ML20043F667

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Training Material for E-111 Emergency Diesel Generator Course, Chapter 13 (3-16), Case Studies: Lessons Learned, and Concerns
ML20043F667
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Issue date: 02/12/2020
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Office of the Chief Human Capital Officer, Woodard Corp
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Gary Callaway
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Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns

13. CASE STUDIES: LESSONS 13.1 EDG STARTING FAILURES LEARNED, AND CONCERNS Defective Air Start Motors Learning Objectives Bench testing of two new air start motors to As a result of this lesson, you will acquire be installed on an EDG determined that they knowledge of previous and potential EDG were defective. The motors, Ingersol-Rand failures, as well as concerns about ongoing series 89, had been assembled with an issues that can impact these vital systems. incorrect pinion engagement piston at the That information will enable you to better factory. The root cause was one assembler evaluate Licensee Event Reports (LER's), technician pulling the air start motor parts as well as relevant Information Notices and from memory instead of using the pick list for Generic Letters that pertain to EDGs. You the job. A total of seven NPP's had been will then have better understanding of: shipped air start motors with the wrong pinion engagement piston, which would
1. Various failure scenarios involving have either prevented an EDG start or emergency diesel generators and their compromised the engine's fast start support systems. capability. The first few starts may have been acceptable, until the elastomer seal
2. The significance and safety implications (O-ring) used instead of metal had been of individual licensee LERs and other abraded. All affected air start motors were documents regarding EDG issues. recalled and accounted for. See Figure 13-1 and 10 CFR 21- 0095, 20 October 2008.
3. The potential reliability impact of things beyond the EDG's boundaries, including Malfunctioning Speed Switch Circuits lightning, underground cable faults, grid anomalies, switchyard failures, etc. At two nuclear stations a malfunctioning annunciator power supply (dc) within the
4. The potential unintended consequences EDG's gauge board panel caused electrical of events in the vicinity of the EDG, such noise (ac ripple) in the speed switch circuit.

as maintenance/cleaning activity or fire That resulted in the speed switch changing suppression system actuation. state prematurely, thereby preventing EDG start. The underlying cause was a failed or

5. Possible shortcomings in the licensee's degraded filter capacitor in the dc power operational or maintenance procedures supply. In the previous 7 years there had for EDGs and their support systems. been 10 cases where speed switch issues had prevented start, several involving the
6. The likely effectiveness of licensee same failure cause. Electrolytic capacitors corrective actions for EDG failures. degrade with time and dc power supplies for control equipment need to be checked
7. "Aging" issues and other ongoing periodically to verify ripple voltage is within concerns regarding EDG systems. limits. See Information Notice 2010-23.

Rev 3/16 13-1 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Painting Activities and Cleaning Agents Searching through the NRC archives will reveal still more of these events, such as IN There have been numerous cases where 91-46, Degradation of Emergency Diesel nearby painting or cleaning activities have Generator Fuel Oil Delivery Systems." It had adverse impact on EDGs, as well as describes EDGs rendered inoperable by auxiliary feedwater pumps, a high pressure paint on fuel rack components, or on their coolant injection pump, radiation monitors, exciter commutator rings. Another report fire detection and suppression equipment, describes a contractor's use of undiluted etc. At least three reactor trips resulted. A muriatic acid to clean the concrete floor of listing and brief description for each one is the EDG room, causing severe corrosion of available in ADAMS under Accession No electrical controls and circuits. Licensees ML091600446. need to apply the lessons learned from all such cases and increase prevention efforts.

In a recent, very typical case, a drop of paint on an EDG fuel rack prevented the governor 13.2 CONTROLS-RELATED FAILURES from moving it from the normal standby (closed) position upon a start signal. As a Spurious Shutdown (Design Oversight) result, the EDG failed to start and was declared inoperable. IN 2009-14 attributed In some EDG designs, the starting air the problem to numerous work control system also performs a critical control shortcomings including inadequate function that may necessitate ensuring supervision, communications issues, lack of availability of the starting air system training or adherence to procedures, etc. throughout the duration of certain analyzed Nevertheless, the failure could have been events, such as station blackout. At one prevented with a thorough EDG readiness NPP the EDGs are individually supported by inspection and checkout following the work. non-safety related air compressors, powered by non-class1E power supply, that A previous report described an EDG that maintain sufficient inventory of high was cleaned with a solvent that removed pressure starting air in the safety related fuel rack lubrication, leaving a white residue accumulators. This air provides motive and some coagulated lubricant that bound it, force for the engine starting system and also preventing any rack movement by the supplies a pneumatic control logic system governor. To prevent a recurrence the that trips the EDG when certain non-licensee implemented new procedures to emergency engine parameters are sensed require cleaning and lubrication of the rack, to exceed its set limits. Air pressure loss, plus verification of free movement, after any following an engine start, may be due to cleaning or painting. In a similar case, a system leakage or through a tripped engine cleaning agent was used that contained a protection sensor that reached an solvent that caused the plastic parts of 16 unacceptable level. When the EDG is safety-related control switches to bond, operating in the emergency mode, the thereby preventing their operation. These declining control air pressure first un-are described by IN 93-76. bypasses the protective trips that were Rev 3/16 13-2 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns bypassed for the emergency mode, and adjacent electrical contact opening causing further decrease in pressure results in an failure. EMI and RFI must be considered.

engine trip. This problem emphasizes the need for licensees to ensure reliability of Improperly Diagnosed Governor Failures systems that perform critical support functions for safety-related systems. More During 1992 to 1994, several plants than one station was found to have this replaced governor units because of erratic issue. The preferred solution is to have an oscillatory operations. Factory tests of the assured means of maintaining air pressure governors disclosed that the governors were as needed for controls during an extended not faulty. Root Cause Analysis disclosed EDG run, without the necessity of operator that licensees were using a large power-action. See IN 98-41. type relay, which operates at low voltage and milliamp currents, in the governor Inadvertent EDG Start feedback droop circuit. This type relay was inappropriate for an electronic type While performing a load rejection test of the application. The relay is located in the A unit EDG in accordance with IEEE 387 electric control panel, not the governor.

