ML070390582
| ML070390582 | |
| Person / Time | |
|---|---|
| Issue date: | 02/08/2007 |
| From: | William Reckley NRC/NRO/DNRL/NGIF |
| To: | |
| References | |
| DG-1145, RG-1.206 | |
| Download: ML070390582 (5) | |
Text
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power Chapter 8. Electric Power The ac and dc electric power systems are the source of power for station auxiliaries during normal operation, and for the protection system and engineered safety features during abnormal and accident conditions. Thus, the COL applicant should provide information in Chapter 8 of the final safety analysis report (FSAR) on establishing the functional adequacy of the offsite power systems and the safety-related onsite ac and dc electric power systems, as applicable to either a passive or non-passive designs and ensuring that these systems have adequate redundancy, independence, and testability in conformance with the current criteria established by the U.S. Nuclear Regulatory Commission (NRC).
l For passive designs that are exempted from providing two offsite power sources required by GDC-17, the l COL applicant should provide information on the single designated offsite power circuit from the transmission network powering the safety-related onsite dc power systems.
8.1 Introduction The COL applicant should provide a brief description of the utility grid and its interconnection to the nuclear unit and other grid interconnections. The applicant should describe those onsite ac and dc loads that are added to the certified design and the function performed by these loads.
The application document should provide a regulatory requirements applicability matrix that lists all design bases, criteria, regulatory guides, standards, and other documents that will be implemented in the design of the electrical systems that are beyond the scope of the design certification. The specific information identified in Section C.I.8.1 of this guide should be included in the application document.
8.2 Offsite Power System 8.2.1 Description The offsite power system is the preferred source of power for the reactor protection system and engineered safety features during abnormal and accident conditions. It includes two or more physically independent circuits from the transmission network for non-passive designs and at least one offsite circuit for the passive designs. It encompasses the grid, transmission lines (overhead or underground),
transmission line towers, transformers, switchyard components and control systems, switchyard battery systems, and so forth.
The COL applicant should provide information concerning offsite power lines coming from the transmission network to the plant switchyard. The circuits from the transmission network that are designated as two offsite power circuits and are relied upon for accident mitigation should be identified and described in sufficient detail to demonstrate conformance with General Design Criteria (GDCs) 2, 4, 5, 17, and 18, as set forth in Appendix A to Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50). The discussion should include the independence between these two offsite power sources to ensure that both electrical and physical separation exists, in order to minimize the chance l of simultaneous failure. For passive designs, provide information on the single designated offsite power l source with having sufficient capacity and capability from the transmission network designed to power the safety-related systems and other auxiliary systems under normal, abnormal, and accident conditions.
l The This offsite power source should be designed to minimize to the extent practical the likelihood of its failure under normal, abnormal, and accident conditions.
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power The COL applicant should perform a failure mode and effects analysis of the switchyard l components to assess the possibility of simultaneous failure of both circuits (failure of one the designated l offsite circuit for passive designs) as a result of single events, such as a breaker not operating during fault conditions, a spurious relay trip, a loss of a control circuit power supply, or a fault in a switchyard bus or transformer. The capacity and electrical characteristics of transformers, breakers, buses, transmission l lines, and the preferred power source for each path (for non-passive designs) should also be provided to demonstrate that there is adequate capability to supply the maximum connected load during all plant conditions.
The COL applicant should identify the equipment that must be considered in the specification of offsite power supplies, the acceptance testing performed to demonstrate compliance, the effects that must be considered, the margins that are applied, and how the design incorporates these requirements for offsite power supplies, including high-voltage transmission networks, medium-voltage distribution networks, switchyard equipment (bus work, transformers, circuit breakers, disconnect switches, surge protective devices, control, communication, grounding, and lightning systems), switching capacitors, and offsite power supplies.
For non-passive designs, the COL applicant should provide information on location of rights-of-ways, transmission towers, voltage level, and length of each transmission line from the site to the first major substation that connects the line to the grid. All unusual features of these transmission lines should be described. Such features might include (but are not limited to) crossovers or proximity of other lines (to ensure that no single event such as a tower falling or a line breaking can simultaneously affect both circuits), rugged terrain, vibration or galloping conductor problems, icing or other heavy loading conditions, and high thunderstorm occurrence rate in the geographical area. For passive designs, l provide the above related information as it relates to for the single designated offsite power circuit from the transmission network.
