ML20043F672
| ML20043F672 | |
| Person / Time | |
|---|---|
| Issue date: | 02/12/2020 |
| From: | Office of the Chief Human Capital Officer, Woodard Corp |
| To: | |
| Gary Callaway | |
| Shared Package | |
| ML20043F634 | List:
|
| References | |
| Download: ML20043F672 (22) | |
Text
Chapter 1 DIESEL GENERATORS AS EMERGENCY POWER SOURCES
About the EDG Course, and Chapter 1 Broad focus: Theory, construction, operational considerations, regs, monitoring, case histories, lessons learned, concerns, Goal: To equip you with Foundational knowledge of EDGs, their operation, care, what can go wrong, things to watch for.
Classroom reinforced by "walkarounds" + "hands-on" training Chapter 1: Regulatory basis for EDGs + key criteria for them.
NRC requires that we cover this material Even experienced hands may benefit from brief review of key underlying docs. Chapter 1 can also be a convenient reference.
Chapter 1 Learning Objectives This lesson sets the stage for later Chapters by giving students a fundamental understanding of:
The regulatory basis for NPPs to have redundant power systems (onsite, offsite), and key criteria applicable to them.
Three fundamental performance requirements for EDGs.
Why diesel engines are used instead of other engine types.
Overview of key regs, codes, guides, standards that apply to emergency power systems, and how they're used by licensee.
The major components of a diesel generator system.
10 CFR 50 Successor document to the Atomic Energy Commission (AEC)
General Design Criteria (GDC) of 10 JUL 1967, used for NPP starting construction before 1972.
10 CFR 50 Appendix A, General Design Criterion (GDC) 17 requires both off-site and onsite power systems:
"to permit functioning of structures, systems, and components important to safety."
It further requires independence, redundancy, and testability of on-site power systems, to assure they can perform their vital safety functions assuming a single failure
Independence is the absence of shared components that could result in simultaneous failure of both units. Includes physical and electrical separation, so a transformer, cable tray fire, etc. would not impact operation of the other unit.
Redundancy is required to achieve desired operational reliability, and to accommodate "down time" for testing and maintenance.
Dual EDG installation, where the required power is available with either "unit" out of service.
Testability is self-explanatory. EDG qualification, site acceptance, and surveillance testing are discussed in Chapter 11.
Each power source must have the capacity and capability to assure that:
- 1. "Fuel design limits and design conditions of the reactor coolant pressure boundary are not exceeded" for any anticipated occurrences, and
- 2. The "core is cooled and containment integrity and other vital functions are maintained in the event of postulated accidents."
Loss of Offsite Power (LOOP) is one 'postulated' accident but more complex scenarios considered in selecting, designing EDG systems.
RG 1.9 Rev 4 (Appendix B of Student Manual)
Successor to AEC Safety Guide 9. It covers every EDG must meet to perform its design function per referenced Standards:
- 1. To "...start and accelerate a number of large motor loads in rapid succession while maintaining voltage and frequency within acceptable limits...."
- 2. To "...provide power promptly to engineered safety features if a loss of offsite power and an accident occur during the same time period...."
- 3. To "...supply power continuously to the equipment needed to maintain the plant in a safe condition...."
Why DIESEL Power?
Two considerations determine the choice of engines for EDGs:
- 1. Based on plant-specific accident analysis, how fast must electrical power be restored to support Emergency Core Cooling System (ECCS) operation, to prevent core damage Many reactor designs needed ECCS power within 15-30 seconds. For a safety margin, 10 seconds was required.
- 2. What power supplies are readily available that could reliably pick up heavy step loads beginning in just 10 seconds?
Diesels had needed fast start capability, muscle to rapidly assume heavy loads, were of proven reliability, and had been accepted for the Naval Reactors program
Early Plants Licensed under AEC Criteria Some key AEC requirements (still GDC of record at many older NPPs):
Criterion 38: Reliability & Testability of Engineered Safety Features Criterion 39: Emergency Power for Engineered Safety Features Criterion 48: Testing of Operational Sequence of (ECCS)
The AEC had other criteria which also formed the basis for those currently appearing in 10 CFR 50 Appendix A. Some early plants have voluntarily adopted *portions* of more current EDG criteria.
(No further time will be spent on early criteria.)
Plants Licensed by NRC to GDC of 10CFR50 Some key design criteria of 10 CFR 50 Appendix A:
Criterion 17: Electrical Power Systems To recap, it requires both on and off-site power, plus Independence, Redundancy, Testability.
Criterion 18: Inspection and Testing of Electrical Power Systems Requires provisions for assuring operability and for testing the full operational sequence and performance under conditions as close to design as practical.
Criterion 33, 34, 35, 38, 41, and 44 These establish the criteria for specific safety systems to perform, even with Loss of Offsite Power (LOOP) and the single failure of a source of onsite power (e.g. one EDG train).
"Top Level" NRC Regs for NPP Licensing, Construction, Commissioning, Operation:
10 CFR 50.10 License required 10 CFR 50.23 Construction permits 10 CFR 50.34 - Details the contents of applications, technical information. Of particular significance to EDG selection:
Preliminary safety analysis report Final safety analysis report Describe facility, design basis, operational limits, plus detailed safety analyses of its structures, systems, components, etc.