and RG 1.9, an unanticipated start of the B unit EDG occurred. Evaluation indicated Changes in resistance of the contacts that at the time of the unanticipated start, a provided the sensing circuit with improper "large" load (an auxiliary feed pump) was and erratic signals. Replacement with a started. The ensuing voltage dip amounted proper relay for the application eliminated to approximately 80% of rated voltage on recurrence. Control relays are designed the emergency bus causing under-voltage such that their contacts have more stable, relays to drop out, immediately starting the lower contact resistance than power relays, B unit EDG. The components of the system making them suitable for electronics use.

functioned properly. A procedural deficiency was identified, in that operators Defective Governor Drive Couplings should have been informed an EDG start may occur when starting this large load. Flexible drive couplings used on a vertical drive shaft to transmit power from the engine Load Sequencer Failure gear train to the governor, so it can sense engine speed and regulate it, were A licensee made upgrades in ESF load fabricated of Isoprene instead of the sequencing by replacing the electro- specified Neoprene. The isoprene material pneumatic relays with newer solid state type is not suitable for the high temperature, oil microprocessor units. However, the rich environment of the engine gear case replacement modification design failed to and is susceptible to failure, which would consider the high magnetic environment in make the governor inoperative. Several which the microprocessor units were to be utilities were supplied with the defective located. The panel location subjected the parts, subsequently recalled and replaced.

units to intense magnetic flux created by Neoprene was specified for this dynamic, Rev 3/16 13-3 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns torque transmitting application because of Defective Governor DRU IC Chips its strength and inherent resistance to the chemicals present in the environment. The Four Woodward governors failed, three of manufacturing error illuminated the need for them during initial test and one after improvements in the supplier's ability to approximately a year of service. Each distinguish these materials from one failure was indicated by the inability to adjust another. Ironically, 23 years previously a frequency (engine RPM) due to a defective Part 21 report (Transamerica Delaval #112) CMOS IC chip in the digital reference unit had been issued to document a similar (DRU), and each occurred when a problem, including a change in the original raise / lower signal was given. Analysis by coupling material from Isoprene to the Woodward found evidence of internal present Neoprene. See Figure 13-2 and aluminum conductor corrosion, most likely 10 CFR 21-0090, 16 September 2005. the result of delaminating of the IC package from the chips lead frame. DRUs produced Ignored Circuit Breaker Problem between November 2000 and November 2005had potentially defective IC chips by Following an automatic reactor trip, a non- the same semiconductor manufacturer and safety related electrical circuit breaker did needed to be replaced. The first failed unit not automatically open to isolate an was reported by Fairbanks Morse in 2004.

electrical fault because it did not have (See 10 CFR 21- 0088.) After it became control power to its trip circuit. The lack of apparent that DRU's shipped over a five control power was due to a faulty fuse year period were suspect, 10 CFR 21- 0091 assembly in the circuit breakers control was issued on 23 January 2006, power circuit. The licensees corrective action program showed that the control Replacement Time-Delay Relays Used in power indicating lights on the front panel of EDG Logic Susceptible to EMI Failure the breaker had not been illuminated for approximately one year! Brunswick replaced Allen Bradley 700RTC-series time delay relays during a refueling Previously NRC issued IN 1991-78 to inform outage and subsequently experienced EDG licensees of the importance of control power failure. Investigation determined the relays for circuit breakers used in safety-related would cycle each time they saw a transient applications. Later, IN 2007-34 highlighted produced by operation of other relays on the the importance of identifying possible circuit. Comparison of old and new relays causes for breaker problems including the determined A-B had changed the design to lack of control power indication. This latest use a Complex Programmable Logic Device case highlighted the necessity of having (CPLD) due to obsolescence of the IC chip control power indication for both safety- in this commercial relay. Transient Voltage related and non-safety related applications, Suppressors (TVS) were installed to prevent as the latter can clearly impact vital safety recurrence of EMI-induced failures. See systems. See IN 2010-09 and ADAMS info Part 21 Report of 25 June 2015 and also under Accession No. ML100880412. ML15149A148.

Rev 3/16 13-4 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns 13.3 ENGINE-MECHANICAL FAILURES Defective Nordberg Engine Valve Seats Crankcase Explosions (Recap) A significant safety hazard was reported by the manufacturer regarding the potential of Chapter 12 covered the problem of 13 Nordberg engine valve seat inserts to 'drop' crankcase explosions in Cooper-Bessemer from the bore of the cylinder head into the KSV engines. The manufacturer and the cylinder with probable resulting damage to licensees involved eventually found and the cylinder head, power valves, piston, corrected the causes, although hindsight cylinder liner, exhaust manifold and indicates that effort should have proceeded turbocharger. This could result in loss of the more rapidly, considering the seriousness of intended 'Safety Function' of the EDG. The the problem. Whether that conclusion is problem was attributed to the originally considered to be fair or not, any licensees specified amount of interference fit for the having an effective lube oil analysis and inlet and exhaust valve seat inserts, in the trending program would have been made area between the cylinder head bore and aware of the ongoing engine damage in time the inserts." This did not become apparent to prevent catastrophic failure. until field failure(s) occurred outside the US.

The manufacturing specification was Defective Diesel Cam Roller Bushings corrected and the two affected NPP's were alerted of the problem. See 10 CFR 21 The (fuel pump) cam roller bushings for Notification dated 13 June 2006.

Fairbanks Morse OP engines shipped to 15 NPP's may have been made from an Engine Damage Caused by Maintenance incorrect leaded brass material which is much softer than the specified bronze A routine lubricating oil analysis identified a material. The bushings made from the soft high concentration of chromium in the oil of material wear out quickly (in one case, less the B unit EDG. This caused the unit to be than 55 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br /> of engine run). This results in declared inoperable, as chromium is a key a shorter fuel injection pump stroke, poor element used in cylinder liners and piston fuel injection characteristics, more exhaust rings. Internal inspection found significant opacity, and decreased engine power. scoring of those components. Two days earlier similar damage to the cylinder liner EDGs with this defect may not be able to and piston rings of the D unit EDG had been achieve their maximum load rating and, found and it was being repaired.

therefore, may not be able to perform their intended safety function. Fairbanks Morse Further investigation found that sand implemented inspections and supplier (aluminum oxide) was in the combustion air certification of cam hardness 30 July 2001. intake manifold of both EDGs. It was Therefore, all cam roller bushings shipped concluded the sand originated from recent prior to that date are considered suspect. cleaning-coating of the water side of the For additional information see 10 CFR 21 combustion air intercoolers. Inadequate Notification by FM, dated 9 April 2007. protection of the air side of these heat Rev 3/16 13-5 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns exchangers during sand blasting allowed ESI improved their rebuild documentation the sand to become lodged in the fins. and all possibly affected heads in stock or Subsequent operation of these units installed on engines were inspected. The introduced the sand into the cylinders where plants affected were Cooper, South Texas, abrasive action caused scoring of the Bryon. See Part 21 Report of 23 April 2013.

cylinder liners and piston rings.

