non-proprietary regulatory gap analysis results ...gap analysis results – regulations summary...

TM© 2012 NuScale Power, LLC

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Regulatory Gap Analysis Results:Regulations Requiring Further Consideration

Derick Botha and Gary Becker

December 3, 2012

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© 2012 NuScale Power, LLC2

Agenda• Purpose• Background• Regulatory gap analysis process• Gap analysis results – regulations• Summary• Feedback and next steps

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Purpose• Review gap analysis approach in assessing regulations• Discuss regulations requiring further consideration

– 17 regulations identified in summary report

– 3 regulations added after summary report submittal

• Obtain NRC feedback on proposed resolution for regulatory gaps

• Obtain NRC feedback on additional pre-application interactions planned for selected regulatory gaps

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Background• Design-Specific Review Standard (DSRS) approach

(from SECY-11-0024)– update of introduction of Standard Review Plan (SRP) describing

risk-informed review and integrated review process

– DSRS contains selected sections modified for NuScale design

– DSRS references the unchanged SRP sections

• Pre-application outcomes (October 2011 meeting) – agreement on applicability of requirements and guidance

• Gap analysis process and scope presented (May 2012 meeting)

• Submitted gap analysis summary report (July 2012)

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Background

DSRS & SRP

sections

Gap analysis summary report• Proposed DSRS section

roadmap• Regulatory gaps

Gap analysis tables in electronic reading room• Regulations• SRP acceptance criteria

and sub-tier guidance• Regulatory guides

Design description• Design overview• Categorization of

structures, systems, and components (SSCs)

Content outline(covered in DSRS engagement as

needed)

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Gap Analysis Process – Scope• 10 CFR Parts 1 through 199, with particular focus on

– 10 CFR 52– 10 CFR Parts 20, 50, 51, 73, and 100 as specified in 10 CFR 52.48

• Standard Review Plan (NUREG-0800) including sub-tier guidance– regulatory guides (RGs), including RG 1.206– NUREGs– TMI requirements and unresolved / generic safety issues– NRC documents (SECYs and associated SRMs)– NRC generic communications – industry codes and standards

• Interim Staff Guidance relevant to applicants for design certification

• Regulatory guides – Division 1, 4, 5, and 8 in addition to RGs referenced in SRP

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Gap Analysis Process – Regulations

Adequate level of safety

Functional purpose of

LWR requirements,

guidance

Functional purpose and

design criteria for NuScale

Compare

Existing regulation

applies

Existing regulation partially applies

Existing regulation does not

apply

NuScale unique feature/

requirement

Resolution

SMR reactor safety functions,

functional analysis,SSCs design criteria,

safety analysis, LBEs DID

Existing LWR requirements,

GDCs, guidance

SMR reactor design and PRA use

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Gap Analysis Process – Regulations• Summary report identified17 regulations requiring further consideration

– Regulations that would not apply to NuScale as it would for current light-water reactor (LWR) designs

– Considering literal language of rule

• Design literally meets rule: specific approach warrants pre-application interaction

• Departures: Applicable to design certification or combined license application but not appropriate to apply to NuScale design

• Propose resolution taking into account

– regulatory intent

– NuScale design considerations

– regulatory history including statements of consideration

– regulatory precedent

• Feedback on proposed resolution to meet regulation or form of departure

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Gap Analysis Results – Regulations Summary Table

