ML24221A015

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Sdaa FSER - Chapter 8 - Electric Power
ML24221A015
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Site: 05200050
Issue date: 11/04/2024
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8 ELECTRIC POWER

THIS NRC STAFF DRAFT SE HAS BEEN PREPARED AND IS BEING RELEASED TO SUPPORT INTERACTIONS WITH THE ACRS. THIS DRAFT SE HAS NOT BEEN SUBJECT TO FULL NRC MANAGEMENT AND LEGAL REVIEWS AND APPROVALS, AND ITS CONTENTS SHOULD NOT BE INTERPRETED AS OFFICIAL AGENCY POSITION.

8.1 Electric PowerIntroduction

This chapter of the final safety evaluation report (SER) documents the U.S. Nuclear Regulatory Commission (NRC) staffs (hereinafter referred to as the staff) review of Chapter 8, Electric Power, of the NuScale Power, LLC (hereinafter referred to as NuScale or the applicant),

Standard Design Approval Application (SDAA), Part 2, Final Safety Analysis Report (FSAR).

The staffs regulatory findings documented in this report are based on Revision 1 of the SDAA, dated October 31, 2023 (Agencywide Documents Access and Management System Accession No. ML23306A033).

This chapter of the SDAA includes the FSAR for Section 8.1, Introduction; Section 8.2, Offsite Power System; Section 8.3, Onsite Power Systems; and Section 8.4, Station Blackout.

NuScale submitted this SDAA for its small modular reactor (SMR) standard plant design.

The staff reviewed the design of the electric power systems that are necessary for the safe design and operation of the plant, or whose failure might adversely affect their safety-related function, in accordance with the applicable design-specific review standards (DSRS) or NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition (SRP), as applicable, and consistent with the graded review approach described in SER Section 1.9. SER Section 8.1.1 contains the introduction for the SDAA review, and Sections 8.1, 8.2, 8.3.1, 8.3.2, and 8.4 contain the staffs technical evaluations and conclusions based on this review.

In this chapter, the staff uses the term not safety related to refer to certain structures, systems and components (SSCs) that do not fall under the definition of safety-related SSCs given in Title 10 of the Code of Federal Regulations (10 CFR) 50.2, Definitions. Some of the SSCs that are not safety related are considered to be important to safety as that term is used in Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR Part 50, Domestic Licensing of Production and Utilization Facilities. Institute of Electrical and Electronics Engineers (IEEE) Standard (Std.) 308-2001, IEEE Standard Criteria for Class 1E Power Systems for Nuclear Power Generating Stations, defines Class 1E as the safety classification of the electric equipment and systems that are essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal or that are otherwise essential in preventing significant release of radioactive material to the environment. The staff endorsed IEEE Std. 308-2001 in Regulatory Guide (RG) 1.32, Criteria for Power Systems for Nuclear Power Plants. Furthermore, 10 CFR 50.49(b)(1) has a footnote that states that safety-related electric equipment is referred to as Class 1E equipment in IEEE Std. 323-1974, IEEE Standard for Qualifying Class IE Equipment for Nuclear Power Generating Stations, as endorsed in RG 1.89, Environmental Qualification of Certain Electric Equipment Important to Safety for Nuclear Power Plants. RG 1.89 indicates that safety-related equipment is known as Class 1E. In this chapter, the staff refers to non-Class 1E equipment as not safety related.

8-1 The electric power system for the NuScale US460 design comprises a non-Class 1E alternating current (AC) power system and a non-Class 1E direct current (DC) power system. Non-Class 1E and non-risk-significant electric pow er systems for NuScale include normal AC and DC power systems that supply plant loads during startup and shutdown, normal operation, and off-normal conditions. The NuScale US460 design does not depend on, and therefore does not use or include, a Class 1E emergency onsite (AC or DC) power system.

The staff reviewed the non-Class 1E and non-risk-significant electric power systems (1) to verify that their failure will not prevent safe shutdown of the plant or result in an unacceptable release of radioactivity to the environment and (2) fo r compliance with the applicable requirements and conformance to the relevant guidance.

The SSCs are classified according to nuclear safety classification, seismic category, and quality group. FSAR Section 3.2, Classification of Structures, Systems, and Components, discusses the safety and risk significance of SSCs and provi des the safety and risk categorization of SSCs for the NuScale US460 design. SER Sections 3.2 and 17.4 include further evaluation of the classification of SSCs. As discussed in SER Section 3.2, a category B2 designation is given to SSCs that are determined to be both not safety related and not risk significant. FSAR Table 8.3-2, Classification of Structures, Systems, and Components, lists the classifications of SSCs.

This list identifies the electrical main equipm ent and auxiliary systems located in various areas of the power plant (i.e., the switchyard, batteries and chargers, backup power supplies, and other such systems) as category B2. SER 19.1 describe and further evaluate the acceptability of the electrical systems safety-signific ance and risk-significance categorizations.

8.1.1 Introduction

The NuScale Power Plant standard design is modular with six nuclear power modules (NPMs).

It is passive and has safety-related systems for safe shutdown, core and spent fuel assembly cooling, containment isolation and integrity, and reactor coolant pressure boundary (RCPB) integrity. Safe operation of this design does not depend on onsite or offsite AC or DC electric power, including that from the transmission grid. An auxiliary AC power source may also provide power to the plant. The onsite electric power system includes AC power systems and DC power systems and a backup power supply system (BPSS) consisting of backup diesel generators.

SER Sections 8.2, 8.3.1, and 8.3.2 discuss and evaluate the offsite and onsite power systems.

The applicant addressed station blackout (SBO), defined as a complete loss of offsite and onsite AC power with a turbine trip. The NuScale passive plant design does not rely on the use of onsite or offsite AC power for the performance of the safety-related functions for any design-basis event (DBE).

8.1.2 Technical Evaluation of Exemptions

This section addresses the evaluation associated with exemptions NuScale requested for General Design Criterion (GDC) 17, Electri c power systems, and GDC 18, Inspection and testing of electric power systems, in Appendix A to 10 CFR Part 50 and the electric power provisions in GDC 33, 34, 35, 38, 41, and 44. It should be noted that the applicant has requested exemption for all provision of GDC 33, however, only the electrical provisions are addressed in this SER.

8-2 GDC 17 requires the following:

Electric power systems. An onsite electr ic power system and an offsite electric power system shall be provided to permit functioning of structures, systems, and components important to safety. The safe ty function for each system (assuming the other system is not functioning) shall be to provide sufficient capacity and capability to assure that (1) specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents.

The onsite electric power supplies, including the batteries, and the onsite electric distribution system, shall have sufficient independence, redundancy, and testability to perform their safety functions assuming a single failure.

Electric power from the transmission network to the onsite electric distribution system shall be supplied by two physically independent circuits (not necessarily on separate rights of way) 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. A switchyard common to both circuits is acceptable. Each of these circuits shall be designed to be available in sufficient time following a loss of all onsite alternating current power supplies and the other offsite electric power circuit, to assure that specified acceptable fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded. One of these circuits shall be designed to be available within a few seconds following a loss-of-coolant accident to assure that core cooling, containment integrity, and other vital safety functions are maintained.

Provisions shall be included to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies.

GDC 18 requires the inspection and testing of the offsite and onsite power systems important to safety and states the following:

Electric power systems important to safety shall be designed to permit appropriate periodic inspection and testing of important areas and features, such as wiring, insulation, connections, and switchboards, to assess the continuity of the systems and the condition of t heir components. The systems shall be designed with a capability to test periodically (1) the operability and functional performance of the components of the system s, such as onsite power sources, relays, switches, and buses, and (2) the operability of the systems as a whole and, under conditions as close to design as practical, the full operation sequence that brings the systems into operation, including operation of applicable portions of the protection system, and the transfer of power among the nuclear power unit, the offsite power system, and the onsite power system.

8-3 GDC 33, Reactor coolant makeup, states the following:

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 are not exceeded as a result of reactor coolant loss due to leakage from the reactor coolant pressure boundary and rupture of small piping or other small components which are part of the boundary. The system shall be designed to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished using the piping, pumps, and valves used to maintain coolant inventory during normal reactor operation.

GDC 34, Residual heat removal, states the following:

A system to remove residual heat shall be provided. The system safety function shall be to transfer fission product decay heat and other residual heat from the reactor core at a rate such that specified acceptable fuel design limits and the design conditions of the reactor coolant pressure boundary are not exceeded.

Suitable redundancy in components and features, and suitable interconnections, leak detection, and isolation capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

GDC 35, Emergency core cooling, states the following:

A system to provide abundant emergency core cooling shall be provided. The system safety function shall be to transf er heat from the reactor core following any loss of reactor coolant at a rate such that (1) fuel and clad damage that could interfere with continued effective core cooling is prevented and (2) clad metal-water reaction is limited to negligible amounts.

Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

GDC 38, Containment heat removal, states the following:

A system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any loss-of-coolant accident and maintain them at acceptably low levels.

8-4 Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

GDC 41, Containment atmosphere cleanup, states the following:

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, consistent with the functioning of other associated systems, the concentration and quality of fission products released to the environment following postulated accidents, and to control the concentration of hydrogen or oxygen and other substances in the containment atmosphere following postulated accidents to assure that containment integrity is maintained.

Each system shall have suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) its safety function can be accomplished, assuming a single failure.

GDC 44, Cooling water, states the following:

A system to transfer heat from structur es, systems, and components important to safety, to an ultimate heat sink shall be provided. The system safety function shall be to transfer the combined heat load of these structures, systems, and components under normal operating and accident conditions.

Suitable redundancy in components and features, and suitable interconnections, leak detection, and isolation capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.

NuScale stated, in SDAA Part 7, Exemptions, Section 4, that it requests an exemption from GDC 17 because the design contains no safety-related functions that rely on electric power.

NuScale stated that the design of the NuScale Power Plant provides passive safety systems and features to accomplish plant safety-related functions without reliance on electric power, and that the design, therefore, meets the underlying intent of GDC 17 without the need for the electric power systems specified in GDC 17. NuScale further stated that it requests exemption from the GDC 18 requirements for inspection and testing of electric power systems and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 to address conforming changes and that the underlying intent of these requirements, to ensure sufficient electric power is available to accomplish the safety functions of the respecti ve systems, is met without reliance on electric power.

8-5 For offsite power, FSAR Section 8.2 states that the passive design of the plant does not rely on AC power and does not require an offsite pow er system to perform safety-related or risk-significant functions. SER Section 8.2 contains the staffs evaluation of offsite power. SER Section 15.0.0.6.2 states that offsite power is not credited to mitigate Chapter 15 events.

Therefore, the staff finds that offsite power is not needed for accident mitigation or safe shutdown and thereby is non-safety related.

For the onsite AC systems, FSAR Section 8.3 st ates that the onsite power systems include AC power systems, and the plant safety-related functions are achieved and maintained without reliance on onsite AC electric power. Further, t he applicant stated that the onsite power systems do not perform any risk-significant functions. SER Section 8.3.1 contains the staffs evaluation of the onsite AC systems. SER Section 15.0.0.6.2 states that the normal AC power systems are not safety related and are not credited to mitigate Chapter 15 events. Therefore, the staff finds that the onsite AC systems are not needed for accident mitigation or safe shutdown and thereby are non-safety related.

In SRM-SECY-19-0036, Staff RequirementsSEC-19-0036Application of the Single Failure Criterion to NuScale Power LLCs Inadvertent Actuation Block Values, dated July 2, 2019 (ML19183A408), the Commission stated the following:

In any licensing review or other regul atory decision, the staff should apply risk-informed principles when strict, prescriptive application of deterministic criteria such as the single failure criterion is unnecessary to provide for reasonable assurance of adequate protection of public health and safety.

Consistent with the SRM-SECY-19-0036, a risk-informed and graded approach commensurate with the design type and features that acknowl edges the mitigative measures available to ensure reasonable confidence of public health and safety is acceptable. Further, this holistic approach considers realistic conditions, plant behaviors, and operator responses in conjunction with the agencys deterministic assumptions and anal yses to provide context and perspective to making risk-informed decisions.

For the DC onsite systems, in SER Section 8.3.2, the staff used a risk-informed, graded approach to evaluate the augmented design, qualification, and quality assurance (QA) provisions of the Augmented DC power syst em (EDAS) as supported by SRM-SECY-19-0036.

In SER Section 8.3.2, the staff finds the EDAS is non-safety related with augmented provisions and is acceptable. Chapter 19 discusses the availability controls related to the EDAS. The staff finds that the augmented quality and availability controls for the DC systems are acceptable.

Consistent with SRM-SECY-19-0036, the staff has the discretion to reasonably credit SSCs that are not safety related and reasonable operator actions to make a risk-informed decision regarding the safe shutdown of the plant. Therefore, using risk-informed decision-making and a graded approach, the staff finds the DC systems, including the EDAS, are not safety related and have augmented provisions.

Therefore, the staff finds that the NuScale US460 design meets the underlying intent of GDC 17 without the need to rely on the offsite or onsite el ectric power systems in the manner specified in GDC 17 because the AC and DC systems are not safety related. NuScale further stated that exemption from the GDC 18 requirements for ins pection and testing of electric power systems and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 is requested to address conforming changes. It also noted that the underlying intent of these requirements, to ensure

8-6 sufficient electric power is available to accomplish the safety functions of the respective systems, is met without reliance on electric power.

The staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems bec ause they are not needed to (1) achieve or maintain safe shutdown, (2) ensure specified acceptable fuel design limits and design conditions of the RCPB are not exceeded as a result of anticipated operational occurrences, and (3) maintain core cooling, containment integrity, and other vital functions during postulated accidents. Further, the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. Based on the non-Class 1E classification of the onsite and offsite electric power systems, and on the anal ysis described in Section 8.1.3 to support the findings required by 10 CFR 50.12, Specific exem ptions, the staff approves exemption from GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44.

