~ MITSUBISHI HEAVY INDUSTRIES, LTD.

1-1, WADASAKI-CHO, 1-CHOME, HYOGO-KU, KOBE, 652-8585 JAPAN

November 16, 2018

Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Attention: Mr. George Wunder

Docket No. 52-021 MHI Ref: UAP-HF-18006

Subject: MHl's Response to US-APWR DCD RAI No.1100-9574 (SRP 08.02)

Reference: 1) "Request for Additional Information No. 1100-9574, SRP Section 08.02 -Offsite Power System:," dated October 16, 2018.

With this letter, Mitsubishi Heavy Industries, Ltd. (MHI) submits to the U.S. Nuclear Regulatory Commission (NRG) a document entitled "Response to US-APWR DCD RAI No. 1100-9574 (SRP 08.02)."

Enclosed is the response to the questions contained within Reference 1.

Please contact Mr. Joseph Tapia, Principal Consulting Engineer, Mitsubishi Nuclear Energy Systems, Inc. if the NRG has questions concerning any aspect of this letter. His contact information is provided below.

Sincerely,

Takayuki Mori,

Engineering Manager Global Nuclear Project Department Nuclear Energy Systems Division Power Systems Mitsubishi Heavy Industries, Ltd.

Enclosures:

1. Response to US-APWR DCD RAI No. 1100-9574 (SRP 08.02)

CC: G. Wunder J. Tapia

Contact Information Joseph Tapia, Principal Consulting Engineer Mitsubishi Nuclear Energy Systems, Inc. 13860 Ballantyne Corporate Place, Suite 250 Charlotte, NC 28277 E-mail: joseph_tapia@mnes-us.com Telephone: (202) 631 -1002

Enclosure 1

Docket No. 52-021 UAP-HF-18006

Docket No. 52-021 MHI Ref: UAP-HF-18006

Response to US-APWR DCD RAI No. 1100-9574 (SRP 08.02)

November 2018

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION

RAINO.:

SRP SECTION:

US-APWR Design Certification

Mitsubishi Heavy Industries

Docket No. 52-021

NO. 1100-9574

08.02 - OFFSITE POWER SYSTEM

APPLICATION SECTION: SRP 8.02, BTP 8-9

DATE OF RAI ISSUE: 10/16/2018

QUESTION NO. : 08.02-19

11/16/2018

10 CFR Part 50, Appendix A, General Design Criterion (GDC) 17, "Electric Power Systems," requires, in part, that an onsite electric power system and an offsite electric power system with adequate capacity and capability shall be provided to permit functioning of structures, systems, and components important to safety .... 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.

The staff has determined that the applicant, in response to Request for Additional Information (RAI) 1096-8266, Question 08.02-18, did not completely address detection and mitigation strategies as described in Branch Technical Position (BTP) 8-9, "Open Phase Conditions (OPC) in Electric Power System." Therefore, the staff requests that the applicant address the following in response to this RAI:

a. Clarify whether the Combined License (COL) applicant will address the details of the specific design of OPC during the COL stage. If the applicant decides to address the conceptual design of OPC during the COL stage, please provide a COL Item in the Design Control Document (DCD), Tier 2, Table 1.8-2 and Section 8.2.4, "COL Information." If not, please provide the information stated below.

In response to RAI 1096-8266, the applicant stated the undervoltage detection system can detect all OPC on the secondary side of the unit auxilary transformer (UAT) and reserve auxilary transformer (RAT). During an OPC, if the secondary side of the transformer is regenerating a lost phase, there will be no change in voltage magnitude that would actuate the undervoltage relays. However, there will be a change in the phase angle and the current on the secondary side of the transformer. Since the undervoltage relays will be incapable of detecting the loss of phase as a function of phase angle, clarify how the undervoltage detection system can detect all OPC on the secondary side of the UATs and RA Ts. Please discuss and/or provide simulations and analysis that demonstrates that the undervoltage detection system can perform this capability. Additionally, describe whether

08.02-19-1

phase unbalance or negative-sequence relays will be used detect OPC. If so, provide description how it will be used to detect OPC.

b. In response to RAI 1096-8266, the applicant stated that the non-safety related OPC system installed in the high side of the RAT was connected to the safety-related buses. Please clarify the isolation that exist between the non-safety related and safety-related system and indicate whether it will meet the guidance in RG 1. 75 which endorses IEEE Std. 384-1992, and RG 1.32 which endorses IEEE Std. 308-2001.

c. US-APWR DCD, Tier 1, Table 2.6.1-3, ITAAC Item 28, Design Commitment states:

The Class 1 E equipment is protected from open phase conditions.