Proposed resolution Future

engagement 10 CFR Subject

1 50.54(m)(2)(i) and (iii) Minimum Licensed Operator Staffing Requirements Exemption Y 2 50.62(c)(1) Reduction of Risk from ATWS Events Potential Exemption Y 3 50.44(c)(2) Combustible Gas Control Complies with rule Y 4 50, App. K ECCS Evaluation Models Complies with rule Y 5 50.34(f)(2)(vi) Reactor Coolant System Venting Complies with rule6 50.46a Reactor Coolant System Venting Complies with rule7 GDC 17 Electric power systems Departure Y 8 GDC 27 Combined reactivity control systems capability Departure9 GDC 33 Reactor coolant makeup / inventory control Departure Y 10 GDC 55 Containment isolation Departure Y 11 GDC 56 Containment isolation Departure Y 12 GDC 57 DHR / Containment isolation Departure Y 13 GDC 40 Testing of containment heat removal system Not applicable14 GDC 41 Containment atmosphere cleanup Complies with rule15 GDC 42 Inspection of containment atmosphere cleanup systems Not applicable16 GDC 43 Testing of containment atmosphere cleanup systems Not applicable17 50.34(f)(2)(xv) Containment Purging/Venting Capability and Isolation Not technically relevant18 50.34(f)(2)(xii) Auxiliary Feedwater System Actuation and Flow Indication Not technically relevant19 50.34(f)(1)(ii) Evaluation and Design Review of AFW System Not technically relevant20 50.34(f)(2)(iv) Safety Parameter Display System (SPDS) Complies with rule

Changed from gap analysis summary reportAdded to list in gap analysis summary report submittal

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Gap Analysis Results – RegulationsFramework for presenting gaps• Regulatory requirement summary• Regulatory purpose• NuScale design considerations• Statement of regulatory gap• Pre-application plan

– proposed resolution

– future interactions

• Gap analysis impact

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50.54(m)(2)(i), (iii) – Staffing Requirements

Regulatory Requirement Summary• Each licensee shall meet the minimum licensed operator staffing

requirements in the following table: [50.54(m)(2)(i)]

Pre-Application PlanProposed resolution: exemption required

• Define appropriate staffing requirements for NuScale design

Future interactions:• HFE Program Plan submittals

• Planned HFE workshops

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50.62(c)(1) - Reduction of Risk from ATWS Events

Regulatory Requirement Summary and Purpose• Each pressurized water reactor must have equipment from sensor

output to final actuation device, that is diverse from the reactor trip system, to automatically initiate the auxiliary (or emergency) feedwater system and initiate a turbine trip under conditions indicative of an ATWS.

• ATWS rule was written for specific plant designs

NuScale Design Considerations• Have to consider AOOs, plant response, and I&C implementation

appropriate to address ATWS conditions for NuScale design

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50.62(c)(1) Reduction of Risk from ATWS Events

Pre-Application PlanProposed resolution: Potential exemption required

• To be discussed in future pre-application interactions

Future interactions: Present ATWS approach as part of DSRS engagement on chapters 15.8 and 7

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50.44(c)(2) – Combustible Gas Control

Regulatory Requirement Summary• All containments must have an inerted atmosphere, or

must limit hydrogen concentrations in containment …

Regulatory purpose• Section 50.44 provides requirements for the mitigation of

combustible gas generated by a beyond-design-basis accident.

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NuScale Design Considerations

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• Convective mixing of containment atmosphere, no sub-compartments

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Statement of Regulatory Gap

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Containment must have an inerted

atmosphereGAP?

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Pre-Application PlanProposed resolution: no exemption required

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• Complying with portions of the rule that apply to inerted containments

Future interactions: Cover along with other requirements of 50.44 as part DSRS engagement on Chapter 6.2.5

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Gap Analysis Impact• Different approach from Gap Analysis Summary Report

– Previously proposed partial exemption for 10 CFR 50.44(c)(2)

• SRP sections that address rule– Section 6.2.5, “Combustible Gas Control in Containment”

– Section 3.8.1, “Concrete Containment”

– Section 3.8.2, “Steel Containment”

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10 CFR 50, Appendix K – ECCS Evaluation Models

Regulatory Requirement Summary• 10 CFR 50.46: ECCS cooling performance during LOCAs

must be calculated with an acceptable evaluation model using either– a best-estimate evaluation model or

– a conservative evaluation model (10 CFR 50, Appendix K)

• Appendix K provides required and acceptable features of a conservative ECCS Evaluation Model for example– The rate of energy release… from the metal/water reaction shall

be calculated

– shall include a provision for predicting cladding swelling and rupture

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NuScale Design Considerations• ECCS active components: vent valves and recirculation

valves• Containment wall facilitates ECCS heat removal • Core remains covered for design basis events - no large-

break LOCA• Integral reactor with no piping loops – no cold leg break• Natural circulation flow – no reactor coolant pump trip

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Appendix K identifies required and acceptable features of ECCS evaluation models for large PWRs

GAP?

