BWR Vent Order
Implementation Workshop II
April 9 -10, 2014
Baltimore
Workshop Purpose and Plan
•
Phase 1 (wet well) template for Overall
Implementation Plans for NRC Order EA-13-109.
•
Review 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.
BWR Mark I/II Severe Accident Vent Order
Key Dates
•
Order issued June 6, 2013; two phases

Severe accident wetwell vent by June 30, 2018

Severe accident drywell vent by June 30, 2019
o
•
Option to demonstrate drywell vent not needed
Guidance NEI 13-02 R.0 and JLD-ISG-2013-02 R.0

Phase 1 (WW) Guidance issued November 2013

Developing template for Overall Integrated Plan for meeting
Order.

BWROG developing engineering guidance for vent.
• Phase 2 (DW) Guidance by April 2015
Venting and Filtering Strategies
BWR Mark I and II
•
•
•
Prevent core damage during SBO/ELAP
 Venting via hardened wetwell vent
 Water injection via FLEX
Following core damage during SBO/ELAP,
prevent containment failure
 Venting via hardened wetwell and/or drywell
vent
 Water injection via “beyond FLEX”
Filtering releases via containment water injection
and pressure control
Phase 1 Activities Timeline
Post OIP Template Development
•
June 2014
•
July – Aug 2014 – Develop 6-month status
•
Oct 2014
– Phase 1 pilot plant ISE issued
•
•
•
Dec 2014
– All Phase 1 plant ISE issued
Dec 2014
– 1st 6-month status due
– Phase 1 OIP due
template
Estimated Phase 2 Guidance
Timeline
Mar 2014
Apr – May 2014
Jun – Sep 2014
Oct 2014
Nov 2014
Dec 2014
Feb 2015
Mar 2015
Mar 2015
Apr – May 2015
May – Jul 2015
Aug 2015
Sep 2015
Oct 2015
Dec 2015
– NEI Working Group define goals and approach for Phase 2
– NEI WG draft 13-02 Phase 2 scope from Industry perspective
– NRC/NEI Draft 13-02 Phase 2 scope
– NEI/BWROG Industry Comment and Feedback
– NEI Phase 2 Draft Revision Provided to NRC for reference in
ISG
– NRC publish draft ISG for public comment
– NRC Public comment period closed
– NRC Issues approved ISG
– NEI/NRC Workshop on Phase 2
– NRC/NEI OIP Template structure and content without Pilots
– NRC/NEI OIP Template Pilots including Option for No DW Vent
Pilot
– NEI/BWROG Draft OIP To Industry for Comment for Workshop
– NEI/NRC OIP Workshop on Pilots and Template use
– NEI OIP finalized and included in a revision to 13-02
– Stations OIP due to NRC
INDUSTRY DOCUMENT OVERVIEW AND
STRUCTURE
Industry Documents
•
Template timeline
•
FAQ & White Paper Process
•
Selected Template Elements



Generic
Plant Hatch Pilot
Nine Mile Point 2 Pilot
Template Development Information
and Key Dates
• Template Development
 Pilot plant(s) identified – Hatch as MK I & NMP2 as MK II
 Draft template by January 20, 2014 – Presented on Jan 15
 Final Draft template March 15, 2014 – After Pilots
 NEI 13-02 Revision for OIP template and FAQs by April 21,
2014
• NRC-NEI Joint Template Meetings




January 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 Baltimore
• NRC-NEI Check-up Conference Call Proposed
for May 7
Frequently Asked Questions
•
Clarification items brought to industry NEI 13-02 core team
•
NEI 13-02 Core Team to provide consensus response
•
Select FAQs presented to the NRC staff in draft version
(interpretation FAQs)
•
Final FAQ documented on NEI website
•
Clarification items larger than FAQ will be resolved via other
means of NEI 13-02 revision or white paper endorsement
•
Phase 2 revision of NEI 13-02 will incorporate appropriate
FAQs or white papers
Frequently Asked Questions
FAQ Number
HCVS-01
HCVS-02
HCVS-03
HCVS-04
HCVS-05
HCVS-06
