ML17188A464

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LLC Response to NRC Request for Additional Information No. 40 (Erai No. 8839) on the NuScale Design Certification Application
ML17188A464
Person / Time
Site: NuScale
Issue date: 07/07/2017
From: Wike J
NuScale
To:
Document Control Desk, Office of New Reactors
References
RAIO-0717-54783
Download: ML17188A464 (16)
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Text

RAIO-0717-54783 July 7, 2017 Docket No.52-048 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738

SUBJECT:

NuScale Power, LLC Response to NRC Request for Additional Information No.

40 (eRAI No. 8839) on the NuScale Design Certification Application

REFERENCE:

U.S. Nuclear Regulatory Commission, "Request for Additional Information No.

40 (eRAI No. 8839)," dated May 26, 2017 The purpose of this letter is to provide the NuScale Power, LLC (NuScale) response to the referenced NRC Request for Additional Information (RAI).

The Enclosure to this letter contains NuScale's response to the following RAI Questions from NRC eRAI No. 8839:

08.02-8 08.02-9 08.02-10 This letter and the enclosed response make no new regulatory commitments and no revisions to any existing regulatory commitments.

If you have any questions on this response, please contact Darrell Gardner at 980-349-4829 or at dgardner@nuscalepower.com.

Sincerely, Jennie Wike Manager, /LFHQVLQJ Manager /LFHQVLQJ

NuScale Power, LLC Distribution: Gregory Cranston, NRC, TWFN-6E55 Omid Tabatabai, NRC, TWFN-6E55 Samuel Lee, NRC, TWFN-6C20 (QFORVXUH1X6FDOH5HVSRQVHWR15&5HTXHVWIRU$GGLWLRQDO,QIRUPDWLRQH5$,1R

NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

RAIO-0717-54783 :

NuScale Response to NRC Request for Additional Information eRAI No. 8839 NuScale Power, LLC 1100 NE Circle Blvd., Suite 200 Corvalis, Oregon 97330, Office: 541.360.0500, Fax: 541.207.3928 www.nuscalepower.com

Response to Request for Additional Information Docket No.52-048 eRAI No.: 8839 Date of RAI Issue: 05/26/2017 NRC Question No.: 08.02-8 FSAR Tier 2 Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems states that 10 CFR 50.65(a)(4) is guidance (G) for Section 8.2 on osite power systems. FSAR Tier 2 Section 8.2.3.2, Analysis of Osite Power System Conformance with Regulatory Framework, states that the development and implementation of the maintenance rule (10 CFR 50.65) including the identi"cation of SSCs that require assessment in accordance with 10 CFR 50.65(a)(4), is described in FSAR Tier 2 Section 17.6, Maintenance Rule. FSAR Tier 2 Section 17.6 includes COL item 17.6-1 that a COL applicant that references the NuScale Power Plant design certi"cation will describe the program for monitoring the eectiveness of maintenance required by 10 CFR 50.65.

Also for the osite power system, FSAR Tier 2 Table 8.1-1 states the maintenance rule is guidance whereas FSAR Tier 2 Section 8.2.3.2 indicates that the maintenance rule is applicable per COL item 17.6-1.

QUESTION: Please explain whether the maintenance rule should be listed as A (applicable) in FSAR Tier 2 Table 8.1-1 for the osite power system.

NuScale Response:

FSAR Table 8.1-1 has been revised to include the 10 CFR 50.65(a)(4) criteria as A (acceptance criteria) for FSAR Section 8.2, Osite Power System.

Impact on DCA:

Table 8.1-1 has been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary

Tier 2 NuScale Final Safety Analysis Report RAI 08.02-2, RAI 08.02-4, RAI 08.02-8 Table 8.1-1: Acceptance Criteria and Guidelines for Electric Power Systems Criteria Title Applicable Section (Note 1) Remarks 8.2 8.3.1 8.3.2 8.4 Offsite Onsite Onsite DC Station Power AC Power Power Blackout System System System

1. 10 CFR 50, Appendix A, General Design Criteria for Nuclear Plants
a. GDC 2 Design bases for protection against A A §8.2 - ADAMS Accession natural phenomena No. ML090260039
b. GDC 4 Environmental and dynamic effects A A §8.2 - ADAMS Accession design bases No. ML090260039
c. GDC 5 Sharing of structures, systems, and A A §8.2 - ADAMS Accession components Nos. ML11133A334 and ML090260039
d. GDC 17 Electric power systems The NuScale design supports an exemption from GDC 17.
e. GDC 18 Inspection and testing of electric The NuScale design supports an power systems exemption from GDC 18.