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Pre-Application PlanProposed resolution: No exemption required• NuScale ECCS evaluation models for small-break

LOCAs only need to address technically relevant features required by Appendix K

Future interactions: present implementation as part of DSRS engagement on Chapter 6.3

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Precedent

• ABWR – SAFER application methodology - Appendix K peak cladding temperatures (PCT) calculated

compared to a statistically calculated 95% probability value

• ESBWR has no core uncovery– simplified statistical approach based on chimney height, not PCT

• AP1000 – voluntary use of statistical uncertainty analysis to justify relaxation of all but the required

conservatisms contained in current ECCS evaluation models

– small-break LOCA response using Appendix K

• EPR– methodology used to analyze LBLOCA is a best-estimate EM based on non-parametric

statistics.

– small-break LOCA response using Appendix K

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Gap Analysis Impact • Gap Analysis Summary Report did not propose a

resolution for Appendix K• SRP sections that address rule

– Section 4.2, “Fuel System Design”

– Section 6.2.1.3, “Mass and Energy Release Analysis for Postulated Loss-of-Coolant Accidents (LOCAs)”

– Section 6.2.1.5, “Minimum Containment Pressure Analysis for Emergency Core Cooling System Performance Capability Studies”

– Section 6.3, “Emergency Core Cooling System”

– Section 15.0.2,” Review of Transient and Accident Analysis Method”

– Section 15.6.5, “Loss-of-Coolant Accidents Resulting From Spectrum of Postulated Piping Breaks Within the Reactor Coolant Pressure Boundary”

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50.34(f)(2)(vi), 50.46a – Reactor Coolant System Vents

Regulatory Requirement Summary*

• Each reactor must provide high point vents for – the reactor coolant system (RCS)

– the reactor vessel head

– other systems required to maintain adequate core cooling if accumulation of noncondensible gases would cause loss of function of these systems

*Both 50.34(f)(2)(vi) and 50.46a are applicable to design certification applicants and are substantively similar

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Regulatory Requirement Summary

• Design requirements– remotely operated from control room

– vents and associated components must meet GDCs and Appendix B

– designed to ensure • vents will perform safety functions

• no inadvertent or irreversible actuation of a vent

– operation shall not lead to unacceptable increase in probability of LOCA or challenge to containment integrity

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Regulatory Purpose

• Accumulation of noncondensible gases in RCS could interfere with adequate core cooling

• Ability to vent gases supports long-term core cooling via natural or forced circulation

• Provides assurance that vents maintain reactor coolant pressure boundary integrity

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• Integral reactor pressure vessel – core, steam generators, pressurizer

– the reactor vessel high point is also the RCS and pressurizer high point

– no other systems require venting to support core cooling

• ECCS reactor vent valves– at reactor vessel high point

– vent to containment


Containment

Reactor vent valves

Reactor recirculation valves

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NuScale Design Considerations• ECCS vent valves provide inherent RCS venting capability

– vent noncondensible gases to containment when ECCS actuated

– vented gasses will not interfere with ECCS cooling

– will not challenge containment integrity

• ECCS vent valves meet design requirements– safety-related system

– operable from control room

• Does not affect LOCA probability– no additional components or controls

– failure and inadvertent actuation are analyzed events

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ECCS valves serve as RCS high point vents in NuScale

design without separate vents

Must provide high point vents for

reactor, RCS, and other systems as

necessary

GAP?

