----- Forwarded by Jaime Pagan/RTP/USEPA/US on 12/08/2008 10:32 AM -----

Robin Weeks 

<Robin.Weeks@kirbycorp

.com>

12/05/2008 05:00 PM

To Jaime Pagan/RTP/USEPA/US@EPA

cc

Subj

ect

Jaime,

I understand the attached letter from the EMA has been sent to your attention. As a supplier to 

the nuclear power industry of emergency diesel generators, we at Engine Systems, Inc. have an 

interest in this issue as well. I would like to state our support for an exemption for emergency 

and station blackout diesel generators for large engines as discussed in the letter, as well as for 

any size engine used in this critical application. For the reasons stated below, we believe that 

the public interest is better served by providing reliable emergency diesel power for nuclear 

applications.

Safety-Related Components

Emergency diesel generators (EDGs) are required by the US Nuclear Regulatory Commission 

to be qualified for safety related service. There are a number of existing standards such as 

IEEE 387, IEEE 344, IEEE 323, and USNRC Reg Guide 1.9 among others that state the 

requirements for diesel generator qualification and reliability. My company and the nuclear 

power industry spends a great deal of resources in qualifying diesels and diesel components for 

this demanding service, as well as maintaining them over the life of the nuclear power plant, 

typically 40 years in the past, but now being extended to 60 years.

Nuclear power plants utilize commercial power sources to operate and control the reactor, 

reactor coolant pumps, and all of the normal power needs at the plant. Diesel engines have a 

long history of providing emergency backup power during loss of offsite power (LOOP) events. 

Items that provide the safety-related function are defined as components that assure:

The integrity of the reactor coolant pressure boundary

The capability to shut down the reactor and maintain it in a safe shutdown 

condition; or

The capability to prevent or mitigate the consequences of accidents which could 

result in potential offsite exposures

Note that the exposure being mentioned, is the public exposure to a radiation release from a 

nuclear power plant.

Class 1E components are the electrical components and systems in a nuclear power plant that 

have a safety-related function. Emergency diesel generators are classified as 1E components. 

IEEE 323 states:

"Class 1E equipment in nuclear power generating stations must meet its safety functional 

requirements throughout its installed life. This is accomplished by a thorough program of quality 

assurance, design, qualification, production, transportation, storage, installation, maintenance, 

periodic testing, and surveillance."

Diesel Engine Operation

The above requirements, particularly with respect to testing and surveillance has meant in the 

past that nuclear power operators start their diesel generators monthly, operate them for a 1-2 

hours, and then keep them in a standby mode until the next monthly surveillance run is initiated. 
Every refueling outage which is either on an 18 or 24 month cycle, the operators typically run 

their diesel for 24 hours.

Over the course of an entire year, these units may have fewer than 50 running hours 

accumulated. They have so few hours in fact, that the scheduled maintenance of these diesels 

is based on calendar time, not running hours as it typical of commercially operated units.

It is an open question as to whether or not diesel exhaust aftertreatment equipment can be 

successfully qualified for 1E safety-related service. One of the critical issues for qualification is 

that the safety-related component must be functional both during and after a design basis 

seismic event. If the component fails during a seismic event such that the diesel engine cannot 

operate, then the diesel generator has failed to meet it safety-related function.

In addition, if the exhaust aftertreatment were to require maintenance during operation of the 

diesel generator in an emergency, due to a failure of one of its systems or components, or due 

to a more routine service issue, then it could also prevent the diesel generator from performing 

its safety-related function, thus placing the public at risk.

In addition, emergency diesel generators are typically required to start and be ready to load 

(operating at rated voltage and frequency) in 10-15 seconds. Typical exhaust aftertreatment 

systems are not functional during such a rapid startup, and would therefore be ineffective. It 

may also be the case that the diesel is started but left unloaded during a loss of coolant incident 

(LOCA), wherein the normal commercial power supply remains available. In this case the 

exhaust temperature of the diesel engine may be too low for the exhaust aftertreatment 

equipment to function properly. 

While a solution may be to provide an auxiliary burner in the exhaust system to artificially 

elevate temperatures, this is a poor use of the limited volume of onsite stored diesel fuel which 

is devoted to the emergency needs of the diesel genset. Again, this could potentially put the

public at risk if the LOCA were followed by LOOP.

We believe it is not in the best interest of public safety for an emergency diesel generator which 

operates so few hours per year to be burdened with the additional exhaust aftertreatment 

systems required by 40CFR60. There is little to no environmental benefit, but there exists a 

potential risk to the public that the emergency diesel will be unavailable to the operate when 

required.

A requirement for exhaust system aftertreatment makes a great deal of sense for protecting the 

environment in commercial applications such as baseload power production, or peaking service. 

These are operations where the diesel engine would either be operating around the clock for 

baseload applications, or for 6-8 hours or more each day in peaking service. This is not the 

case with backup emergency power at nuclear stations.

Since emergency diesel engines operate rarely except for once per month surveillance testing, 

they have an insignificant impact to the environment. Nevertheless the complexity, added cost, 

physical size, and ongoing maintenance activities that would be associated with exhaust 

aftertreatment systems for these engines is apparently being ignored in favor of regulating 

diesel engines broadly regardless of application. More importantly, reliability may be adversely 

affected which is directly related to public safety in the event of an accident.

We believe that the risks associated with a potential release of radiation to the public far exceed 

any benefit derived from exhaust aftertreatment systems for emergency diesel generators. 

Much like the fire pump engine case, where the benefits of a reliable diesel engine far exceed 

any short term increased diesel emissions during the course of operating during this critical 

mission, we believe the public interest is to ensure the proven reliability of emergency diesel 

generators is maintained.

We urge the EPA to provide the exemptions requested in the EMA letter. We also encourage 

this exemption to be extended to all emergency diesel generators and station blackout diesel 

generators provided to nuclear power plants, regardless of cylinder displacement.
Thank you,

Robin L Weeks

Applications Engineer

Engine Systems, Inc.

(252) 407-8517

fax (252) 446-1134