HCVS-07
HCVS-08
HCVS-09
NEI 13-02
Subject
Section
4.2.2, 4.2.3 HCVS Primary Controls and Alternate Controls and
Monitoring Locations
1.2.6 HCVS Dedicated Equipment
1.2.5, 1.2.6, HCVS Alternate Control Operating Mechanisms
4.2.3
4.1.5 HCVS Release Point
4.1.4, 4.1.6, HCVS Control and ‘Boundary Valves’
6.2
Multiple FLEX Assumptions/HCVS Generic Assumptions
4.2.5 Consideration of Release from Spent Fuel Pool
Anomalies
4.2.2, 4.2.4 HCVS Instrument Qualifications
Multiple Use of Toolbox Actions for Personnel
FAQ HCVS-01, 02, 03, 04, 05, 06, 07 and 08 have been submitted for NRC Concurrence
White Paper Topics
• HCVS-WP-01: HCVS Dedicated Motive Force
 Scope of operator actions for selected HCVS electrical and
pneumatic supplies
• HCVS-WP-02: HCVS Cyclic Operations Approach
 Accident sequence
 Number of vent cycles
 Radiological limitations from HCVS operation
• HCVS-WP-03: Hydrogen/CO Control Measures
 Passive measures
 Active measures
• HCVS-WP-04: FLEX/HCVS Interactions
 Portable equipment use under severe accident and BDBEE
conditions
OUTLINE OF PHASE 1 TEMPLATE
Template Elements
Template Goals:
 Use Hybrid 050/049 Template with Order and ISG
(NEI 13-02) Cross Reference
 Directly align to the ISG
o Describe the phased approach to implementation
o Big picture schedule statement
o Wetwell performance objectives
 Discuss the section 1.1 objectives of attachment 2 in
order
 Discuss the requirements in sections 4.1, 4.2 and 6.1
and appendix's F and G of NEI 13-02
o Drywell performance objectives
o Quality standards
o Programmatic requirements
 Linkage to ISE or SE
Template Elements
Proposed Template with Order and ISG (NEI 13-02) Cross
Reference:
Introduction
Part 1: General Integrated Plan Elements and Assumptions
Part 2: Boundary Conditions for WW Vent with specifics about the compliance
actions relative to the ISG and NEI 13-02 section 2
Part 3: Boundary Conditions for DW Vent with specifics about the compliance
actions relative to the ISG and NEI 13-02 section 3
Part 4: Programmatic Controls, Training, Drills and Maintenance Elements
Part 5: Milestone table elements
Attachment 1: Portable Equipment
Attachment 2: Sequence of Events Timeline
Attachment 3: Conceptual Sketches
Attachment 4: Failure Evaluation Table
Attachment 5: References
Attachment 6: Changes/Updates to this OIP
Attachment 7: Open Items in HCVS OIP
Template Elements
Part 1: General Integrated Plan Elements
and Assumptions

Key Site assumptions to implement
NEI 13-02 strategies
o Grouping of Assumptions as FLEX,
Generic and Site Specific.
o Considering making an FAQ on FLEX
assumptions and one on Generic to
use as a reference in the template.
Template Elements
Part 2: Boundary Conditions for WW Vent
with specifics about the compliance actions
relative to the ISG and NEI 13-02 section 2

Severe Accident
o First 24
o Beyond 24 hours
 Support Equipment Functions
o BDBEE Venting
o Severe Accident Venting
17
Template Elements
Part 4: Programmatic Controls, Training, Drills and
Maintenance Elements
Part 5: Milestone table elements
Attachments
 Attachment 1: Portable Equipment
 Attachment 2: Sequence of Events Timeline
o Operator action constraints timeline is determined based
on the following sequences:
o Sequence 1 is a FLEX run with Venting in a BDBEE without
core damage.
o Sequence 2 is based on SECY-12-0157 results for a
prolonged SBO (ELAP) with the delayed loss of RCIC
o Sequence 3 is based on SOARCA results for an SBO
(ELAP) with failure of RCIC to inject.