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Pre-Application PlanProposed resolution: no exemption required• NuScale ECCS vent valves meet requirement for high

point vents

Precedent:• BWRs: inherent venting capability via SRVs• AP1000: ADS first stage credited as pressurizer high

point vent

Future interactions: DSRS development only

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Gap Analysis Impact

• Different approach from Gap Analysis Summary Report

– Previously proposed normal RPV vent line met literal language of high point vent rules, with no safety function related to core cooling

• SRP sections that address rule

– Section 5.4.12, “Reactor Coolant System High Point Vents”

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Appendix A to Part 50

General Design Criteria for Nuclear Power Plants

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GDC 17 – Electric Power SystemsRegulatory Requirement Summary

Electric power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits…designed and located so as to minimize to the extent practical the likelihood of their simultaneous failure under operating and postulated accident and environmental conditions.

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Regulatory Purpose

• Ensure reliable power to accomplish safety functions

– SAFDLs and RCPB design conditions not exceeded as a result of AOOs

– core cooling, containment integrity, etc. maintained for postulated accidents

• Traditional LWRs require A/C power for safety system function

– either onsite or offsite A/C necessary

– independent offsite circuits increase reliability

GDC 17 – Electric Power Systems

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GDC 17 – Electric Power SystemsNuScale Design Considerations

• A/C power not required for safe shutdown, core cooling, or containment integrity

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– nonsafety-related onsite and offsite power sources provided

• Redundant circuits from transmission network not necessary to ensure safety

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GDC 17 – Electric Power SystemsStatement of Regulatory Gap

NuScale design does not require

two offsite circuits

Two physically independent offsite

electrical power circuits required to

ensure safety functions are accomplished

GAP

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GDC 17 – Electric Power SystemsPre-Application Plan

Proposed resolution: departure from GDC 17

• Design certification scope will include one offsite circuit

• Underlying purpose of the rule met without need for two offsite circuits

Precedent:• SECY-94-084: evaluate LOOP challenges against

coping capability

• AP1000 (exemption)

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GDC 17 – Electric Power SystemsPre-Application Plan

• Future interactions:– Upcoming engagement on Class 1E power system approach

– Discuss departure implementation in DSRS Ch. 8 engagement

Gap Analysis Impact

• Identified in Gap Analysis Summary Report• SRP sections that address rule

– Section 8.2, “Offsite Power System”

– Section 8.3.1, “AC Power Systems (Onsite)”

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GDC 27 – Reactivity Control SystemsRegulatory Requirement Summary

The reactivity control systems shall be designed to have a combined capability, in conjunction with poison addition by the emergency core cooling system, of reliably controlling reactivity changes to assure that under postulated accident conditions and with appropriate margin for stuck rods the capability to cool the core is maintained.

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GDC 27 – Reactivity Control Systems

Regulatory Purpose• GDC 27 provides assurance reactor can be shut down

and core coolability maintained in event of an accident• “In conjunction with poison addition by the emergency

core cooling system” – large LWR ECCS inject large volumes of borated water to control

inventory

– any poison added by ECCS injection can be credited in accident response for meeting reactivity control

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NuScale Design Considerations• ECCS has no makeup function

– no RCS inventory added by actuation– no poison addition via borated makeup

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GDC 27 includes “poison addition by the emergency core cooling system” among the reactivity control systems

GAP?

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Pre-Application PlanProposed resolution: no departure required• NuScale design will meet regulatory requirements

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Gap Analysis Impact

• Different approach from Gap Analysis Summary Report based on design change

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– Section 4.3, “Nuclear Design”

– Chapter 15, “Transient and Accident Analysis”

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GDC 33 – Reactor Coolant MakeupRegulatory Requirement Summary

A system to supply reactor coolant makeup for protection against small breaks in the reactor coolant pressure boundary shall be provided. The system safety function shall be to assure that specified acceptable fuel design limits (SAFDLs) are not exceeded….