8.1-8

f. GDC 33 Reactor coolant makeup The NuScale design supports an exemption from GDC 33.
g. GDCs 34, 35, 38, 41, 44 Residual heat removal, emergency The plant design complies with a core cooling, containment heat set of principal design in lieu of removal, containment atmosphere these GDC, as described in Section cleanup, cooling water 3.1.4.
h. GDC 50 Containment design basis Containment vessel penetration assemblies are not included in the scope of the onsite electrical power system.

Penetration assemblies are part of the containment design.

2. Regulations (10 CFR 50 and 10 CFR 52)
a. 10 CFR 50.34 Contents of applications; technical information
i. 10 CFR 50.34(f)(2)(v) Additional Three Mile Island (TMI)- A A Draft Revision 1 related requirements (Item I.D.3)

Introduction ii. 10 CFR 50.34(f)(2)(xiii) Additional TMI-related requirements The NuScale design supports an (Item II.E.3.1) exemption from 10CFR50.34(f)(2)(xiii).

Table 8.1-1: Acceptance Criteria and Guidelines for Electric Power Systems (Continued)

Tier 2 NuScale Final Safety Analysis Report Criteria Title Applicable Section (Note 1) Remarks 8.2 8.3.1 8.3.2 8.4 Offsite Onsite Onsite DC Station Power AC Power Power Blackout System System System iii. 10 CFR 50.34(f)(2)(xx) Additional TMI-related requirements The NuScale design does not (Item II.G.1) include pressurizer relief valves or block valves, and the the design supports an exemption from the pressurizer level indicator portion of 10CFR50.34(f)(2)(xx).

b. 10 CFR 50.55a(h) Codes and standards A A
c. 10 CFR 50.63 Loss of all alternating current power G A
d. 10 CFR 50.65(a)(4) Requirements for monitoring the GA A A Development and implementation effectiveness of maintenance at of the Maintenance Rule program is nuclear power plants discussed in Section 17.6.
e. 10 CFR 52.47(b)(1) Contents of applications; technical A A A A Paragraph (b)(1), as it relates to information ITAAC (for design certification) sufficient to assure that the SSCs in 8.1-9 this area of review will operate in accordance with the certification.
f. 10 CFR 52.80(a) Contents of applications; additional N/A for NuScale, this rule pertains to technical information applications referencing an early site permit or a standard design certification.
3. Regulatory Guides (RGs)
a. Regulatory Guide 1.6 - March 1971 Safety Guide 6 - Independence G G Between Redundant Standby (Onsite)

Power Sources and Between Their Distribution Systems

b. Regulatory Guide 1.32 - Revision 3, Criteria for Power Systems for Nuclear G G G As it relates to the EDSS; see March 2004 Power Plants Section 8.3.2
c. Regulatory Guide 1.47 - Revision 1, Bypassed and Inoperable Status G G As it relates to the EDSS; see February 2010 Indication for Nuclear Power Plant Section 8.3.2 Draft Revision 1 Safety Systems
d. Regulatory Guide 1.53 - Revision 2, Application of the Single-Failure G G As it relates to the EDSS; see Introduction November 2003 Criterion to Safety Systems Section 8.3.2

Response to Request for Additional Information Docket No.52-048 eRAI No.: 8839 Date of RAI Issue: 05/26/2017 NRC Question No.: 08.02-9 DSRS Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems states that SECY 94-084, Policy and Technical Issues Associated with RTNSS in Passive Plant Designs, 1994 and SECY 95-132, Policy and Technical Issues Associated with RTNSS in Passive Plant Designs, 1995 are guidance (G) as it relates to the inclusion of an alternate power source to non-safety loads 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 osite power requirements to support non- safety-related, risk-signi"cant active systems identi"ed through the Regulatory Treatment of Non-safety Systems (RTNSS) process.