3/10/2016
18
Representative BWR Venting Timelines
SBO
t=0s
Anticipatory
Venting
RCIC
starts
t ≈.5 m
Case 1
Ref: Plant
t ≈ 5 hrs
t ≈ 18 hrs
No Injection
No Injection
Portable generator providing power
to Safety Related 480VAC System
(Ref Plant OIP)
Containment Venting
(anticipatory venting not represented in SECY-12-0157)
Level at
TAF
t ≈ 23 hrs
Core
Damage
Vessel
Breach
Case 2
Ref: SECY-12-0157
t ≈ 24 hrs
t ≈ 34 hrs
Containment Venting
(based on exceeding PCPL)
Core
Damage
Vessel
Breach
Case 3
Ref: SOARCA
t ≈ 1 hr
t≈ 8 hr
Legend
Adequate core cooling maintained
Injection Lost
Increased shine and leakage of radionuclides primarily from
Wetwell
HCVS Post Core Damage Dose Evaluation Required
References:
Case 1: Reference Plant FLEX Overall Integrated Plan
Case 2: SECY-12-0157 – ML12344A030
Case 3: SOARCA – ML13150A053
Not to scale
REVIEW OF KEY ELEMENTS OF PHASE 1
OVERALL INTEGRATED PLAN TEMPLATE
Hatch SA HCVS Pilot Template
Elements
Review of Plant Hatch completion of
items in revision C3 of the Severe
Accident HCVS OIP Template
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
Hatch OIP Major Elements
• Adding Site Characteristics important to
HCVS
 Control Building and Rx Building
Layout
 Main Stack and vent pipe locations
• Time and Environmental Constraint Items
 Rupture disc
 HCVS Operation
 Battery power actions
 >24 Hour motive force
NMP2 OIP
Site Characteristics Important to HCVS
• The primary location for HCVS operation will
be the Main Control Room
• The alternate location for HCVS operation will
be the Reactor Building track bay, northeast
side of Reactor Building, ground elevation
• The HCVS release point will be at least 3 feet
above the top of the Reactor Building on the
northwest side of the Reactor Building
Hatch HCVS Venting Timelines
t ≈.5 m t = 1 hr
t=0s RCIC
ELAP
SBO starts Declared
Blow rupture
disc
t ≈ 18 hrs
t ≈ 7 hrs
Anticipatory
Venting
No Injection
No Injection
Containment Venting
(anticipatory venting
not represented in
SECY-12-0157)
t ≈ 10 hrs
Portable generator in place
for FLEX and HCVS loads.
Level at
TAF
t ≈ 23 hrs
Containment Venting
(based on preventing exceeding PCPL)
Level
at
TAF
t ≈ 1 hr
Core
Damage
t ≈ 2 hr
t≈ 8 hrs
Core
Damage
t ≈ 24 hrs
t ≈ 11 hrs
Begin monitoring at MCR or ROP
HCVS pneumatic and battery status.
No replenishment expected to be
required before t = 24 hours
Vessel
Breach
Case 1
FLEX Successful
Ref: HNP FLEX OIP
Vessel
Breach
t ≈ 34 hrs
t ≈ 24 hrs
Replenishment of HCVS
power and pneumatic
supplies
t ≈ 12 hrs
Transfer to
HCVS Battery
t ≈ 11 hrs
t ≈ 12 hrs
Legend
Adequate core cooling maintained
Injection Lost
Increased shine and leakage of radionuclides primarily from
Wetwell
HCVS Post Core Damage Dose Evaluation Required
HCVS Time evaluation required
Case 2
RCIC Late Failure
Ref: SECY-12-0157
t ≈ 24 hrs
Case 3
RCIC Early Failure
Ref: SOARCA
References:
Case 1: HNP FLEX Overall Integrated Plan
Case 2: SECY-12-0157 – ML12344A030
Case 3: SOARCA – ML13150A053
Not to scale
NMP2 OIP
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.
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 13-02 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
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]
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
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 generator
• The 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
Hatch OIP Major Elements
• Vent characteristics
 Boundary valve use and cross flow
 Remote operating station use
 FLEX type actions
 Electric power details
• Milestone schedule
NMP2 OIP Differences
NMP2 OIP Differences
NMP2 OIP Differences
Drywell piping and valve
configuration shown for
completeness, not for
Phase 1 compliance
NMP2 OIP Differences
Equipment Usage
• NMP2 will utilize a mixed system, sharing the
following components
 Containment penetrations
 Inboard and Outboard PCIVs
 Piping to HCVS vent tee
• Boundary with interfacing systems limited to
 20” AOV to Standby Gas Treatment System
(GTS)
 2” SOV bypass around 20” AOV to GTS
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
containment
• Most plants implemented a GDC-56 exemption
as part of the plant design basis for an
alternate configuration
• The inboard PCIV will be located outside the
containment and thereby significantly improve
the reliability of the HCVS system
NMP2 OIP Differences
Discharge Point
• NMP2 will utilize a release point above the
Reactor Building roof independent of the
metrological stack
• Follows criteria per FAQ HCVS-04
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 operation
• On loss of AC power, a battery capable of supplying
HCVS loads for at least 24 hours will supply HCVS
loads without Operator action