13.4 FIRE PROTECTION SYSTEM NOTE: It was found that three years earlier ISSUES, BUILDING FIRES a similar situation had occurred. Two combustion air intercoolers had been Deaths Due to Inadvertent Discharge of cleaned by sand blasting. However, prior to CO2 Fire Protection Systems reinstallation, maintenance personnel had observed the sand in the air side of the inter- Carbon Dioxide (CO2) fire suppression coolers, so they were cleaned before being systems are common in nuclear power installed. Obviously, no lesson was learned plants, protecting spaces such as cable from that previous incident, as the spread rooms, switchgear rooms, and EDG procedure should have been modified to rooms. CO2 suppresses fire by displacing prevent recurrence. See IN 90-80. Oxygen and smothering it. Personnel will be similarly affected unless they evacuate Valve Keeper Seals Missing from Rebuilt immediately. CO2 installations protecting an Cooper KSV Engine Heads, Allowing EDG room will also stop the engine if its Keepwarm Oil to Enter Cylinders. intake air comes from the room instead of being ducted in from outdoors.

South Texas reported lube oil was expelled from a cylinder as the engine was barred Several NPP's and other nuclear facilities (one of their routine EDG pre-start checks). have experienced inadvertent discharges of They found all eight keeper sealstwo each their CO2 systems. Each of these incidents on four valvesmissing on that rebuilt head. underscored the critical need to have self-Figure 13-3 illustrates the seal locations. contained breathing apparatus (SCBA) immediately available and plant personnel The lube oil in the cylinder originated in the trained in their use. The SCBA should be keepwarm system that provides a constant the type with integral radio communications flow of oil through the engine during standby and also compatible with corrective lenses.

(including the valve rocker arm assembly).

Depending on part tolerances and wear, Other necessary measures include having some can leak onto valve stems and the clearly marked and quickly accessible exits missing valve keeper seals are designed to from spaces protected by CO2. The lack of prevent it from running down the valve stem such measures contributed to one fatality and into the engine. During a long standby and several life-threatening injuries at the period, cylinder hydraulic lock could occur, Idaho National Engineering Laboratory in so this case is a testament to the practice of 1999 when a CO2 system discharged with barring or slow-rolling EDGs before start. no warning. The accident investigation Rev 3/16 13-6 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns board determined that since 1975 there 23 related an incident in which a Halon 1301 have been a total of 63 deaths and 89 manual release ("pull") station was mistaken injuries as a result of unintended discharge for a fire alarm system manual station, with of these fire suppression systems. the predictable outcome. Some systems installed in the 1970's and 1980's were No reports of unintended discharge of a CO2 susceptible to being activated from nearby system in an EDG room were found in public portable radio communications devices and documents at NRC. However, the potential in one case at a NPP the Halon system was exists for such an event to occur and impact triggered by a camera flash while the control the EDG and / or personnel. It is important panel cover was off. (See IN 97-82).

that licensees consider such an eventuality and take measures to assure that the only NOTE: A number of Information Notices result from a CO2 discharge would be the have been issued regarding problems with intended fire suppression. Toward that end, fire protection equipment, including recalls some licensees have changed these of defective sprinkler heads (sticking O-rings systems to be activated only by manual that prevented sprinkler actuation by a fire),

means. Another very desirable feature is a defective fire hydrants, etc..

mechanical time delay that has an integral CO2-driven siren. Located in the piping just EDG Building Fires Resulting from downstream of the high pressure CO2 tanks, Improper Roof Repairs it sounds for a brief period to warn of the impending release of gas into the space. After 21 hours2.430556e-4 days <br />0.00583 hours <br />3.472222e-5 weeks <br />7.9905e-6 months <br /> of a 24-hour endurance run For more information see IN 99-05. (surveillance test) of the E-3 emergency diesel generator, combustible roofing Inadvertent Discharge of Halon 1301 or material on the EDG building caught fire Clean Agent Gaseous Fire Suppression near the diesel exhaust pipe penetration (roof stack) area. The roofing material was Unlike CO2, Halon 1301 and the alternate in contact with the steel penetration sleeve "clean agent" fire suppression gasses put the EDG exhaust pipe passes through. The out fires without adverse effect on people, if root cause was improper installation of applied in the proper concentration. When roofing materials during re-roofing.

they come into contact with a fire they do decompose into some compounds that When the EDG is running the temperature should not be breathed, so evacuation or of the exhaust stack reaches approximately SCBA gear are still advised. If used to 900ºF, while asphalt roofing paper ignites at protect an EDG room they have the same about 400ºF. The consequences of this potential to stop the engine as CO2 if the "non-safety-related modification" once again combustion air intake is in the EDG room. demonstrate that any work in the vicinity of the EDG requires administrative oversight Because all gaseous agent fire suppression and inspection. While roof work is in systems are rather complex, there is greater progress that should include a fire watch potential for inadvertent discharge. IN 2007- and extinguishers. See IN 2007-17.

Rev 3/16 13-7 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns NOTE: Another Information Notice gave the 13.5 ENGINE COOLING FAILURES details of other recent fires at NPP's.

Several were caused by a lack of sufficient Fouled Heat Exchangers switchgear maintenance, an increasing concern as the ages of plants approach or The EDGs in this discussion were tandem surpass their original design lifetime and it units, two diesel engines powering one becomes difficult or impossible to obtain generator. The 1A generator was powered spares. As previously discussed, this is also by engines A and B. The 1B generator was true for some EDG components, including powered by engines C and D. Both legacy governors and voltage regulators. generator sets were operating under load, Some important firefighting lessons were supplying a 480 volt essential power bus.

also learned and they have potential Approximately 30 minutes into the run, implication for EDGs, though the described engine D (generator set 1B) tripped on fires did not directly involve those systems. high jacket water temperature. Shortly See IN 2002-27. afterwards the C engine tripped, also from an over-temperature condition.

