Commercial Nuclear Power
Fact, Fiction and Perception
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First Things First…
Forget everything that you’ve learned
about nuclear power from this guy
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About Me:
Larry Reynolds
30 Years Experience in Nuclear Power
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• I entered into the nuclear power field
when I enlisted in the US Navy.
• I served aboard the USS Pogy (SSN 647)
as a Nuclear Mechanic and Reactor
Plant Operations Supervisor.
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• I came to Illinois to work at the
Braidwood Nuclear Station in Southwest
Will County.
• I first worked at Braidwood writing
instructions for Mechanical Maintenance
tasks.
• I later provided oversight of their
Preventive Maintenance Program.
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• I then worked as a ‘Work Week Manager’ to
provide overall scheduling and
coordination of all work in the plant for
a given week (5 week rotation).
• I retired from Exelon (Braidwood Station)
last August.
• I currently work at HydroAire in Chicago
at their Nuclear Pumps Division.
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Part 1:
The Theory
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The Theory? - How Does
it Work?
At it’s simplest, nuclear
power plants use the heat
created by the nuclear fission
of U235 (Uranium) to make
steam. The steam is used to
spin a turbine which is
coupled to a generator. This
produces electricity.
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The Theory - How Does it
Work?
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Definitions:
• Core: The area of the reactor that houses the fuel
assemblies
• Fission: The process of splitting atoms (usually U235)
• Fission Product: smaller molecules created by the
fission of Uranium – these are often unstable
(radioactive)
• Fusion: The process of combining atoms (usually H2)
• Free Neutron: A neutron that is not part of a
molecule – it’s by itself
• Fast Neutron: A free neutron that has most of the
original energy that it gained from the fission
process
• Thermal (or slow) Neutron: A free neutron that has
lost most of its energy to the moderator
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Definitions:
• Poison: A material placed in a reactor to absorb
neutrons so that the fission reaction can be
controlled or stopped (Usually Boron or Hafnium)
• Control Rod: A rod that is made from a Reactor Poison
and is located in the middle of most fuel bundles.
They are raised or lowered to control reactor power.
They can also be rapidly inserted into the fuel
bundle during an automatic shutdown of the reactor.
• SCRAM: Slang for an automatic or manual shut down of
the reactor. This is performed by causing a rapid
insertion of control rods. The term originated at
the first test reactor at Fermi Lab in Chicago
(Safety Control Rod Ax Man)
• Moderator: A substance with a low molecular weight
used to slow neutrons (common moderators are water,
helium and graphite)
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The Theory
So what heats up the water?
The Fission Process for U235
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Keff= number of neutrons in one generation
number of neutrons in preceding generation
keff =ϵ•Lf•p•Lth•f•n
keff = the effective multiplication factor of neutrons in the core
If keff is greater than 1, the chain reaction is supercritical, and the neutron population will
grow exponentially.
If keff is less than 1, the chain reaction is subcritical, and the neutron population will
exponentially decay.
If keff = 1, the chain reaction is critical and the neutron population will remain constant.
ϵ=
Fast fission factor
total number of fission neutrons
number of fission neutrons from just thermal fission
Lf =
Fast neutron non-leakage probability
The probability that a fast neutron will not leak out of the system
p=
Resonance escape probability
Fraction of fission neutrons that manage to slow down from fission to
thermal energies without being absorbed
Lth =
Thermal neutron non-leakage probability
The probability that a thermal neutron will not leak out of the core
f=
Thermal utilization factor
Probability that a neutron that gets absorbed does so in the fuel material
n=
Thermal Fission Factor
The number of fission neutrons produced per absorption in the fuel
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WHAT THE WHO!!!????
A reactor that is ‘critical’ simply means
that it is neither gaining or losing
‘free’ neutrons in the core. In other
words, the power level is stable –
neither increasing or decreasing.
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Part 2:
The
Perception
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The reality is that
there is a lot of
misinformation about
Nuclear Power.
What does a
Nuclear Plant look
like?
Like this, Right?
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This is actually a Coal
Burning Power Plant
These large
cooling towers
are used in
many different
types of power
plants.
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Perception
• Three Mile Island was the worst incident at a
commercial US plant, yet no radiation was
released. Public outcry after this incident
was responsible for many utilities abandoning
plans for construction of new plants. Some
of these plants were already in the process
of being constructed.
• The Chernobyl accident released large amounts
of radiation in Russia and caused many
deaths. Many people assume that an accident
like Chernobyl could happen here. US
Regulations prohibit a design like that used
at Chernobyl and also prohibit the type of
testing that was being performed that led to
the accident.
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Part 3:
Practical
Application
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Application
•
Nuclear Power is unique:
– People tend to be frightened of what they don’t understand, and
nuclear power is complicated.
– The US Government and US Nuclear Plant Licensees (owners) both
have roles in the safe operation of Nuclear Power Plants in the
US.
– The NRC must approve the design of any nuclear plant prior to
start of construction.
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Application
• Because of the severe consequences of a nuclear
accident, the nuclear industry is highly
regulated.
