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NuclearPlantJournal.com Nuclear Plant Journal, September-October 2014
Research &
Development
Maintenance Rule
In the late 1980s, the U.S. Nuclear
RegulatoryCommissionbegan to consider
a rule to monitor the effectiveness of
the maintenance programs at nuclear
power plants in the United States. After
extensive deliberations, the NRC decided
that this need could best be addressed
through a risk-informed, performance-
based regulation. In July 1991, the
NRC published the Maintenance Rule
(10CFR50.65), which went into effect in
July 1996 as the first performance-based
regulation for the U.S. nuclear power
industry.
Because many of the people
originally involved in the development
and implementation of the Maintenance
Rule have retired or left the industry, the
“institutional” memory is at risk. In 2003,
therefore, EPRI published a history of the
rule through its Maintenance Rule Users
Group. In 2013, in response to various
changes in Federal rules affecting nuclear
plants
(10CFR50.65,
Maintenance
Rule
), in applicable NRC Regulatory
Guides, and in inspection procedures and
interpretations, EPRI decided to revise
the Maintenance Rule history and capture
some of the reasoning behind these
changes. This history is documented in A
History of the Maintenance Rule, 10 CFR
50.65, Requirements for Monitoring the
Effectiveness of Maintenance at Nuclear
Power Plants - Revision 1 (3002002864).
One significant issue addressed in
the document is the change in regulatory
position on whether components
referenced in plant emergency operating
procedures (EOP) need to be included
in the Maintenance Rule scope. For
years, as explained in industry reference
NUMARC 93-01, the accepted position
had been that if a component was listed
in the EOP and provided “significant
value” to accident mitigation, it would
be in scope; likewise, components that
provided no real mitigation purpose
would not be in scope. Interpretation of
“significant value” lacked consensus,
however; and coupled with NRC
retirements and reorganizations, this led
to any component called out in the EOP
as being in scope regardless of the degree
of mitigation provided. Revision 4A to
NUMARC 93-01 and subsequent NRC
endorsement of the revision in March
of 2011 removed the ambiguity to make
compliance more consistent, clearly
defining what equipment used in EOPs
would be in Maintenance Rule scope.
The Maintenance Rule history document
thoroughly examines this evolution.
Notably, the Maintenance Rule (or
a similar regulatory construct) is used
in several other countries, including
Spain, Brazil and Mexico; and at least
one utility, Korea Hydro Nuclear Power
(KHNP), uses the rule for guidance even
though it is not a national regulation. The
history document provides background
information and analysis that personnel
in these countries can use to better
understand how the rule got to where
it is today and how it can be applied
effectively.
Contact: Marty Bridges, telephone:
Microwave Technology
As nuclear power plants age, they
must increasingly inspect components
not originally designed for inspection.
In many cases, this requires the use of
nontraditional nondestructive evaluation
(NDE) techniques. For example, rubber
expansion joints historically have not
been inspected, partly due to limited
inspection options. At some plants,
these components have been replaced at
regular intervals – typically every five
years – without a strong technical basis
supporting the decision; at other plants,
these joints have operated safely with no
issues for 15-25 or more years.
EPRI evaluated several NDE
techniques, and identified microwave
and millimeter-wave techniques as
viable inspection options for rubber
expansion joints. These techniques use
light from the microwave region of the
electromagnetic spectrum to penetrate
and image dielectric materials (generally
nonmetallic
and
nonconductive
materials). They can identify internal
structure in dielectric materials, measure
material properties related to aging
processes, and detect defects. Microwave
inspection also may be applicable to
other nonmetallic materials such as high-
density polyethylene (HDPE), which
may gain greater use in nuclear power
plants in the future.
This work also has shown that
microwave and millimeter- wave
inspections can detect surface cracking
and corrosion in metals. The resolution
of these techniques is very fine, similar
Microwave techniques can distinguish
tight cracks in metals. Microwave
technology also may be valuable in
imaging cracks beneath nonmetallic
paints or coatings, which is not currently
possible with visual techniques.
EPRI has fabricated a number of
metallic and nonmetallic samples, and
will be performing inspections to evaluate
benefits and limitations, with a goal to
initiate technology transfer to the nuclear
industry within the next two years.
Contact: JeremyRenshaw, telephone:
(70) 595-2501, email:
.
Loss of Offsite Power
Tool
Recent events, such as the earthquake
and tsunami that led to the accident at
Fukushima and the tornado at Browns
Ferry, have highlighted the importance
of reliable offsite power for nuclear
power plants. Likewise, regional power
outages, such as the one that occurred
in September 2013 in Arizona-Southern
California, show that the transmission
grid can be vulnerable to large area
disruptions. Through the Technology