Issues Potentially Affecting Nuclear Facility Fire Safety Investigation found the jacket water heat exchangers were fouled. This reduced the Underwriters Laboratories and the Defense ability of the engine to reject heat, which led Logistics Agency have recently issued alerts to overheating. It would have made the regarding fire protection equipment: These EDG inoperable during an emergency.

include notice of counterfeit fire protection items including fire hose, fire extinguishers, Corrective action included cleaning the heat sprinkler hangers, and various types of fire exchangers for both generator sets. It was sprinklers. All have fake UL labels or other determined that the annual schedule for certifying agency marks. Licensees can go cleaning them was not adequate. The to on-line resources for more details and info frequency for this preventive maintenance on how to tell pedigree parts from the fakes. item was upgraded to quarterly.

Also, UL issued notice of changes in their NOTE: There is always increased potential electrical cable-rating certification program. for fouling and scaling when an on-site water Testing of electrical cables currently having supply is used in a heat exchanger. Also, at a 2-hour fire resistance rating per ANSI / UL some sites water temperature may rise high 2196 revealed they no longer consistently enough to compromise heat exchanger met the criteria. Therefore, three classes of efficiency, resulting in a risk of EDG over-such cable can no longer bear the UL mark. heating when running near rated load.

Licensees should be aware of these issues Water Leaking Into Cylinder as they maintain required fire protection features and manage their procurement During an engine bar or slow-roll check process. See IN 2013-02. preparing for a routine EDG surveillance Rev 3/16 13-8 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns test, several pints of water were found in an NOTE: Not all licensee's "bar over" EDGs engine cylinder. The pre-run check enabled before a surveillance or post-maintenance the licensee to avert severe engine damage. run, as puts them temporarily out-of-service After removing the cylinder module, it was while this is being done (engine is locked found that a small leak path had slowly out, petcocks are open). However, diesel developed on the head gasket, allowing the manufacturers recommend it, especially jacket cooling water to intrude into the after a significant period without being run.

cylinder. The engine had been run 7 days In these two cases, that practice certainly earlier without difficulty. Apparently, a prevented extended "out-of-service" time, sufficient amount of fluid had leaked after and would have done so for the prior case.

that previous test to partially fill the cylinder with water. The licensee determined that if EMD Jacket Water Pump with Incorrect the EDG had been started without first being Impeller Orientation.

checked for water in the cylinders, it would have been severely damaged by hydraulic EMD engines have two centrifugal engine lockup of the cylinder. jacket water pumps (one for each bank) and both rotate in the opposite direction from the While performing a previous bar / slow-roll crankshaft. In nuclear applications the EMD check in 1987, the licensee discovered the is frequently used in tandem, two engines same condition on another EDG, caused by driving one generator in between them.

a cracked cylinder. Five years previous, an That arrangement requires the engines to EDG at another facility had been severely run in opposite rotation from each other.

damaged because it was started after water Therefore, the water pumps for left hand leaked into a cylinder through a cracked rotation engines use different impellers than cylinder wall, and they learned from that. the pumps for right hand rotation engines.

Because of the incompressible nature of Grand Gulf reported a pump with the wrong water, lube oil, and fuel oil, the presence of impeller, which results in lower output from significant amounts of fluid in an engine the pump, degrading engine cooling. The cylinder can cause hydraulic lockup during engine could have failed when running near the compression stroke. When the force full rated load. ESI improved visual aids and from the starter and other firing cylinders advised licensees to check impellers on all tries to overcome this lockup, the engine can pumps in stock, and on potentially affected be severely damaged. The fluid can come EDGs. See Part 21 Report, 30 March 2011.

from a number of sources such as a leaking head gasket, a cracked cylinder or head, or 13.6 FUEL OIL / LUBE OIL RELATED a defective fuel injector. For the Fairbanks Morse OP engine, it can occur if the pre-lube Leaks Caused by Fatigue Cracking system is run for more than a short period prior to start, as lube oil for the upper crank Several NPP sites have experienced leaks area can pool under the top pistons and leak in the piping for fuel oil, lubricating oil, and down. See IN 91-62. water. Many of these leaks resulted from Rev 3/16 13-9 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns fatigue cracks in welded joints, induced by reveal this problem, as the licensee may not normal engine vibration. Some involved operate any EDG long enough to observe Fairbanks Morse OP engines produced at a the effect of cold fuel oil. Most of the fuel time when partial-penetration welded joints used during these tests will be from day were used in the fabrication process. Those tanks, which are at a much higher met the procurement specifications and temperature due to being located in the such welds are actually stronger than the EDG rooms. In contrast, an accident may piping. However, full-penetration weld joints require continuous operation of the per ASME Code Section III, Class 3 (now emergency diesel generators for several used by the manufacturer) have more days. The warmer fuel in the day tanks resistance to fatigue cracking. would be depleted and the EDGs would then be required to perform on fuel oil at a This type problem is certainly not unique to temperature near the outside temperature.

the FM OP, which typically has perhaps 200 welds on the skid-mounted components. Fuel oil that is not properly specified The Owner's Group has actively pursued (procured) for the lowest-use temperature this issue and some licensee's have the site could experience may lead to a replaced the piping or welds in areas of common-mode failure of all the emergency concern. All licensees need to be aware of diesel generator units. The specified pour the potential for fatigue cracking of any point of the fuel oil should be at least 10ºF model EDG and its components, especially below the lowest ambient temperature the as running hours increase. See IN 98-43. fuel may be exposed to. In cold climates that may require fuel tanks and lines to be Cold Fuel Oil Concerns insulated and provided with heat tracing in order to maintain a proper viscosity and NRC electrical distribution safety functional avoid the formation of wax crystals. See IN inspections have determined that multiple 94-19.

sites have fuel specifications that do not adequately assure the proper cold weather Cylinder Failures Caused by Improper characteristics. Specifically, the pour point Fuel Oil and cloud point criteria were inappropriate for the potential lowest temperatures at the Following 110 percent load surveillance sites. That could result in loss of fuel flow tests, engine clattering was noted, and the during EDG run, either from filter-injector engine was shut down. Inspection revealed clogging by wax crystals or from the fuel oil two badly overheated pistons, scored liners, dropping below the specified "pour point" (at and badly worn connecting rod and wrist pin which it will cease to flow). The most bearings. Based on the appearance of the concern is for sites with above-ground fuel parts, the engine would have seized and / or tanks or above-ground fuel piping without connecting rods would have broken if heat tracing powered from a safety source. operation had continued. Unfortunately, this was the tip of the iceberg, as other EDG Routine surveillance runs are not likely to engines at the site had similar damage.