8.1.3 Evaluation for Meeting the Exemption Criteria of 10 CFR 50.12

Under 10 CFR 52.7, Specific exemptions, the Commission may, upon application by any interested person or upon its own initiative, grant exemptions from the requirements of 10 CFR Part 52, Licenses, Certifications, and Approvals for Nuclear Power Plants. As 10 CFR 52.7 further explains, the Commissions consideration will be governed by 10 CFR 50.12, which states that an exemption may be granted when (1) the exemptions are authorized by law, will not present an undue risk to public health and safety, and are consistent with the common defense and security, and (2) special circumstances are present. Specifically, 10 CFR 50.12(a)(2) lists six special circumstances for which an exemption may be granted. It is necessary for one of these special circumstances to be present for the NRC to consider granting an exemption request.

8.1.3.1 Authorized by Law

The NRC staff has determined that granting the applicants proposed exemptions will not result in a violation of the Atomic Energy Act of 1954, as amended, or the Commissions regulations because, as stated above, 10 CFR Part 52 allows the NRC to grant exemptions. Therefore, as required by 10 CFR 50.12(a)(1), the staff finds that the exemption is authorized by law.

8.1.3.2 No Undue Risk to Public Health and Safety

The proposed exemptions will not impact the cons equences of any DBE or create new accident precursors. The design does not rely on electric power systems to provide sufficient capacity and capability to ensure that (1) specified acceptable fuel design limits and design conditions of the RCPB are not exceeded as a result of anticipated operational occurrences and (2) the core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents. Therefore, as required by 10 CFR 50.12(a)(1), the staff finds that the exemptions pose no undue risk to public health and safety.

8.1.3.3 Consistent with the Common Defense and Security

The proposed exemptions do not affect the design, function, or operation of any structures or plant equipment necessary to maintain a safe and secure plant status. In addition, the proposed exemptions do not impact the security power system and have no impact on plant security or safeguards procedures. Therefore, as required by 10 CFR 50.12(a)(1), the staff finds that the exemptions do not impact the common defense and security.

8-7 8.1.3.4 Special Circumstances

Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii), are present whenever application of the regulation in the particular circumstances would not serve the underlying purpose of the rule or is not necessary to achieve the underlying purpose of the rule. SER Section 8.1.2 discusses GDC 17, GDC 18, and the electric power provisions in GDC 33, 34, 35, 38, 41, and 44. The underlying purpose of the requirement in GDC 17 to provide onsite and offsite electric power systems to the plant is to ensure sufficient power to accomplish safety functions.

The underlying purpose of the requirement in G DC 18 to design electric power systems to permit inspection and testing is to ensure the capability for periodic inspection and testing of the power systems important to safety that are subject to GDC 17. The underlying purpose of the electric power provisions in GDC 33, 34, 35, 38, 41, and 44 is to ensure that the safety functions described in each of these GDC can still be accomplished when the onsite and offsite electric power systems are not available.

The NuScale US460 design does not rely on power to accomplish safety-related or important-to-safety functions, and therefore the underlying intent of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 is met without the need for onsite and offsite electric power systems that are important to safety.

The staff finds that the NuScale US460 design meets the underlying purpose of these regulations because the onsite and offsite electric power systems are not classified as Class 1E; the onsite and offsite electric power systems are not needed to permit the functioning of SSCs important to safety; and electric power is not needed to (1) achieve or maintain safe shutdown, (2) ensure specified acceptable fuel design limits and design conditions of the RCPB are not exceeded as a result of anticipated operational occurrences, and (3) maintain core cooling, containment integrity, and other vital functions during postulated accidents.

8.1.4 Conclusion

For the reasons given above, as set forth in 10 CFR 50.12(a), the staff concludes that the proposed exemptions requested in SDAA Part 7, Section 4 and Section 5, regarding requirements stated in GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 are authorized by law; will not present an undue risk to public health and safety; and are consistent with the common defense and security. Also, the special circumstances described in 10 CFR 50.12(a)(2)(ii) are present, in that the application of GDC 17, GDC 18, and the electric power provisions in GDC 33, 34, 35, 38, 41, and 44 in the particular circumstances is not necessary to achieve the underlying pur pose of these rules. Therefore, the staff concludes that an exemption from the requirem ents of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 is justified and approved.

8.2 Offsite Power System

8.2.1 Introduction

The offsite power system for the NuScale Power Plant includes connections to a transmission grid, micro-grid, or dedicated service load, as stated in FSAR Section 8.2. Section 8.2 further indicates that the boundary between the onsite AC power system and the offsite power system is at the point of common coupling where the plant switchyard and utility grid conductors are connected. The offsite power system is not requi red to achieve and maintain safe shutdown.

8-8 FSAR Section 8.2 states that the passive design of the NuScale Power Plant does not require an offsite power system to perform safety-rela ted or risk-significant functions, and the design supports exemption from GDC 17 and 18. The objective of the staffs review is to determine whether the offsite power system satisfies the requirements in 10 CFR 52.137(a)(15) and GDC 5, Sharing of structures, systems, and co mponents, and whether it will perform its design function during all plant operating and accident conditions. In addition, the staff reviewed the technical basis for the applicants requested exemption from GDC 17, 18, 33, 34, 35, 38, 41, and 44.

8.2.2 Summary of Application

FSAR: The applicant provided a system description in FSAR Section 8.2, summarized, in part, as follows:

The offsite power system includes connections to a transmission grid, micro-grid, or dedicated service load. The boundary between the onsite alternating current (AC) power system and the offsite powe r system is at the point of common coupling where the plant switchyard and utility grid conductors are connected.

The switchyard is part of the high voltage AC electrical distribution system.

The passive design of the plant does not rely on AC power and does not require an offsite power system to perform safe ty-related or risk-significant functions.

Accordingly, the NuScale US460 design supports an exemption from GDC 17 and GDC 18. Therefore, this section provides the relevant regulatory framework, but the acceptance criteria within the Design Specific Review Standard (DSRS) are not applicable to the NuScale US460 design as there are no Class 1E power distribution systems.

During normal operations with at least one NuScale Power Module operating, the associated turbine generator is the source of power to the onsite AC power system as described in Section 8.3.1. A single turbine generator has sufficient capacity to meet the maximum expected total auxiliary AC load requirements for up to six NuScale Power Modules such that excess power is supplied to the offsite power system if one or more turbine generators are operating.

If provided, offsite power is the primary source for plant startup. The plant has the capability to start up and operate independently from the offsite power system in island mode as discussed in Section 8.3.1.

ITAAC: There are no inspections, tests, analyses, and acceptance criteria (ITAAC) associated with the offsite power system.

Technical Specifications: There are no technical specifications applicable to the offsite power system.

8.2.3 Regulatory Basis

DSRS Section 8.2 provides the relevant NRC re quirements for the offsite power system and the associated acceptance criteria, as summarized below:

  • GDC 2, Design bases for protection against natural phenomena, as it relates to the SSCs of the offsite power system being capable of withstanding the effects of natural phenomena

8-9

  • GDC 4, Environmental and dynamic effects design bases, as it relates to protection of the SSCs of the offsite power system from dynamic effects, including the effects of missiles that may result from equipment failures during normal operation, maintenance, testing, and postulated accidents
  • GDC 5, as it relates to the sharing of SSCs of the preferred power systems, including the switchyard and all circuits from the switchyard to the onsite power distribution systems of each module
  • GDC 17, as it relates to the preferred power systems (1) capacity and capability to permit functioning of SSCs important to safety, (2) provisions to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit, the loss of power from the transmission network, or the loss of power from the onsite electric power supplies, (3) physical independence, (4) availability, and (5) capability
  • GDC 18, as it relates to the inspection and testing of the offsite electric power system
  • GDC 33, 34, 35, 38, 41, and 44, as they relate to the operation of the offsite electric power system in GDC 17 to ensure that the safety functions of the systems described in GDC 33, 34, 35, 38, 41, and 44 are accomplished under the assumption of a single failure, where applicable
  • 10 CFR 52.137(a)(15), as it relates to the ability for a passive design to cope with an SBO for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with no operator actions

The applicant requested exemption from GDC 17, GDC 18, and the electric power provisions in GDC 33, 34, 35, 38, 41, and 44. It should be noted that the applicant has requested exemption for all provision of GDC 33, however, only the electrical provisions are addressed in this SER.

The following guidance is available:

  • RG 1.32, which endorses IEEE Std. 308-2001, relates to the availability and number of immediate access circuits from the transmission network.
  • RG 1.68, Initial Test Programs for Water-Cooled Nuclear Power Plants, relates to the initial test program.
  • RG 1.155, Station Blackout, relates to the adequacy of the alternate AC (AAC) power source and the independence of the AAC power source from the offsite and onsite power systems and sources. New applications must provide an adequate AAC source of diverse design (with respect to AC onsite emergency sources) that is consistent with the guidance in RG 1.155 and is capable of powering at least one complete set of normal safe-shutdown loads.
  • RG 1.204, Guidelines for Lightning Protection of Nuclear Power Plants; IEEE Std. 665-1995 (reaffirmed 2001), IEEE Guide for Generating Station Grounding; IEEE Std. 666-1991 (reaffirmed 1996), IEEE Design Guide for Electric Power Service Systems for Generating Stations; IEEE Std. 1050-1996, IEEE Guide for Instrumentation and Control Equipment Grounding in Generating Stations; and IEEE Std. C62.23-1995 (reaffirmed 2001), IEEE Application Guide for Surge Protection of Electric Generating

8-10 Plants, relate to the design, installation, and performance of station grounding systems and surge and lightning protection systems.

  • RG 1.206, Applications for Nuclear Power Plants, relates to power system analytical studies and stability studies to verify the capability of the offsite power systems and their interfaces with the onsite power system.
  • SECY-91-078, Chapter 11 of the Electric Power Research Institutes (EPRIs Requirements Document and Additional Evolutionary Light Water Reactor (LWR)

Certification issues, dated March 25, 1991 (ML12255A549), relates to the interface between the onsite AC power system and the offsite power system.

  • SECY-94-084, Policy and Technical Issues Associated with the Regulatory Treatment of Non-Safety Systems in Passive Plant Designs, dated March 28, 1994 (ML003708068),

relates to the policy and technical issues associated with the regulatory treatment of non-safety systems (RTNSS) affecting passive plant designs.

  • SECY-95-132, Policy and Technical Issues Associated with the Regulatory Treatment of Non-Safety Systems (RTNSS) in Passive Plant Designs (SECY-94-084), dated May 22, 1995 (ML003708005), relates to the policy and technical issues associated with the RTNSS affecting passive plant designs.
  • SRP Branch Technical Position (BTP) 8-3, Stability of Offsite Power Systems, relates to stability studies for the electrical transmission grid that would be used to provide offsite power sources to the plant.
  • SRP BTP 8-6, Adequacy of Station Electric Distribution System Voltages, relates to adverse effects on the Class 1E loads that can be caused by sustained degraded grid voltage conditions when the Class 1E buses are connected to offsite power.

8.2.4 Technical Evaluation

8.2.4.1 Compliance with GDC 2 and GDC 4

GDC 2 states that SSCs important to safety shall be designed to withstand the effects of natural phenomena without loss of capability to perform t heir safety functions. Thus, GDC 2 requires that the offsite power system retain the capability to perform its functions during the most severe natural phenomena that have been reported historically for the site and surrounding area.

GDC 4 states that SSCs important to safety shall be designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. These SSCs shall be appropriately protected against dynamic effects that may result from equipment failures and from events and conditions outside the nuclear power unit.

As discussed in DSRS Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems, GDC 2 and GDC 4 do not apply to the offsite power system. Specifically, the offsite power system is not safety related and does not perform or support an important-to-safety

8-11 function. Therefore, the staff finds that GDC 2 and GDC 4 do not apply to the NuScale offsite power system design.

8.2.4.2 Compliance with GDC 5

The GDC 5 requirement relates to the sharing of SSCs of the preferred (offsite) power systems, including the switchyard and all circuits from the switchyard to the onsite power distribution systems of each module.

FSAR Table 8.1-1 indicates that GDC 5 is not applicable for the offsite power systems. FSAR Section 8.2.1 states that the passive design of the plant does not rely on AC power and does not require an offsite power system to perform safety-related or risk-significant functions. The NuScale US460 design does not rely on electric grid connections and grid stability for safe operation, and the NuScale US460 design does not rely on AC or DC power systems for safe shutdown and accident mitigation. Therefore, the staff finds that GDC 5 is not applicable.

8.2.4.3 Compliance with GDC 17

GDC 17 states that offsite power shall be provided to allow SSCs important to safety to function and that two physically independent circuits shall supply electric power from the transmission network to the onsite distribution system.

FSAR Section 8.2.1, Description, states the following:

The passive design of the plant does not rely on AC power and does not require an offsite power system to perform safe ty-related or risk-significant functions.

Accordingly, the NuScale US460 design supports an exemption from GDC 17 and GDC 18.

SDAA Part 7 discusses NuScales request for exemption from GDC 17. SDAA Part 7, Section 4.2.1, Technical Basis, states that safety-related functions are achieved and maintained with no reliance on electric power. As discussed in SER Section 8.1.4, the staff approves the exemption from GDC 17. Therefore, the staff determined that, due to the approved exemption, the applicants design is exempt from the requirements of GDC 17 with respect to the offsite power system.

8.2.4.4 Compliance with GDC 18

GDC 18 discusses the inspection and testing of electric power systems important to safety.

FSAR Table 8.1-1 states that the NuScale US460 design supports an exemption from GDC 18.