The staff is unclear on whether ITAAC Item 28 includes OPC detection, alarm, and monitoring in the control room since the design commitment, the Inspections, Tests, Analyses, or the Acceptance Criteria do not include language that includes these three OPC features. Please provide an explicit statement in ITAAC Item 28 that clarifies that OPC monitoring/detecting/alarming in the control room are verified by the ITAAC.

ANSWER: a. The Combined License (COL) applicant will address the details of the specific design of

OPC Detection and Protection system during the COL stage. COL Item "COL 8.2(12)" will be added in the Design Control Document (DCD), Tier 2, Table 1.8-2 and Section 8.2.4, "COL Information", as follows and shown in Attachment 1.

COL 8.2(12) The COL applicant is to determine the specific type of the OPC detection devices which properly address and meet the requirements of 8.1. & 8.2. of BTP 8-9, taking into account the site-specific design configuration, installation condition, (field) performance testing and qualification status, and operation experiences of the OPC Detection and Protection system. The COL applicant is also to provide the detailed design of the OPC Detection and Protection system for the COL applicant site. The COL applicant is to perform a field simulation on the site-specific design of the offsite power system to ensure that the settings of the OPC Detection and Protection system are adequate and appropriate for the COL applicant site.

b. In order to have a clear separation between the non-safety related OPC system installed in the high side of the RAT (UAT) and the safety-related buses, the OPC detection and protection system designs are modified. Revised circuit designs are shown at Figure-1 and Figure-2. The main design concept does not change, but the OPC detection signal inputs to the Lockout Relay of the RAT or UAT, not to the safety-related buses. By having this design change, direct interfaces

· between the non-safety related OPC system installed in the high side of the RAT (UAT) and the safety-related buses can be completely eliminated.

(note) Since a "Safety Injection signal" from the safety system is needed for use in the alarm system and non-safety l&C system, this "Safety Injection signal" input to the non-safety l&C system has already been provided with appropriate separation devices. Because of this, there is no need for additional design modifications related to the OPC detection and protection system.

08.02-19-2

Safety ¢=i

SI

Safety

¢:::::I

SI

Non-safety

c:::>

RAT3(4) High voltage side

OPC detection devices System 1 System 2

Figure-1 (RAT)

MT High voltage side

OPC detection devices

UAT4 Lockout Relay Lockout Relay

Figure-2 (MT)

08.02-19-3

Alarm

28

c. ITAAC Item 28 will be changed to include confirmation of OPC detection, alarm, and monitoring in the control room. Revised ITAAC Item 28 is shown as follows and in Attachment 2.

Table 2.6.1-3 AC Electric Power Systems Inspections, Tests, Analyses, and Acceptance Criteria (Sheet 8 of 8)

Design Commitment Inspection, Test, Analyses Acceptance Criteria The Class 1 E equipment is 28.i Analysis will be performed 28.i A report exists and concludes protected from open phase verify the Class 1 E equipment that the Class 1 E equipment is conditions with monitoring, is protected from open phase protected from open phase detecting and alarming in the condition. condition by open phase main control room. protection system.

28.ii Inspection and test will be 28.iiThe as-build protection system performed to verify the as-built bounds the result of analysis protection system bounds the for Class 1 E equipment result of analysis for Class 1 E protection from open phase equipment protection from condition. open phase condition and to The as-built detection system verify that open phase design monitors, detects and condition will be monitored, alarms in the main control detected and alarmed in the room. main control room.

Impact on DCD

There is impact on the DCD Chapter 8 Section 8.2 and Figure 8.3.1-2, and Tier 1 Section 2.6. (See Attachment 1 and Attachment 2)

Impact on R-COLA

The R-COLA will be updated to be consistent with DCD revision.

Impact on PRA

There is no impact on the PRA.

Impact on Technical / Topical Reports

There is no impact on technical / topical reports.