• Prior to start of operation, each plant must receive
a license to operate from the NRC that has the force
of law and covers design, maintenance, testing and
operations of the plant.
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Application
•
Because of the severe consequences of a nuclear
accident, the nuclear industry is highly regulated.
• Nuclear workers have FBI background checks and drug
screening prior to being allowed unescorted access to a
nuclear plant. Random checks are required as long as access
is allowed.
• Every year each nuclear plant employee must complete
training on emergency procedures, security protocols,
radiation safety and other topics important to nuclear
safety.
• The NRC requires positive ID of each employee prior to entry
into the plant (security badges and hand scanners).
• All employees and packages are screened prior to entry in
the plant (similar to airport screening).
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Application
• Because of the severe consequences of a nuclear
accident, the nuclear industry is highly
regulated.
• Drills that simulate various emergency scenarios are
held on a regular basis to test the communication,
response and coordination between each Nuclear Plant,
Response Centers, State and Local Governments.
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Application
• Nuclear industry regulations
(continued):
• Fences, key-carded doors and an armed security force are
all used to enforce security. Each plant has a unique
Security Plan based on it’s location and plant
geography. Each plan must be approved by the NRC and
includes the design of the permanent structures as well
as number of guards on staff, the type of weapons onsite, etc.
• Periodic drills are performed
staff response to a simulated
simulates an attempt to enter
reactor with both sides using
to test plant security
attack. A ‘ninja force’
the plant and damage the
laser tag rifles.
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Application
• Nuclear industry regulations
(continued):
• Almost every activity at a nuclear plant is
performed using a procedure or set of work
instructions that is reviewed against the
plant’s operating license prior to approval
to ensure that all regulations are met.
• Every component (and sub-component) that is
important to nuclear safety has been
evaluated in detail to ensure that it can
be relied upon to perform as required. This
includes detailed analysis of breaking
strength, resistance to corrosion, and
other pertinent material attributes. All
parts used must have traceability and
documentation of all phases of manufacture
and testing.
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Application
USS Thresher: Poor materials and construction
caused sinking of this submarine. As a result,
the US Navy implemented SUBSAFE program to ensure
quality of materials used in submarines. This
method was also adopted at nuclear plants shortly
thereafter.
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Application
– In addition to careful selection,
testing and documentation of
replacement parts, all maintenance
must be planned and scheduled to
ensure that:
• Removal of equipment from service will not
violate any part of the operating license
due to loss of redundancy
• Procedures and work instructions are used
to ensure work is performed correctly
• Radiation and contamination exposure are
minimized (Time, Distance, Shielding)
• Equipment is scheduled to be operated (or
exercised) at periodic intervals to prove
to the NRC that it could operate as
designed in an emergency.
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Application
– As a result of all of these processes and
regulations, the majority of workers at a
nuclear plant spend a great deal of their
time performing engineering analysis, work
planning, scheduling or documentation
tasks.
– Most nuclear workers receive very little
radiation. An airline pilot receives more
radiation in a year than most nuclear plant
workers.
– Major repair work, and all repair work
inside of the containment building is
performed during a refueling outage. This
is when the reactor is shut down to allow
for replacement of fuel bundles. This is
also a key to lowering radiation dose rates
to workers performing maintenance.
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Application
• INPO (Institute for Nuclear Power Operations) was
formed shortly after the nuclear incident at Three
Mile Island in December 1979.
• INPO Mission . . . to promote the highest levels
of safety and reliability – to promote excellence
– in the operation of commercial nuclear power
plants.
• INPO conducts evaluations of Plants to ensure that
they are operated in a safe and reliable manner.
These evaluations also establish and communicate
‘best practices’ across the nation (and world - by
participation in WANO).
• Provides an independent assessment of the quality
of operations at a power plant. INPO allows the
nuclear industry to ‘self-police’ itself.
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Part 4:
Comparisons
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Comparisons:
• Nuclear
– Larger Nuclear plants have
capacities of 1200Mw and can
generate an average of 20,000,000
MwHr in a year (2 unit site).
– Power plants (not just nuclear)
can kill fish in large numbers due
to the heating of river, lake and
sea water.
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Comparisons:
• Nuclear
– Nuclear plants generate low level waste as
well as spent fuel. The government has
agreed to take on the responsibility for
disposal of spent nuclear fuel.
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Comparisons:
A single uranium
fuel pellet the
size of a pencil
eraser contains
the same amount
of energy as
17,000 cubic
feet of natural
gas, 1,780
pounds of coal
or 149 gallons
of oil.
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Comparisons:
Nuclear energy data
• A typical nuclear power plant generates 20
tons of used nuclear fuel in a year. This
used fuel is stored on site in spent fuel
pools or NRC approved storage units.
• About 95 % of LLRW decays to background
levels within 100 years or less.
• Low-level radioactive waste is stored in
special disposal facilities across the
nation. These disposal facilities also
store Low-level radioactive waste from
medical and industrial sources.
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Comparisons:
• Wind
– Most wind energy comes from turbines that can be as
tall as a 20-story building and have three 200-footlong (60-meter-long) blades.