SDAA Part 7, Section 4.1.1, states that no safety-related functions in the NuScale US460 standard design rely on electric power and use passive safety systems and features to accomplish safety-related functions without reliance on electric power. SDAA Part 7, Section 4.2.2, states, in part, that AC and DC power systems are non-safety-related and non-Class 1E systems. The electric power systems are not relied on to perform safety functions or meet the acceptance criteria of GDC 17. Therefore, conformance with the inspection and testing provisions of GDC 18 is unnecessary to verify electric power system capabilities.

Furthermore, FSAR Section 8.3 states that the design does not rely on AC or DC power systems, and the staff finds that the onsite and o ffsite electric power systems do not warrant a Class 1E designation and are nonClass 1E systems. As discussed in SER Section 8.1.4, the

8-12 staff approves the exemption from GDC 18. Therefore, the staff determined that, due to the approved exemption, the applicants design is ex empt from the requirements of GDC 18 with respect to the capability of inspection and testing of the offsite power system and equipment.

8.2.4.5 Compliance with GDC 33, 34, 35, 38, 41, and 44

GDC 33, 34, 35, 38, 41, and 44 state requirements for safety systems for which access to both offsite and onsite electric power sources must be provided. Compliance with these criteria requires that capability be provided for reactor coolant makeup (GDC 33), residual heat removal (GDC 34), emergency core cooling (GDC 35), containment heat removal (GDC 38), containment atmosphere cleanup (GDC 41), and cooling water for SSCs important to safety (GDC 44). The applicant has requested exemption from these criteria in SDAA Part 7.

DSRS Section 8.2 states the following:

Passive reactor designs incorporate passive safety-related systems for core cooling and containment integrity and, therefore, do not depend on the electric power grid connection and grid stability for safe operation. They are designed to automatically establish and maintain safe-shutdown conditions after DBEs for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, without operator action, following a loss of both onsite and offsite AC power sources. Consequently, such passive reactor designs are not required to meet the requirements of GDC 33, 34, 35, 38, 41, and 44 for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

FSAR Section 8.2.2.1 states that the NuScale plant design complies with a set of principal design criteria in lieu of GDC 33, 34, 35, 38, 41, and 44 and that these principal design criteria do not include requirements for electric power systems. FSAR Section 8.4.1, SBO Analysis and Results, states that a safe and stable shutdow n is automatically achieved and maintained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without operator actions.

Furthermore, FSAR Section 8.3 states that the design does not rely on AC or DC power systems, and the staff finds that the onsite and o ffsite electric power systems do not warrant a Class 1E designation and are not safety related. As discussed in SER Section 8.1.4, the staff approves the exemption from the electric power provisions of GDC 33, 34, 35, 38, 41, and 44.

Therefore, the staff determined that, due to the exemption, the applicant is not required to meet the electric power provisions of GDC 33, 34, 35, 38, 41, and 44.

8.2.4.6 Compliance with 10 CFR 52.137(a)(15) and Conformance to Regulatory Guide 1.155

Consistent with the guidance in DSRS Section 8.2.II, compliance with the requirements of 10 CFR 52.137(a)(15) requires that each light-water-cooled nuclear power plant (NPP) be able to withstand or cope with (and recover from) an SBO. Furthermore, DSRS Section 8.2.II states that, if a passive design can cope with an SBO for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with no operator actions and with the use of only Class 1E DC power, 10 CFR 52.137(a)(15) is satisfied. RG 1.155 discusses the independence of an AAC power source from the offsite and onsite power systems and sources.

The staff reviewed the offsite power system to ensur e that the failure of the offsite system will not affect the NuScale Power Plants ability to cope with an SBO. FSAR Section 8.4.1 states that a safe and stable shutdown is automatically achieved and maintained for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without operator actions. Additionally, the NuScale US460 design has onsite DC power systems that are non-Class 1E and not safety related. SER Section 8.4 contains the staff evaluation on the capability of withstanding or coping with, and recovering from, an SBO of a specified duration.

As described in FSAR Section 8.4, the NuScale Power Module design does not rely on onsite or offsite AC power for the performance of safety-related functions during a DBE, and as a result,

8-13 the design does not include emergency onsite AC power. The staff finds that the offsite power system is not needed to demonstrate compliance with 10 CFR 52.137(a)(15) and conformance to the guidance in RG 1.155.

8.2.4.7 Compliance with Generic Letter 2007-01 and RG 1.218

In Generic Letter (GL) 2007-01, Inaccessible or Underground Power Cable Failures that Disable Accident Mitigation Systems or C ause Plant Transients, dated February 7, 2007 (ML070360665), and the associated summary report, dated November 12, 2008 (ML082760385), the NRC staff discusses cable failures and finds that (1) the predominant factor contributing to cable failures at NPPs appears to be the presence of water or moisture or exposure of cables to submerged conditions, and (2) licensees should have a program for using available diagnostic cable testing methods to assess the cable condition. FSAR Table 1.9-2 states that GL 2007-01 partially conforms and states, in part, that

the electrical power systems do not include power cables that provide power to equipment with risk-significant or safety-related functions. The scope of compliance with the issues addressed by GL 2007-01 is limited to power cables within the scope of 10 CFR 50.65.

The staff agrees with the partial conformance to GL 2007-01, where it is limited to power cables within the scope of 10 CFR 50.65.

RG 1.218, Condition Monitoring techniques for Electric Cables Used in Nuclear Power Plants, provides information on monitoring the performanc e of electric cables used in NPPs. FSAR Table 1.9-2 and FSAR Section 8.2.2, Analysis, state that RG 1.218 is not applicable.

The staff agrees with the applicant that RG 1.218 addresses monitoring the performance of electric cables used in NPPs. The staff determined that, due to the exemptions from GDC 17 and GDC 18, the applicant is not required to provide an inspection, monitoring, or testing program for cables that connect offsite power to safety buses, cables that connect an emergency diesel generator (EDG) to a safety bus, or cables that provide power to an active emergency core cooling system (ECCS).

8.2.4.8 Conformance to Regulatory Guide 1.32

RG 1.32 is related to the criteria for power systems and endorses IEEE Std. 308-2001. IEEE Std. 308-2001 discusses the offsite power system in Section 5.2.3, Preferred Power Supply, and states that the preferred power supply consists of two or more circuits from the transmission system.

FSAR Table 8.1-1 states that RG 1.32 does not apply to the offsite power system. The staff agrees with the applicant that RG 1.32 addresses design criteria for safety-related power systems. The NuScale US460 design does not depend on offsite AC power for safe operation and does not rely on offsite AC power to support any safety-related function. Therefore, the staff finds that RG 1.32 is not applicable to the NuScale US460 design in regard to the offsite power system.

8.2.4.9 Conformance to Regulatory Guide 1.68

DSRS Table 8.1-1 states that RG 1.68 may be used as guidance for offsite power systems.

FSAR Table 8.1-1 states that RG 1.68 is used as guidance for FSAR Section 8.2.

8-14 The staff agrees with the applicant that RG 1.32 addresses design criteria for safety-related power systems. The NuScale US460 design does not depend on offsite AC power for safe operation and does not rely on offsite AC power to support any safety-related function.

Therefore, the staff finds that RG 1.68 is not applicable to the NuScale US460 design with regard to the offsite power system.

8.2.4.10 Conformance to Regulatory Guide 1.204

DSRS Section 8.2 states that adequate provisions are made in the design of the plant and the offsite and onsite power systems for grounding, surge protection, and lightning protection. The staff evaluated the plant/station grounding systems, the methods of equipment and structural grounding, AC power system neutral grounding and ground fault current limiting features, surge and lightning protection features for outdoor equipment and circuits, and the measures for isolation of instrumentation grounding systems. RG 1.204, IEEE Std. 665-1995 (reaffirmed 2001), IEEE Std. 666-1991 (reaffirmed 1996), IEEE Std. 1050-1996, and IEEE Std. C62.23-1995 (reaffirmed 2001) provide acceptabl e guidelines for the design, installation, and performance of station grounding systems and surge and lightning protection systems, as discussed in DSRS Section 8.2. FSAR Table 8.1-1 and Table 1.9-2, Conformance with Regulatory Guides, state that RG 1.204 does not apply to offsite power systems with respect to FSAR Section 8.2.

The NuScale US460 design does not rely on an electric power grid connection and grid stability for safe operation, and the design of the switchyard and connections would not be required to show compliance with RG 1.204 or industry standards to demonstrate compliance with GDC 17.

Furthermore, FSAR Section 8.3 states that the design does not rely on AC or DC power systems. The staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation, and they are non-Class 1E systems. As discussed in SER Section 8.1.4, the staff approves the exemption from GDC 17. Therefore, the staff determined that, due to the exemption, the guidance in RG 1.204 and the IEEE standards discussed above does not apply to the design of the switchyard and connections.

8.2.4.11 Conformance to Regulatory Guide 1.206 and SRP Branch Technical Position 8-3

FSAR Table 8.1-1 states that RG 1.206 is not applicable to FSAR Section 8.2, and SRP BTP 8-3 is used as guidance for FSAR Section 8.2. The NuScale US460 design does not rely on electric grid connections and grid stability for safe operation and does not rely on AC or DC power systems. Therefore, the staff finds that RG 1.206 and SRP BTP 8-3 are not applicable.

8.2.4.12 Conformance to SRP Branch Technical Position 8-6

SRP BTP 8-6 discusses adverse effects on the Class 1E loads that can be caused by sustained degraded grid voltage conditions when the Class 1E buses are connected to offsite power.

FSAR Table 8.1-1 states that SRP BTP 8-6 is not applicable. Further, FSAR Section 8.2.2 states that SRP BTP 8-6 does not apply to the offsite power system. In addition, FSAR Section 8.2.2.1 states that the offsite power system does not supply power to Class 1E loads and does not support safety-related functions. The staff finds that SRP BTP 8-6 does not apply to offsite power systems, since the offsite power system does not warrant a Class 1E designation, and offsite power systems are not safety-related systems, as discussed in SER Section 8.1.4.

8-15 8.2.4.13 Conformance to SRP Branch Technical Position 8-9

On July 27, 2012, the staff issued NRC Bulletin 2012-01, Design Vulnerability in Electric Power System, (ML12074A115) to all holders of operating licenses and combined licenses (COLs) requesting information about facilities electric power system designs. The intended purpose of the bulletin was to affirm that all plants comply with the GDC 17 requirements and to evaluate whether any further regulatory action is warranted to address this design vulnerability. SRP BTP 8-9 discusses the vulnerability of the electric power system design resulting from open phase conditions in offsite electric power systems.

FSAR Table 8.1-1 states that SRP BTP 8-9 is not applicable for FSAR Section 8.2, and Bulletin 2012-01 is used as guidance for Section 8.2 on open phase conditions in the grid.

FSAR Section 8.2 states that the offsite power system does not support safety-related functions, and failures of the offsite power system, including open phase conditions or an SBO, do not prevent the operation of safety-related functions. Furthermore, FSAR Section 8.2.2.1 states the following:

If the offsite power system is supplying pow er to the onsite AC power system, the electrical isolation between the augmented DC power system and equipment with safety-related functions, which is described in Section 7.1.2, ensures that the open phase conditions described in BTP 8-9 would not prevent the performance of safety-related functions.

DSRS Section 8.2,Section III, Item 3.H, states that (1) no single event, including a single protective relay, interlock, or switchgear failure, in the case of loss of all standby power sources, will prevent the separation of the offsite power system from the onsite distribution system, and (2) the offsite power system and standby pow er supplies should not have common-mode failures. In general, a failure modes and effects analysis for the offsite system evaluates the effects of failures, including loss of a relay or switchgear, and an open phase event.

NuScale requested exemption from GDC 17, and an AC equipment failure caused by an open phase condition does not prevent the operation of safety-related equipment. FSAR Section 8.3 states that the design does not rely on AC or DC power systems, and the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. As discussed in SER Se ction 8.1.4, the staff approves the exemption from GDC 17. Therefore, the staff determined that, due to the exemption, SRP BTP 8-9 is not applicable to the NuScale US460 design.

8.2.4.14 Conformance to SECY-91-078, SECY-94-084, and SECY-95-132

DSRS Table 8.1-1 states that SECY-94-084 and SECY-95-132 provide guidance that relates to the inclusion of an alternate power source to non-safety loads for evolutionary plant designs.

DSRS Section 8.2.III.3.A states that, for SECY-94-084 and SECY-95-132, the NuScale US460 design review should identify any offsite power requirements to support non-Class 1E, risk-significant, active systems identified through the RTNSS process. SER Section 19.3 further discusses and evaluates the RTNSS.

FSAR Table 8.1-1 states that SECY-94-084 and SECY-95-132 provide guidance for the offsite power system. FSAR Section 8.2.2 explains that, for conformance to SECY-94-084 and SECY-95-132, the offsite power system has no safety-related or risk-significant loads and an AAC source or safety-related EDG is not needed, consistent with the guidance in the Commission papers. The staff finds that SECY-94-084 and SECY-95-132 are not applicable

8-16 since the offsite power system has no safety-related or risk-significant loads and is a non-safety-related system.

The applicant stated, in FSAR Table 8.1-1, that SECY-91-078 does not apply to the offsite power system. The staff finds that since the NuScale US460 design is a passive plant design and offsite power can be classified as a non-Class 1E system, as discussed in SER Section 8.1.4, SECY-91-078 is not applicable to the NuScale US460 design.

8.2.5 Combined License Information Items

No COL items are provided for this section.

8.2.6 Conclusion

As set forth above, the staff has reviewed all the relevant information that is applicable to GDC 5, 10 CFR 52.137(a)(15), and conformance to RGs, standards, and BTPs committed to by the applicant. The staff also assessed the technical basis for the applicants requested exemption from GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44. The staff also reviewed the COL information items in FSAR Table 1.8-1. The staff concludes that the applicant has provided sufficient information in the FSAR and identified necessary analyses to support the bases for its conclusions about the offsite power system design. The staff concludes that the design of the NuScale offsite power system meets the appropriate regulatory requirements listed in FSAR Section 8.2.2 and shown in the staffs technical evaluations in SER Section 8.2.4. Additionally, the staff determined that the applicants design is exempt from the requirements of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 with respect to the offsite power system, as discussed in SER Section 8.1.4.