Rev 3/16 13-10 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns All fuel injectors were coated with paraffin Lube Oil Incompatibility with Low-S Fuel such that several cylinders were either not (Low-Sulfur Fuels: 500ppm maximum S) firing or were producing only a small amount of power. As a consequence, other properly During pre-operational testing of a new firing cylinders were operating in a severely EDG, wide fluctuations in the crankcase overloaded condition in order to make up the pressure were noted, as well as lube oil power. This was confirmed by records of seeping out the crankshaft seal. After extremely low and high exhaust gas inspection and further analyses, heavy temperatures from respective cylinders. carbon-like build-up was found on pistons Analysis of the fuel oil disclosed non- and behind the piston rings, plus scuffing of specification fuel. Draining the tanks and the cylinder walls, in this and other EDGs.

replacing the fuel corrected the cause of this problem. This is yet another case that A root cause analysis team was formed and supports fuel analysis and trending. by a process of elimination settled on possible fuel oil-lube oil incompatibility.

High Pressure Fuel Leak They found that compatibility depends, in part, on the type of fuel being burned, as the During a post-maintenance test run of a 4- lubricating oil contains an additive package stroke cycle diesel engine, a maintenance that neutralizes the products of combustion, supervisor noticed fuel spraying from the most importantly sulfuric acid, to prevent high pressure line for cylinder 1R. He engine corrosion. The amount of additive immediately ordered the unit shut down. A needs to be adjusted as a function of the fire hazard existed since the number 1R fuel sulfur content of the fuel oil.

pipe was in close proximity to the hot exhaust piping and right bank turbocharger! The lubricating oil originally selected was an American Petroleum Institute (API) CD-The immediate corrective action required grade synthetic oil. For the fuel oil used in replacement of the high pressure fuel pipe. the engines at that time, the specification Since this type of fuel leakage was not was for sulfur content not to exceed 0.30 uncommon, the engine manufacturer percent. In early 1995, the supplier of fuel developed a double wall fuel pipe for oil switched to "low sulfur" fuels having 0.05 replacement, one with more gradual bends. percent (500ppm) or less in order to meet With the outer wall, should a leak develop in new Environmental Protection Agency the high pressure pipe, the fuel would be requirements intended to reduce sulfuric captured and directed to a return or drip line. acid emissions. With the reduced amount of The fuel would then be returned to the fuel sulfur, there would be more unreacted oil storage tank. additive in the lubricating oil, resulting in the formation of deposits when some of the oil Pre-operational and post-operational walk- was burned. These deposits built up behind around inspections are important, as are the piston rings, forcing the rings to extrude those conducted during the run. This case and come into contact with the cylinder liner could have easily resulted in a serious fire. wall, resulting in scuffing.

Rev 3/16 13-11 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns After this problem was identified, the safety- all of them are manageable using ordinary related EDG was rebuilt with new cylinder means and methods. Alert licensees with a liners, pistons, and piston rings. On the proactive, condition based approach to EDG basis of the findings of the root cause system maintenance will not be impacted by analysis team, the safety-related EDG was the changes in Sulfur content from 3000ppm supplied with different lubricating oil, an API to 50ppm and now 15ppm. It will simply CG-4 grade mineral-based oil. A series of require them to evaluate potential ULSD acceptance tests were then run to validate impacts and, in concert with their fuel oil, the root cause. After 90 hours0.00104 days <br />0.025 hours <br />1.488095e-4 weeks <br />3.4245e-5 months <br /> of operation lube oil, additive, and filter suppliers, as well the safety-related EDG was inspected and as tank monitoring specialists, take the no abnormal conditions were found. See IN measures needed to ensure their plant 96-67. operations remain consistent with their current design and licensing basis.

NOTE: Another characteristic of synthetic lubricating oil was identified during review of Several diesel fuel properties other than this event. Synthetic oils contain diester sulfur concentration change as a result of additives required to improve solubility of oil moving to ULSD. Any of the following additives. In diesel engines with low oil characteristics may adversely affect diesel sump temperatures, water may accumulate engine performance. See IN 2006-22.

in the sump because the temperature is too low to vaporize it. This water might cause Energy Content hydrolysis of the diesters and the resulting acids would react with calcium in the In general, the processing required to additive to form insoluble compounds reduce sulfur to 15 ppm also reduces the (soaps). These compounds may clog filters aromatics content and density of diesel fuel, and degrade diesel engine performance. resulting in a reduction in volumetric energy content (BTU/gallon). The drop in energy 13.7 CONCERNS FOR ULTRA-LOW content is 1.2 percent, or more. Less energy SULFUR FUEL, REQUIRED IN content of the fuel can reduce the 2010 (ULS = 15PPM MAX S) instantaneous output rating of the diesel engine. The reduced output rating may be ULSD has a number of properties that have less than the value specified in the plants potential to degrade or render inoperable design and licensing basis, potentially the associated diesel engine or may create rendering the diesel inoperable.

a condition that is inconsistent with current plant design and licensing bases. The The reduced energy capacity of the ULSD ULSD issue effects all licensee diesel may result in increased fuel consumption generators that are safety-related and / or such that the onsite fuel storage capacity for important to safety, thereby, presenting a the emergency diesel generators may be possible common mode failure. However, insufficient to satisfy the plants design and although there are *potential* effects from licensing basis for diesel operation duration ULSD fuel oil, experience has taught us that before offsite replenishment is needed.

Rev 3/16 13-12 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Fuel Particulate Build-up Increases Incompatible Metals Additives to increase lubricity and to inhibit There are no known compatibility issues corrosion used by different refineries and with aluminum, carbon steel, stainless steel, wholesale suppliers can react or become and bronze. However, copper and zinc are unstable in storage, which can result in incompatible with ULSD because both are increased fuel particulates that may foul or oxidative catalysts that will accelerate the plug filters and fuel injection equipment, and formation of sediments, gels, and soaps can affect suitability of some testing (ASTM D975, Appendix X2.7.2).

methods.

Lubricity Some nuclear plant licensees using ULSD have observed an increase in the rate of Lubricity is a measure of the fuels ability to particulate buildup in samples from their lubricate and protect the various parts of the diesel fuel oil storage tanks. engines fuel injection system from wear.

