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Operating Experience Smart Sample (OpESS) FY 2008-01

ANegative Trend and Recurring Events Involving Emergency Diesel Generators@

Highlighted documents have an active hyperlink. 

OBJECTIVE: 

To support NRC inspector’s review of emergency diesel generators (EDGs) problems by giving 

performance insights and related operating experience (OpE) references. This OpESS provides 

follow-up for NRC IN 2007-27, ARecurring Events Involving Emergency Diesel Generator 

Operability@ and NRC Information Notice 2007-36: Emergency Diesel Generator Voltage Regulator 

Problems. This OpESS is a voluntary inspection activity performed under the baseline program. 

BACKGROUND: 

Based on the recent negative trend information and several EDG issues and concerns, the OpE 

clearinghouse and NRR management directed development of this Operating Experience Smart 

Sample (OpESS) to focus inspector attention in this area. 

NRR staff review of recent operating experience related to EDG failures identified several recurring 

events and general negative trends, [see NRC Information Notice, IN 2007-18 “Recurring Events 

Involving Emergency Diesel Generator Operability “ issued on August 6, 2007, an the NRC 

Information Notice 2007-36: “Emergency Diesel Generator Voltage Regulator Problems” issued on 

November 15, 2007 . The staff noted that since the beginning of 2004, eight of the 27 “greater than 

Green” inspection findings within the mitigating systems cornerstone have been EDG-related, (one 

Yellow and seven White findings). These EDG related findings generally involved either the failure 

to take prompt corrective action, the failure to perform adequate post-maintenance testing, or the 

failure to follow procedures. 

One recurrent issue that continues to stand out involves the vibration-induced failure of EDG piping 

and tubing. In many cases, piping/tubing failures occurred after minor leaks were already identified 

and not immediately or properly repaired by the licensee. One licensee recently noted that (1) the 

training for their employees did not cover common tubing failure mechanisms and (2) their 

managers and supervisors were not aware of industry operating experience relating to these types 

of failures. 

To prevent these types of failures, it is important that EDG piping and tubing be properly routed, 

supported and maintained. This topic was previously addressed in 1989 by NRC IN 89-07, “Failures 

of Small-Diameter Tubing in Control Air, Fuel Oil, and Lube Oil Systems Which Render Emergency 

Diesel Generators Inoperable,” dated January 25, 1989.

One means of measuring EDG reliability is the NRC Mitigating System Performance Index (MSPI). 

The MSPI Performance Indicator for Emergency AC Power Systems measures the sum of the 

unavailability of the emergency AC power plus the unreliability for the emergency AC power system 

during the previous twelve quarters. 

NRR OpE staff noted that seven units were listed as “WHITE” in the 2nd Quarter 2007 for this 

Emergency AC power system performance indicator. The seven units were: Brunswick 1 & 2, 
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Cooper, Kewaunee and the Oconee site, a three unit site which is unique as it relies on hydro units 

for its emergency AC power source. 

The reliability of EDGs can be one of the key factors affecting the risk of core damage (due to 

station blackout event potential). Assuring the high reliability and availability of EDGs at nuclear 

power plants contributes greatly to reducing the probability of a station blackout event and 

improving overall nuclear plant safety. 

As stated in Regulatory Guide 1.155 “Station Blackout,” section 1.2, Reliability Programs: 

The reliable operation of onsite emergency AC power sources should be ensured by a reliability 

program designed to maintain and monitor the reliability level of each power source over time for 

assurance that the selected reliability levels are being achieved. An EDG reliability program would 

typically be composed of the following elements or activities (or their equivalent): 

1. Individual EDG reliability target levels consistent with the plant category and coping duration 

selected from Table 2 [of Regulatory Guide 1.155] 

2. Surveillance testing and reliability monitoring programs designed to track EDG performance and 

to support maintenance activities 

3. A maintenance program that ensures that the target EDG reliability is being achieved and that 

provides a capability for failure analysis and root-cause investigations 

4. An information and data collection system that services the elements of the reliability program 

and that monitors achieved EDG reliability levels against target values 

5. Identified responsibilities for the major program elements and a management oversight program 

for reviewing reliability levels being achieved and ensuring that the program is functioning properly. 