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GDC 33 – Reactor Coolant MakeupRegulatory Purpose

• Protection against small breaks in the RCPB

• Provide sufficient reactor coolant makeup capacity to maintain reactor coolant system (RCS) water inventory and prevent the violation of SAFDLs

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GDC 33 – Reactor Coolant MakeupNuScale Design Considerations

• Reactor coolant from leaks and breaks is retained within containment vessel

• ECCS actuation returns water accumulated in containment vessel to the core through natural circulation

• Steam generator tube leaks are retained through feed and steam isolation

• For breaks inside containment, integrated module design– retains total reactor coolant inventory

– keeps core covered

– provides adequate core cooling

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GDC 33 – Reactor Coolant MakeupNuScale Design Considerations

• Chemical and volume control (CVC) system provides nonsafety-related reactor coolant makeup and letdown capability

– accommodates minor RCS leakage during normal operation

– maintains level during reactor heatup and cooldown

– not relied upon to prevent core uncovery or provide core cooling in the event of a postulated leak or break in the RCPB

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GDC 33 – Reactor Coolant MakeupStatement of Regulatory Gap

For small breaks, integral module

design with ECCS to retain reactor coolant inventory

For protection against small

breaks, makeup system required to

maintain core coolant inventory

and prevent violation of SAFDLs

GAP

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GDC 33 – Reactor Coolant MakeupPre-Application Plan

Proposed resolution: departure from GDC 33• alternative design-specific principal design criterion

– assurance of adequate reactor coolant inventory

Precedent:• Safety evaluation report for Clinch River Breeder Reactor (NUREG-0968)

• Pre-application safety evaluation report for PRISM (NUREG-1368)

Future interactions: present implementation as part of DSRS engagement on Chapter 9

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GDC 33 – Reactor Coolant MakeupGap Analysis Impact

• Identified in Gap Analysis Summary Report


– Section 9.3.4, “Chemical and Volume Control System”

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GDCs 55, 56 – Containment Isolation


• Each line that is part of RCPB (GDC 55) or connectsdirectly to containment atmosphere (GDC 56) must havetwo containment isolation valves (CIVs), in series– combinations of locked closed and/or automatic CIVs, (simple

check valves allowed only inside containment)

– one inside and one outside containment

– outside valve “as close to containment as practical”

– take position of greater safety upon loss of power

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• Additional provisions– Allows for “demonstrat[ion] that the containment isolation

provisions for a specific class of lines . . . are acceptable on someother defined basis”• SRP 6.2.4 accepts some other configurations with criteria and

requirements (instrument lines, ESF, and safe shutdown lines)

– “Other appropriate requirements to minimize the probability orconsequences of an accidental rupture…shall be provided asnecessary to assure adequate safety.” (GDC 55 only)

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Regulatory Purpose

• Allow normal or emergency fluid passage through containment boundary while preserving ability to limit escape of fission products from postulated accidents

• Provisions are intended to increase isolation reliability

– two-barrier philosophy to account for single failure

– diverse locations (leakage inside containment, common-cause failure of both CIVs)

– prescriptive requirements draw from large LWR experience (many penetrations, large valves, normal containment leakage)

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NuScale Design Considerations }}3(a)

• Small lines and isolation valves• Very low-leakage containment vessel• Harsh containment vessel (CNV) conditions

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NuScale Design Considerations• Proposed design: {{

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GDCs 55 and 56 require one CIV inside containment and one outside containment

GAP

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GDC 57 – Containment Isolation


• GDC 57 “closed system”

– line penetrating containment that is not part of RCPB and notconnected directly to containment atmosphere

• Must have– one containment isolation valve outside containment

– locked closed, automatic, or remote manual

– located “as close to containment as practical”

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Regulatory Purpose

• Same purpose as GDCs 55 and 56.

• Follows the same “two isolation barrier” approach– for closed systems, first barrier is the closed system itself

– failures must occur in system inside containment and the CIV forrelease outside containment

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• Most closed systems will meet GDC 57 (MS and FW)

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GDC 57 requires one CIV outside containment

GAP

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GDCs 55-57 – Containment Isolation

Pre-Application PlanProposed resolution: departures from GDCs 55, 56 & 57

}}3(a)

– detailed design information required to support departures

Future interactions: specific engagement as design progresses

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GDCs 55-57 – Containment Isolation

Gap Analysis Impact

• Not addressed in Gap Analysis Summary Report

– new gap due to design progression


– Section 6.2.4, “Containment Isolation System”

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GDC 40 – Testing of Containment Heat Removal System