08.02-19-4

1. Introduction and General DESCRIPTION OF THE PLANT

Attachment 1 (1/3) US-APWR Design Control Document

Table 1.8-2 Compilation of All Combined License Applicant Items for Chapters 1-19 (Sheet 18 of 39)

COL ITEM NO. COL ITEM

COL 8.2(5) The COL Applicant is to provide detail description of alternate preferred power.

COL 8.2(6) Deleted

COL 8.2(7) The COL Applicant is to address protective relaying for each circuit such as lines and buses.

COL 8.2(8) The COL Applicant is to address switchyard de power as part of switchyard design description.

COL 8.2(9) The COL Applicant is to address switchyard ac power as part of switchyard design description.

COL 8.2(10) The COL Applicant is to address transformer protection corresponded to site-specific scheme.

COL 8.2(11) The COL Applicant is to address the stability and reliability study of the offsite power system. The stability study is to be conducted in accordance with 8TP 8-3 (Reference 8.2-17). The study should address the loss of the unit, loss of the largest unit, loss of the largest load, or loss of the most critical transmission line including the operating range, for maintaining transient stability. A failure modes and effects analysis (FMEA) is to be provided. The grid stability study shows in part that, with no external electrical system failures, the grid will remain stable and the transmission system voltage and frequency will remain within the interface requirements (±10% for voltage and ±5% for frequency) to maintain the RCP flow assumed in the Chapter 15 analysis for a minimum of 3 seconds following reactor/turbine generator trip.

COL 8.2(12) f)eletee The COL aQ.Q.licant is to determine the SQ.ecific t'i,Q.e of the OPC detection devices which Q.roQ.erl'i. address and meet the reguirements of 8 .1. & 8 .2. of 8TP 8-9 taking into account the site-sQ.ecific design configuration, installation condition (field) Q.erformance testing and gualification status and OQ.eration exQ.eriences of the OPC Detection and Protection S'i.Stem. The COL aQ.Q.licant is also to Q.rovide the detailed design of the OPC Detection and Protection S'i.Stem for the COL aQ.Q.licant site. The COL aQ.Q.licant is to Q.erform a field simulation on the site-sQ.ecific design of the offsite Q.ower S'i.Stem to ensure that the settings of the OPC Detection and Protection S'i.Stem are adeguate and aQ.Q.roQ.riate for the COL aQ.Q.licant site.

COL 8.2(13) The COL AQ.Q.licant is to Q.rovide surveillance reguirements for the device(s) used to detect OQ.en Q.hase condition on the high voltage side of the RA Ts and MT with Qr without grounding.

COL 8.3(1) The COL Applicant is to provide transmission voltages. This includes also MT and RAT voltage ratings.

COL 8.3(2) The COL Applicant is to provide ground grid and lightning protection.

COL 8.3(3) The COL Applicant is to provide short circuit analysis for ac power system, since the system contribution is site specific.

COL 8.3(4) Deleted

Tier 2 1.8-24 RevisieR 4

DCD_08.02-19

I DCD_08.02-17 S01

8. ELECTRIC POWER

Attachment 1 (2/3) US-APWR Design Control Document

COL 8.2(12) Oe.'eted The COL applicant is to determine the specific type of the OPC detection devices which properly address and meet the requirements of 8.1. & 8.2. of 8TP 8-9, taking into account the site-specific design configuration, installation condition. (field) performance testing and qualification status, and operation experiences of the OPC Detection and Protection system. The COL applicant is also to provide the detailed design of the OPC Detection and Protection system for the COL applicant site.

DCD_08.02-19

The COL applicant is to perform a field simulation on the site-specific design of the off site power system to ensure that the settings of the OPC Detection and Protection system are adequate and appropriate for the COL applicant site.

COL 8.2(13) The COL Applicant is to provide surveillance requirements for the DCD_oa.02-

device(s) used to detect open phase condition on the high voltage side 17 so1

8.2.5

8.2-1

8.2-2

8.2-3

8.2-4

8.2-5

8.2-6

8.2-7

8.2-8

8.2-9

8.2-10

Tier 2

of the RA Ts and MT. with or without grounding.

References

IEEE Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers, IEEE Std C57.12.00, 2000.

IEEE Standard for Preferred Power Supply (PPS) for Nuclear Power Generating Stations (NPGS), IEEE Std 765, 2006.

