Document ID: EPA-HQ-OAR-2010-0295-0019
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-06-16T04:00Z

----- 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

Subject

 

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.

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ሀĀ᐀¤㜀$␸䠀$摧惲&؀rovide 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