The testing of EDGs to ensure operability is discussed extensively in NRC Regulatory Guide 1.9, 

“Application and Testing of Safety-Related Diesel Generators in Nuclear Power Plants” was 

revised in March 2007, (Revision 4). As stated in the RG 1.9 Section (D); “Implementation: Except 

in those cases in which an applicant or licensee proposes or has previously established an 

acceptable alternative method for complying with specified portions of the NRC’s regulations, the 

methods described in this guide will be used in evaluating (1) submittals in connection with 

applications for construction permits, standard plant design certifications, operating licenses, early 

site permits, and combined licenses; and (2) submittals from operating reactor licensees who 

voluntarily propose to initiate system modifications involving diesel generators used as onsite 

emergency electric power systems.” 

SOURCE DOCUMENTS: 

1) NRC Information Notices (4): 

NRC IN 2007-27, ARecurring Events Involving Emergency Diesel Generator Operability@ 

(Available in ADAMS ML071760544) 

NRC Information Notice 2007-36: Emergency Diesel Generator Voltage Regulator Problems.

(Available in ADAMS ML072780394) 

NRC IN 98-43: “Leaks in the Emergency Diesel Generator Lubricating Oil and Jacket Water Piping”

(Available in ADAMS ML031040540) 

 
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NRC IN 89-07, “Failures of Small-Diameter Tubing in Control Air, Fuel Oil, and Lube Oil Systems 

Which Render Emergency Diesel Generators Inoperable,” (Available in ADAMS ML031180501)

3) NRC REGULATORY GUIDE 1.9, APPLICATION AND TESTING OF SAFETY-RELATED DIESEL 

GENERATORS IN NUCLEAR POWER PLANTS , revised March 2007, (Revision 4).

 

4) Baseline inspection procedures are to be used for performing this OpESS and can include 

inspection procedures used for performing EDG system alignment inspection, EDG surveillance 

testing, post maintenance testing or PI&R corrective action follow-up inspections related to EDG 

issues. Links to these baseline procedures are provided in the inspection guidance section.

CORNERSTONES: Mitigating Systems (100%) 

APPLICABILITY: All licensed operating commercial nuclear reactors with EDGs. Applicable portions 

of this guidance may also be useful for inspecting sites using station blackout (SBO) or safe shut down 

facility diesel generators or for diesel-driven pumps. 

INSPECTION GUIDANCE: 

$ IP-71111.04, AEquipment Alignment” 

$ IP-71111.15 “Operability Evaluations”

$ IP-71111.19 “Post Maintenance Testing”

$ IP-71111.22 “Surveillance Testing”

$ IP-71152 “Problem Identification and Resolution” 

The above procedures provide baseline inspection program attachments that are used to support 

various EDG inspections and follow-up on EDG issues. Review, as applicable – (ideally during a 

complete walkdown per IP-71111.04, “Equipment Alignment,” for the site specific EDGs, using the 

additional EDG inspection guidance described below and in this OpESS Attachment): 

1) Review the Background and Source Document Sections of this OpESS and the related documents 

as needed to obtain a general understanding of some of the various EDG concerns (i.e., vibrationinduced failures of EDG piping and tubing and failure to take prompt corrective action, especially 

related to repair of EDG fluid leaks or inadequate EDG post-maintenance testing, etc.). 

2) During equipment alignment walkdowns, surveillance testing or post maintenance testing look for 

signs of excessive tubing / piping vibration and for any signs of leaks and click to view a previous 

NRC Information Notice 98-43: Leaks in the EDG Lubricating Oil and Jacket Cooling Water Piping). 