The processing required to reduce sulfur to Fuel System Seal Leaks 15 ppm also removes naturally-occurring Non-nuclear industry operating experience lubricity agents in diesel fuel. Rotary and using ULSD shows an increased incidence distributor type fuel pumps are completely of fuel system leaks at points where fuel-lubricated resulting in high sensitivity to elastomers (O-rings) are used to seal joints, fuel lubricity. Refiners treat the diesel fuel with most leaks occurring at the fuel pump with additives on a batch to batch basis to and injectors. The evidence to date ensure adequate lubricity. Therefore, receipt suggests the problem is linked to a reduction of ULSD with inadequate lubricity is in the aromatics content of the ULSD which possible, but unlikely.

affects seal swelling, as does seal material and age of the material. 13.8 COMBUSTION / VENTILATION AIR Compatibility with Lubricating Oil Engine Exhaust and /or Room Cooling Exhaust Recirculation to Intake(s)

See previous discussion for IN 96-62. The concerns for ULSD mirror those for LSD and Manufacturers' ratings of emergency diesel the industry has learned much about them. generators for specific applications are based upon specific maximum for EDG Microbial Growth room temperature and combustion air inlet temperature, non-contaminated combustion Diesel fuel that was desulfured at the air with proper oxygen content, and specific refinery through hydrocracking (versus maximum for intake air depression and hydrotreatment) may have a greater exhaust back pressure.

propensity for microbial growth due to an increased concentration of n-alkanes (linear Several licensees have discovered molecules). problems in one or more of these areas.

Rev 3/16 13-13 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Most often there has been a problem with Cleaning Effect:

combustion exhaust and /or room cooling exhaust recirculation back into the room, B5 has a solvent effect that loosens and /or combustion air intakes. Root accumulated sediment in fuel oil storage Causes have been lack of consideration of tanks, possibly clogging filters. If fact, it will other roof top or adjacent structures, the actually dissolve some kinds of paint if left effects of wind direction/pressure, and the on long enough. Licensees can clean tanks, suction created by the air intakes. upgrade filters, and check filters more often before any use of B5 (if they are even aware Recently when a manufacturer provided up- of it).

rating modifications of 10 percent for installed EDG units, the licensee could not Water:

take advantage of it without first eliminating up to 15 percent recirculation of engine and B5 contains suspended water particles from ventilation exhausts back into the engine its manufacturing process. The water will, in combustion and cooling air intakes. time, fall out of suspension and form "dirty water" in the fuel oil storage tank, which 13.9 SPECIAL CONCERNS FOR eventually leads to the formation and growth BIODIESEL FUEL (B5) of algae. Licensees can use a moisture dispersant and biocide, add a fuel-water In 2008 the American Society for Testing separator to the system, and keep tanks and Materials approved a change to ASTM topped off.

D975-08a, Standard Specification for Diesel Fuel Oils. Effective in early 2009, No. 2 Biodegradation:

petrodiesel fuel oil could have up to 5%

biodiesel blend (B5) without being so B5 is biodegradable, and the presence of labeled, as if still a petroleum-only product. water, heat, oxygen, and other impurities accelerate the degradation of the fuel The NRC is very concerned at the potential supply. Storage for longer than 3-6 months implications of this action. Their position is not recommended.

included this statement: "The introduction of biodiesel blends into the No. 2 diesel fuel Material Incompatibility:

supply raises potential generic applicability and common-cause failure concerns Brass, bronze, copper, lead, tin, and zinc in because of the possibly adverse physical tanks and fittings may accelerate the properties associated with biodiesel use in oxidation process of B5, creating fuel diesel engines including the safety-related insolubles or gels and salts. Licensees emergency diesel generators (EDGs)." should avoid using zinc linings, copper pipes and fittings, or brass regulators with B5.

For the reasons discussed below, a B5 They should also verify that elastomeric blend could be problematic for EDGs and materials, such as hoses, gaskets, and O-other safety function diesel engines: rings are compatible with B5.

Rev 3/16 13-14 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Temperature Protection: The arrangement included one watt-hour meter to sum the power to both safety Biodiesel's components have higher cloud busses. This interconnection of protection points than petroleum components and they and metering circuits between two safety vary considerably with the source of the busses was identified by the inspectors as a biodiesel feedstock, which is not even common-mode failure vulnerability. A specified in B5 blends. failure on this interconnected circuit, such as a fire-induced cable fault or watt-hour meter The net effect of unlabeled B5 diesel fuel oil failure, would be interpreted by the may not be known for some years. It is yet protection system as an electrical bus fault another reason for licensees to have an on both safety busses. Consequently, the effective program of fuel oil sampling, test, relay logic would lock out both redundant and analysis. For additional information see safety buses and prevent re-energization IN 2009-02. from any power source.

13.10 SWITCHYARD / DISTRIBUTION The licensee modified the wiring in the overcurrent protection circuits to align each Single-Failure and Fire Vulnerability of monitoring circuit to one safety bus and to Electrical Safety Buses disconnect the watt-hour meters. In this corrected configuration, each circuit is During a triennial fire protection inspection contained within one switchgear, so that a of a nuclear power station, NRC inspectors single fault or a fire will affect only one safety discovered an electrical protection and bus.

metering circuit which, if damaged, could electrically lock out redundant safety buses NOTE: Chapter 1 introduced the concept and prevent re-energization of the buses that onsite power supplies are required to be from either of the offsite power sources or redundant and independent, such that safety functions could not be compromised emergency diesel generators (EDGs).

by a single failure in either one. Following the situation described above, inspectors The safety buses were normally powered by found similar single-point vulnerabilities at one of two offsite sources. Each bus also five other NPPs and concluded that such had an EDG for standby power. The problems were likely widespread.

electrical protection and metering system used current transformers for measuring Large Transformer Failures power consumption and sensing overloads or faulted conditions. The protection and Industry operating experience has indicated metering circuit for each offsite power an increasing trend in large transformer supply included three CTs at the feeder failures. Improved preventive maintenance breaker to each safety bus, phase over-and monitoring practices have helped to current relays, and ground overcurrent identify some problems before they relays, all connected in a basic residual developed to the point of failure, but the scheme.