8.3 Onsite Power Systems

8.3.1 Alternating Current Power Systems

8.3.1.1 Introduction

The NuScale onsite power system is designed to provide electric power to the plant loads during all modes of plant operation.

The onsite power system includes AC and DC power systems. This section discusses the AC power system for plant loads, and SER Section 8.3.2 discusses the DC system. NuScale states in Section 8.3 that the plant safety-related functions are achieved and maintained without reliance on electric power; therefore, neither the AC nor DC power systems are needed to be safety related (i.e., Class 1E). The objective of the staff review is to determine that the onsite AC power system will perform its design function during all plant operating conditions and that the NuScale US 460 standard design establishes nonreliance on electric power for accident conditions.

8.3.1.2 Summary of Application

FSAR: The applicant provided a system description in FSAR, Section 8.3.1, summarized, in part, as follows:

8-17 The onsite AC power systems distribute AC power to the onsite DC power systems (through battery chargers) and to the plant AC electrical loads during startup and shutdown, normal operation, and off-normal conditions. The NuScale US460 design does not use nor include an emergency onsite AC power system. The onsite AC power systems are shared among the NuScale Power Modules and include the following:

  • normal power distribution system

- high voltage AC electrical distribution system (EHVS) with nominal bus voltage of 13.8 kV and 345 kV switchyard

- medium voltage AC electrical distribution system (EMVS) with nominal bus voltage of 4.16 kV

- low voltage AC electrical distribution system (ELVS) with nominal bus voltage of 480 V

  • backup power supply system (BPSS).

ITAAC: There are no ITAAC associated with the onsite AC power system.

Technical Specifications: There are no technical specifications applicable to the onsite AC power system.

8.3.1.3 Regulatory Basis

DSRS Section 8.3.1 contains the relevant NR C requirements for the onsite AC power system and the associated acceptance criteria, as summarized below. (DSRS Section 8.3.1 also provides review interfaces with other DSRS sections.)

  • GDC 2, as it relates to the SSCs of the AC power system being capable of withstanding the effects of natural phenomena without the loss of the capability to perform their safety functions.
  • GDC 4, as it relates to the SSCs of the AC power system being capable of withstanding the effects of missiles and environmental conditions associated with normal operation, maintenance, testing, and postulated accidents.
  • GDC 5, as it relates to the sharing of SSCs of the AC power systems.
  • GDC 17, as it relates to the onsite AC power systems (1) capacity and capability to permit functioning of SSCs important to safety, (2) independence, redundancy, and testability to perform its safety function assuming a single failure, and (3) provisions to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit or the loss of power from the transmission network. (The applicant requested an exemption from this criterion.)
  • GDC 18, as it relates to inspection and testing of the onsite power systems. (The applicant requested an exemption from this criterion.)
  • GDC 33, 34, 35, 38, 41, and 44, as they relate to GDC 17 to ensure the accomplishment of the safety functions as described therein. (The applicant requested an exemption from the electric power provisions in these criteria.)
  • GDC 50, as it relates to the design of containment electrical penetrations that contain circuits of the AC power system and the capability of electric penetration assemblies in

8-18 containment structures to accommodate a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations.

  • 10 CFR 50.34(f)(2)(xx), as it relates to Additional TMI Item II.G.1. (The applicant requested an exemption from this criterion.)

The guidance and acceptance criteria for meeting the above regulatory requirements in accordance with the DSRS are as follows:

  • RG 1.6, Regulatory Positions D.1, D.3, and D.4, as they relate to the independence between redundant onsite AC power sources and between their distribution systems
  • RG 1.32, as it relates to the design, operation, and testing of the safety-related portions of the onsite AC power system
  • RG 1.53, as it relates to the application of the single-failure criterion
  • RG 1.63, as it relates to the capability of electric penetration assemblies in containment structures to withstand a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations (GDC 50)
  • RG 1.68, as it relates to initial test programs for the onsite AC power systems for water-cooled NPPs
  • RG 1.75, as it relates to the physical independence of the circuits and electrical equipment that comprise or are associated with the onsite AC power system
  • RG 1.81, as it relates to the sharing of the SSCs (power sources) of the AC power system
  • RG 1.106, Thermal Overload Protection for Electrical Motors on Motor-Operated Valves, as it relates to safety-related motor-operated valves (MOVs) of the onsite AC power system
  • RG 1.118, as it relates to the capability to periodically test the onsite AC power system (GDC 18)
  • RG 1.153, as it relates to the design, reliability, qualification, and testability of the power, instrumentation, and control portions of safety systems of nuclear plants, including the application of the single-failure criterion in the onsite DC power system
  • RG 1.155, as it relates to the capability and the capacity of the onsite AC power system for an SBO, including the operation of the AAC power source(s)
  • RG 1.204, as it relates to the design, installation, and performance of station grounding systems and surge and lightning protection systems

8-19

  • RG 1.218, as it relates to monitoring the condition of cables within the onsite AC power system that have been determined to fall within the scope of the Maintenance Rule
  • SRP BTP 8-2, which states that EDGs should not be used for peaking service
  • SRP BTP 8-6, as it relates to the analysis, testing, and selection of the undervoltage and degraded voltage setpoints and associated time delays
  • SRP BTP 8-9, as it relates to providing protection to safety-related AC loads in the event of an open-phase condition on the high side of a unit auxiliary transformer (UAT)
  • SECY-91-078, as it relates to the interface between the onsite AC power system and the offsite power system
  • SECY-94-084, as it relates to the policy and technical issues associated with the RTNSS affecting passive plant designs
  • SECY-95-132, as it relates to the policy and technical issues associated with the RTNSS affecting passive plant designs

8.3.1.4 Technical Evaluation

FSAR Section 8.3 states that the plant safety-related functions are achieved and maintained without reliance on electric power; th erefore, neither the AC power systems nor the DC power systems are safety-related (Class 1E). The onsite power systems do not perform any risk-significant functions.

FSAR Section 8.3.1.1, System Description, states that the normal source of onsite AC electric power is from the operating NPM turbine generators through the EHVS, the EMVS, and the ELVS. The EHVS contains the switchyard, which is connected to the offsite transmission grid, a micro-grid, or both.

In FSAR Section 8.3.1.1.1, Backup Power Supply System, the applicant states that the back up diesel generators provide backup power to EDAS and selected loads via connection to the EMVS. SER Section 8.3.1.4.4 describes and evaluat es BDGs, which are non-safety systems.

FSAR Section 8.3.1.1 discusses island-mode operation. In island mode, the plant turbine generators provide power to onsite and offsite AC loads. The staff did not review island mode since it is not credited to meet any regulatory or safety-related criteria.

Compliance with GDC 2

GDC 2 requires that SSCs important to safety be capable of withstanding the effects of natural phenomena without the loss of the capability to perform their safety functions.

The NuScale US460 design is a passive design, and the applicant stated in FSAR Section 8.3.1.2.2 that the onsite AC power system does not contain SSC that are required to function in the event of natural phenomena. Accordingly, t he applicant stated non-safety-related SSC with the potential for adverse seismic interaction with Seismic Category I SSC are designed to Seismic Category II requirements so that their failure does not affect the ability of safety-related SSC to perform their intended functions. SER Chapter 3 evaluates seismic qualification.

8-20 Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. Therefore, since the onsite AC power system is not safety related and not important to safety, and with the exception of potential adverse seismic interactions, its failure does not affect the ability of safety-related SSCs to perform their function. The staff finds that the application of seismic Category II requirements (as referenced above) to the onsite AC power system is an acceptable m eans to address adverse seismic interactions. Therefore, the staff finds that the onsite AC power sy stem meets the requirements of GDC 2.

Compliance with GDC 4

GDC 4 requires that SSCs important to safety be capable of withstanding the effects of missiles and environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including LOCAs.

The NuScale US460 design is a passive design, and the onsite AC power systems do not perform any risk-significant functions. In FSAR Section 8.3.1.2.2, the applicant stated the onsite AC power system does not contain SSC requir ed to function under adverse environmental conditions associated with postulated accidents, including a loss-of-coolant accident. The applicant further stated that non-Class 1E AC power system SSCs are designed to operate within the environmental conditions associated with normal operation, maintenance, and testing.

Failure of the onsite AC power system com ponents does not introduce adverse environmental conditions that would affect the ability of any sa fety-related SSC to perform its intended function.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. Since the onsite AC power sy stem is not safety related, and is not important to safety, the staff finds it is not required to meet the requirements of GDC 4.

Compliance with GDC 5

GDC 5 requires SSCs important to safety to not be shared among other nuclear units unless it can be shown that such sharing will not signific antly impair their ability to perform their safety functions.

FSAR, Section 8.3.1.2.2, Onsite Alternating Current Power System Conformance with Regulatory Framework, states onsite AC power systems are shared among the NPMs and that failures affecting the onsite AC power system s do not affect the ability to achieve and maintain NPM safety functions, including a DBE in one NPM.

The applicant stated that, as described in FSAR Table 8.3-2, the EHVS, EMVS, and ELVS systems are non-Class 1E syst ems whose functions are not safety related and not risk significant. Because the onsite power systems are not required nor credited to support DBE mitigation, EHVS failures do not affect the ability to achieve and maintain safety-related functions for any NPM, including a DBE in one NPM, consistent with GDC 5.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The onsite AC power syst em is not safety related and although common to

8-21 all of the NPMs, its loss does not prevent safe shutdown of all the NPMs even if one is undergoing an accident. Therefore, the staff finds that the onsite power system design complies with the requirements of GDC 5 and is acceptable.

Compliance with GDC 17

GDC 17 states that AC onsite power shall be provided to permit functioning of SSCs important to safety and electric power from the onsite AC electric power supplies to the onsite distribution system.

The applicant has requested an exemption to GDC 17, as described in SDAA Part 7.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The staff approves the ex emption request to GDC 17. Therefore, the staff determined that due to the exemption, the applicant s design is exempt from the requirements of GDC 17 with respect to the onsite AC power system.

Compliance with GDC 18

Compliance with GDC 18 requires that electric power systems important to safety be designed to permit appropriate periodic inspection and testing of key areas and features to assess their continuity and the condition of their components. These systems shall be designed to test periodically (1) the operability and functional perfor mance of the components of the systems, such as onsite DC power sources, relays, switches, and buses, and (2) the operability of the systems as a whole and, under conditions as clos e to design as practicable, the full operation sequence that brings the systems into operation, including operation of applicable portions of the protection system and the transfer of power among the nuclear power unit, the offsite power system, and the onsite power system.

The applicant has requested an exemption to GDC 18, which is included in SDAA Part 7.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The staff approves t he exemption request from GDC 17 and GDC 18.

Therefore, the staff determined that due to the exemption, the applicants design is exempt from the requirements of GDC 18 with respect to the onsite DC power system.

Compliance with GDC 33, 34, 35, 38, 41, and 44

GDC 33, 34, 35, 38, 41, and 44 identify plant sa fety-related functions, including electric onsite AC power system requirements for those functions. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff als o finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The staff also addresses, in Section 8.1.2 of this report, the applicants request for exemption from the electric power provisions of GDC 33, 34, 35, 38, 41, and 44. Based upon the findings with regard to the exemption request, the onsite AC power system is a non-Class 1E system and therefore, the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 are not applicable.

8-22 Compliance with GDC 50

Compliance with GDC 50 requires that the reactor containment structure, including access openings, penetrations, and containment heat removal systems, be designed so that the containment structure and its internal compartments can accommodate, without exceeding the design leakage rate and with sufficient margin, the calculated pressure and temperature conditions resulting from any LOCA. Containment electrical penetration assemblies (EPAs) must therefore be designed to accommodate, without exceeding their design leakage rate, the calculated pressure and temperature conditions resulting from a LOCA. This criterion applies specifically to ensure the integrity of the EPAs in the event of design-basis LOCA conditions. The focus of the Chapter 8 portion of the review of the EPAs is circuit protection. The staff uses RG 1.63 as a guide to evaluate the circuit protection for the circuits that penetrate containment. The structural integrity and environmental qualification aspects of the EPAs are evaluated in Section 6.2.1 and Section 3.11, respectively, of this SER.

In FSAR, Section 8.3.1.2.1, the applicant stated the following with regard to electrical circuits that penetrate the containment:

The design of electrical penetration assemblies (EPAs) conforms to General Design Criterion (GDC) 50. This section describes the electrical design requirements for EPAs as they relate to compliance with GDC 50. The containment system, including EPAs, can accommodate the calculated pressure and temperature conditions resulting from a loss-of-coolant accident in accordance with GDC 50 as described in Section 6.2.1. The mechanical design requirements for EPAs are described in Section 3.8.2. The environmental qualification requirements fo r EPAs are described in Section 3.11.2.

The electrical penetration assemblies are designed in accordance with Institute of Electrical and Electronics Engineers (IEEE) Standard 317-1983 (Reference 8.3-9) as endorsed by Regulatory Guide (RG) 1.63. The EPAs are provided with external circuit protection per Section 5.4 of IEEE Standard 741-1997 (Reference 8.3-10), which is consistent with the 1986 version endorsed by RG 1.63 with the following clarifications.

Self-limiting circuits are those circuits t hat use EPAs, are not equipped with protection devices, and are supported by analysis that determines that the maximum fault current in these circuits would not damage the penetration if that current is available indefinitely.

For these circuits, consideration of special protection devices is not required. For circuits that are not self-limiting, primary and backup protective devices are provided. Electrical penetration assemblies are designed to withstand the maximum available fault and overload currents for the time sufficient for operation of backup devices in case of failure of the primary protection devices.