• A FLEX portable diesel will be connected to repower
the 600 volt power within 8 hours to repower the
HCVS battery charger
• A 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 switch
• Station batteries will not be utilized for HCVS loads
NMP2 OIP Differences
NMP2 OIP Differences
Containment Protection Features
• Inadvertent actuation protection is provided by
keylock switches used to power up the HCVS panel
• Additional 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 leads
• There are no rupture discs in the NMP2 HCVS
design
NMP2 OIP Differences
Remote Manual Mechanisms
• Manual valves in the pneumatic supply lines
will provide alternate means for HCVS valve
operation
• Electrical power is not required for this method
• A manual override for HCVS valve solenoids is
being considered
• A handwheel for the PCV is being considered,
but will not be credited due to environmental
concerns in proximity to the valve
Hatch OIP Major Elements
• Portable equipment use
 Without core damage
 With core damage
• Example Drawings
 Electrical
 Mechanical
 Plant Layout
NMP2 OIP Differences
Drywell piping and valve
configuration shown for
completeness, not for
Phase 1 compliance
NMP2 OIP Differences
Table 4A: Wetwell HCVS Failure Evaluation Table
Functional Failure
Mode
Failure Cause
Alternate Action
Fail to Vent (Open)
on Demand
Valves fail to open/close due to loss of normal
AC power/DC batteries
Valves fail to open/close due to depletion of
dedicated power supply
Valves fail to open/close due to complete loss
of power supplies
Valves fail to open/close due to loss of normal
pneumatic supply
None required – system SOVs utilize
dedicated 24-hour power supply
Recharge system with FLEX provided
portable generators
Manually operate backup pneumatic
supply/vent lines at remote panel
No action needed. Valves are provided with
dedicated motive force capable of 24 hour
operation
Replace bottles as needed and/or recharge
with portable air compressors
Manually operate backup pneumatic
supply/vent lines at remote panel
N/A
Valves fail to open/close due to loss of
alternate pneumatic supply (long term)
Valve fails to open/close due to SOV failure
Fail to stop venting
(Close) on demand
Spurious Opening
Spurious Closure
Not credible as there is not a common mode
failure that would prevent the closure of at
least 1 of the 3 valves needed for venting.
Not credible as key-locked switches prevent
mispositioning of the HCVS CIVs and PCV.
Valves fail to remain open due to depletion of
dedicated power supply
Valves fail to remain open due to complete
loss of power supplies
Valves fail to remain open due to loss of
alternate pneumatic supply (long term)
Failure with Alternate
Action Prevents
Containment Venting?
No
No
No
No
No
No
No
N/A
No
Recharge system with FLEX provided
portable generators
Manually operate backup pneumatic
supply/vent lines at remote panel
Replace bottles as needed and/or recharge
with portable air compressors
No
No
No
BWROG Companion Guideline
for NEI 13-02
Progress between Workshops
Pat Fallon - DTE
Dennis Henneke - GEH
BWR Vent Order Implementation Workshop II
4/9/14 • Baltimore, MD
Introduction
• The BWROG Implementation Guidelines
supporting NEI 13-02 (referred to as the
Companion Document) is developed to:
- Provide guidance on “how to” meet the “what”
requirements in NEI 13-02 and NRC Order EA-13109.
- Include discussion previously removed from 13-02,
due to level of detail (e.g. Hydrogen
Overpressure).
BWROG Companion Document
• Beginnings:
- Started as discussion point during formulation of NEI-13-02
• NEI-13-02 was created to work with EA-13-109 to fully define
acceptable equipment and man-machine interface to make a
successful Severe Accident Capable Hardened Vent.
• NEI-13-02 did NOT contain any “how to” elements for
implementation.
• NEI-13-02 was endorsed (largely) by the NRC due to multiple
interface sessions with a small industry team and NEI.
• NEI-13-02 needed to have additional industry input to create a
workable method for HCVS implementation that would allow use
of work conducted for EA-12-050 and still meet the intents of NEI13-02.
BWROG Companion Document
• Thanks to the Authors:
-
Pat Fallon - DTE
Shayne Tenace - Exelon
Bob Cowen - GEH
David Burch - Entergy
Deep Ghosh - SNC
Bob Ginsberg – Duke Energy
Frank Loscalzo - TVA
-
Dennis Henneke - GEH
Scott Wood - Energy NW
Harold Trenka - Exelon
Phil Amway - Exelon
Keith Ward – Duke Energy
Glen Seeman – GEH
Rich Centenaro - PPL
Also THANKS to the large group of reviewers and
commenters.
BWROG Companion Document
• First Pass
- Introduced the concept at first HCVS Workshop in
Baltimore 11-13-2013.
- Slides 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.
