Option 4 – Check Valve at (or near) Release Point AdvantagesDisadvantagesEliminates detonation concernNo operator action requiredAdditional maintenanceAdditional failure modes (inability of check valve to open or to close once opened)Adds challenges to support and maintain a large mass at the end of the vent.
109 Option 4Install minimal leakage check valve at or near the outlet to the ventAt completion of venting, closed check valve will seal (with very minimal leakage) the contained volume of steam, H₂ and N₂With minimal oxygen constituent leaking in coupled with lack of mixing forces, deflagrable mixture is extremely unlikely
110 Option 4 – Design Considerations Place check valve just above roof level or adjacent to parapet (if mounted on building exterior wall) to facilitate support, maintenance and testing.Consider placing low dP rupture disc or PVC cap over valve for protectionConsider nitrogen blanketing of system for corrosion preventionConsider installing permanent work platform for maintenance and testing
111 Option 5 –Control Valve (or FCV) at (or near) Release Point AdvantagesDisadvantagesEliminates detonation concernActive featureManpower requirementAdditional maintenance and testingAdditional failure modeAdds challenges to support and maintain a large mass with an offset actuator at the end of the vent.
112 Option 5 Configuration – Downstream Control Valve
113 Option 5Similar to Option 4 as containment is extended (once venting system has begun to be used) to the release pointBased on higher pressure inside vent pipe volume, this eliminates leakage into that contained volume
114 Option 5 – Design Considerations As with Option 4, place control valve (or FCV) just above roof level or adjacent to parapet (if mounted on building exterior wall) to facilitate support, maintenance and testing.Consider placing low dP rupture disc or PVC cap over valve for protectionConsider nitrogen blanketing of system for corrosion preventionConsider installing permanent work platform for maintenance and testingReference HCVS-FAQ-05 for valve and valve testing requirements
115 Option 6 – Design Using Expansion Chambers/Mufflers to Reduce Detonation Load Detonation shock wave loads can be mitigated by rapid expansion and contractions in the exhaust pipeProper acoustic design using such devices works to counteract the axial forces from a detonation
116 Option 6 – Design Considerations Must consider additional flow resistanceMust take into account complexity associated with design and constructability of system using these devicesWill still be some residual loading associated with minimized shock waves (due to detonation) which will need to be considered in design
117 Options Not Considered Feasible Incorporation of Detonation/Flame ArrestorsConsideration of a Recombination Device or DevicesConsideration of a Venturi Mixing DeviceConsideration of Heating Downstream Piping