Circuits contained in some of the EPAs support safety-related functions and are classified as Class 1E. Protection devices fo r non-Class 1E circuits using EPAs are not required to be treated as Class 1E.

As described in Section 7.1.2, divisional separation for Class 1E circuits is in accordance with Reference 8.3-6, which is endorsed by RG 1.75, Physical Independence of Electric Systems.

Based upon its review of the above design criteria, the staff finds that the EPA circuit protection is in conformance with the provisions of RG 1.63. Specifically, Class 1E circuits are provided with

8-23 Class 1E protection, non-Class 1E circuits are provided with non-Class 1E protection, and the self-limiting circuits are not provided circuit protection. Therefore, the staff finds that the NuScale EPA design meets the requirements of GDC 50 with respect to circuit protection and is acceptable.

Compliance with 10 CFR 50.34(f)(2)

Certain regulations at 10 CFR 50.34(f)(2) pertain to additional TMI-related requirements for the onsite electrical power system (i.e., 10 CFR 50.34(f)(2)(v) addresses bypass and inoperable status indications to be provided for safety syst ems (SER Section 7.2.13 addresses this item);

10 CFR 50.34(f)(2)(xiii) addresses the power supply and control for the pressurizer heaters; and 10 CFR 50.34(f)(2)(xx) addresses the pressu rizer relief valves, block valves, and level indicators).

In SDAA Part 7, Sections 11 and 12, the applicant requested an exemption to 10 CFR 50.34(f)(2)(xx) and 10 CFR 50.34(f)(2)(xiii), respectively. In SDAA, Part 7, Section 11.1.1, the applicant made the following statement:

NuScale Power, LLC (NuScale), requests an exemption from the portions of 10 CFR 50.34(f)(2)(xx) applicable to pressurizer level indicators.

10 CFR 50.34(f)(2)(xx) specifies power requirements for pressurizer relief valves, block valves, and level indicators. The under lying purpose of the rule is to enable natural circulation core cooling in a loss of offsite power condition. The US460 standard design does not rely on pressurizer level indication to achieve and maintain natural circulation in a loss of electric power condition, and therefore meets the underlying purpose of the rule.

As for 10 CFR 50.34(f)(2)(xiii), the applicant made the following statement in SDAA Part 7, Section 12.1.1:

NuScale Power, LLC (NuScale), requests an exemption from 10 CFR 50.34(f)(2)(xiii),

which requires providing power supplies for pressurizer heaters and associated motive and control interfaces to establish and maintain natural circulation in hot standby conditions. The underlying purpose of the rule is to enable natural circulation core cooling in a loss of offsite power condition. The NuScale US460 standard design does not rely on pressurizer heaters to achiev e and maintain natural circulation in a loss of electric power condition, and therefore meets the underlying purpose of the rule.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety.

The exemption for 10 CFR 50.34(f)(2)(xx) and 10 CFR 50.34(f)(2)(xiii) is discussed in Section 5.4.5 of this report.

Compliance with 10 CFR 50.55a(h)

Under 10 CFR 50.55a(h), the NRC requires compliance with the relevant positions for plant protection and safety systems for design, reliab ility, qualification, and testability of the power and instrumentation and control portions of the safety systems outlined in RG 1.153. The onsite electrical AC power system equipment with respec t to the design of instrumentation and control

8-24 equipment and circuits is not a protection syst em and does not perform any safety-related functions. Therefore, the staff finds that the onsite AC system is not required to conform to 10 CFR 50.55a(h) and IEEE Std. 603-1991. SER Section 7.2.13 addresses and provides the staffs evaluation of compliance with 10 CFR 50.55a(h) in regard to monitoring systems.

Conformance to Regulatory Guide 1.6

RG 1.6 describes an acceptable degree of independence between redundant standby (onsite) power sources and between their distribution systems, as part of compliance with GDC 17. In FSAR Table 8.1-1, RG 1.6 is not applicable nor used as guidance for the onsite AC electric power system design. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a C lass 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety, as th e onsite AC power system is not safety related, and therefore, RG 1.6 is not applicable, since there are no Class 1E distribution systems that need to be independent from the standby power sources.

Conformance to Regulatory Guide 1.32

RG 1.32 pertains to the design, operation, and testing of the safety-related portions of the onsite AC power system. In FSAR Table 8.1-1, RG 1.32 is not applicable nor used as guidance for the onsite AC electrical power system design.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The onsite AC power system is not safety related and, therefore, RG 1.32 is not applicable, since RG 1.32 only pertains to the safety-related portions of the onsite AC power system.

Conformance to Regulatory Guide 1.53

RG 1.53 pertains to the application of the single-failure criterion. In FSAR Table 8.1-1, RG 1.53 is not applicable nor used as guidance for the onsite AC electrical power system design.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety.. The onsite AC power syst em is not safety related and, because the single failure criterion is not applied to systems not safety related, RG 1.53 is not applicable.

Conformance to Regulatory Guide 1.63

RG 1.63 pertains to the capability of EPAs in containment structures to withstand a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations to meet the requirement of GDC 50. Mechanical integrity during and following a LOCA is addressed in SER Sections 3.11 and 6.2.1.

The staffs evaluation and approval of the EPA circuit protection aspects of the NuScale US460 design is discussed in SER Section 8.3.1.4.7.

8-25 Conformance to Regulatory Guide 1.68

FSAR Table 8.1-1 states that RG 1.68 may be used as guidance for the initial test program for the onsite power systems.

SER Section 14.2 describes and evaluates the initial test program for the onsite AC system.

Conformance to Regulatory Guide 1.75

RG 1.75 pertains to the physical independence of the Class 1E circuits and electrical equipment that comprise or are associated with the onsite AC power system. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit t he functioning of SSCs important to safety. The onsite AC power system neither contains nor s upports safety-related SSCs, and the staff finds RG 1.75 is not applicable. SER Chapter 7 evaluates electrical isolation with respect to the module protection system (MPS).

Conformance to Regulatory Guide 1.81

RG 1.81 provides guidance in support of GDC 5 with respect to the sharing of Class 1E power sources within the onsite AC power system. The staff evaluated the FSAR with respect to RG 1.81 as it relates to the sharing of the AC power sources. The staff concludes, in SER Section 8.3.1.4.3, that the onsite AC power system complies with GDC 5 in that there are no Class 1E circuits in the design. Therefore, RG 1.81 is not applicable to the NuScale US460 design since RG 1.81 pertains to safety-related systems.

Conformance to Regulatory Guide 1.106

The RG 1.106 provides guidance with respect to thermal overload protection for Class 1E MOVs. In FSAR Table 8-1.1, the applicant stated that the NuScale US460 design does not include safety-related MOVs. Therefore, the staff determined that this RG is not applicable to the onsite AC power system to power any sa fety-related MOV as there are no safety-related MOVs.

Conformance to Regulatory Guide 1.118

RG 1.118 pertains to the capability to periodically test the safety-related onsite AC power system (GDC 18).

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. Since RG 1.118 pertains to the safety-related onsite AC power system and the NuScale onsite AC power system is not safety related, the staff f inds that RG 1.118 is not applicable.

Conformance to Regulatory Guide 1.153

The staff evaluated the FSAR with respect to RG 1.153 as it relates to the design, reliability, qualification, and testability of the power, instrumentation, and control portions of safety systems of nuclear plants, including the application of the single-failure criterion in the onsite AC power

8-26 system. As endorsed by RG 1.153, IEEE Std. 603-1991 provides a method acceptable to the staff to evaluate all aspects of the electrical portions of the safety-related systems, including basic criteria for addressing single failures. The SER Chapter 7 discusses the evaluation of IEEE Std. 603-1991 and 10 CFR 50.55a(h).

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety.. The onsite AC power system is not safety related and therefore, the staff finds that RG 1.153 is not applicable since the RG applies only to safety-related systems.

Conformance to Regulatory Guide 1.155

RG 1.155 pertains to the capability and the capacity of the onsite AC power system to accommodate an SBO, including the operation of the auxiliary AC power source. SER Section 8.4 contains the staff evaluation of the SBO capability of the AC power system.

Conformance to Regulatory Guide 1.204

RG 1.204 endorses IEEE Std. 665-1995 (reaffirmed 2001), IEEE Std. 666-1991 (reaffirmed 1996), IEEE Std. 1050-1996, and IEEE Std. C62.23-1995 (reaffirmed 2001). In FSAR Table 8.1-1, RG 1.204 is not applicable nor used as guidance for the onsite AC electric power system design. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power sy stems are not needed to permit the functioning of SSCs important to safety. The onsite AC power sy stem is not safety related and therefore, the staff finds that RG 1.204 is not applicable and is one means of compliance with GDC 2. The staffs evaluation to GDC 2 is in Section 8.3.1.4.1 of this report NuScale US460 design.

Conformance to Regulatory Guide 1.218

RG 1.218 pertains to monitoring the condition of cables that have been determined to fall within the scope of the Maintenance Rule (10 CFR 50.65). FSAR Table 8-1.1 states that RG 1.218 is limited to cables determined within the scope of 10 CFR 50.65. SER Section 17.6 provides the staffs evaluation of the Maintenance Rule.

Conformance to Branch Technical Positions

SRP BTP 8-2 states that EDG sets should not be used for peaking service. The intent of SRP BTP 8-2 is to ensure that the provision of GDC 17 is met with respect to minimizing the probability of concurrent loss of electric power sources, which would preclude the use of onsite AC power sources for purposes other than supplying standby power when needed. In FSAR Table 8.1-1, the applicant stated that, because the NuScale US460 design does not rely on AC power sources for the performance of safety-related functions, and the guidance of BTP 8-2 does not need to be applied. The staff finds that BTP 8-2 is not applicable to the NuScale US460 design, since there are no Class 1E power sources or EDG sets.

SRP BTP 8-6 discusses how adverse effects on the Class 1E loads can be caused by sustained low grid voltage conditions when the Class 1E buses are connected to offsite power. FSAR Section 8.1.3, states that the loss of voltage or degraded voltage condition on the electrical power systems does not adversely affect the performance of plant safety-related functions. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do

8-27 not warrant a Class 1E designation and are not safe ty-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The staff finds that BTP 8-6 is not appl icable since the onsite AC system is not safety related and, therefore, a loss of voltage or degraded voltage condition would not impact the onsite AC system.

SRP BTP 8-9 discusses the electric power system design vulnerability due to open phase conditions in offsite electric power systems. The basis for SRP BTP 8-9 is to provide protection to safety-related AC loads in the event of an open phase condition. SER Section 8.2.4.13 describes and evaluates SRP BTP 8-9.

Conformance to SECY-91-078, SECY-94-084, and SECY-95-132

SECY-91-078 pertains to the interface between t he offsite AC power system and the Class 1E onsite power system. In FSAR, Table 8.1-1, the applicant stated that this guidance does not apply to the NuScale US460 design. This guidance pertains to GDC 17, and the applicant has requested an exemption from GDC 17. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. Since the onsite AC power system is not safety related, the staff finds that SECY-91-078 is not applicable since it pertains to the interface between the offsite AC power system and the Class 1E onsite system.

DSRS Table 8.11 states that SECY-94-084 and SECY-95-132 provide guidance that relates to the inclusion of an alternate power source to loads that are not safety related for evolutionary plant designs. DSRS Section 8.2.III.3.A states that, for SECY-94-084 and SECY-95-132, the NuScale US460 design review should identify any offsite power requirements to support non-Class 1E, risk-significant active systems identified through process. SER Section 19.3 further discusses and evaluates the RTNSS; no RTNSS SSCs are determined to meet the RTNSS criteria.

8.3.1.5 Combined License Information Items

No COL items are provided for this section

8.3.1.6 Conclusion

As set forth above, the staff has reviewed all of the relevant information that is applicable to the NuScale onsite AC power system design and evaluated its compliance with GDC 2; GDC 4; GDC 5; requested exemption from GDC 17 and GDC 18 and applicable portions of GDC 33, 34, 35, 38, 41 and 44; GDC 50; 10 CFR 50.34(f)(2); 10 CFR 50.55a(h); and conformance to applicable RGs and standards committed to by the applicant. The staff concludes that the applicant has provided sufficient information in the FSAR and identified necessary analyses to support the bases for its conclusions on its onsit e AC power system design. The staff concludes the design of the NuScale onsite AC power system design meets the appropriate regulatory requirements as shown in the staffs technical evaluations in Section 8.3.1.4 of this report.

Additionally, the staff determined that the applicants design is exempt from the requirements of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44, with respect to the onsite AC power system, as discussed in Section 8.1.2 of this report.

8-28 8.3.2 Direct Current Power Systems

8.3.2.1 Introduction

The onsite DC power systems include the EDAS and the normal DC power system (EDNS).

The objective of the NRC staff review is to determine that the onsite DC power systems satisfy the requirements of GDC 2, 4, 5, 17, and 18 and will perform their design function during all plant operating and accident conditions.

8.3.2.2 Summary of Application

FSAR: The applicant has provided system description on the EDAS in FSAR Section 8.3.2.1.1, summarized here, in part, as follows.

The EDAS comprises two DC subsystems that provide a continuous, failure-tolerant source of 125 VDC power to assigned plant loads during normal plant operation and for a specified minimum duty cycle following a loss of AC power. The EDAS-common (EDAS-C) plant subsystem serves plant commo n loads that have functions that are not specific to a single NPM. These functions include main control room (MCR) emergency lighting and post-accident monitoring (PAM) information displayed in the MCR. The EDAS-module-specific (EDAS-MS) plant subsystem consists of separate and independent DC electrical power supply systems, one for each NPM.