10 CFR 50.36 - Covers specifications intended to define safety system Limiting Conditions for Operation (LCOs).
"Top Level" NRC Regulations (continued) 10 CFR 50.54, 50.56, and 50.57 Pertain to licensing 10 CFR 50.63 Station Blackout (SBO), the loss of all AC power.
Additional source of functional regulatory requirements that involve Emergency Diesel Generators. Target EDG reliability is used to determine station blackout coping capability.
These criteria are implemented into site-specific system design, using NRC Reg Guides plus incorporated codes and standards developed by ANSI, IEEE, NFPA, etc., or by industry groups
Selected Implementing Documents RG 1.6 - "Independence Between Redundant Standby (Onsite)
Power Sources and Between Their Distribution Systems" RG 1.9, Rev 4 (March 2007) -
This RG introduced 3 fundamental performance requirements for EDGs. It incorporates portions of GDC 17 Electric Power Systems, and GDC 18 Inspection and Testing of Electrical Power Systems. RG 1.9 references several IEEE documents:
continued
IEEE 387 (1972, 1977, 1984, 1995) - "IEEE Standard Criteria for Diesel-Generator Units Applied as Standby Power Supplies for Nuclear Power Generating Stations." Note: Not all plants are committed to use IEEE 387, especially if licensed prior to 1972.
IEEE 387-1995 gives the design basis for nuclear service EDGs as 4000 starts and 6000 operating hours, over a specified service life of 40 years Very different from commercial service, has profound impact on maintenance and testing, plus design implications. IEEE 387-1995 is Appendix C.
RG 1.32 - "Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants." Implements portions of GDC 17.
IEEE 308 - "Standard Criteria for Class 1E Power Systems for NP Generating Stations." (Criteria for independence, redundancy)
RG 1.75 - "Physical Independence of Electric Systems." This is implemented via IEEE 384, "Standard Criteria for Independence of Class 1E Equipment and Circuits."
RG 1.93 - "Availability of Electric Power Sources." Provides guidance for application of 10 CFR 50.36, esp. 50.36(c)(2),
"Limiting Conditions for Operation," (LCO) when less than the number of power supplies required by GDC 17 are available.
RG 1.137 Rev 2 (2013) - "Fuel-Oil Systems for Standby Diesel Generators." Implemented via ANSI N195 / ANS 59.51 - "Fuel Oil Systems for Emergency Diesel Generators."
Regulatory Guide 1.155 - "Station Blackout" and 10 CFR 50.63, "Loss of all Alternating Current Power." Specified SBO duration shall be based on the redundancy and reliability of on-site EPS.
Licensee Implementation of Design Criteria The licensee's documentation of EDG System design will include:
System drawings and isometrics System specifications Equipment specification Purchase specifications Installation and Test Criteria Plant TSs are required to prescribe LCO for EDGs and other req'd safety systems. If any safety limit exceeded, reactor must be shut down. LCOs and associated safety limits, limiting safety system settings, and limiting control settings are also covered in the plant Final Safety Analysis Report / Updated Final Safety Analysis Report.
Highlights of FSAR / UFSAR FSAR/UFSAR Chapter 8, Section 8.3(4), Onsite Emergency (AC)
Power Systems: The bulk of the plant-specific design criteria applied by the licensee to the EDGs is typically included here.
FSAR/UFSAR Chapter 9, Plant Auxiliary Systems: Typically includes design criteria for EDG support systems: Fuel Oil, Jacket Water, Lube oil, Starting Air, etc.
FSAR/USFAR Chapter 14/15, Accident (Safety) Analysis: Covers generic plant design basis events or accidents where EDGs are required to mitigate resulting effects. They range from an SIAS (EDG just starts, runs in standby mode in case needed) to more complex, serious events.
Diesel Generator Fundamentals Each EDG system is an independent, redundant electrical power plant within the nuclear power plant. Largest and most complex NPP safety system, has a critical role.
EDG design criteria applied to each plant are listed or referenced, by revision date, in the licensee's design and equipment specs.
Note: Subsequent updates of regulatory criteria may be difficult, or impractical, for a licensee to back-fit (and that is not required)
The major components of the generator are as follows:
Generator housing and stator Generator rotor and exciter Voltage Regulator EDG emergency trip controls and relays
Major components of the engine and its support systems are:
Governor Starting System (air or electric)
Fuel Oil Delivery System Combustion Air Intake Exhaust System Lubrication System Cooling (Jacket Water) System Crankcase Ventilation EDG start logic controls and relays Emergency run controls and Relays Figure 1-1 "Diesel Generator Systems" (RG 1.9, Fig. 1) illustrates an EDG system, including most of its support systems
Figure 1-1 Diesel Generator Systems In Summary
- 1. Both offsite and onsite power systems are required by 10 CFR 50 Appendix A, Criterion 17.
- 2. Key documents include NRC Regulatory Guide 1.9 Rev 4 (2007),
IEEE Standard 387-1995, 10 CFR 50.xx, others.
- 3. Diesel engines are used principally for their fast start capability.
- 4. EDG systems must be redundant, independent, and testable.
- 5. EDGs must stay within electrical limits when subjected to heavy step loads, cope with loss of off-site power plus an accident, and carry full load for the safety design basis time.
- 6. Licensees EDG System design basis and documentation are plant-specific. They prescribe the equipment and its LCO.
END OF CHAPTER 1