The COL applicant should describe and provide layout drawings of the circuits that connect the onsite distribution system to the offsite power supply. This should include transmission lines, switchyard arrangement (breakers and bus arrangements), switchyard control systems and power supplies, location of switchyard (in plant), interconnections between switchgear, cable routing, main generator disconnect and its control system and power supply, and generator breakers and load break switch. For passive l designs, the above information should be provided as it relates to the single designated offsite power circuit from the transmission network.
For non-passive designs, the COL applicant should indicate if generator breakers are used as a means of providing immediate access from the offsite power system to the onsite ac distribution system by isolating the unit generator from the main step-up and unit auxiliary transformers and allowing backfeeding of power through these circuits to the onsite ac distribution system. If so, provide sufficient information for the staff to evaluate the generator circuit breakers and load break switches.
The COL applicant should discuss the stability of the local area grid network. This should identify the equipment that must be considered for review and approval by the appropriate grid reliability planning and coordination organization(s). Discuss the maximum and minimum switchyard voltage that must be maintained by the transmission system provider/operator (TSP/TSO) without any reactive power support from the nuclear power plant. Describe the formal agreement or protocol between the nuclear power plant and the TSP/TSO of the preferred offsite power capable of supporting plant startup, and to shut down the plant under normal and emergency conditions.
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power The COL applicant should describe the capability of the TSP to analyze contingencies on the grid involving the largest generation unit outage, critical transmission line outage, and other contingencies under varying power flows in response to market conditions and system demands.
The COL applicant should include a description of the analysis tool used by the TSO to determine, in real time, the impact of the loss or unavailability of various transmission system elements on the condition of the transmission system. In addition, the applicant should provide information on the protocols in place for the nuclear power plant to remain cognizant of grid vulnerabilities, in order to make informed decisions regarding maintenance activities that are critical to the plants electrical system (Maintenance Rule, 10 CFR 50.65).
8.2.2 Analysis For non-passive designs, the COL applicant should provide an analyses to demonstrate compliance with GDC 17 and 18, and to indicate the extent to which the recommendations of RG 1.32 are followed.
l For all passive and non-passive designs, the COL applicant should provide an analysis of the stability of the grid. This analysis should include the worst case disturbances for which the grid has been analyzed and considered to remain stable and to describe how the stability of the grid is continuously studied as the loads grow and additional transmission lines and generators are added. Also to provide the assumptions and conclusions that demonstrate that the acceptance criteria required for the continued safe operation of the nuclear unit and the stability of the grid have been addressed. Identify the approving grid organization for the reliability studies, and identify any potential limits that may be imposed on the operation of the nuclear plant. Provide a discussion of grid availability, including the frequency, duration and causes of outages over the past 20 years for both the transmission system accepting the units output and the transmission system providing the preferred power for the units loads.
The COL applicant should provide the results of steady-state and transient analyses to demonstrate compliance with final paragraph of GDC-17. The results of the grid stability analysis must show that loss of the largest single supply to the grid does not result in the complete loss of preferred power. The analysis should also consider the loss, as a result of a single event, of the largest capacity being supplied to the grid, removal of the largest load from the grid, or loss of the most critical transmission line. In determining the most critical transmission line, consider lines that use a common tower to be a single line. This could be the total output of the station, the largest station on the grid, or possibly several large stations if these use a common transmission tower, transformer, or breaker in a remote switchyard or substation. For passive designs, this analysis should show that the single l designated offsite circuit from the transmission network is not lost during the above events contingencies.
l In addition, grid stability analysis should demonstrate that the grid remains stable for a minimum of three l seconds following a turbine trip to support assumptions made in the safety analyses for passive designs, l such as the AP-1000.
8.3 Onsite Power Systems 8.3.1 AC Power Systems 8.3.1.1 Description
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power Since the design of onsite power system is included in the certified design and the offsite power system is within the scope of the COL applicant, it needs to provide information primarily on the interfaces between onsite and offsite power systems. The COL applicant should describe how independence is established between the onsite and offsite power systems. Two aspects of independence should be addressed in each case:
- physical independence
- electrical independence In ascertaining the independence of the onsite power system with respect to the offsite power system, the applicant should describe the electrical ties between these two systems, and should provide the physical arrangement of the interface equipment. For non-passive designs, it should also demonstrate that no single failure will prevent separation of the redundant portions of the onsite power systems from the offsite power systems. Following a loss of offsite power, the safety buses are solely fed from the standby power systems. Under this situation, describe the design of the feeder-isolation breaker in each offsite power circuit that must preclude the automatic connection of preferred power to the respective safety buses upon the loss of standby power. For passive designs, the applicant should describe the electrical ties between the offsite power circuit and the onsite system that supplies power to charge and, should provide the physical arrangement of the interface equipment.