The EDAS-MS consists of four power c hannels and EDAS-C consists of two power divisions. The EDAS-MS and EDAS-C are capabl e of providing uninterrupted power to their loads. The EDAS-MS channels A and D have a specified minimum battery duty cycle of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and EDAS-MS channels B and C have a specified minimum battery duty cycle of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The EDAS-C power divisions have a specified minimum battery duty cycle of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The 24-hour battery duty cycle of EDAS-MS channels A and D is specified to preclude unnecessary ECCS valve actuation for a minimum of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following a postulated loss of AC power, unless a valid ECCS actuation signal is received (Section 6.3.2 contains additional information on ECCS operation). The 72-hour battery duty cycle for EDAS-MS channels B and C and EDAS-C provides a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of DC electrical power for MCR normal and emergency lighting and certain equipment supporting PAM. These EDAS-MS and EDAS-C functions are not credited to meet the acceptance criteria for design basis event analyses in Chapter 15.

The applicant has provided a system description on the EDNS in Section 8.3.2.1.2 of the application, summarized here, in part, as follows.

The EDNS is a non-Class 1E DC power system classified as non-safety-related and non-risk-significant. The EDNS does not serve safety-related loads, and it does not have safety-related functional requirements during plant startup, normal operation, shutdown, or abnormal operation.

The EDNS is shared among the NPMs and provides both DC power and AC power (through inverters) to non-safety-related loads that support functions related to investment protection and power generation (i.e., the loads that are part of plant permanent non-safety systems).

ITAAC: There are no ITAAC associated with this section of the FSAR.

8-29 Technical Specifications: None.

8.3.2.3 Regulatory Basis

Section 8.3.2 of the NuScale DSRS gives the relevant requirements of the Commissions regulations for the onsite DC power systems and the associated acceptance criteria, as summarized below. (DSRS Section 8.3.2 also gives the review interfaces with other DSRS sections.)

  • GDC 2, as it relates to SSCs of the DC power system being capable of withstanding the effects of natural phenomena without the loss of the capability to perform their safety functions.
  • GDC 4, as it relates to SSCs of the DC power system being protected against dynamic effects, such as the effects of missiles, and to accommodate the effects of environmental conditions associated with normal operation, maintenance, testing, and postulated accidents.
  • GDC 5, as it relates to multimodule sharing of the DC power system SSCs.
  • GDC 17, as it relates to the onsite DC power systems (1) capacity and capability to permit functioning of SSCs important to safety, (2) independence, redundancy, and testability to perform its safety function assuming a single failure, and (3) provisions to minimize the probability of losing electric power from any of the remaining supplies as a result of, or coincident with, the loss of power generated by the nuclear power unit or the loss of power from the transmission network. (The applicant requested an exemption from this criterion.)
  • GDC 18, as it relates to inspection and testing of the onsite power systems. (The applicant requested an exemption from this criterion.)
  • GDC 33, as it relates to reactor coolant makeup (The applicant requested an exemption from this criterion)
  • GDC 34, 35, 38, 41, and 44, as they relate to GDC 17, to ensure that the safety functions so described are accomplished. (The applicant requested an exemption from the electric power provisions of these criteria.)
  • GDC 50, as it relates to the design of containment electrical penetrations containing circuits of the AC and DC power system and the capability of EPAs in containment structures to withstand a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations.
  • 10 CFR 50.34(f)(2)(xx), as it relates to Additional TMI Item II.G.1. (The applicant requested an exemption from this criterion.)

8-30 The NRC has the following guidance and acceptance cr iteria for meeting the above regulatory requirements, per the DSRS:

  • RG 1.6, Regulatory Positions D.1, D.3, and D.4, as they relate to the independence between redundant onsite DC power sources and between their distribution systems
  • RG 1.32, as it relates to the design, operation, and testing of the safety-related portions of the onsite DC power system
  • RG 1.53, as it relates to the application of the single-failure criterion
  • RG 1.63, Revision 3, issued February 1987, as it relates to the capability of electric penetration assemblies in containment structures to withstand a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations (GDC 50)
  • RG 1.68, as it relates to demonstrating compliance with the NRC regulations as they pertain to initial test programs for light-water-cooled NPPs
  • RG 1.75, as it relates to the physical independence of the circuits and electrical equipment that comprise or are associated with the onsite DC power systems
  • RG 1.81, as it relates to the sharing of SSCs (power sources) of the DC power system
  • RG 1.106, as it relates to safety-related valves
  • RG 1.118, as it relates to the capability to periodically test the onsite AC and DC power systems (GDC 18)
  • RG 1.128, as it relates to criteria for vented lead-acid storage batteries
  • RG 1.129, as it relates to criteria for vented lead-acid storage batteries
  • RG 1.153, as it relates to the design, reliability, qualification, and testability of the power, instrumentation, and control portions of safety systems of nuclear plants, including the application of the single-failure criterion in the onsite DC power system
  • RG 1.155, as it relates to the capability and the capacity of the onsite DC power system for an SBO
  • RG 1.212, as it relates to guidance for defining the DC load and size of lead-acid batteries needed to supply the defined load for full-float stationary battery applications to support NPP operations
  • RG 1.218, it relates to monitoring the condition of cables that have been determined to fall within the scope of the Maintenance Rule
  • SECY-91-078, as it relates to the interface between the onsite AC power system and the offsite power system
  • SECY-94-084, as it relates to the policy and technical issues associated with the RTNSS affecting passive plant designs.

8-31

  • SECY-95-132, as it relates to the policy and technical issues associated with the RTNSS affecting passive plant designs

8.3.2.4 Technical Evaluation

DSRS Section 8.3.2 discusses the relevant requirements of the Commissions regulations for the onsite DC power systems and the associ ated acceptance criteria. The relevant requirements are discussed in Section 8.3.2.2 of this report. This section discusses how NuScale has met or addressed those regulatory requirements for EDAS-MS. As the EDNS is non-safety and non-risk significant, the staffs review focuses on EDAS, including EDAS-MS and EDAS-C.

FSAR Section 8.3.2.1.1 states that augmented design requirements are applied to the EDAS batteries and EDAS distribution panels as described in FSAR Table 8.3-2. Therefore, the portions of the EDAS system with augmented provisions are the batteries and distribution panels, and the staffs review focuses on the portions of EDAS-MS and EDAS-C that have augmented design requirements.

FSAR Section 8.3.2.1.1 states that control over the reliability and availability of the EDAS-MS power circuitry and supply are included in the owner-requirements manual, described in FSAR Section 16.1. The staffs review of the owner-requirements manual is in SER Section 16.

Further, FSAR Section 8.3.2.1.1 states that EDAS is included in the maintenance rule program in accordance with 10 CFR 50.65. SER Section 17.6 provides the staffs evaluation of the Maintenance Rule. FSAR Section 8.3.2.1.1 further states that:

The requirement to include EDAS-MS within the owner-controlled requirements manual, as well as adherence to the requirements inherent to the maintenance rule (i.e., system performance and the requirement to assess and manage risk) ensures that the functionality (availability and reliability) of EDAS-MS is maintained consistent with the Probabilistic Risk Assessment modeling in [FSAR] Section 19.1:

  • common cause failure remains the dominant failure
  • reliability is equivalent to a typical Class 1E system
  • test and maintenance unavailability, excluding batteries, is minimal and limited to a single channel
  • test and maintenance unavailability of batteries is negligible.

Staffs review of PRA is in SER Chapter 19.

Augmented Design Requirements

FSAR Table 8.3-3 provides the specific augmented provisions. Regarding quality assurance, Table 8.3-3 states that the graded QA program is in the QA Program Description (QAPD), and the staffs evaluation of the QAPD is in SER Chapter 17.

For environmental qualification, the applicant stated in Table 8.3-3 that the batteries are located in a mild environment and qualified to IEEE Std. 323-2003. While IEEE Std. 535 pertains to the qualification of vented lead-acid batteries, currently, there is no existing qualification methodology of valve-regulated lead-acid batteries. The staff finds the use of IEEE Std. 323-2003, a consensus standard with good engineering practice, reasonable for environmental qualification of valve-regulated lead-acid batteries.

8-32 Regarding the batteries, in Table 8.3-3, the applicant states that design and installation is per IEEE Std. 1187-2013; sizing is per IEEE Std. 485-2020 as endorsed by RG 1.212, Revision 2; instrumentations, indication, and alarms is per IEEE Stds 946-2020, 1491-2012, 1187-2013, 1188-2005 (R2010) with 2014 amendment. The staff addressed sizing in SER Section 8.3.2.4.23. The staff finds the use of IEEE 1187-2013, a consensus standard with good engineering practice, reasonable for design and installation of valve-regulated lead-acid (VRLA) batteries. Further, the staff finds that the use of IEEE Stds 946-2020, 1491-2012, 1187-2013, 1188-2005 (R2010) with 2014 amendment reasonable for instrumentations, indication, monitoring, and alarms since these standards provide good engineering practice related to instrumentation, indication, monitoring, and alarms.

In Table 8.3-3, the applicant states that identification and independence is per IEEE Std. 384-1992, with modification with RG 1.75. The staffs evaluation pertaining to the conformance to RG 1.75 is in SER Section 8.3.4.15.

In Table 8.3-3, the applicant states that the single failure criterion is applied to EDAS SSC that provide electrical power to prevent unintended ECCS valve actuation per IEEE 379-2020 as endorsed by RG 1.53 (CONFIRMATORY ITEM).The staffs evaluation pertaining to the conformance to RG 1.53 is in SER Section 8.3.2.4.12.

Regarding common-cause failure, NuScale indicated in Table 8.3-3 that common-cause failure probability is minimized to the extent practicable via, but not limited to, 1) independence, including appropriate use of physical separation and electrical isolation; 2) protection from environmental and dynamic effects of internal equipment failures design requirements; 3) design, environmental qualification, and quality a ssurance provisions; 4) HVAC systems; 5) protection from natural phenomena; 6) location within SC-1 structures; and 7) battery supply immediately available during normal operations and following loss of power from the AC system.

The staff evaluated compliance with GDC 2 and GDC 4 in Sections 8.3.2.4.1 and 8.3.2.4.2, respectively. The staffs evaluation pertaini ng to independence and the conformance to RG 1.75 is in SER Section 8.3.4.15. The staff finds the description for minimizing CCF probability adequate and therefore, acceptable.

In FSAR Table 8.3-3, the applicant stated that equipment protection and coordination studies are performed in accordance with IEEE Stds. 242-2001, 946-2020, and 1375-1998. Since these consensus standards contain good engineering judgement and practices pertaining to protection, the staff finds the use of these standards reasonable.

Regarding isolation with Class 1E, as discussed in Table 8.3-3, the staffs evaluation is in SER Chapter 7. Table 8.3-3 states that controls and indication are provided inside and outside the MCR and instrumentation, indication, and alarming features are consistent with IEEE Stds 946-2020, 1491-2012, 1187-2013, 1188-2005 (R2010) with 2014 amendment. As these standards provide good engineering practice related to instrumentation, indication, monitoring, and alarms, the staff finds the description related to the location of instrumentation, indication, and alarms reasonable.

Table 8.3-3 addresses maintenance, surveillance and testing, such that periodic inspection is performed, preoperational testing is performed according to FSAR Section 14.2, and battery maintenance is performed per IEEE Std. 1188-2005 (R2010) with 2014 amendment. Further, FSAR Section 8.3.2.1.1 states that EDAS is included in the maintenance rule program in accordance with 10 CFR 50.65. SER Section 17.6 provides the staffs evaluation of the Maintenance Rule. The staffs evaluation of preoperational testing is in SER Section 14. The

8-33 staff finds the use of IEEE Std. 1188-2005(R 2010) reasonable for the maintenance of VRLA batteries as it is a consensus standard providing good engineering practices.

Lastly, pertaining to multi-unit station considerations, in Table 8.3-3, the staffs evaluation on GDC 5 is in Section 8.3.2.4.3 of this report.

On the basis of its review of the information provided in FSAR Table 8.3-3, the staff considers that the description for the augmented design, qualification, and quality assurance provisions in Table 8.3-3 is adequate and acceptable.

Compliance with GDC 2

Compliance with GDC 2 requires that NPP SSCs important to safety be designed to withstand the effects of natural phenomena such as earthquake, tornado, hurricane, flood, tsunami, or seiche without losing the capability to perform their intended safety functions.

With regard to the DC power system, this criterion requires that the capability for important-to-safety portions of the onsite DC power system to perform its functions must be protected from the most severe natural phenomena that historically have been reported for the site and surrounding area. Therefore, the important-to-safety portions of the DC power system and its components are normally located in seismic Category I (SC-I) structures that provide protection from the effects of tornadoes, tornado missiles, and floods.

FSAR Section 8.3.2.2.1 states, in part, the following:

The EDAS is augmented to comply with GDC 2 requirements for increased reliability and availability. The EDAS structures, systems, and components are located in Seismic Category I areas of the plant, specifically in the Reactor Building and in areas of the Control Building (CRB) that are designed to withstand the effects of and function following natural phenomena such as earthquakes, tornadoes, hurricanes, floods, and externally-generated missiles.

The EDAS structures, systems, and co mponents are further augmented by applying design, qualification, and QA provisions ty pically applied to Class 1E DC power systems using a graded approach. The graded approach is reflected in the EDAS design, qualification, and QA provisions detailed in this Chapter and the Quality Assurance Program Description. Augmented DC power system SSC that provide backup DC electrical power meet Seismic Category I standards per IEEE Std 344-2013.

The staff finds that the EDAS complies with GDC 2 as the EDAS components are located in SC-I structures.

Compliance with GDC 4

Compliance with GDC 4 requires SSCs important to safety (1) to be designed to accommodate the effects of, and be compatible with, the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents and (2) to be appropriately protected against dynamic effects that may result from equipment failures, including missiles.