FSAR Tier 2 Section 8.1.4.3, Regulatory Requirements and Guidance states that the design of NuScale electrical systems conforms to the Commission-approved positions in Sections F, Station Blackout and G, Electrical Distribution of SECY-94-084 related to passive plant electrical systems. Also, FSAR Tier 2 Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems states that SECY 94-084, and SECY 95-132 are guidance (G) for the osite power system. However, FSAR Tier 2 Section 8.2 does not provide any discussions on the above Commission papers.

QUESTION: Please provide a discussion regarding how the NuScale design conforms to SECY 94-084 and SECY 95-132 for the osite power system and include a discussion in FSAR Tier 2 Section 8.2.

NuScale Response:

The design of the osite power system considered the guidance of SECY 94-084 Parts F and G, which were con"rmed in SECY 95-132. The applicable portions of these SECY documents on the electrical systems are described in FSAR Section 8.1.4.3. These SECY documents also establish expectations for a RNTSS process for nonsafety-related plant systems. FSAR Section 17.4.3 describes the NuScale methodology to establish risk signi"cance of SSC. FSAR Section 19.3 describes the process for identifying nonsafety-related SSC that perform risk-signi"cant functions in accordance with RTNSS criteria. These processes did not identify any safety-NuScale Nonproprietary

related or risk-signi"cant loads for the osite or onsite AC power systems. The NuScale RTNSS evaluation process supports a demonstration of conformance with SECY 94-084 Parts F and G as described below.

According to SECY 94-084 Parts F and G, an evaluation of the osite power system against the RTNSS criteria supports a conclusion that passive plants do not require an alternate AC power source to support safe shutdown in the event of a loss of the normal AC power source or to reduce risk from a Station Blackout (SBO) event. FSAR Section 8.2.3.2 indicates there are no safety-related or risk-signi"cant loads for the osite power system. The SBO coping capability for the 72-hour duration included in SECY 94-084 Part F is described in FSAR Section 8.4. The lack of safety-related and risk-signi"cant loads and the SBO coping capability of the passive NuScale design obviate the need for an alternate AC power source.

See also the NuScale response to RAI 08.02-10, which addresses the need for an alternate AC power source as discussed in SECY 91-078.

NuScale has revised FSAR Section 8.2, Osite Power System, to re"ect the above discussion.

Consistent with Section III.5.A of NuScale DSRS 8.3.1, AC Power Systems (Onsite), FSAR Section 8.3.1.2.7 was revised to more directly address conformance with the RTNSS process and the subject SECY documents as they apply to the onsite AC power systems. Similarly, FSAR Section 8.3.2.2.2 was revised to address the DC systems' conformance with the SECY documents. Conforming revisions to FSAR Table 1.9-7, Conformance with Advanced and Evolutionary Light Water Reactor Design Issues (SECYs and Associated SRMs), were also made.

Impact on DCA:

FSAR Sections 8.2, 8.3.1.2, 8.3.2.2 and FSAR Table 1.9-7 have been revised as described in the response above and as shown in the markup provided in this response.

NuScale Nonproprietary

Tier 2 NuScale Final Safety Analysis Report RAI 08.02-9 Table 1.9-7: Conformance with Advanced and Evolutionary Light Water Reactor Design Issues (SECYs and Associated SRMs)

Doc ID Title Conformance COL Comments Section Status Applicability SECY-89-013 Design Requirements Related to the Conforms Applicable Addressed through SECY-90-016 and SECY -

Evolutionary Advanced Light Water Reactors 087. See Table 1.9-8 for further information.

SECY-90-016 Evolutionary Light-Water Reactor (LWR) Partially Applicable This SECY was directed towards evolutionary 19.1 Certification Issues and Their Relationship to Conforms ALWR designs. The applicability of certain SECY- 19.2 Current Regulatory Requirements90-016 issues to passive plants was later established in SECY-93-087 and/or SECY 084. As a passive ALWR design, the NuScale design conforms to the passive plant guidance of SECY-93-087 and SECY-94-084, rather than that of SECY-90-016. See Table 1.9-8 for further information.

SECY-90-241 Level of Detail Required for Design Conforms Applicable Incorporated into 10 CFR 52 and implementing -

Certification under Part 52 NRC guidance documents.