BWROG Companion Document Outline
(11-13-13 Version)
5.0
PROGRAMMATIC CONTROLS
5.1 Environmental conditions &
Methods to Confirm for Each
Site
5.2 Seismic and External Hazard
Conditions & Relation to
Seismic/Flood Reanalysis
5.3 Quality Requirements &
Interface with other
Standards
5.4 Maintenance Requirements
& Interface with
Maintenance Rule/INPO
Standards
TBD
TBD
TBD
TBD
BWROG Companion Document Outline
(4/6/14 version)
5.0
PROGRAMMATIC CONTROLS
5.1 Environmental conditions &
Methods to Confirm for Each
Site
5.2 Seismic and External Hazard
Conditions & Relation to
Seismic/Flood Reanalysis
5.3 Quality Requirements &
Interface with other
Standards
5.4 Maintenance Requirements
& Interface with
Maintenance Rule/INPO
Standards
Keith Ward
Scott Wood
Keith Ward
Scott Wood,
Jesse Lucas
Pat/Phil
Amway
Frank Loscalzo
Pat/Phil
Amway
Frank Loscalzo
Guidance added on
environmental conditions and
HCVS-FAQ-04
Guidance added on Seismic,
wind loading and other items
Guidance added on
instrument quality and HCVSFAQ-08/OIP Template
Guidance added on
programmatic requirement
and interface with OIP
Template
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.
BWROG Companion Document
• Evolution:
- February, 2014:
•
•
•
•
Document Pages: from 96 to 127
Sections with guidance: 69
New Appendices: 4
Contributors: 18
- March, 2014
•
•
•
•
•
Document pages: from 127 to 138
Sections with guidance: 77
New Appendices: 5
Contributors: 16
Interfaces with 9 HCVS-FAQs, 3 HCVS-WPs, and OIP Template
(alignment)
BWROG Companion Document Content (April 2014)
• Section 4.1
- Vent Capacity determination methods and criteria to
allow < 1% Steam discharge
- Multi-purpose penetrations (HCVS-FAQ-02, -05) to
discuss requirements for use and testing of PCIVs
- Routing 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.
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 gas
Combined WW/DW piping
Fault/Failure evaluations
• Evaluation should include any systems or operations
used for Hydrogen Control.
BWROG Companion Document Content (April 2014)
• Section 4.2
- Inadvertent actuation prevention
- Primary/Alternate Controls areas (See HCVS-FAQ01, -02)
- Vent Monitoring (See HCVS-FAQ-02, -08)
- Operational Hazards (See HCVS-FAQ-01, -02, -03)
- Design to Minimize Operator actions (See HCVSFAQ-02)
BWROG Companion Document Content (April 2014)
• Section 5
- Environmental conditions
- Seismic and external conditions
- Quality (See HCVS-FAQ-08)
- Maintenance (Tie to Template Part 4)
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 6
- Accessibility and feasibility
- Procedures (Tie to Template Part 4)
- Training (Tie to Template Part 4)
• Appendices
- Roadmap (shows FAQ Ties)
- Source Term and Dose method defined
- Combustible and Flammable gases methods
- Pipe sizing methodologies (NEW)
- Load combination methodologies (NEW)
- Use of MAAP for timing, Dose Estimate, or estimating number of cycles
(NEW).
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.
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.
FREQUENTLY ASKED QUESTIONS
and
WHITE PAPERS
FAQ 01
•
HCVS-FAQ-01: Primary and Alternate Controls and Monitoring locations
Q: What conditions have to be considered in the design and location of the Primary
and Alternate Controls locations?
o Order Element 1.2.4 states, “operations from a control panel located in the
main control room or a remote but readily accessible location.”
o Order Element 1.2.5 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:
o Accessibility
o Habitability
o Staffing sufficiency
o Communication capability with vent use decision makers
FAQ 02
• HCVS-FAQ-02: Dedicated Equipment
Q: What is the meaning of “Dedicated” in order element 1.2.6, “Order
Reference: 1.2.6 – 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]”.
o Using this literal interpretation, the words of Order element 1.2.6
means that all equipment associated with the HCVS should be
permanently installed and only serve the HCVS function.
o 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.
o The intent of “dedicated” as it is used in Order EA-13-109 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.
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:
o 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.
o Containment Isolation valves in the HCVS system may provide a containment isolation
function independent of the HCVS function.
o Containment Isolation valve position indication for valves in the HCVS may be used for postaccident indications.
o 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:
o Containment penetrations
o Containment isolation valves
o System boundary valves
o Piping
o Instrumentation
o Wiring, conduit and connection points used to service non-dedicated components
o DC battery systems
 The above components need not be dedicated, but they support the HCVS functionality when
containment venting using the HCVS system is required. Compliance with NEI 13-02 guidance
will ensure that this condition is met.
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 Element 1.2.5.
 The examples of alternate operating mechanisms provided in Order element
1.2.5 (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:
o Separate electrical components with diverse and flexible power supplies
(such as the normal valve operators with FLEX power)*
o Solenoid valves with manual overrides that may be used to manually
operate vent valves without electrical power
o Manual valves in pneumatic supply and vent lines that may be used to
manually operate vent valves independent of solenoid valves or electrical
power
o Hydraulic operators
* NEI 13-02 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.