In FSAR Section 8.3.2.2.1, the applicant stated, in part, the following with regard to GDC 4:

8-34 The EDAS complies with GDC 4 requirements. The EDAS design accommodates the effects of environmental conditions by applying augmented provisions for the design, qualification, and QA typically applied to Class 1E DC power systems using a graded approach. The graded approach is reflected in the EDAS design, qualification, and QA provisions detailed in this Chapter and as described in Section 17.5. The EDAS is located in a mild environment as defined in 10 CFR 50. 49(c), such that it is not subject to the requirements of 10 CFR 50.49. The physical locations of the EDAS-MSs and EDAS-C within the Reactor Building and the CRB, respectively, provide the EDAS with protection from dynamic effects, including the effects of missiles, pipe whipping, and discharging fluids.

The Reactor and Control Building HVAC system s provide EDAS structures, systems, and components with ventilation including cooling, heating, humidity control, and hydrogen dilution in accordance with Reference 8.3-7, Reference 8.3-8, and Reference 8.3-12. The BPSS delivers backup power to heating, ventilation, and air conditioning systems serving the battery and associated charger rooms to avoid prolonged periods of high ambient temperature.

The EDAS batteries are environmentally qualified per Reference 8.3-13.

The harsh environment is not applicable to the EDAS. The design would meet the same guidance governing environmental qualification for mild environments as that applied to a Class 1E electrical system. The augmented provisions assume that the EDAS will not be located in an area that would experience environmental conditions considered a harsh environment. These systems will be located in a mild environment as defined in 10 CFR 50.49(c), such that they would not be subject to the requirements of 10 CFR 50.49, Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants, for harsh environments.

Since the EDAS will be located in a mild environment, and in the SC-I RXB and CRB, the staff has reasonable assurance that the EDAS meets the requirements of GDC 4.

Compliance with GDC 5

Compliance with GDC 5 requires that SSCs important to safety not be shared among nuclear power units unless such sharing will not significantly impair their ability to perform their safety functions, including, in the event of an accident in one unit, an orderly shutdown and cooldown of the remaining units.

In FSAR Section 8.3.2.2.1, the applicant stated, in part, the following with regard to GDC 5:

.the EDAS-MS is not shared among NPMs. S pecifically, portions of the EDAS that supply electrical power to the MPS are not shared. Each NPM is provided with a dedicated EDAS-MS. The module-specific subsystem meets the provisions of regulatory position C.1 of Regulatory Guide 1.81, Revision 1, as described in Table 1.9-2.

Sharing of the EDAS-C is shown on Figure 8.3-3. A postulated loss of power or power fluctuation on the EDAS-C would not result in adverse interactions among NPMs, and would not impair the performance of safety -related functions necessary to achieve and maintain safe shutdown of the NPMs.

8-35 Because the EDAS-MS is not shared between NPMs, the staff finds that the EDAS-MS meets the requirements of GDC 5.

EDAS-C serves plant common loads that have functions that are not specific to a single NPM, including MCR emergency lighting and PAM information displayed in the MCR, as stated in FSAR Section 8.2.3.1.1. Because the loss of the EDAS-C would not impair the performance of safety-related functions necessary to achiev e and maintain safe shutdown and EDAS-C is shared among NPMs, the staff finds the requirements of GDC 5 are not applicable to EDAS-C.

Compliance with GDC 17

GDC 17 states that an onsite power system (both AC and DC) shall be provided to permit the functioning of SSCs important to safety and that it shall have sufficient independence, redundancy, and testability, assuming a single failure, to support those SSCs in performing their safety functions. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E des ignation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. NuScale US460 design The staff approves the exemption from GDC 17. Therefore, the sta ff determined that, due to the exemption approved in Section 8.1.2 of this report, the applicants des ign is exempt from the requirements of GDC 17 with respect to the onsite DC power sy stem, specifically, EDAS-MS and EDAS-C.

Compliance with GDC 18

Compliance with GDC 18 requires that electric power systems important to safety be designed to permit appropriate periodic inspection and testing of key areas and features to assess their continuity and the condition of their components. These systems shall be designed to test periodically (1) the operability and functional performance of the components of the systems, such as onsite DC power sources, relays, switches, and buses, and (2) the operability of the systems as a whole and, under conditions as close to design as practicable, the full operation sequence that brings the systems into operation, including operation of applicable portions of the protection system and the transfer of power among the nuclear power unit, the offsite power system, and the onsite power system.

It is important to note that, although the applicant stated in its application that GDC 18 is not applicable as a requirement, FSAR Section 8.3.2.3, states that periodic inspection and testing is performed on the EDAS for operational, commercial, and plant investment protection purposes and the EDAS is designed to permit appropriate periodic inspection and testing to assess the operability and functionality of the systems and the condition of their components. Further, the applicant states that protection devices are capable of being tested, calibrated, and inspected.

The staff finds the program as described in FSAR Section 8.3.2.3, to be acceptable since periodic inspection and testing are performed on the EDAS systems.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The staff approves the ex emption from GDC 17 and GDC 18. Therefore, the

8-36 applicants design is exempt from the requirements of GDC 18 with respect to the onsite DC power system specifica lly, EDAS-MS and EDAS-C.

Compliance with GDC 33, 34, 35, 38, 41, and 44

The staff evaluated the FSAR with respect to the operation of the onsite electric power system.

GDC 33, 34, 35, 38, 41, and 44 identify plant sa fety-related functions, including electric power system requirements for those functions. The NuScale US 460 design accomplishes the safety-related functions addressed by these GD C via passive systems without reliance on electric power.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety, and the staff approves the exemption from the electric power provisions of GDC 33, 34, 35, 38, 41, and 44.

Compliance with GDC 50

Compliance with GDC 50 requires that the reactor containment structure, including access openings, penetrations, and containment heat removal systems, be designed so that the containment structure and its internal compartments can accommodate, without exceeding the design leakage rate and with sufficient margin, the calculated pressure and temperature conditions resulting from any LOCA. Containment electric penetrations must therefore be designed to accommodate, without exceeding their design leakage rate, the calculated pressure and temperature conditions resulting from a LOCA. This criterion applies specifically to ensuring the integrity of containment electrical penetrations in the event of design-basis LOCA conditions. The focus of the Chapter 8 portion of the review of the EPAs is circuit protection. The staff uses RG 1.63 as a guide to evaluate the circuit protection for the circuits that penetrate containment.

The structural integrity and environmental qualification aspects of the EPAs are evaluated in Chapter 6 and Chapter 3, respectively, of this SER.

Based upon its review of the design criteria, the staff finds that the EPA circuit protection is in conformance to the provisions of RG 1.63. Specifically, Class 1E circuits are provided with Class 1E protection, non-Class 1E circuits are provided with non-Class 1E protection, and the self-limiting circuits are not provided with circuit protection. Therefore, the staff finds that the NuScale EPA design meets the requirements of GDC 50 with respect to circuit protection and is acceptable.

Circuit protection for the instrumentation and control cables is evaluated in Chapter 7 of this SER.

Compliance with 10 CFR 50.34(f)(2)(v)

The regulation in 10 CFR 50.34(f)(2)(v) states that the applicant shall provide for automatic indication of the bypassed and operable status of safety systems. The staff evaluated the FSAR with respect to the automatic indication of the bypassed and operable status of safety systems. In FSAR Table 8.1-1, the applicant stated that this requirement is not applicable to the NuScale electric power systems, which are not safety related. SER Section 7.2.13 addresses this item.

Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds

8-37 that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. The regulation in 10 CFR 50.34(f)(2)(v) and associated guidance apply to safety-related systems and, because the onsit e DC systems, EDAS-MS and EDAS-C, are non-Class 1E systems, the staff finds that 10 CFR 50.34(f)(2)(v) and associated guidance are not applicable.

Compliance with 10 CFR 50.55a(h)

The staff evaluated FSAR Section 8.3.2, with respect to the incorporation of IEEE Std. 603-1991.

The applicant stated in FSAR Table 8.1-1, with regard to 10 CFR 50.55a(h), that NuScale electrical systems are not protection systems and do not perform safety-related functions. The staff finds that, because the EDAS is not safety related, the requirements of 10 CFR 50.55a(h) are not applicable. The staff evaluates compliance with 10 CFR 50.55a(h) with respect to monitoring and protection systems in Chapter 7 of this report.

Conformance to Regulatory Guide 1.6

RG 1.6 describes an acceptable degree of independence between redundant standby (onsite) power sources and between their distribution systems, as part of compliance with GDC 17. FSAR Table 8.1-1 states that RG 1.6 is not applicable to onsite DC systems. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety.

Since the staff approved the GDC 17 exempt ion and the onsite DC systems are not safety-related, the staff finds that RG 1.6 is not applicable.

Conformance to Regulatory Guide 1.32

The staff evaluated the FSAR with respect to RG 1.32, as it relates to the design, operation, and testing of the safety-related portions of the onsite DC power system. RG 1.32, Revision 3, endorses IEEE Std. 308-2001. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff also finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety. As the EDAS is not safety-related, the staff finds that RG 1.32 is not applicable to EDAS.

Conformance to Regulatory Guide 1.53

The staff evaluated the FSAR with respect to RG 1.53, as it relates to the application of the single-failure criterion to the electric power portions of plant safety systems. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related sy stems. The staff also finds that the onsite and offsite power systems are not needed to permit t he functioning of SSCs important to safety.

Conformance to Regulatory Guide 1.63

The staff evaluated the FSAR with respect to RG 1.63 as it relates to the capability of electric penetration assemblies in containment structures to withstand a LOCA without loss of mechanical integrity and the external circuit protection for such penetrations and one method to meet the requirements of GDC 50. In Table 8.1-1, the applicant states that RG 1.63 is used as guidance for onsite DC systems. The staffs ev aluation and approval of the EPA circuit

8-38 protection aspects with regard to conformance to RG 1.63 is in SER Section 8.3.1.4.13 and compliance with GDC 50 in SER Section 8.3.2.4.7.

Conformance to Regulatory Guide 1.68

DSRS Table 8.1-1 states that RG 1.68 may be used as guidance for the initial test program for the onsite DC power systems. FSAR Section 8.3.2.2.1, states that the EDAS preoperational testing is performed as part of the Initial test program described in FSAR Section 14.2.12. SER Section 14.2 evaluates the initial test program for the EDAS.

Conformance to Regulatory Guide 1.75

The staff evaluated FSAR with respect to RG 1.75, as it relates to the physical independence of the circuits and electrical equipment that comprise or are associated with the onsite DC power system. RG 1.75 discusses the independence of the electrical circuits and does not differentiate between AC and DC power systems. In FSAR Section 8.3.2.2.1, the applicant stated, with regard to RG 1.75, the physical separation, electrical independence, and identification criteria of RG 1.75 and IEEE Std. 384-1992 are applied to the EDAS as an augmented quality provision. The staff finds this acceptable for EDAS. The staff evaluates electrical isolation with respect to the MPS in SER Section 7.1.2.4.1.

Conformance to Regulatory Guide 1.81

The staff evaluated FSAR with respect to RG 1.81, as it relates to the sharing of SSCs of the DC power system. Regulatory Position C.1 of RG 1.81 states that multiunit sites should not share DC systems. FSAR Table 1.9-2 states that the NuScale US460 design partially conforms to RG 1.81, EDAS-MS meets the provisions of RG 1.81 Regulatory Position C.1, Regulatory Position C.2 is not appliable since the design does not include emergency AC power, Regulatory Position C.3 is not applicable because the design does not include emergency power systems, and that EDAS-MS is not shared between modules. The staff discusses the applicability of RG 1.81 to the DC systems in SER Section 8.3.2.4.3, with regard to GDC 5.

Conformance to Regulatory Guide 1.106

RG 1.106 provides guidance with respect to thermal overload protection for Class 1E MOVs. In FSAR Table 8-1.1, the applicant stated that the NuScale US460 design does not include safety-related MOVs. Therefore, the staff determined that RG 1.106 does not apply to EDAS, as it has no safety-related MOVs.

Conformance to Regulatory Guide 1.118

The staff evaluated the FSAR with respect to RG 1.118, as it relates to the capability to periodically test the onsite DC power system. It is important to note that, although the applicant stated in FSAR Table 8-1.1 that RG 1.118 is not applicable to EDAS, FSAR Section 8.3.2.3, states that periodic inspection and testing is performed on the EDAS for operational, commercial, and plant investment protection purposes and the EDAS is designed to permit appropriate periodic inspection and testing to assess the operability and functionality of the systems and the condition of their components. Further, the applicant states that protection devices are capable of being tested, calibrated, and inspected. The staff finds the program as described in FSAR Section 8.3.2.3, to be acceptable since periodic inspection and testing are performed on the EDAS systems.

8-39 Conformance to Regulatory Guide 1.128

The staff evaluated FSAR with respect to RG 1.128, as it relates to the installation of vented lead acid-storage (VLA) batteries in the onsite DC power system. In FSAR Table 8-1.1, the applicant stated with regard to RG 1.128, vented lead-acid batteries are not included in the design. The staff finds RG 1.128 generally not applicable to the EDAS system because RG 1.128 relates to VLA batteries and the NuScale US460 design uses VRLA batteries. The staff finds installation of VRLA batteries is addressed in IEEE Std. 1187-2013, IEEE Recommended Practice for Installation Design and Installation of Valve-Regulated Lead-Acid Batteries for Stationary Applications, which the applicant is applying to the NuScale US460 design.

Conformance to Regulatory Guide 1.129

The staff evaluated the FSAR with respect to RG 1.129, as it relates to maintenance, testing, and replacement of VLA storage batteries in the onsite DC power system. In FSAR Table 8-1.1, the applicant stated with regard to RG 1.129, vented lead-acid batteries are not included in the design.

The staff finds RG 1.129 not generally applicable to the EDAS system because RG 1.129 relates to VLA batteries, and the NuScale US460 design uses VRLA batteries. The staff finds that maintenance, testing, and replacement of VRLA batteries is addressed in IEEE Std. 1188-2005, (R2010) with 2014 amendment IEEE Recommended Practice for Maintenance, Testing, and Replacement of Valve-Regulated Lead-Acid (VRLA) Batteries for Stationary Applications, which the applicant is applying to the NuScale US460 design, as stated in FSAR Table 8.3-3.