1.9-264 SECY-90-377 Requirements for Design Certification under Conforms Applicable Incorporated into 10 CFR 52 and implementing -

10 CFR Part 52 NRC guidance documents.

SECY-91-074 Prototype Decisions for Advanced Reactor Conforms Applicable Incorporated into 10 CFR 52 and implementing -

Designs NRC guidance documents.

SECY-91-078 Chapter 11 of the Electric Power Research Not Applicable Not Applicable SECY-91-078 pertains to evolutionary ALWR 8.1.4 Institutes (EPRI's) Requirements Document designs and is not directly applicable to passive and Additional Evolutionary Light plant designs.

WaterReactor (LWR) Certification Issues SECY-91-178 ITAAC for Design Certifications and Conforms Applicable Incorporated into 10 CFR 52 and implementing 14.3.2 Conformance with Regulatory Criteria Combined Licenses NRC guidance documents.

SECY-91-210 ITAAC Requirements for Design Review and Conforms Applicable Incorporated into 10 CFR 52 and implementing -

Issuance of FDA NRC guidance documents.

SECY-91-229 Severe Accident Mitigation Design Conforms Not Applicable Incorporated into NRC Orders, regulatory 19.2.6 Alternatives for Certified Standard Designs guidance, and pending rulemaking.

SECY-91-262 Resolution of Selected Technical and Severe Conforms Applicable Incorporated into NRC Orders, regulatory -

Accident Issues for Evolutionary Light-Water guidance, and pending rulemaking.

Draft Revision 1 Reactor (LWR) Designs SECY-92-053 Use of Design Acceptance Criteria During Conforms Applicable Incorporated into NRC Orders, regulatory 14.3.6 the 10 CFR Part 52 Design Certification guidance, and pending rulemaking.

Reviews

Table 1.9-7: Conformance with Advanced and Evolutionary Light Water Reactor Design Issues (SECYs and Associated Tier 2 NuScale Final Safety Analysis Report SRMs) (Continued)

Doc ID Title Conformance COL Comments Section Status Applicability SECY-92-092 The Containment Performance Goal, Conforms Applicable Incorporated into NRC Orders, regulatory -

External Events Sequences, and the guidance, and pending rulemaking.

Definition of Containment Failure for Advanced LWRs SECY-93-087 Policy, Technical, and Licensing Issues See Table 1.9-8. See Table 1.9-8. None. -

Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs SECY-94-084 Policy and Technical Issues Associated with Partially Applicable Incorporated into 10 CFR 52 and implementing 5.4 the Regulatory Treatment of Non-Safety Conforms NRC guidance documents. 8.1.48.1 Systems in Passive Plant Design (RTNSS) The NuScale Fire Protection System does not 8.3.18.2 contain any RTNSS equipment. However, 8.3.28.3 Section C, Safe Shutdown Requirements, of the 8.4 SECY discusses the stable shutdown condition 9.2.5 for passive ALWR which is applicable to the Appendix 9A NuScale Power Plant. 15.0.4 1.9-265 19.3 SECY-94-302 Source-Term-Related Technical and Conforms Applicable Incorporated into 10 CFR 52 and implementing -

Licensing Issues Relating to Evolutionary and NRC guidance documents.

Passive Light-Water-Reactor Designs SECY-95-132 Policy and Technical Issues Associated with Conforms Applicable Incorporated into 10 CFR 52 and implementing 8.1.1 Regulatory Treatment of Non-Safety Systems NRC guidance documents. 8.1.48.1 in Passive Plant Designs 8.3.18.2 8.3.28.3 8.4 19.3 Conformance with Regulatory Criteria SECY-14-038 Performance-Based Framework for Nuclear Conforms Applicable None. 13.3 Power Plant Emergency Preparedness Oversight SECY-14-088 Proposed Options to Address Lessons- Not Applicable Applicable Site-specific requirements. Not Learned Review of the U.S. Nuclear Applicable Regulatory Commissions Force-On-Force Draft Revision 1 Inspection Program in Response to Staff Requirements Memorandum - COMGEA/

COMWCO-14-0001

NuScale Final Safety Analysis Report Offsite Power System Branch Technical Position 8-3 Revision 3 The performance of grid stability studies is site-specific and is addressed in Section 8.2.3.1.