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: 1.2.2 – The HCVS shall discharge the effluent to a release
point above main plant structures.”
o 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).
o 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.
o The Plant Stack provides an acceptable release point
o Sites may take exception to this guidance with reasonable basis
 Guidance 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)
FAQ 05
• 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.
o 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.
3/10/2016
68
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.
o

PCIVs – Testing criteria for PCIVs will not change.
o

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.
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.
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
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-12-051
Level 2 with either on-site or off-site
resources such that no contribution to
analyzed source term need be considered
FAQ 07
•
HCVS-FAQ-07: Spent Fuel Pool
 NRC comment: Item requires further information and clarification.
o 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-13-109 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-12-049 provides multiple mitigation actions
to protect SFP cooling and Order EA-12-051 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.
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?
o Order Element 1.2.4 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.”
o Order Element 1.2.5 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.”
o Order Element 1.2.6 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.”
FAQ 08
•

HCVS-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.
o
o
o
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 space
HCVS controls and instrumentation located outside the MCR will be
similar to other instrumentation and controls found in plant locations
outside the MCR.
o
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.
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:
oOpening doors when room temperatures become
elevated
oUsing flashlights to supplement pathway use
oExchange of personnel, use of ice vests, etc. when
action is in an uncomfortable environment, not life
threatening
oUtilizing small fans for air movement, possibly
powered from small portable generators and
extension cords
BWR Vent Order
Implementation Workshop II
April 9 -10, 2014
Baltimore
White Paper 01
• HCVS-WP-01: HCVS Dedicated Motive Force
 Scope of operator actions for selected HCVS electrical and
pneumatic supplies
 Some components in the HCVS system are powered
electrically or pneumatically by non-dedicated sources as
described in the plant CLB documents. Examples include:
o Inverters that supply AC power to solenoids for Primary
Containment Isolation valves may be the same power
source used for HCVS solenoids,
o Station batteries that supply DC power to HCVS solenoids
may also supply other containment isolation valves,
o 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,
o 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.
White Paper 01
•
HCVS-WP-01: HCVS Dedicated Motive Force
 Conclusion:
o
o
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.
White Paper 02
HCVS-WP-02: Approach
• Objectives:
 Minimize analysis required
 Maintain simplicity
 Maintain BWR fleet consistency
• Sequence per Diagram
• HCVS Cycling Evaluation
•
Generic Radiological Analysis
 Scaled approach based upon capability to perform actions based on the
results from bounding curve
o Vent line dose curves (generated based on 1465 release fractions and timing) use
simplified assumptions for “base” curve – 7 day curve
o Sensitivity cases performed to evaluate reasonableness
o Operator 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 piping
 Optional Site Analysis utilizing 1465 and site characteristics
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.
o Thus a generic number of 8 cycles is reasonable
 Consequently, the number of Drywell and Wetwell vent
cycles within the first 24 hours could be established based
on the previous slide.
o Thus a generic number of 12 cycles is reasonable
 The 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 EA13-109 and the actual benefits have not yet been fully
established as part of the filtering strategies rulemaking.
White Paper 02
HCVS-WP-02: Radiological
• Appendix G of NEI 13-02 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 event
Size of core, containment, and vent pipe
Decay
Core fraction release during phases
Decontamination factor (changes with pool temp & pH,
location of discharge)
Time of swapover from WW to DW
Deposition in containment
Deposition in piping
Suppression pool bypass (Mark II containments)
SRV Function
White Paper 02
HCVS-WP-02: Generic Radiological Analysis
• MAAP runs to calculate fission product distribution
 Test case assumed 4 hour operation of RCIC
 Core damage at approximately 6 hours
 Vessel breach at 15 hours
• RADTRAD results using NUREG-1465 with limited pool
scrubbing and deposition
• NUREG-1465 releases
 Plot shifted by 6 hours to account for 4 hours of RCIC
operation
As expected, NUREG-1465 appears to be bounding
White Paper 03
•
HCVS-WP-03: Hydrogen/CO Control Measures
Option
Description
Advantages
1
Design the entire vent piping beyond Completely passive
the primary containment isolation
• Allows venting start/stop
valves to withstand flammable gas
with any valve
detonation.
1. Requires minimal
modification to existing or
as designed system
2. Eliminates detonation
concern
Disadvantages
1. May require valve(s) to be upgraded due to
loading
2. May require upgraded piping
3. May require upgraded pipe supports
4. Requires more rigorous stress and support
analysis
1. Active feature
2. Manpower requirement
3. Additional maintenance
4. Additional failure mode
2
Install a purge system to prevent
flammable gas detonation.