For non-passive designs, if non-Class 1E loads are connected to the Class 1E buses that were not included in the certified design (i.e., plant-specific loads), the COL applicant should demonstrate that the design will not result in degradation of the Class 1E system. Describe the design of the isolation device through which standby power is supplied to the non-Class 1E load, including control circuits and connections to the Class 1E bus. To ensure physical separation between the Class1E equipment and the non-1E equipment, including cables and raceways, describe how the recommendations of Regulatory Guide 1.75 are followed and provide justifications for any exceptions.
For non-passive designs, the COL applicant should describe the means of identifying the non-1E components, including cables, raceways, and terminal equipment. Provide information on the identifying scheme used to distinguish between redundant Class 1E systems and non-Class 1E systems and their associated cables, raceways without the need to consult reference material.
For non-passive designs, the COL applicant should also describe how the diesel generators are sized to accommodate the added non-Class 1E loads.
8.3.1.2 Analysis For non-passive designs, the COL applicant should provide analyses to demonstrate non-safety loads if connected to the Class 1E buses that were not included in the certified design (i.e., plant-specific loads) do not result in degradation of the Class 1E system. In addition, indicate the extent to which the recommendations of Regulatory Guide 1.75 and other appropriate criteria and standards are followed in this regard.
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power 8.3.1.3 Electrical Power System Calculations, and Distribution System Studies for AC Systems COL applicants that reference a certified design do not need to include this information unless design changes are made to the certified design.
8.3.2 DC Power Systems 8.3.2.1 Description l Since the design of dc power systems is included in the certified design, the COL applicant needs l to should describe if non-Class 1E loads that were not included in the certified design (i.e., plant-specific loads) are connected to the Class 1E dc system. It should demonstrate that the design will not result in l degradation of the Class 1E dc system. In addition, describe the design of the isolation device through which dc power is supplied to the non-Class 1E loads. To ensure physical separation between the Class1E equipment and the non-1E equipment, including cables and raceways, describe how the recommendations of Regulatory Guide 1.75 are followed.
The COL applicant should describe the means of identifying the non-1E components, including cables, raceways, and terminal equipment. Provide information on the identifying scheme used to distinguish between redundant Class 1E systems and non-Class 1E systems and their associated cables, raceways without the need to consult reference material.
The COL applicant should also describe how the batteries are sized to accommodate the added non-Class 1E loads.
8.3.2.2 Analysis The COL applicant should provide analyses to demonstrate that non-safety loads connected to Class 1E dc system buses do not result in degradation of the Class 1E dc system. In addition, indicate the extent to which the recommendations of Regulatory Guide 1.75 are followed in this regard.
8.3.2.3 Electrical Power System Calculations, and Distribution System Studies for DC Systems COL applicants that reference a certified design do not need to include this information unless design changes are made to the certified design.
l 8.4 Station Blackout (SBO) (For Non-Passive Designs only) 8.4.1 Description The COL applicant should describe how the alternate alternating current (AAC) power source if provided to mitigate station blackout is independent from the offsite power system. Describe the physical arrangement of circuits and incoming source breakers [to the affected Class 1E bus(es)],
separation and isolation provisions (control and main power), permissive and interlock schemes proposed for source breakers, source initiation/transfer logic, that could affect the ability of the AAC power source to power safe shutdown loads, source lockout schemes, and bus lockout schemes in arriving at the determination that the independence of the AAC power source is maintained.
Preliminary Work Product to Support February 13, 2007, Public Meeting RG 1.206 Section C.III.1-8, Electric Power The COL applicant should describe how the AAC power source components are physically separated and electrically isolated from offsite power components or equipment, as specified in the separation and isolation criteria applicable to the units licensing basis and the criteria of Appendix B to Regulatory Guide 1.155.
The COL applicant should identify local power sources and transmission paths that could be made available to resupply power to the plant following a loss of a grid or SBO.
The COL applicant should describe the procedures and training provided for the plant operators for an SBO event of the specified duration and recovery therefrom.
8.4.2 Analysis The COL applicant should provide an analysis to demonstrate that no single-point vulnerability exists whereby a single active failure or weather-related event could simultaneously fail the AAC power source and offsite power sources. The power sources should have minimum potential for common failure modes.