Branch Technical Position 8-6 Revision 3 Branch Technical Position (BTP) 8-6 addresses the adequacy of offsite system voltages to Class 1E (safety-related) loads. The offsite power system does not supply power to Class 1E loads and does not support safety-related functions. Accordingly, BTP 8-6 is not applicable to the offsite power system.

Branch Technical Position 8-9 Revision 0 The BTP 8-9 addresses the effects of transmission grid open-phase conditions as identified in NRC Information Notice 2012-03 and NRC Bulletin 2012-01. This guidance involves protection from a common cause AC power failure due to open phase conditions in the offsite power sources that are credited for GDC 17 and the effect on onsite safety-related buses and safety-related loads. The offsite power system does not support safety-related functions. In addition, there are no failures of the offsite power system, including open phase conditions or a station blackout, that will prevent the operation of safety-related functions.

If the offsite power system is supplying power to the onsite AC power system, the electrical isolation between the highly reliable 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.

Regulatory Guide 1.32 Revision 3 Regulatory Guide 1.32 addresses design criteria for safety-related power systems. The NuScale Power Plant does not rely on an offsite power system to support or perform safety functions. Accordingly, Regulatory Guide 1.32 is not applicable to the offsite power system.

Regulatory Guide 1.68 Revision 3 COL Item 8.2-3: A COL applicant that references the NuScale Power Plant design certification will describe the testing of the switchyard and the connections to an offsite power system, if provided, consistent with Regulatory Guide 1.68, Revision 3.

RAI 08.02-9 SECY 94-084 and SECY 95-132 FSAR Section 17.4.3 describes the NuScale methodology to establish risk significance of SSC. The NuScale process for evaluating SSC against the RTNSS criteria is described in FSAR Section 19.3. This process did not identify any safety-related or risk-significant loads for the offsite power system.

Tier 2 8.2-3 Draft Revision 1

NuScale Final Safety Analysis Report Offsite Power System RAI 08.02-9 The lack of safety-related and risk-significant AC loads and the 72-hour SBO coping capability of the passive NuScale design as described in Section 8.4 obviate the need for an alternate AC power source or a safety-related emergency diesel generator, consistent with SECY 94-084 Parts F and G which were confirmed in SECY 95-132.

Tier 2 8.2-4 Draft Revision 1

NuScale Final Safety Analysis Report Onsite Power Systems Branch Technical Position 8-2, Rev. 3 The intent of Branch Technical Position (BTP) 8-2 is to ensure that the provision of GDC 17 is met with respect to minimizing the probability of concurrent loss of electrical power sources. This guidance precludes the use of onsite standby AC power sources for purposes other than supplying standby power when needed.

With the NuScale Power Plant non-reliance on AC power for the performance of safety-related functions, the concurrent loss of onsite and offsite AC power sources would have no significant adverse effect on plant safety. Notwithstanding this conclusion, for operational, commercial, and plant investment protection purposes, the BDGs are used only to supply standby power to designated loads when needed, and are not interconnected with other AC power sources, except for short periods to perform load testing.

As described in Section 8.3.1.1, there are certain operating conditions during which the AAPS may be interconnected with other AC power sources (e.g., one or more NPM turbine generators or offsite power sources, if available). The NuScale design does not rely on AC power sources for the performance of safety-related functions, and the guidance of BTP 8-2 need not be applied to the AAPS.

Branch Technical Position 8-4, Rev. 3 Branch Technical Position 8-4 establishes the acceptability of disconnecting power to electrical components of a fluid system as one means of designing against a single failure that might cause an undesirable component action. Removal of electric power from safety-related valves is not used in the NuScale Power Plant design as a means of satisfying the single failure criterion. Therefore, this BTP is not applicable to the NuScale design.

Branch Technical Position 8-5, Rev. 3 Branch Technical Position 8-5 provides supplemental guidance for implementing RG 1.47 in the onsite AC power system. The conformance to RG 1.47 is described above.

Branch Technical Position 8-6, Rev. 3 The undervoltage provisions contained in BTP 8-6 are not relevant to the NuScale Power Plant design because a loss of voltage or a degraded voltage condition on the offsite power system would have no reasonable likelihood of adversely affecting the performance of plant safety-related functions.

Branch Technical Position 8-9, Rev. 0 The criteria specified in BTP 8-9 relevant to passive plant designs are considered as described in Section 8.2.