3
Design the system downstream of
1. Minimizes piping potentially Downstream portion of piping still subject to
the secondary containment isolation
affected by detonation
disadvantages listed for Option 1
valve (or flow control valve) to
2. Overall system failure
• Adds additional valve to the system
withstand flammable gas
modes are reduced
• Additional maintenance and testing of the
detonation. Once CIVs are opened,
because of the reduced
added valve
subsequent vent start/stop cycles are
valve cycles within the
• Additional failure mode (potential failure of the
controlled by the single downstream
system (PCIVs will remain
additional valve)
valve
open when vent is lined up)
White Paper 03
•
HCVS-WP-03: Hydrogen/CO Control Measures
Option
Description
Advantages
4
Install a check valve at the exhaust 1. No operator action
end of the vent stack to eliminate
required
the ingress of air to the vent pipe
2. Eliminates detonation
when venting stops and the steam
concern
condenses.
5
Install the secondary containment
1. Eliminates detonation
isolation valve (or flow control valve)
concern
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.
6
Design and install expansion
chambers/mufflers in the exhaust
pipe to reduce the detonation load.
1. Completely passive
2. Minimizes detonation
concern
Disadvantages
1. Additional maintenance
2. Additional failure modes (inability of check valve
to open or to close once opened)
1. Active feature
2. Manpower requirement
3. Additional maintenance and testing
4. Additional failure mode
5. Adds challenges to support and maintain a large
mass with an offset actuator at the end of the
vent.
1. Potentially requires valve(s) to be upgraded due
to loading
2. Potentially requires upgraded piping
3. Potentially requires upgraded pipe supports
4. Potentially requires more rigorous stress and
support analysis
5. May impose excessive flow restriction
6. May not reduce loading sufficiently
White Paper 04
• HCVS-WP-04: FLEX/HCVS Interactions
 The purpose of this paper is to define the relationships between
Order EA-12-049, Mitigation Strategies (aka FLEX) and Order EA13-109, Severe Accident Hardened Containment Vent System (aka
SA HCVS).
o 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.
o 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.
o Where necessary, interpretations of these relationships are based
on the order language and the corresponding NEI guidance
documents (NEI 12-06 and 13-02).
HCVS-WP-03 - Hydrogen/Carbon
Monoxide Control Measures
Bob Cowen, PE
Senior Engineer – GEH
BWR Vent Order Implementation Workshop II
April 9 – 10, 2014 • Baltimore, MD
EA-13-109 Basics
The HCVS…
• 1.2.10 – 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.
• 1.2.11 – 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.
Here’s the scenario…
1.
Station is in a severe accident with fuel damage
2.
Containment has been vented several times
3.
Once the most recent venting is complete, vent is isolated
4.
Remaining steam begins to condense in vent line
5.
Reduction of gas volume in vent causes air to be drawn in
6.
Mixing has the potential to cause deflagrable/detonable mixture to be
created in the vent pipe
7.
There must be enough mixture to support DDT (L/D may be as low as 10)
8.
There are catalyst particles or another ignition source available
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.
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.
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).
To Reiterate – Basic Hydrogen Vent Design
Philosophies
Either 1. Design your vent system such that it can
accommodate a detonation and continue to
effectively operate, …or
2. Design your vent system such that a
flammable mixture cannot be achieved (such
that a deflagration cannot occur –
deflagration proof).
HCVS Design Options for Combustible Gas
Optio Description
n
1
Design for Detonation
2
3
4
Category
Accommodate
Detonation
Install Purge System for Entire HCVS Deflagration
Proof
Install Downstream Control Valve
Hybrid
(or FCV)-Extend
Containment/Partial Detonation
Proof
Install Check Valve at Release Point Deflagration
(Extend Containment)
Proof
Option 1 – Design Entire System for Detonation
Advantages
Disadvantages
1.Completely passive
1.Requires valve(s) to be
upgraded due to loading
2.Potentially requires
upgraded piping
3.Requires upgraded pipe
supports
4.Requires more rigorous
stress and support
analysis
Option 1 – Piping
Pipe Size ->
12”
14”
16”
18”
Grade A
Schedule 40
Schedule 40
Schedule 40
Schedule 60
Grade B
Standard
Schedule 40
Schedule 40
Schedule 40
Grade C
Standard
Standard
Standard
Schedule 40
Notes:
• Schedule 40 pipe use for Grade A 16” and schedule 40 use for Grade B 18” are
considered marginal
• Color for effect only, indicates departure from Std. schedule
• It is understood that such static loading will mainly manifest in pipe hoop stress
• Corrosion Allowance of 0.020” is Considered
• All Piping SA-106 - Service Level C Allowables
Option 1 – Valving
• Existing vent system valves are typically AirOperated 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).