Shared Emergency and Shutdown Electric Systems for Multi-Unit Nuclear Power Plants, Regulatory Guide 1.81 Revision 1, January 1975.

IEEE Standard Criteria for Class 1 E Power Systems for Nuclear Power Generating Stations, IEEE Std 308, 2001 .

Loss of all alternating current power, NRC Regulations Title 10, Code of Federal Regulations, 10 CFR Part 50.63.

Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants, NUMARC 93-01 , 2000.

Requirements for monitoring the effectiveness of maintenance at nuclear power plants, NRC Regulations Title 10, Code of Federal Regulations, 10 CFR Part 50.65.

IEEE Standard for Generating Station Grounding, IEEE Std 665, 1995.

IEEE Design Guide for Electric Power Service Systems for Generating Stations,_IEEE Std 666, 1991 .

IEEE Guide for Instrumentation and Control Equipment Grounding in Generating Stations, IEEE Std 1050, 1996.

8.2-12 RevisieR 4

8. ELECTRIC POWER

Attachment 1 (3/3) US-APWR Design Control Document

emergency shutdown of the plant due to any electrical fault in the 26 kV system or associated equipment and circuits, the fault is isolated by opening the main circuit breaker on the high voltage side of the MT and all incoming circuit breakers of the MV buses connected to the UAT power source; and all affected MV buses are automatically transferred to the RAT source. The MV Class 1 E buses are not affected since these are normally fed from the RATs. The UAT incoming breakers to these buses is locked out and blocked from closing.

Unit synchronization is normally through the GLBS. Synchrocheck relays are used to ensure proper synchronization of the unit to the offsite power system.

High voltage circuit breakers are sized and designed in accordance with IEEE Std C37.010 and C37.06 (Reference 8.2-14, 8.2-15). High voltage disconnecting switches are sized and designed in accordance with IEEE Std C37.32 (Reference 8.2-16).

The MTs, UATs and RATs have differential , over-current, sudden pressure and ground over-current protection schemes per IEEE Std 666 (Reference 8.2-9). The COL Applicant is to provide site-specific protection scheme.

Detection device{s) are provided on the high voltage side of the RATs and MT, respectively. to address the NRC Bulletin 2012-01 (Reference 8.2-18). The detection device(s) detect open phase condition on the high voltage side of the RATs and MT, with or without grounding. An alarm is initiated in the MCR for open phase and the offsite power circuit to Class 1 E buses is isolated and transferred to another offsite power source or to a Class 1 E GTG automatically upon detection of the open phase condition. The COL Applicant is to provide the details of the specific design of OPC Detection and Protection system during the COL stage. The COL Applicant is to provide the required surveillance requirements for the device(s) used to detect open phase condition. with or without grounding.

Isolated phase busduct provides the electrical interconnections between generator load terminals to the GLBS, the GLBS to the MT and the disconnect links on the high voltage side of the UATs, and the UAT disconnect links to the UATs. Non-segregated phase bus ducts/cable buses provide electrical connections between the low voltage side of the UATs and RATs to the 13.8 kV and 6.9 kV MV switchgear. The non-segregated phase bus ducts/cable buses from the UATs and RATs are physically separated to minimize the likelihood of simultaneous failure.

Each of the single phase transformers of the MT is provided with disconnect links so that a failed transformer may be taken out of service and the spare transformer can be connected. All UATs are also provided with disconnect links so that a failed transformer can be taken out of service. With one UAT or one RAT out of service, all MV buses will have access to at least one offsite power source.

[[The MT, UATs and RATs are located in the transformer yard adjacent to the turbine building (T/8) , and the RATs are separated from the MT and the UATs by 3-hour rated fire barriers.]] Cables associated with the normal preferred and alternate preferred circuits are physically separated from each other to minimize common cause failure[[, even supposing that these circuits share a common underground duct bank]] . In accordance with the guidance of Generic Letter 2007-01 , for preventing the degradation of medium

Tier 2 8.2-4 RevisieR 4

DCD_08.02-17 S01

DCD_08.02-19

2.6 ELECTRICAL SYSTEMS

Attachment 2(1/2)

US-APWR Design Control Document

14. The UATs power feeders are separated from RATs power feeders.

15. The MT and GLBS power feeders are separated from the RATs power feeders.

16. The de control power for Class 1 E switchgear and load centers of each division is supplied from the same division of the de system.