RAI 08.02-9 SECY 94-084 and SECY 95-132 Tier 2 8.3-19 Draft Revision 1

NuScale Final Safety Analysis Report Onsite Power Systems FSAR Section 17.4.3 describes the NuScale methodology to establish risk significance of SSC. The NuScale process for evaluating SSC against the RTNSS criteria is described in FSAR Section 19.3. This process did not identify any safety-related or risk-significant loads for the onsite AC power systems.

RAI 08.02-9 The lack of safety-related and risk-significant AC loads and the 72-hour SBO coping capability of the passive NuScale design as described in Section 8.4 obviate the need for an alternate AC power source or a safety-related emergency diesel generator, consistent with SECY 94-084 Parts F and G, which were confirmed in SECY 95-132.

8.3.1.2.8 Electrical Power System Calculations and Distribution System Studies for Alternating Current Systems Load-flow studies, short-circuit studies, and motor-starting studies for the AC power system are performed using the Electrical Transient Analyzer Program (ETAP) (Reference 8.3-11).

Load-Flow Studies and Undervoltage or Overvoltage Protection Load-flow studies are performed to evaluate whether an acceptable voltage range is maintained at equipment terminals under worst case loading conditions. Voltage drop at equipment terminals is also calculated for the largest motor starting condition. The studies confirm that terminal voltage of equipment meets the acceptable voltage ranges.

Short-Circuit Studies Analyses are performed to evaluate worst-case, bolted, three-phase short-circuit fault currents in the onsite AC power system. The analyses are performed to evaluate acceptable ratings for equipment, such as circuit breakers and switchgear bus work.

The short-circuit current results are compared with and must be less than the acceptance criteria (including at least five percent margin), which are the applicable circuit breaker interrupting and close and latch ratings and maximum bus bracing current capabilities. Table 8.3-1 provides nominal equipment ratings for the AC power system.

Containment electrical penetration assembly overload and short-circuit over-current protection is described in Section 8.3.1.2.5.

Equipment Sizing Studies Equipment sizing was developed from a load list and subsequently verified using the ETAP load flow, voltage regulation, and short-circuit analysis results. Worst case loading was determined and equipment was selected that enveloped the load requirements. Major AC distribution equipment ratings are listed in Table 8.3-1.

Tier 2 8.3-20 Draft Revision 1

NuScale Final Safety Analysis Report Onsite Power Systems The EDSS conforms to 10 CFR 50.55a(h) and IEEE Standard 603-1991 (and hence RG 1.153) to the extent described in Reference 8.3-1.

Regulatory Guide 1.155 (August 1998)

Regulatory Guide 1.155 provides guidance for implementing the station blackout requirements of 10 CFR 50.63. The extent to which the NuScale Power Plant design conforms to RG 1.155 is described in Section 8.4.

Regulatory Guide 1.160, Rev. 3 Regulatory Guide 1.160 provides guidance for monitoring the effectiveness of maintenance at nuclear power plants. The development and implementation of the maintenance rule (10 CFR 50.65) program, including the identification of SSC that require assessment per 10 CFR 50.65(a)(4), is stated in Section 17.6.

Regulatory Guide 1.212 The EDSS and EDNS batteries are sized per IEEE Standard 485-1997 as endorsed by Regulatory Guide 1.212 (November 2008).

Regulatory Guide 1.218 (April 2012)

Regulatory Guide 1.218 provides guidance for monitoring the condition of cables that have been determined to fall within the scope of the maintenance rule (10 CFR 50.65). The development and implementation of the maintenance rule program, including the identification of SSC that require assessment per 10 CFR 50.65(a)(4), is stated in Section 17.6.

Branch Technical Position 8-4, Rev. 3 Branch Technical Position 8-4 establishes the acceptability of disconnecting power to electrical components of a fluid system as one means of designing against a single failure that might cause an undesirable component action. Removal of electric power from safety-related valves is not used in the NuScale Power Plant design as a means of satisfying the single failure criterion. Therefore, this BTP is not applicable to the NuScale design.

Branch Technical Position 8-5, Rev. 3 The onsite DC power systems conform to BTP 8-5 to the extent described in the discussion of conformance with 10 CFR 50.34(f)(2)(v) above.