Valve Changeout
Changeout of a Torus Vent CIV
• A 900# Valve and actuator will be significantly heavier
than the existing CIV
• Consideration must be given to “Torus Attached
Piping”
• NUREG-0661 (for Mark I), Section 4.1, Subsection 3
cites affected appurtenances
• NUREG-0487 (and Supplements) is the applicable
document for Mark IIs
• If there are interfaces with other systems (e.g., SGTS),
the isolation valve(s) for that system will be affected
Option 2 – Install a Purge System
Advantages
Disadvantages
1.Requires minimal
modification to
existing or as
designed system
2.Eliminates
detonation concern
1.Active feature
2.Manpower requirement
3.Additional maintenance
4.Additional failure modes
5.Potentially difficult to operate
manually at the remote panel.
May need to be automatic
from both locations
Option 2 Configuration – Purge
Option 2
• Consider active or passive design
• Tie purge gas supply close to Control Valve
• Use Argon gas due to relatively high
molecular weight and plentiful supply
• Site to perform volumetric calc and assure
that vent is filled at completion of purging
• Assure that ample Argon pre-staged or
available for maximum venting cycles
Option 2 – Design Considerations
• Maximum Steam Condensation Rate Calc
- Worst case (coldest) ambient temperature
(outside) must be considered
- Worst case building temperature (adjacent
to pipe) must be considered
- Insulation must be considered
Option 3 – Install Downstream Control Valve
Advantages
Disadvantages
1.Minimizes piping
1.Downstream portion of piping still
potentially affected by
subject to disadvantages listed for
detonation
Option 1
2.Adds additional valve to the system
3.Additional maintenance and testing
of the added valve
4.Additional failure mode (potential
failure of the additional valve)
Option 3 Configuration – Interim Control Valve
Option 3
• Extends containment such that upstream
piping is inerted (steam, nitrogen) during
‘standby’ periods
• Design of downstream piping has option to
consider –
- Designing shorter section for detonation
- Installing minimal capacity purge system
Option 3 – Design Considerations
• If Designing for Detonation
- If possible, place control valve at convenient
location prior to last vertical leg of pipe to
minimize complexity of stress analysis
- Design 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
Option 3 – Design Considerations (cont.)
• If Designing Using Purge
- Consider opportunity for easy tie-in to argon tank
array
- Potentially 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
Option 4 – Check Valve at (or near) Release
Point
Advantages
1.Eliminates detonation
concern
2.No operator action
required
Disadvantages
1.Additional maintenance
2.Additional failure modes
(inability of check valve to
open or to close once
opened)
3.Adds challenges to support
and maintain a large mass
at the end of the vent.
Option 4 Configuration – Downstream Check
Valve
Option 4
• Install minimal leakage check valve at or near
the outlet to the vent
• At completion of venting, closed check valve
will seal (with very minimal leakage) the
contained volume of steam, H₂ and N₂
• With minimal oxygen constituent leaking in
coupled with lack of mixing forces, deflagrable
mixture is extremely unlikely
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 protection
• Consider nitrogen blanketing of system for corrosion
prevention
• Consider installing permanent work platform for
maintenance and testing
Option 5 –Control Valve (or FCV) at (or near)
Release Point
Advantages
1.Eliminates
detonation
concern
Disadvantages
1.Active feature
2.Manpower requirement
3.Additional maintenance and testing
4.Additional failure mode
5.Adds challenges to support and
maintain a large mass with an offset
actuator at the end of the vent.
Option 5 Configuration – Downstream Control
Valve
Option 5
• Similar to Option 4 as containment is
extended (once venting system has begun to
be used) to the release point
• Based on higher pressure inside vent pipe
volume, this eliminates leakage into that
contained volume
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 protection
• Consider nitrogen blanketing of system for corrosion
prevention
• Consider installing permanent work platform for
maintenance and testing
• Reference HCVS-FAQ-05 for valve and valve testing
requirements
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 pipe
• Proper acoustic design using such devices
works to counteract the axial forces from a
detonation
Option 6 – Design Considerations
• Must consider additional flow resistance
• Must take into account complexity associated
with design and constructability of system
using these devices
• Will still be some residual loading associated
with minimized shock waves (due to
detonation) which will need to be considered
in design
Options Not Considered Feasible
• Incorporation of Detonation/Flame Arrestors
• Consideration of a Recombination Device or
Devices
• Consideration of a Venturi Mixing Device
• Consideration of Heating Downstream Piping
Questions ??