ML19149A317
| ML19149A317 | |
| Person / Time | |
|---|---|
| Site: | 05200045 |
| Issue date: | 06/19/2019 |
| From: | James Shea NRC/NRO/DLSE |
| To: | Michelle Catts GE Hitachi Nuclear Energy |
| Shea J | |
| Shared Package | |
| ML19149A284 | List: |
| References | |
| Download: ML19149A317 (6) | |
Text
8.0 ELECTRIC POWER SYSTEMS 8.3.4.4 Isolation Between Class 1E Buses and Loads Designated as Non-Class 1E 8.3.4.4.1 Regulatory Criteria In the GE-Hitachi Nuclear Energy (GEH), Advanced Boiling-Water Reactor (ABWR) Design Control Document (DCD) Revision 6, GEH (the applicant) proposed a design change to add non-safety Reactor Building (RB) external connections for providing electrical power to the safety related 480 volts alternating current (VAC) RB 1E power centers from an external power source. These additional 480V electrical connections to the safety-related 480V system would improve the diversity and defense in depth during beyond design-basis events and could provide a potential Combined License (COL) applicant the means for meeting the Title 10 Code of Federal Regulations (10 CFR) 50.155, Mitigation of Beyond-Design Basis Events rule.
In a letter dated July 20, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12125A385), the U. S. Nuclear Regulatory Commission (NRC) staff identified 28 items for GEHs consideration as part of their application to renew the ABWR Design Certification (DC). The applicant was requested by the staff in Item No. 26, of the July 20, 2012, staff letter to address ABWR DCD design changes related to aspects of the NRC Fukushima Near Term Task Force Recommendation 4.2 regarding mitigation strategies for beyond-design-basis external events based on the NRC policy, at that time, which was outlined in a Staff Requirements Memorandum SECY-12-0025, Proposed Orders and Requests for Information in Response to Lessons Learned from Japans March 11, 2011, Great Tohoku Earthquake and Tsunami, (ADAMS Accession No. ML12039A111) dated February 17, 2012.
In a letter dated January 23, 2017 (ADAMS Accession No. ML17025A386), GEH provided supplemental information for GEHs response to Item 26 of the NRC suggested ABWR design changes for consideration as part of their application to renew the ABWR DC. The applicant narrowed the scope of Item No. 26 to exclude changes directly related to SECY-12-0025, pending final rulemaking for the Mitigation of Beyond-Design Basis Events (MBDBE) rule. As such, GEH retained the related design change of non-safety RB external connections for providing electrical power to the safety-related 480 VAC RB 1E power centers from an external power source as an operational enhancement to provide additional defense in depth. These proposed ABWR design enhancements could provide a potential COL applicant the means for meeting the MBDBE rule requirements of 10 CFR 50.155.
These proposed changes do not fall within the definition of a modification. Therefore, in accordance with 10 CFR 52.59(c), these design changes are amendments, as this term is defined in Chapter 1 of this supplement and will correspondingly be evaluated using the regulations in effect at renewal. The applicable regulatory requirements for evaluating the proposed DCD design amendments to add RB external connections for providing electrical power to the safety related 480 VAC RB 1E power centers are as follows:
General Design Criteria (GDC) 17, Electric power systems, requires, in part, that nuclear power plants have onsite and offsite electric power systems to permit the functioning of structures, systems, and components that are important to safety. The onsite system is required to have sufficient independence, redundancy, and testability to perform its safety function, assuming a single failure. The independence of safety-related equipment and circuits, 8.3.4.4-1
and auxiliary supporting features is established and maintained via physical separation and electrical isolation.
Regulatory Guide (RG) 1.75, Criteria for Independence of Electrical Safety Systems, provides regulatory guidance addressing independence and specifically, physical separation and electrical isolation.
8.3.4.4.2 Summary of Technical Information Item 26 from the staff letter dated July 20, 2012, requested that the applicant address the design related aspects of Fukushima Recommendation 4.2 regarding mitigation strategies for beyond-design-basis external events as outlined in Attachment 2 of the Commission Order-EA-12-049 (ADAMS Accession No. ML12054A735), Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, issued on March 12, 2012.
Recent NRC actions involving a pending final rulemaking for the MBDBE rule, were discussed during a public teleconference held December 1, 2016. Under the latest public information regarding the pending final rule, there will be no requirements applicable to applicants for a standard design certification (or a renewal, as in the case of the ABWR application). It is expected that the final rule will be effective before the ABWR design certification renewal would be completed. On that basis, in a letter dated December 6, 2016, GEH informed the NRC of its plans to submit a revised response for addressing Item 26 by the end of January 2017. In its January 23, 2017, letter the applicant provided the updated GEH response for Item 26, maintaining some enhanced design features related to mitigating strategies that may be used by a potential COL applicant to satisfy the MBDBE rule requirements including enhancements to the 480 VAC RB 1E power centers.
GEH revised ABWR DCD Revision 6, Tier 1, Section 2.12.1, and Figure 2.12.1a; and ABWR DCD Tier 2, Table 1.9-1, Section 8.3.1.1.2.1, Figure 8.3-1, Sheet 3, and Section 8.3.4. The applicants proposed changes will add RB external connections for providing electrical power to the 480 VAC RB 1E power centers from an external power source.