– The largest wind turbines being manufactured today
can produce 2 Mw each with adequate wind.
– Wind turbines only work when the wind is blowing
(Duh!).
– This would mean that to equal a nuclear power plant,
a wind farm would need 600 wind turbines. Typical
spacing is 7X the rotor diameter or every 1400 feet.
Placed in a single row, this would be 840,000 feet
long (or 160 miles long – or 180 square miles if
placed in a grid).
– DOE documents estimate bird kills from wind turbines
at about 1 bird per Mw per year (or 1200 birds per
year in the above example). They also estimate that
in areas with bats, the bat kill would be 30 bats per
Mw per year (36,000 bats per year in the above
example).
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Comparisons:
• Solar
– The amount of electricity produced by a
multi-reactor nuclear power plant would
require more than 60 square miles of
photovoltaic panels
• Fossil (Oil, Natural Gas and Coal)
– Carbon Dioxide emissions (acid rain)
– Like nuclear plants, these plants can also
result in fish kills
• Conservation
– Use less electricity
– Buy products that have a minimal of
processing (extensive processing usually
means extensive electrical usage)
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FAQ’s:
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FAQ’s:
• What is used nuclear fuel?
– Used uranium fuel assemblies from commercial reactors
still have 90 percent of the original potential energy.
They are currently stored at nuclear energy facilities
where they are used.
• How is used nuclear fuel stored?
– Most plants store used fuel in steel-lined, concrete
vaults filled with water, which acts as a natural
barrier for radiation from the used fuel. The water
also keeps the fuel cool while it becomes less
radioactive. The water itself does not leave the used
fuel pool, rather is constantly circulated to maintain
a suitable temperature.
– After at least five years of storage in the used fuel
pool, the rods can be moved into large, heavily
shielded concrete and steel storage containers, whose
designs must be approved by the Nuclear Regulatory
Commission. There it awaits removal by the U.S.
Department of Energy to a disposal facility.
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FAQ’s:
• What is low-level radioactive waste?
– Low-level radioactive waste is a byproduct of
the uses of radioactive materials. This
includes waste from electricity generation,
medical diagnosis and treatment, biomedical and
pharmaceutical research and manufacturing.
– It is solid material that is transported under
strict regulations established by the U.S.
Department of Transportation and the Nuclear
Regulatory Commission.
– Low-level radioactive waste usually consists of
items such as gloves and other protective
clothing, glass and plastic laboratory
supplies, machine parts and tools, and
disposable medical items that have come in
contact with radioactive materials.
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FAQ’s:
• What is radiation?
– The radiation one associates with a nuclear power
plant are particles, such as alpha rays and gamma
rays, emitted as a result of the fission process.
• Do nuclear power plants release radioactive
material?
– Yes, but in small levels that are regulated by the
federal government. Nuclear power plants produce
radioactive gases and liquid wastes during normal
operation. A plant has tanks designed to store gas
and liquid radioactive materials that are generated
during normal operation. The radioactive material is
held for a period of time to allow for the
radioactivity level to decrease before being treated
and/or released in a planned, monitored way. This
keeps the amount of radioactive material in releases
low and well within federal limits.
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FAQ’s:
•
How did the 2011 nuclear accident in Japan affect the
nuclear energy industry?
– In the United States, the nuclear energy industry and the NRC
immediately took steps to make facilities even safer than
before the accident. Most other countries took a similar
approach to the United States and kept their facilities
operating. Germany and Switzerland are phasing out their
nuclear energy facilities. Japan shut down its plants, but has
restarted one and may restart others after they make safety
upgrades.
– The industry quickly implemented a safety enhancement strategy
to ensure that plants have the additional equipment needed to
respond to extreme natural events such as the tsunami in Japan.
The industry initiative will provide additional sources of
water and electric power to keep the reactor and used fuel pool
cool if electricity from the grid is unavailable, as it was in
Japan.
– Additional generators, batteries, water pumps and other
emergency equipment have been purchased at each site. In
addition, regional response centers in Tennessee and Arizona
will maintain more emergency equipment that can be dispatched
quickly to any facility that needs it.
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QUESTIONS ???
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Links:
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http://www.nei.org/Knowledge-Center/Nuclear-Statistics
http://www.hydroinc.com/
http://www.exeloncorp.com/locations?energy=nuclear
http://environment.nationalgeographic.com/environment/globalwarming/wind-power-profile/
http://windeis.anl.gov/guide/basics/
http://energy.gov/eere/wind/frequently-asked-questions-about-windenergy
http://energy.gov/sites/prod/files/2015/03/f20/AWWI-Wind-WildlifeInteractions-Factsheet.pdf
http://www.riverkeeper.org/campaigns/stop-polluters/powerplants/power-plant-fish-kills/
http://thebulletin.org/nuclear-energy-different-other-energysources/why-nuclear-power-unique-uniquely-dangerous
http://www.cracked.com/personal-experiences-1848-i-work-in-nuclearpower-plant-5-insane-realities.html
http://www.nrc.gov/about-nrc.html
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