17. Equipment and circuits of each division of the Class 1 E electric power system are uniquely identified.

18. The Class 1 E equipment is protected from sustained degraded voltage conditions.

19. There is no provision for automatic connection between redundant Class 1 E buses.

20.a Displays of voltage and current of the Class 1 E medium voltage buses are provided in the MCR.

20.b Controls are provided in the MCR and locally to open and close the Class 1 E 6.9kV switchgear and 480V load center buses incoming circuit breakers identified in Table 2.6.1-2.

20.c Displays of the Class 1 E 6.9kV switchgear and 480V load center buses incoming circuit breakers listed in Table 2.6.1-2 are provided in the MCR.

21 . Class 1 E ac electric distribution system overcurrent protection is set for proper coordination.

22. The post-fire safe-shutdown circuit analysis ensures that one success path of shutdown SSCs remains free of fire damage.

23. The potential effects on Class 1 E equipment of harmonics introduced by non-linear loads are maintained within requirements .

24. Deleted .

25. The raceway systems for Class 1 E ac electric power system cables meet seismic Category I requirements.

26. The Class 1 E ac electrical power system cables are routed in raceway systems for Class 1 E ac power system cables within their respective division.

27. The RATs are separated from each other and from the MT and the UATs by partitions or distance to limit the propagation of a fire.

28.

Tier 1

The Class 1 E equipment is protected from open phase conditions with monitoring, detecting and alarming in the main control room .

2.6-3 RevisioR 4

I DCD_08.02-19

2.6 ELECTRICAL SYSTEMS

Attachment 2 (2/2) US-APWR Design Control Document

25.

26.

27.

28.

Tier 1

Table 2.6.1-3 AC Electric Power Systems Inspections, Tests, Analyses, and Acceptance Criteria (Sheet 8 of 8)

Design Commitment Inspections, Tests, Analyses Acceptance Criteria

The raceway systems for Class 25.i Inspections will be performed to 25.i The as-built raceway systems for 1 E ac electric power system verify that the as-built raceway Class 1 E ac electric power cables meet seismic Category I systems for Class 1 E ac system cables are supported by a requirements. electric power system cables seismic Category I structure(s) .

are supported by a seismic Category I structure(s) .

25.ii Analysis of the raceway 25.ii A report exists and concludes systems for Class 1 E ac that the raceway systems for electric power system cables Class 1 E ac electric power will be performed using system cables meet seismic analytical assumptions which Category I requirements. bound the seismic design basis requirements.

25.iii Inspection and analysis will be 25.iii A report exists and concludes performed to verify that the that the as-built raceway systems as-built raceway systems for for Class 1 E ac electric power Class 1 E ac electric power system cables are seismically system cables are seismically bounded by the analyzed bounded by the analyzed conditions. conditions.

The Class 1 E ac electrical 26. Inspection of the as-built Class 26. The as-built Class 1 E ac power system cables are 1 E ac electrical power system electrical power system cables routed in raceway systems for cables routing will be are routed in raceway systems Class 1 E ac electric power performed. for Class 1 E ac power system system cables within their cables within their respective respective division. division.

The RATs are separated from 27. Inspection will be performed of 27. The as-built RA Ts are separated each other and from the MT the arrangement of the as-built from each other and from the MT and the UATs by partitions or RATs, MT and UATs. and the UATs by a minimum of distance to limit the 1-hour rated fire barriers or a propagation of a fire. minimum distance of 30 ft.

The Class 1 E equipment is 28.i Analysis will be performed to 28.i A report exists and concludes protected from open phase verify the Class 1 E equipment that the Class 1 E equipment is conditions with monitoring is protected from open phase protected from open phase detecting and alarming in the conditions. condition by open phase main control room .

protection system.

28.ii Inspection and test will be 28.ii The as-built protection system performed to verify the as-built bounds the result of analysis for protection system bounds the Class 1 E equipment protection result of analysis for Class 1 E from open phase conditions. equipment protection from The as-built detection system open phase conditions and to design monitors, detects and verify that an open phase alarms an open phase condition condition will be monitored, in the main control room . detected, and alarmed in the main control room .

2.6-14 RevisieR 4

DCD_OS.02-18 DCD_08.02-19