Regulatory Requirement SummaryThe containment heat removal system shall be designed to permit appropriate periodic pressure and functional testing to assure (1) the structural and leaktight integrity of its components, (2) the operability and performance of the active components of the system, and (3) the operability of the system as a whole…

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Regulatory Purpose• Ensures reliable performance of containment heat

removal system (required by GDC 38)

• Contemplates testing of active systems such as

– containment spray system

– fan cooler system

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NuScale Design Considerations • No active containment heat removal system as

contemplated by GDC 40– containment vessel submerged in the reactor pool (UHS)

– heat removal by passive heat transfer through the containment vessel steel walls

– no reliance on electrical power, valve actuation, cooling water flow, or other active systems or components

• Passive heat removal performance established as part of design and test program for design certification

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NuScale design has no active

containment heat removal systems

The containment heat removal

system shall be designed to permit

appropriate periodic pressure

and functional testing

GAP

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Pre-Application PlanProposed resolution: no departure required• GDC 40 does not apply to the NuScale design


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Gap Analysis Impact


• SRP sections that address rule– Section 6.2.2, “Containment Heat Removal Systems”

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GDC 41 – Containment Atmosphere Cleanup


Systems to control fission products, hydrogen, oxygen, and other substances which may be released into the reactor containment shall be provided as necessary to

• reduce… the concentration and quality of fission products released to the environment following postulated accidents

• control the concentration of hydrogen or oxygen and other substances in the containment atmosphere following postulated accidents to assure that containment integrity is maintained

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GDC 41 – Containment Atmosphere CleanupRegulatory Purpose

• Provide for containment atmosphere cleanup systems “as necessary” to

– reduce fission product release from containment leakage

– reduce hydrogen or oxygen if required to protect containment integrity from hydrogen combustion

• Contemplates systems such as

– containment spray system

– engineered safety feature (ESF) ventilation filtration system

– hydrogen igniters and hydrogen and oxygen monitors

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• Fission product release passively controlled by– reactor module configuration

– containment vessel design leakage rate

• Containment integrity assured by – robust containment vessel design

– low oxygen content

• Systems to control fission products and combustible gasses not anticipated to be necessary

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Containment atmosphere

cleanup systems are not necessary

for NuScale design


cleanup systems shall

be provided as necessary…

GAP?

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Pre-Application Plan

Proposed resolution: no departure required

• absence of atmosphere cleanup systems in the NuScale design is consistent with the “as necessary” provision of GDC 41

Precedent: AP1000 similar approach (fission products)


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Gap Analysis Impact


• Related SRP sections

– Section 6.2.5, “Combustible Gas Control in Containment”

– Section 6.5.1, “ESF Atmosphere Cleanup Systems”

– Section 6.5.2, “Containment Spray as a Fission Product Cleanup System”

– Section 6.5.3, “Fission Product Control Systems and Structures”

– Section 6.5.5, “Pressure Suppression Pool as a Fission Product Cleanup System”

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GDCs 42 and 43 – Inspection and Testing of Containment Atmosphere Cleanup Systems


The containment atmosphere cleanup systems shall be designed to permit appropriate periodic• inspection of important components...to assure the

integrity and capability of the systems. [GDC 42]• pressure and functional testing to assure structural and

leak-tight integrity of components, operability and performance of active components, and operability of the systems as a whole. [GDC 43]

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Regulatory Purpose

• Ensures performance and reliability of containment atmosphere cleanup systems provided to meet GDC 41

• Contemplates systems such as

– containment spray system and pressure suppression devices

– ESF ventilation filtration system

– hydrogen igniters and hydrogen and oxygen monitors

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cleanup systems are not included in

the NuScale design


cleanup systems shall

be designed to permit inspection

and testing

GAP?