During a public teleconference with GEH, on September 7, 2017 (ADAMS Accession No. ML17311A055), GEH agreed to provide COL information items regarding the design enhancements related to off-site non-safety portable power. A portable power supply could be used during a beyond design basis event to supply site safety related 480 VAC 1E power centers for an extended loss of AC power or as usually referred to as an extended station blackout (SBO) condition. The proposed COL information items are documented in a letter dated October 10, 2017, (ADAMS Accession No. ML17283A305).
GEH proposed adding two COL information items to the ABWR DCD. These COL information items would add actions for a future applicant to (1) describe in the Final Safety Analysis Report (FSAR) the physical location of external connections for a portable diesel generator and (2) develop procedures for connecting the portable external diesel generators.
These ABWR DCD changes are shown on the DCD markups in the GEH January 23, 2017 letter, Enclosure 2 and in the letter dated October 10, 2017, which will be incorporated in Revision 7 of the DCD.
8.3.4.4.3 Technical Evaluation 8.3.4.4-2
As part of its January 23, 2017 submittal, the applicant proposed adding, as an enhancement to the ABWR design features, RB external connections for providing electrical power to the 480 VAC RB 1E power centers. This change enhances the capability to provide electrical power to critical power centers from an external power source. GEH revised ABWR DCD Revision 6, Tier 1, Section 2.12.1, and Figure 2.12.1a; and ABWR DCD Tier 2, Table 1.9-1, Section 8.3.1.1.2.1, Figure 8.3-1 Sheet 3, and Section 8.3.4. DCD Tier 1, Section 2.12.1 identifies the DCD section that discusses the Electrical Power Distribution System. DCD Tier 1, Figure 2.12.1a identifies the Class 1E Electrical Power Distribution System. DCD Tier 2, Table 1.9-1 identifies the Summary of ABWR Standard Plant COL License Information. DCD Tier 2, Section 8.3.1.1.2.1 identifies the DCD section that discusses the Power Centers. DCD Tier 2, Section 8.3.4 discusses the COL License information items.
The applicant also added a new paragraph as shown in the January 23, 2017 letter, Enclosure 2 DCD Tier 2, Section 8.3.1.1.2.1, Revision 6, markup which states that, to cope with an Extended Loss of AC Power (ELAP), external (to the Reactor Building) connections to each 1E RB divisional power center for portable External 480 VAC diesel generators (DG) are installed, normally isolated from the 480 VAC 1E divisional Power Centers by open 1E breakers.
The applicant also proposed adding two COL information items in 1) DCD Tier 2, Section 8.3.4.5, Physical Locations of Connections for Portable External Diesel Generators, which states that the COL applicant will describe in the FSAR the details and physical locations of the connections for the portable external diesel generators; and 2) DCD Tier 2, Section 8.3.4.6, Develop Procedures for Connecting Portable External Diesel Generators, which states that the COL applicant will develop procedures for connecting the portable external diesel generators.
The staff reviewed the proposed changes to ensure that proper connections and isolation are maintained to minimize the probability of losing electric power from the onsite power supplies.
DCD Tier 2, Table 8.1-1, Onsite Power System SRP Criteria Applicable Matrix, and DCD Tier 2, Section 8.3.3.1, Physical Separation and Independence, state that the ABWR design conforms to RG 1.75. GDC 17 requires that independence of safety-related equipment and circuits, and auxiliary supporting features is established and maintained via physical separation and electrical isolation, and furthermore, RG 1.75 provides guidance on physical separation and electrical isolation. The staff verified that the COL applicant will ensure that electrical isolation exists and is maintained when new equipment is installed, or the existing equipment is modified since the applicant provided a COL information item that will require the COL applicant to establish procedures ensuring that isolation is maintained between Class 1E and non-Class 1E systems. The staff also confirmed that the COL applicant will ensure that the interconnections between non-Class 1E equipment and Class 1E equipment will not result in the degradation of the Class 1E system in conformance with GDC 17 and RG 1.75 because the applicant provided a COL information item for the COL applicant to provide the details and physical locations of the connections for the portable external diesel generators. Since the applicant has provided a COL information item for describing in the FSAR the details and physical locations of the connections for the portable external diesel generators and for developing procedures for connecting the portable external diesel generators, the staff finds that the design meets GDC 17 and conforms to RG 1.75, as it relates to physical separation and electrical isolation, and is therefore acceptable.
The staff verified that the proposed changes as discussed above to the DCD have been presented and depicted in the applicants January 23, 2017 letter, Enclosure 2, DCD Revision 6 markups and the October 10, 2017, DCD Markups with the COL information items regarding 8.3.4.4-3
portable power supplies. These proposed DCD Revision 7 changes are being tracked as a Confirmatory Item 8.3.4.4-1.
8.3.4.4.4 Conclusion The staff reviewed the proposed GEH design enhancements that were evaluated as DCD amendments as described in the GEH January 23, 2017 letter, Enclosure 1, Table 1, Item 4, adding RB external connections for providing electrical power to the 480 VAC RB 1E power centers and determined them to be acceptable design enhancements to the ABWR DCD because the proposed changes to the RB 480V 1E power centers design features as described conforms to RG 1.75 and the requirements of GDC 17, Appendix A to 10 CFR Part 50, continue to be met. In addition, per the COL information items in DCD Sections 8.3.4.5 and 8.3.4.6, discussed above, COL applicants referencing the ABWR design will provide the operational and post-construction aspects of GDC 17, as required and therefore the proposed COL information items are acceptable. The proposed DCD markups are treated as a Confirmatory Item 8.3.4.4-1, pending their incorporation into the next revision of the DCD.
8.3.4.4-4