Ensure the licensee has entered these vibration and leak type issues into their CAP, work request 

programs, etc. and addresses them in a timely manner, as appropriate. Note: The common underlying 

cause of these failures often is the inadequate design or installation of the supports for the smalldiameter tubing in a high vibration environment. Inspect the related tubing supports and any grommets 

(rubber vibration dampeners) to verify they are properly installed. 
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3) Closely review any EDG voltage regulator issues and related licensee related corrective actions. 

Ensure EDG voltage regulator is restored to the position specified in the associated surveillance 

procedure following testing. Refer to NRC IN 2007-36,”Emergency Diesel Generator Voltage 

Regulator Problems.”

Note: This completes the OpESS, however, other EDG inspection guidance and an inspection tool for 

consideration by inspectors is provided in the “ATTACHMENT” to OpESS FY2008-01 Negative trend 

and Recurring Events Involving Emergency Diesel Generators.”

REPORTING INSPECTION RESULTS / TIME CHARGES / ADDITIONAL ISSUES: 

Document any inspection result findings, as applicable, in an integrated inspection report (i.e., 

quarterly inspection report/ PI&R or CDBI report) and reference the title/ OpESS number (example: 

AReview of Operating Experience Smart Sample: OpESS FY2008-01,A Negative trend and 

Recurring Events Involving Emergency Diesel Generators.@ If no findings are identified 

document completion of the OpESS using the AOpESS number/ title@ under the applicable 

inspection attachment (i.e., 1R04,) stating that no findings of significance were identified. 

Inspection time for this OpESS is to be charged to the normal baseline procedure under which it is 

being documented (along with any routine preparation and documentation charge times). 
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ATTACHMENT

(OpESS FY2008-01 “Negative trend and Recurring Events Involving Emergency Diesel 

Generators” - (additional inspection guidance for consideration)

1) Inspector sites should consider establishing a site specific EDG inspection notebook that retains 

important reference information and guidance for use related to their site specific EDG inspections, 

operability issue reviews, etc. This handbook can be used during new resident training and during 

turnover at the site. The below information provides some general EDG supplemental inspection 

guidance for consideration in this EDG notebook development. 

2) Review licensee testing and procedures to ensure they conform with NRC Regulatory Guide 1.9, 

that states: “conformance with the guidelines in IEEE Std 387-1995 (Ref. 3) constitutes an 

acceptable method for satisfying the Commission’s regulations with respect to the design, 

qualification, and periodic testing of diesel generators used as onsite electric power systems for 

nuclear power plants,” [note: subject to the exceptions, as discussed in NRC Regulatory Guide 1.9]. 

3) Prior to performing baseline inspections on the EDGs, inspectors should consider reviewing the 

licensee CAP documents (perform a search of the licensee CAP for EDG system related issues) to look 

for negative EDG trends or specific CAP issues that should be examined further. Review Maintenance 

Rule documentation (any “a1” status corrective actions status, etc). Look for incomplete actions, 

inadequate or untimely corrective actions related to EDG issues. 

4) Prior to performing baseline inspections on the EDGs, inspectors should consider reviewing 

outstanding (open) work orders, work history / maintenance records, equipment deficiencies, and any 

temporary system modifications existing on the EDGs. Review these to ensure they have been 

appropriately entered into the licensee’s CAP or other appropriate program and have been resolved or 

are being resolved in a timely manner, appropriate to their level of safety significance. 

5) Review typical operational parameters based on the licensee procedures/vendor guidance/ EDG 

design basis and Technical Specification surveillance requirements for the applicable site EDG to 

ensure that it is operable. Review current or past EDG operating data recorded during testing including 

applicable system engineer EDG trend analysis data, as necessary. 