RAI 08.02-9 SECY 94-084 and SECY 95-132 FSAR Section 17.4.3 describes the NuScale methodology to establish risk significance of SSC. The NuScale process for evaluating SSC against the RTNSS Tier 2 8.3-36 Draft Revision 1

NuScale Final Safety Analysis Report Onsite Power Systems criteria is described in FSAR Section 19.3. This process did not identify any safety-related or risk-significant functions for the onsite DC power systems.

8.3.2.2.3 Electrical Power System Calculations and Distribution System Studies for Direct Current Systems The following subsections describe the calculations and studies that were developed for the DC power systems. The calculations were performed using the ETAP computer software (Reference 8.3-11).

Load-Flow and Voltage-Regulation Studies, and Undervoltage and Overvoltage Protection The DC load-flow analyses were performed for both the EDNS and EDSS to confirm equipment assumptions and select equipment ratings. The margins for load growth were included in the analyses.

The operating voltage range for the EDSS and EDNS was determined by calculation and accommodates equalize charging the batteries at a specified low temperature.

The operating voltage range for the EDSS-MS and the EDSS-C 125 Vdc batteries is 105 Vdc to 140 Vdc. The operating voltage range for the EDNS 250 Vdc batteries is 200 Vdc to 280 Vdc, and the operating range for the EDNS 125 Vdc batteries is 100 Vdc to 140 Vdc.

Short-Circuit Studies Short-circuit analyses are performed for the EDSS-MS, EDSS-C, and the EDNS DC subsystems. These analyses are performed in accordance with IEEE Standard 946-2004 (Reference 8.3-13) methodology and the available short-circuit currents from each battery and connected charger are determined under a worst case short circuit at the battery terminals.

The short-circuit current results are compared to short-circuit current acceptance criteria. Containment electrical penetration assembly overload, short-circuit current capability, and associated overcurrent protection is described in Section 8.3.1.2.5.

Equipment Sizing Studies The DC equipment sizing was developed from a load list and was verified using the ETAP load-flow and short-circuit analysis results. Worst-case loading was determined and the power supply equipment was selected that enveloped the loading requirements. The ratings for the major DC equipment are listed in Table 8.3-3 and Table 8.3-8.

The acceptance criteria for the major DC system components are that the equipment ratings are not exceeded when load-flow, voltage-drop, and short-circuit analyses are performed. The equipment sizing includes additional design margin for future load growth.

Tier 2 8.3-37 Draft Revision 1

Response to Request for Additional Information Docket No.52-048 eRAI No.: 8839 Date of RAI Issue: 05/26/2017 NRC Question No.: 08.02-10 DSRS Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems states that SECY 91-078, Electric Power Research Institute Requirements Document and Additional Evolutionary Light Water Reactor Certi"cation Issues, 1991 is guidance for osite power systems as it relates to the inclusion of an alternate power source to non-safety loads at evolutionary plant designs. However, FSAR Tier 2 Table 8.1-1, Acceptance Criteria and Guidelines for Electric Power Systems states that SECY 91- 078 is not applicable for the osite power system. In addition, FSAR Tier 2 Section 8.1.4.3, Regulatory Requirements and Guidance states that SECY 91-078 is not directly applicable to passive plant designs.

QUESTION: Please clarify the applicability of SECY 91-078 to the osite power system.

NuScale Response:

SECY 91-078 is not applicable to the NuScale osite power system. As described in FSAR Section 8.1.4.3, SECY 91-078 pertains to evolutionary advanced light water reactors and is not applicable to passive plant designs. The NuScale design does not rely on active systems for safe shutdown and consequently the plant design does not need to meet SECY-91-078.

This is consistent with the conclusion in Section 8.5.2.2 of NUREG-1793, Final Safety Evaluation Report Related to Certi"cation of the the AP1000 Standard Design.

Notwithstanding the above, the NuScale design includes features that mitigate the eects of grid events discussed in SECY-91-078. The osite power system, if included as part of a site-speci"c COL application, does not connect to safety-related buses and is not required to provide AC power to safety-related or risk-signi"cant loads. In addition, the island mode feature maintains uninterrupted power to the nonsafety-related AC loads in the event of a loss of grid event as described in FSAR Section 8.3.1.1.1.

Impact on DCA:

There are no impacts to the DCA as a result of this response.

NuScale Nonproprietary

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