Rev 3/16 13-15 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns number of large transformers events has not NRR staff reviewed the available operating decreased and, in fact, continues to rise. experience of cable failures and observed that some cables at nuclear power plants, Transformer failures have resulted in eight which were qualified for 40 years through declared plant events from January, 2007, the licensees equipment qualification to February, 2009, making them the second programs, were failing before the end of leading reason for such declarations. While their qualified life. Staff identified 23 LERs the large transformer failures have generally and two morning reports from 1988 to 2004 been non-safety related, they are within the that described failures of buried medium-scope of the Maintenance Rule, 10 CFR voltage AC and low-voltage DC power 50.65. A review of licensees root cause cables as a result of insulation failure. A evaluations for the large transformer failures particular failure mode of medium voltage show that the events are often the result of cables subject to wet conditions, called ineffective implementation of the water treeing, is shown in Figure 13-4.

transformer maintenance program.

Some utilities have installed an online The most recent Information Notice on this automated oil analysis and monitoring subject included descriptions of specific system to support decisions regarding cable failure occurrences at Monticello, preventive and corrective maintenance to Fermi, Point Beach, Beaver Valley, Wolf improve transformer reliability. IEEE Creek, Callaway, Peach Bottom, Three Mile Standard C57.140-2006, IEEE Guide for Island, and Vermont Yankee nuclear power the Evaluation and Reconditioning of Liquid stations. This underscores concerns that Immersed Power Transformers, provides many licensee are not maintaining safety-guidance on this matter. However, NRC has related power or low voltage cables in their not endorsed this document and the designed and tested environment.

recommendations it contains are not NRC requirements. See IN 2009-10. The NRC issued GL 2007-01 to gather information on inaccessible or underground Submerged Electrical Cable Failures power cable failures for all cables that are within the scope of the Maintenance Rule, In 2006, the NRC began a detailed review of 10 CFR 50.65. The NRC expects licensees underground electrical power cables after to identify conditions that are adverse to moisture-induced cable failures were quality for cables, such as long-term identified at several plants. The cables were submergence in water.

exposed to submergence in water, condensation, wetting, and other stresses. Upon discovery of a submerged condition, Because these cables are generally not the licensee should take prompt corrective designed or qualified for submerged or wet actions to restore the environment to within environments, the possibility that more than the design specifications for the cable, one cable could fail has increased and such immediately determine its operability for the multiple failure could disable safety-related design function, and determine the impact of accident mitigation systems. such adverse environment on the design life Rev 3/16 13-16 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns of the cable. These corrective actions

  • The overall LOOP frequency is more typically involve the removal of water, the than twice as high during the summer installation of a sump pump or repair of the period, compared to the average.

drainage, and cable evaluation including testing where appropriate.

  • The probability of LOOP after a reactor trip is greater during the summer period.

Long-term corrective actions should involve establishing a condition monitoring program

  • All 4 categories of LOOP events (plant, for all cables which are inaccessible and switchyard, grid, and weather-centered) underground and under the maintenance had higher frequencies during the rule, including testing of cables to verify they summer period.

are not degraded, as well as visual inspection of underground cableways for Although no specific recommendations were water accumulation, to assure continued made, these data have a number of cable operability. See IN 2010-26. potential safety implications for licensee operations, including their scheduling of 13.11 GRID RELIABILITY CONCERNS maintenance on EDGs and other safety systems. See IN 2006-06.

LOOP / SBO More Likely in the Summer Grid Reliability Impact on Plant Risk In 2003 the NRC released NUREG-1784, a study showing that switchyard and grid- On 14 August 2003 the largest power related LOOP events occurred mostly outage in U.S. history occurred in the during the summer months. A subsequent Northeastern United States and parts of report confirmed an increased frequency of Canada. Nine U.S. NPPs tripped, of which loss-of-offsite power (LOOP) and station eight lost offsite power, along with one NPP blackout (SBO) events during the summer that was already shut down. The length of period (i.e., May through September). time until power was available to the switchyard ranged from approximately one A new report by INEL, NUREG/CR-6890, hour to six and one half hours. Although the "Re-evaluation of Station Blackout Risk at onsite emergency diesel generators (EDGs)

Nuclear Power Plants," was published in functioned to maintain safe shutdown December 2005 (ADAMS Accession Nos. conditions, this event was significant in ML060200477, -060200479, -060200510). terms of the number of plants affected and The new report confirmed the earlier the duration of the power outage.

observations and showed the following insights regarding seasonal risk trends: The loss of all alternating current (AC) power to the essential and nonessential

  • The SBO risk increased by a factor of switchgear buses at a NPP involves the two during the summer period between simultaneous loss of offsite power (LOOP),

1997 and 2004. There were 22 summer turbine trip, and the loss of the onsite and 2 non-summer LOOP events. emergency power supplies (typically EDGs).

Rev 3/16 13-17 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Such an event is referred to as a station

  • Real-time NPP operator knowledge of blackout (SBO). Risk analyses performed grid status, especially whether loss of the for NPPs indicate that the SBO can be a NPP will result in a LOOP event.

significant contributor to the core damage frequency. Although NPPs are designed to

  • Real-time TSO knowledge of the NPP cope with a LOOP event through the use of status, especially grid-risk-sensitive onsite power supplies, LOOP events are maintenance activities.

considered precursors to SBO. An increase in the frequency or duration of LOOP events

  • Determine if additional NPP operator increases the probability of core damage. training is needed for the above.

It is clear that the grid has become more It is especially important that the NPP stressed. The underlying causes of lower operator know when the trip of the NPP will reserve capacity or coping ability are not as result in a LOOP to the plant. A reduction in important as taking actions to compensate NPP switchyard voltage due to a trip is the for the perceived decrease in grid reliability. main cause of a LOOP event. It is important Complicating the equation is the fact that to understand the transmission systems can LOOP events can have other unpredictable generally tolerate voltages lower than initiators such as natural events, potential required by NPP TS for system, structures adversaries, human error, design problems, and components (SSC) operability. As a etc. In response to grid reliability concerns, result, the TSO will not necessarily keep the the NRC issued Generic Letter 2006-02: transmission system voltage above the level "Grid Reliability and the Impact on Plant needed for the NPP unless the TSO has Risk and the Operability of Offsite Power." been informed of the needed voltage level and agreements have been formalized to A full discussion of GL 2006-02 is beyond maintain the voltage level.

the scope of this Course. Licensees were directed to provide substantial data relative 13.12 THE TICKING CLOCK: AGING to grid concerns. Some of its goals are: ISSUES RELEVANT TO EDGS

  • Better communications between the Post-TMI Load Creep NPP operator and the Transmission System Operator (TSO) regarding grid At first glance this may not seem to be an and plant status. aging issue but the design basis of a plant can become outdated due to changes. As
  • TSO use of analysis tools to determine safety equipment is modified, replaced, or the impact of the loss or unavailability of updated the EDG loads often change. Other various transmission system elements. factors such as ULS diesel fuel oil affect EDG calculations. The issues described by
  • The establishment of protocols between IN 93-17 and the subsequent TI 2515/176 NPP's and TSO's, especially relating to regarding EDG design basis adequacy are communications. also relevant.