To ensure EDG readiness for operation, inspect during routine plant status walkdowns, or during other 

baseline inspections related to the EDG the following items, as necessary. Some of these may need to 

be verified by actual observation during licensee operator rounds, or licensee conducted operational 

testing or surveillance test runs. These EDG operability type items typically include, but are not limited 

to, the following types of operational parameters (which may include minimum/maximum values): 

 Parameter(s) - (minimum /maximum values, as applicable, etc.) 

a.) Starting Air Pressure ________ ________ 

b.) Fuel Oil tank levels: 

 EDG Day tank level _______ ________ 

 

 Main EDG Fuel Oil Storage tank level ________ ________ 

c.) Lubricating oil - proper level _______ ________ 
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 Parameter(s) - (minimum /maximum values, as applicable, etc.) 

d.) Cooling (i.e., jacket) water level ________ ________ 

e.) Cooling water / keep-warm temperatures ________ ________ 

f.) EDG Governor settings proper ________ 

g.) Overspeed trip level (in the correct run position) ________ 

h.) Fuel racks -no paint/ obstructions, and free of binding when licensee moves them by hand ______ 

i.) System valve alignment (using licensee procedures, locked valve control procedures, etc. / using IP71111.04, Equipment Alignment guidance, develop a site specific alignment checklist (note: consider 

periodically checking starting air and fuel transfer valve alignments even during routine plant status 

walkdowns) ______ 

j.) Barring of the engine (performed prior to operation - to check for water/ fuel/ oil leaks into the 

cylinders with the cylinder test valves open and fuel racks in the no fuel position, normally prior to 

licensee surveillance testing ________ [Note: observe during NRC IP-71111.21 Surveillance 

Testing baseline sample, however, this item is not applicable for EDG “fast start” surveillance testing] 

k.) Engine/ generator reaches rated speed (rpm) and voltage and frequency per Tech Specs _______ 

l.) Review additional “operating parameters” and trends to be in accordance with licensee procedure/ 

vendor recommendations during loaded runs (such as trends of jacket water temps, cylinder exhaust 

temperatures and differentials, lube oil temperatures, lube oil pressure, fuel oil pressure and EDG 

crankcase pressure). Especially consider any need for filter or strainer element cleaning / replacement 

that may be indicated by these types of parameters/ trends. ______ 

m.) Check for unusual noises (that may indicate signs of mechanical trouble) and ensure they are 

investigated and documented by the licensee _____ 

n.) Check for unusual smells that may indicate coolant or fuel leaks, over-heating, and for any smoke 

or burned discolored paint, etc. that may indicate problems; ______ 

o.) Review the EDG room for proper transient combustible and fire ignition control (hot work) ______ 

p.) Check the EDG for fluid/air/ exhaust system leaks (cooling system, fuel oil system, lube oil system, 

exhaust system, air system and ensure the licensee is aware / captures these in the appropriate 

response program (CAP or work order/equipment deficiency programs) _____ 

q.) Verify the EDG shuts down properly in accordance with licensee procedure (observing for abnormal 

conditions, such as voltage regulator swings or excessive frequency variations, etc.) _______ 

 

r.) Review operator logs and procedures during and following surveillance testing (to ensure they are 

followed and that the loading; speed and voltage (power factors, etc) are properly conducted and the 

necessary operating data is correct. Pay particular attention to any notes of comments recorded in the 
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procedure(s) by operators that may indicate abnormal conditions exist (verify necessary actions such 

as work orders/ corrective action documents were generated). _______ 

s.) Discuss concerns of EDG performance with the appropriate personnel to gain their insights into 

potential EDG issues, consider including: 

Operator(s) ______ 

Maintenance personnel ______ 

System engineer(s) ______ 

 

t.) Review trending reports and/ or compare operating logs over extended time that may indicate an 

impending or slowly developing issue. ______ 

u.) Review battery / EDG related electrical system information and surveillances ______ 

v.) Review periodically the six month EDG fast load surveillance testing _____ 

w.) For periodic refueling outage EDG testing, as applicable, review the EDG testing response for: 

 

Fast Start _____ 

Loss of Off-site Power (LOOP) ______ 

Safety Injection Actuation System (SIAS) ______ 

Combined SIAS and LOOP _____ 

Largest load rejection _____ 

Design load rejection _____ 

Endurance (i.e., 24 hour run, or 8 hour run) and load margin _____ 

Hot restart _____ 

Synchronizing ______ 

Protective trip bypass ______ 

Test mode override ______ 

[Note: Refer to licensee’s TS, FSAR, EDG licensing basis documents, surveillance testing procedures 

and NRC Regulatory Guide 1.9 , as applicable for additional information guidance related to the above 