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Pre-Application PlanProposed resolution: no departure required

• Do not anticipate the need for atmosphere cleanup systems per GDC 41

• GDCs 42 and 43 do not apply to NuScale design

Precedent: AP1000


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Gap Analysis Impact


• Related SRP sections

– Section 6.2.5, “Combustible Gas Control in Containment”

– Section 6.5.1, “ESF Atmosphere Cleanup Systems”

– Section 6.5.2, “Containment Spray as a Fission Product Cleanup System”

– Section 6.5.3, “Fission Product Control Systems and Structures”

– Section 6.5.5, “Pressure Suppression Pool as a Fission Product Cleanup System”

– Section 6.6, “Inservice Inspection and Testing of Class 2 and 3 Components”

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50.34 – Contents of applications; technical information

(f) Additional TMI-related requirements

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50.34(f)(2)(xv) – Containment PurgingRegulatory Requirement Summary

Provide a capability for containment purging/venting designed to minimize the purging time consistent with ALARA principles for occupational exposure.

Provide and demonstrate high assurance that the purge system will reliably isolate under accident conditions.

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50.34(f)(2)(xv) – Containment PurgingRegulatory Purpose

• Large LWRs: containment personnel access during operations necessitates containment purging/venting

• Post-TMI concern over radiological consequences of containment purging/venting

– balance occupational and public exposure from normal purging

– risk of accident while purging system open

• Requires actions to restrict purging/venting and reliably isolate on demand

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50.34(f)(2)(xv) – Containment PurgingNuScale Design Considerations

• No containment purging/venting system as contemplated by rule– Compact containment vessel does not allow for personnel access

during operation

– Containment only opened during cold shutdown

– NuScale containment remains sealed during operations, no direct path to the environs

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50.34(f)(2)(xv) – Containment PurgingStatement of Regulatory Gap

NuScale design does not include a

purging/venting system

Provide purging designed to

minimize purging time, reliable

isolation

GAP?

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50.34(f)(2)(xv) – Containment PurgingPre-Application Plan

Proposed resolution: no exemption required• Containment purging/venting requirements are not

technically relevant to NuScale design


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50.34(f)(2)(xv) – Containment PurgingGap Analysis Impact



– Section 6.2.4, “Containment Isolation System”

– BTP 6-4, “Containment Purging During Normal Plant Operations”

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50.34(f)(2)(xii) – AFW System Actuation and Flow Indication

Regulatory Requirement Summary Provide automatic and manual auxiliary feedwater (AFW) system initiation, and provide auxiliary feedwater system flow indication in the control room (TMI Action Item II.E.1.2)

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Regulatory Purpose• Ensure timely initiation of the AFW system with loss of feedwater

(GDC 20)

• Provide instrumentation and controls for direct verification of AFW system performance (GDC 13)

NuScale Design Considerations• NuScale design does not include an AFW system

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NuScale design does not include an AFW system

PWR designs are required to have automatic and manual AFW

system initiation and AFW system flow indication in the control room

GAP

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Pre-Application PlanProposed resolution: no exemption required• 50.34(f)(2)(xii) is not technically relevant to NuScale

designFuture interactions: DSRS development only

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– Previously proposed AFW requirement would apply to DHR

– DHR actuation and indication designed will be for NuScale-specific transients and system characteristics

• SRP sections that address rule– DSRS Section 7.2, “System Characteristics”

– Section 10.4.9, “Auxiliary Feedwater System (PWR)”


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50.34(f)(1)(ii) – Auxiliary Feedwater Design Evaluation

Regulatory Requirement SummaryPerform an evaluation of the proposed auxiliary feedwater

system (AFWS), to include (applicable to PWRs only): (A) A simplified AFWS reliability analysis using event-tree

and fault-tree logic techniques. (B) A design review of AFWS.(C)An evaluation of AFWS flow design bases and criteria.

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Regulatory Purpose• Post-TMI requirement to ensure reliable AFW capability

for large PWRs• Reliability requirement based on CE, B&W, and

Westinghouse plant-specific design bases • Design basis functions were intended to prevent and

mitigate small-break loss-of-coolant accidents (LOCAs)

NuScale Design Considerations• NuScale design does not include an AFW system

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NuScale design does not include an AFW system

Perform an evaluation of the

proposed auxiliary feedwater system

GAP?