Rev 3/16 13-18 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Underground Fuel Tanks Electric Cable Insulation Degradation All UG steel fuel tanks will eventually leak. Concerns about submerged electrical cable It's only a question of when. Coatings and failures have already been discussed in this well-maintained cathodic protection will Chapter. NRC Generic Letter 2007-01 had delay the inevitable but licensees must be a broader perspective, all underground or vigilant for tank problems, as water and rust inaccessible cables within the scope of 10 will severely compromise EDG fuel oil. An CFR 50.65. It requested licensees provide effective program of fuel oil analysis and a history of failures involving such cables.

trending must be in place. See RG 1.132 Further, it asked them to describe their cable Rev 2 (June 2013). It now specifies flash inspection, testing, and monitoring point as a fuel quality to check before off- programs to detect the degradation of those loading (further tests later), requires tanks to that are inaccessible or underground and be checked for condensate (water) monthly, support EDGs, offsite power, etc.

and sets a 10-year cycle for tanks to be drained, cleaned, and internally inspected. Cross-linked polyethylene insulated cable (Type XLP) has been an electrical industry Replacement Parts Unavailability concern for decades, whether in wet or dry locations. XLP is no longer manufactured This is impacting all NPP systems. For and it deserves special attention. Cable EDGs the concerns include legacy engine monitoring programs must deal with the fact governors, as well as circuit breakers, there is no single non-destructive test to relays, and parts for engine accessories or accurately predict failure.

support systems. Substitution of other components may be necessary. For those seeking more information on this subject, the NRC has issued NUREG/CR-7000 (BNL-NUREG-90318-2009), "Essential NRC has expressed concern about the Elements of an Electric Cable Condition process of Commercial Grade Dedication Monitoring Program."

(CGD), whereby suppliers dedicate ordinary commercial-grade parts for NPP safety function use. This should involve evaluation Battery Expected Life and its Potential of critical characteristics including function, Impact on Surveillance Requirements environmental, seismic, EMI / RFI, etc. In some cases the evaluations can take credit Class IE batteries used to supply DC loads for testing done on similar items. However, at NPPs are the lead-acid type and degrade NRC has found instances where that was over time, primarily due to buildup of Lead improperly applied, or similarity was not Sulfate on the plates. Battery curves will established. Inadequate implementation of typically show the capacity tapering off to the CGD process may result in commercial- 80% at 20 years, the presumed end-of-life.

grade items not being properly applied to At that point IEEE 450-2002, endorsed by perform safety functions. See IN 2014-11. RG 1.129, recommends replacement.

Rev 3/16 13-19 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns These batteries serve a critical function, as The Human Factor: The Heavy Loss of they provide power during station blackout Experienced Personnel (SBO) for EDG starting and loading, many instrumentation and control circuits, and A high percentage of those who entered the emergency lighting. NRC has expressed nuclear industry in its earlier years are concern that NPP Tech Spec Surveillance retiring. Their departure is impacting the Requirements may be non-conservative, as experience level at licensee facilities and they may not consider post-TMI load creep, also within NRC. That poses a challenge for all post-accident DC loads resulting from both regulators and licensees as the nuclear plant Design Basis Events, or operating power industry has to gear up for the new near minimum temperature. Accordingly, an wave of plant construction and operations.

85% capacity assumption at 15 years of It cannot be allowed to impact NPP safety.

service was viewed favorably. Licensees The real challenge is how to assure that.

were also alerted that surveillance criteria might need adjustment to be conservative 13.13 INDUSTRY EDG ACTIVITIES for expected battery life. See IN 2013-05.

The nuclear industry employs several Beyond-Design-Basis Events: Flooding mechanisms to address issues such as EDG failures, events, and mitigation of Fukushima will be studied for decades as a failure impact on operability and reliability.

classic beyond-design-basis event. In that Utilities and EDG manufacturers participate instance, new information had resulted in in Owner's Groups that track specific EDG aging of plant design assumptions. After problems, develop operational and /or Fukushima, NRC focused on a spectrum of maintenance solutions, and also issue potential flooding events: storm surge, river documentation for other EDG users and flooding, dam breakage, etc. Some plants industry support organizations. Owner's have vulnerabilities for flooding from events Groups for Cooper-Bessemer, Fairbanks-less than their design basis, as a result of Morse, EMD, and Cooper Industries/

infrastructure deterioration. See IN 2015-01 Enterprise Group keep abreast of EDG problems through "Alert Lists."

Accumulated Impact of Unnecessary Fast Starts of EDGs Support organizations such as the Electric Power Research Institute (EPRI) and the Some licensees still persist in performing Institute of Nuclear Power Operations fast starts with immediate heavy loading, a (INPO) help disseminate EDG operational topic that has been extensively discussed in and failure data to all Owner's Groups this Manual. They are damaging their EDGs through the Nuclear Plant Reliability Data and taking years off of useful life. This is System (NPRDS). INPO also maintains an particularly troublesome in view of the equipment failure data base (EPIX). The license extension for many plants. They World Association of Nuclear Operators need to understand the new direction of (WANO) serves a similar global role.

IEEE 387-1995 and RG 1.9 Rev 4 Rev 3/16 13-20 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Figure 13-1 Correct and Incorrect Air Start Motor Sub-Assembly Rev 3/16 13-21 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Figure 13-2 Location of Defective DeLaval Governor Drive Coupling Rev 3/16 13-22 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Figure 13-3 Location of Missing Cooper KSV Engine Valve Keeper Seals Rev 3/16 13-23 of 24 USNRC HRTD

Emergency Diesel Generator Case Studies: Lessons Learned, and Concerns Figure 13-4 Depiction of Water Tree in Electrical Cable Insulation (Fault paths utilize microscopic bubbles of ionized gas that conduct)

Rev 3/16 13-24 of 24 USNRC HRTD

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