EDG surveillance test requirements]. 

x.) Review Ten-Year Testing, when applicable, (Independence testing) ______ 

This testing involves demonstrating that the trains of standby electric power are independent at a 

frequency of once every 10 years (during a plant shutdown) or after any modifications that could affect 

emergency diesel generator independence (whichever is shorter) by starting all redundant units 

simultaneously to identify certain common-failure modes undetected in single diesel generator unit 

tests. 

y.) Review EDG control panel switch lineup following testing periodically and during routine plant walk 

downs to ensure they are restored properly and the EDG remains operable and ready to start (verify 

ready to start light indication, as applicable) ______ 

6) Review chemistry test results and analysis for EDG fuel / lube oil samples to ensure that it meets 

TS/ ASTM standards (free of water, etc. per licensee TS and procedures, especially after new 

deliveries). 
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7) During maintenance activities review foreign material exclusion (FME) controls to ensure licensee is 

maintaining system cleanliness. Click to view EDG/FME related Information Notice No. 90-80: Sand 

Intrusion Resulting in Two Diesel Generators Becoming Inoperable. 

 

8) Periodically observe and/or review, as applicable, EDG related In-Service Testing (IST) vibration 

data results and discuss this EDG vibration trend analysis with the appropriate engineer(s). 

 

9) Consider for review any EDG related permanent plant modifications (using IP-71111.17) or any 

EDG related temporary modifications (using IP-71111.23), and temporary scaffolding. 

10) Review, as necessary, any EDG troubleshooting activities to ensure licensee properly identifies 

the root cause under the corrective action process. Diagnostic aids and reference materials that 

may assist the inspectors in this review may include such items as: Piping and Instrumentation 

diagrams (P&IDs), equipment drawings, system descriptions, maintenance/work history records, 

previous operating logs, CAP data base, vendor diagrams/ drawings, manufacturer maintenance 

manuals including; troubleshooting charts, parts lists, and operating experience data including 

INPO EPIX data, vendor owner’s group alert lists, etc. Also observe /conduct discussions between 

and with the system engineer(s), maintenance engineer(s), vendor service representatives and 

various troubleshooting team members and supervisors, as necessary. 

11) Periodically review any EDG engine analysis reports, EDG system health reports, on-line 

computer monitoring programs, or other unique diagnostic tools licensees use for EDG systems for 

any diagnostic or performance trending insights they may provide in following up on EDG related 

issues. 

12) During and following painting in the EDG room verify painting activities do not adversely impact 

the EDGs operability, such as fuel racks locked up due to paint preventing the diesel from reaching 

rated speed. Click to view an IN that describes this type of concern: Information Notice 91-46: 

Degradation of Emergency Diesel Generator Fuel Oil Delivery Systems . 

13) Periodically review various EDG support systems and their capability to support EDG 

operability (i.e., EDG ventilation (heating ventilation and air conditioning), service water or other 

cooling systems, EDG room sumps and drains/ flood control, fire suppression systems, and various 

electrical power supplies to EDG controls and protections. 

14) Periodically review specific electrical components and circuits that affect the EDG operation - 

(i.e., the specific testing of load sequence logic controls and relay testing, SI start initiator relays, 

load shed logic controls and relay testing, exciter and regulator, generator output breaker testing). 

During surveillance testing of the relays, and other specific components that impact EDG operation 

periodically select these surveillances for review (under IP-71111.22 Surveillance Testing). 

15) Inspectors should considering developing and retaining other EDG checklists and guidance 

information, as necessary, for inspecting their site specific EDGs. Inspector developed additional 

Inspector Additional Notes / Remarks: 

 
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 (Use additional pages as necessary) END