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Pre-Application PlanProposed resolution: no exemption required• 50.34(f)(1)(ii) is not technically relevant to NuScale

designFuture interactions: none anticipated

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– Previously proposed AFW requirement would apply to DHR

• SRP sections that address rule– Section 10.4.9, “Auxiliary Feedwater System (PWR)”


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50.34(f)(2)(iv) – Safety Parameter Display System

Regulatory Requirement SummaryProvide a plant safety parameter display console that will display to operators a minimum set of parameters defining the safety status of the plant, capable of displaying a full range of important plant parameters and data trends on demand, and capable of indicating when process limits are being approached or exceeded.

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Regulatory Purpose• Post-TMI requirement to ensure reliable data capability

for operators• New consoles were necessary for existing plants• Most newer plants have integrated safety parameter

display system (SPDS) capabilities into the control room design and displays

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NuScale Design Considerations• The NuScale SPDS will be integrated into the control

room human-system interface design• Dedicated SPDS display, but not a physically separate

SPDS console

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The NuScale design does not

include a separate SPDS console

Provide a plant safety parameter

display console. . .GAP?GAP?

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Pre-Application PlanProposed resolution: no exemption required• Rule does not require a separate, stand-alone SPDS

console• 10 CFR 50.34(f)(2)(iv) is applicable and NuScale design

meets regulatory requirementsPrecedent: EPR (pending)


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Gap Analysis Impact


• SRP sections that address rule– Section 7.0, “Instrumentation and Controls - Overview of Review Process”

– Section 7.5, “Information Systems Important to Safety”

– Section 13.3, “Emergency Planning”

– Section 18, “Human Factors Engineering”

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SummaryRegulations that do not require departures• Design meets rule (9): specific approach warrants pre-application

interaction

• Not applicable (3): requirements addressing systems or features that are not present in the NuScale design

Departures from regulatory requirements• Exemptions (2): design does not literally meet regulatory requirement

• Other departures (6): GDCs or specific aspect of GDC that are not appropriate to apply to the NuScale design

– identify and justify departure in NuScale FSAR (i.e., DCD)

– consistent with introduction in 10 CFR 50, Appendix A

– no exemption required under 10 CFR 52.7 and 10 CFR 50.12

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Summary Table

Changed from gap analysis summary reportAdded to list in gap analysis summary report submittal

Proposed resolution Future

engagement 10 CFR Subject

1 50.54(m)(2)(i) and (iii) Minimum Licensed Operator Staffing Requirements Exemption Y 2 50.62(c)(1) Reduction of Risk from ATWS Events Potential Exemption Y 3 50.44(c)(2) Combustible Gas Control Complies with rule Y 4 50, App. K ECCS Evaluation Models Complies with rule Y 5 50.34(f)(2)(vi) Reactor Coolant System Venting Complies with rule6 50.46a Reactor Coolant System Venting Complies with rule7 GDC 17 Electric power systems Departure Y 8 GDC 27 Combined reactivity control systems capability Departure9 GDC 33 Reactor coolant makeup / inventory control Departure Y 10 GDC 55 Containment isolation Departure Y 11 GDC 56 Containment isolation Departure Y 12 GDC 57 DHR / Containment isolation Departure Y 13 GDC 40 Testing of containment heat removal system Not applicable14 GDC 41 Containment atmosphere cleanup Complies with rule15 GDC 42 Inspection of containment atmosphere cleanup systems Not applicable16 GDC 43 Testing of containment atmosphere cleanup systems Not applicable17 50.34(f)(2)(xv) Containment Purging/Venting Capability and Isolation Not technically relevant18 50.34(f)(2)(xii) Auxiliary Feedwater System Actuation and Flow Indication Not technically relevant19 50.34(f)(1)(ii) Evaluation and Design Review of AFW System Not technically relevant20 50.34(f)(2)(iv) Safety Parameter Display System (SPDS) Complies with rule

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Feedback and Next Steps• 11 regulatory gaps require no further pre-application

discussion• 9 regulatory gaps are subjects of ongoing or future pre-

application discussions• Schedule for future interactions

non-proprietary regulatory gap analysis results ...gap analysis results – regulations summary...

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