Conformance to Regulatory Guide 1.153

The staff evaluated the FSAR respect to RG 1.153, as it relates to the design, reliability, qualification, and testability of the power, instrumentation, and control portions of safety systems of nuclear plants, including the application of the single-failure criterion in the onsite DC power system. As endorsed by RG 1.153, IEEE Std. 603-1991 provides a method acceptable to the staff to evaluate all aspects of the electrical portions of the safety-related systems, including basic criteria for addressing single failures. In FSAR Table 8-1.1, the applicant stated that RG 1.153 is not applicable and not used as guidance for the onsite DC power system. Further, the applicant noted that the system boundary between the non-safety-related EDAS and the safety-related MPS is at the Class 1E isolation device, and the isolation device is considered part of MPS. The staff finds that RG 1.153 is not applicable since EDAS is not safety-related.

The staff evaluates the FSAR with regard to the MPS, IEEE Std. 603-1991 and 10 CFR 50.55a(h) in Chapter 7 of this report.

Conformance to Regulatory Guide 1.155

RG 1.155 relates to the capability and the capacity of the onsite DC power system for an SBO.

The staff evaluates conformance to RG 1.155 in SER Section 8.4.

Conformance to Regulatory Guide 1.212

The staff evaluated the FSAR with respect to RG 1.212, as it relates to the sizing of large lead-acid storage batteries. In FSAR Table 8.1-1, NuScale states that RG 1.21, Revision 2 is used as guidance for the onsite DC systems and the EDAS batteries are sized in accordance with IEEE Std. 485-2020. FSAR Table 8.3-3 states that sizing of the EDAS batteries is per IEEE 485-2020, as endorsed by RG 1.212, Revision 2. Although the NuScale US460 design uses VRLA batteries, the

8-40 staff finds that defining the DC load and size of lead-acid batteries is applicable to VRLA batteries, and thus RG 1.212 can be used. The staff finds NuScale conforms to RG 1.212, as they are applying IEEE Std. 485-2020.

Conformance to Regulatory Guide 1.218

The staff evaluated the FSAR with respect to RG 1.218, as it relates to the condition monitoring techniques of electric cables within the scope of the Maintenance Rule. In FSAR Table 8-1.1, the applicant stated RG 1.218 is limited to cables determined to be within the scope of 10 CFR 50.65.

The staff reviewed the strategy for the applicant to address the Maintenance Rule requirement (10 CFR 50.65) described in FSAR Section 17.6 because the description of a Maintenance Rule program is the COL applicants responsibility, the staff finds that deferring consideration of the guidance in RG 1.218 to the COL is acceptable.

Conformance to SECY-91-078, SECY-94-084, and SECY-95-132

SECY-91-078 pertains to the interface between the offsite AC power system and the Class 1E onsite power system. In FSAR Table 8.1-1, the applicant stated that the guidance does not apply to the NuScale US460 design. This guidance pertains to GDC 17, and the applicant has requested an exemption to GDC 17, as described in SDAA Part 7. Per Section 8.1.2 of this report, the staff finds that the onsite and offsite electric power systems do not warrant a Class 1E designation and are not safety-related systems. The staff als o finds that the onsite and offsite power systems are not needed to permit the functioning of SSCs important to safety.

Since the onsite DC power system is not safety related, the staff finds that SECY-91-078 is not applicable since SECY-91-078 pertains to the interface between the offsite AC power system and the Class 1E onsite system.

DSRS Table 8.1-1 states that SECY-94-084 and SECY-95-132 provide guidance that relates to the inclusion of an alternate power source to loads that are not safety related at evolutionary plant designs. DSRS Section 8.2.III.3.A states that, for SECY-94-084 and SECY-95-132, the NuScale design review should identify any offsite power requirements to support non-Class 1E, risk-significant active systems identified through the RTNSS process. SER Section 19.3 further discusses and evaluates the RTNSS; no SSCs are determined to meet the RTNSS criteria.

8.3.2.5 Combined License Information Items

No COL items are provided for this section

8.3.2.6 Conclusion

As set forth above, the staff has reviewed all of the relevant information that is applicable to the NuScale onsite DC power system design and evaluated its compliance with GDC 2; GDC 4; GDC 5; requested exemption to GDC 17, GDC 18, and applicable portions of GDC 33, 34, 35, 38, 41, and 44; GDC 50; 10 CFR 50.34(f); 10 CFR 50.55a(h); 10 CFR 52.137(a)(15); and conformance to applicable RGs and standards committed to by the applicant. The remaining portions of the exemption request to GDC 33 are addressed in SER Section 9.3.4. The staff concludes that the applicant has provided sufficient information in the SDAA and identified necessary analyses to support the bases for it s conclusions for its onsite DC power system design. The staff concludes the design of the NuScale onsite DC power system meets the appropriate regulatory requirements listed in F SAR Section 8.3.2.2, Design Evaluation, as

8-41 shown in the staffs technical evaluations in Section 8.3.2.4 of this report. Additionally, the staff determined that, due to the exemptions, the applicant s design is exempt from the requirements of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44, with respect to the onsite DC power system, as discussed in Section 8.1.4 of this report.

8.4 Station Blackout

8.4.1 Introduction

In 10 CFR 50.2, an SBO is defined as a complete loss of AC electric power to the essential and nonessential switchgear buses in the NPP. For the NuScale US460 design, an SBO involves a loss of the offsite electric power system (preferre d power system) concurrent with a turbine trip.

An SBO does not include loss of available AC power to buses fed by station batteries through inverters or by AAC sources specifically prov ided for SBO mitigation. The staff reviewed the applicants information to verify that the plant is capable of withstanding and recovering from a complete loss of AC electric power for a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, as described in the FSAR. The staff reviewed and evaluated the application to determine its compliance with the requirements of 10 CFR 52.137(a)(15) and conformance to the applicable guidance.

8.4.2 Summary of Application

FSAR: The applicant has provided a system description in FSAR Section 8.4, summarized, in part, as follows:

The NuScale Power Module (NPM) design does not rely on onsite or offsite AC power for the performance of safety-related functions during a design basis event. As a result, emergency onsite AC power is not included in the design.

The SBO duration for passive plant designs is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> pursuant to Nuclear Regulatory Commission policy provided by SECY-94-084 and SECY-95-132 and the associated staff requirements memoranda. Passive plants are required to demonstrate safety-related functions can be performed without reliance on AC power for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after the initiating event.

ITAAC: There are no ITAAC associated with FSAR Section 8.4.

Technical Specifications: There are no technical specifications for this area of review.

8.4.3 Regulatory Basis

DSRS Section 8.4 provides the relevant NRC requirements for this area of review and the associated acceptance criteria for NuScales plant design, as summarized below. DSRS Section 8.4 also provides review interfaces with other DSRS sections.

The following acceptance criteria are adequate to meet the above requirements:

  • GDC 17, as it relates to the onsite AC power systems (1) capacity and capability to permit functioning of SSCs important to safety, (2) independence, redundancy, and testability to perform its safety function assuming a single failure, and (3) provisions to minimize the probability of losing electric power from any of the remaining supplies as a result of, or

8-42 coincident with, the loss of power generated by the nuclear power unit or the loss of power from the transmission network

  • GDC 18, as it relates to the inspection and testing of the offsite and onsite power systems

The applicant requested exemption from GDC 17 and 18.

The following documents provide additional criteria or guidance in support of the DSRS Section 8.4 acceptance criteria to meet the above requirements:

  • SECY-90-016, Evolutionary Light Water Reactor (LWR) Certification Issues and Their Relationship to Current Regulatory Requirements, and SECY-94-084, as they relate to the use of AAC power sources and the RTNSS process at plants that have passive safety systems
  • SECY-95-132, Policy and Technical Issues Associated with the Regulatory Treatment of Non-Safety Systems (RTNSS) in Passive Plant Designs (SECY-94-084), dated May 22, 1995, relates to the policy and technical issues associated with the RTNSS affecting passive plant designs.
  • RG 1.75, as it relates to the independence of SBO-related power sources and distribution systems between the onsite and offsite AC power systems, especially the isolation capability of the battery chargers for the DC system

8.4.4 Technical Evaluation

The staff reviewed FSAR Section 8.4 to determine whether the design is capable of withstanding and recovering from an SBO as required by 10 CFR 52.137(a)(15). The SBO duration for passive plant designs is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, which is consistent with the NRCs policy in SECY-94-084 and SECY-95-132 and the associated staff requirements memoranda.

8.4.4.1 Compliance with 10 CFR 52.137(a)(15) and Conformance to Regulatory Guide 1.155

Under 10 CFR 52.137(a)(15), the NRC requires that each NPP be capable of withstanding or coping with, and recovering from, an SBO of a specified duration (known as the coping duration) and of maintaining adequate core cooling and appropriate containment integrity for the SBO coping duration. RG 1.155 provides guidance for implementing the SBO requirements of 10 CFR 52.137(a)(15). DSRS Section 8.4 states that, for new advanced light-water-reactor design applications, such as the NuScale application, that use passive safety systems and do not include a spare, full-capacity AAC power source for coping with an SBO, (1) all safety-related functions should be performed without relying on AC power for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> after the initiating event, and (2) the applicant has implemented, as appropriate, an RTNSS process that conforms to RG 1.206, Section C.IV.9, Regulatory Treatment of Non-safety Systems.

RG 1.155 and DSRS Section 8.4 describe an approach acceptable to the staff for meeting the requirements of 10 CFR 52.137(a)(15) that will be applied to the NuScale US460 design.

Aspects of the staffs review for compliance with 10 CFR 52.137(a)(15) are discussed below.

In FSAR Section 8.4.1, the applicant stated that SBO does not pose a significant challenge to the plant, which does not rely on AC power for performing safety functions. Further, the applicant stated that a safe and stable shutdown is automatically achieved and maintained for

8-43 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> without operator actions. SER Chapter 15 contains the staffs review of the acceptance criteria for anticipated operational occurrences and long-term cooling, as they pertain to 10 CFR 52.137(a)(15). The staff finds that the NuScale US460 design complies with 10 CFR 52.137(a)(15) because the applicant demonstrated that safety-related functions can be performed without reliance on AC power for a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following an SBO event, as discussed in SER Chapter 15.

FSAR Table 8.1-1 states that RG 1.155 is used as guidance for FSAR Section 8.4 and that compliance with 10 CFR 52.137(a)(15) is shown without the use of RG 1.155.

8.4.4.2 Compliance with GDC 17

GDC 17 states that AC onsite power shall be provided to permit the functioning of SSCs important to safety and electric power from the onsite AC electric power supplies to the onsite distribution system.

SDAA Part 7 discusses the exemption from GDC 17. SDAA Part 7, Section 4.2.1, states that safety-related functions are achieved and maintained with no reliance on electric power.

Furthermore, FSAR Section 8.3 states that the design does not rely on AC or DC power systems, and that this position is supported by the GDC 17 exemption, as discussed in SER Section 8.1.4.

8.4.4.3 Compliance with GDC 18

GDC 18 relates to the inspection and testing of electric power systems important to safety.

In SDAA Part 7, the applicant stated that the electric power supply systems do not contain any safety-related or risk-significant SSCs that are required to meet GDC 18, and that the AC and DC power systems are not safety related and are non-Class 1E systems. Furthermore, FSAR Section 8.3 states that the design does not re ly on AC or DC power systems, and that this position is supported by the GDC 18 exemption, as discussed in SER Section 8.1.4.

8.4.4.4 Conformance to the Guidelines of SECY-90-016 and SECY-94-084

The guidelines and criteria of SECY 016, as they relate to the use of AAC power sources, pertain to evolutionary advanced light-water-reactor designs and do not directly apply to passive plant designs.

For meeting the guidelines and criteria of SECY-94-084 as they relate to the RTNSS at plants with passive safety systems, the applicant st ated in FSAR Section 8.4.2 that the equipment relied upon to meet 10 CFR 52.137(a)(15) is passive, safety related, and environmentally qualified. The staff considers this acceptable because safety-related equipment is relied on to mitigate an SBO, as discussed in the SER Chapter 15; therefore, SECY-90-0-16 and SECY-94-084 do not apply to the NuScale US460 design for an SBO. The staff further discusses and evaluates this in SER Chapter 19.

8.4.4.5 Conformance to Regulatory Guide 1.75

The guidance in RG 1.75 pertains to the independence of SBO-related power sources and distribution systems between the onsite and offsite AC power systems. In FSAR Section 8.4, the applicant stated that the NPM design does not rely on the use of onsite or offsite AC power for the performance of safety-related functions for any DBE. Although the SBO-related power

8-44 sources and distribution systems neither contain nor support safety-related SSCs, the applicant has stated that it will use the separation criteria in RG 1.75 to maintain separation between the non-Class 1E power system and the Class 1E circuits within the MPS. The staff finds this acceptable for the SBO-related power sources. SER Section 7.1.2.4.2 evaluates electrical isolation with respect to the MPS.

8.4.5 Combined License Information Items

No COL items are provided for this section.

8.4.6 Conclusion

Based on the above review, the staff finds that the NuScale US460 design is acceptable because the applicant demonstrated that safety-related functions can be performed without reliance on AC power for a minimum of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following an SBO event. This demonstration was performed in a manner consistent with RG 1.155, Regulatory Position C.3.2, and meets the requirements of 10 CFR 52.137(a)(15). Additionally, the staff determined that the applicants design is exempt from the requirements of GDC 17, GDC 18, and the electric power provisions of GDC 33, 34, 35, 38, 41, and 44 with respect to SBO, as discussed in SER Section 8.1.4.

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