POWER August 2017 - 52

NUCLEAR
3-D Laser Scanning of Nuclear
Plant Piping Systems Reduces
Radiation Exposure
It's no secret that high-radiation areas are scattered throughout nuclear power
plant facilities. The challenge is getting work done in those areas while
keeping exposure to workers as low as possible. On one project, a novel
3-D laser scanning system was utilized to effectively map piping systems
and determine where high-point vents should be installed, while reducing
time in high-radiation areas and the subsequent dose to workers.
Greg Hoeting
N
uclear power has long been a
clean, dependable source of energy
throughout the world. However, as
power plants age, reliability concerns grow.
Many components make up the infrastructure
of a nuclear power plant, and
unsurprisingly, some of the systems are
contaminated with radioactive material.
Management at nuclear facilities place great
importance on reducing radiation and contamination
exposure to personnel, equipment,
and the surrounding environment.
One of the biggest sources of this radiation
and contamination comes from the vast
network of pipes throughout the plant. In a
pressurized water reactor (PWR), the primary
coolant (water) is transported through
a closed system of pipes and other components.
The radioactive water is pumped under
high pressure to the reactor core where
it is heated by the energy released through
fission of uranium atoms. The heated water
then flows through the pipes to a steam generator,
where thermal energy is transferred to
the secondary system, generating steam that
flows to turbines, spinning electric generators.
If there were to be a failure anywhere
in the piping system, it could force a plant
offline for repairs.
Maintenance Requires an
Innovative Solution
At one Midwestern PWR, there was a concern
that some of these critical piping systems
were experiencing wear from corrosive
agents, which could result in leaks. The problem
had the potential to subject personnel to
dangerous and unexpected situations.
Because the corrosion in question was
occurring on the inside of pipes, it was obviously
an unseen problem during visual
52
inspections. One of the potential sources of
the corrosion was determined to be gases
trapped in the pipes. Gases often accumulate
in system high points. Inside a pipe, an unintended
high point can become a resting spot
for gases and a potential area of concern for
catastrophic corrosive breakdown.
The concern was so significant that the
plant decided to take measurements on several
of its pipe runs to assess the problem.
Once the high points were identified, vents
would be installed to allow trapped gases to
be released, when necessary.
As simple as it sounds, the effort was not
without tremendous risks because many of
the systems were difficult to access and had
high-radiation levels. At the time, the only
known way to measure these systems was
with manual hand tools. The involved process
would have resulted in many personnel
being exposed to high levels of radiation, potential
contamination, and other risks such as
using ladders and scaffolding.
Hand measuring can be an effective tool
for dimensional inspection, but in this case it
was not sufficient. Any high point, as small
as it might be, offered a place for gases to
collect and cause corrosion. Typical conventional
surveying with a tape measure, ladders,
and scaffolding was determined to be
an undesirable method for this facility. The
inaccuracy and potential for human errors
with hand measurements could very well result
in subtle elevation changes being missed.
The contractor responsible for the project immediately
recognized the risk and directed its
client to Exact Metrology Inc. for assistance.
After conferring with project management,
reviewing the site conditions, and
understanding the critical elements of the
project, four metrology professionals from
www.powermag.com
1. High-definition scanning. Leica
ScanStations deliver high-quality 3-D data and
high dynamic range imaging at an extremely
fast scan rate. Long range and angular accuracy
paired with low range noise and survey-grade
dual-axis compensation form the
foundation for highly detailed 3-D color point
clouds mapped in realistic clarity. Courtesy:
Exact Metrology Inc.
Exact Metrology were deployed to the facility.
While donning full anti-contamination
protective suits, the personnel scanned piping
in more than two-dozen rooms throughout
the power plant, utilizing Leica high-definition
scanning (HDS) equipment (Figure 1).
POWER | August 2017
http://www.powermag.com
POWER August 2017

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