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Reactor Concepts Manual

Nuclear Power for Electrical Generation

Nuclear
Power
for
Electrical
Generation
The purpose of a nuclear power plant is not to produce or release “Nuclear Power
...
It should not be surprising, then, that a nuclear power plant
has many similarities to other electrical generating facilities
...


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Reactor Concepts Manual

Nuclear Power for Electrical Generation
Stationary Coil

Drive Shaft

Rotor

Electrical
Output
Flange

Generator Housing

ELECTRICAL GENERATOR

Of the several known methods to produce electricity, by far the most practical for large scale production
and distribution involves the use of an “electrical generator
...
This flow of electrons
is called electricity
...
) must be available to provide the motive force for the rotor
...
e
...


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Reactor Concepts Manual

Nuclear Power for Electrical Generation

H Y D RO ELECTRIC PLAN T

ELEC T RICAL
G E N E RA T O R

W AT ER
IN LET
VALVE

DAM
W AT ER
O U T LET

W AT ER
T U RB IN E

In a hydroelectric power plant, water, flowing from a higher level to a lower level, travels through the
metal blades of a water turbine, causing the rotor of the electrical generator to spin and produce
electricity
...
In the turbine, the steam passes through the blades,
which spins the electrical generator (C), resulting in a flow of electricity
...
The water is then pumped (E)
back to the boiler (F) to be reheated and converted back into steam
...
The NSSS consists of a nuclear
reactor and all of the components necessary to produce high pressure steam, which will be used to turn
the turbine for the electrical generator
...
Unlike a fossil-fueled
plant, the nuclear plant’s energy does not come from the combustion of fuel, but from the fissioning
(splitting) of fuel atoms
...
7%)

Fuel Pellet (3
...
The
uranium starts out as ore, and contains a very low percentage (or low enrichment) of the desired atoms
(U-235)
...
Therefore, the fuel fabrication process
includes steps to increase the number of U-235 atoms in relation to the number of U-238 atoms
(enrichment process)
...
The pellets are stacked into 12-foot
long, slender metal tubes, generally made of a zirconium alloy
...
”
When a tube is filled with the uranium pellets, it is pressurized with helium gas, and plugs are installed
and welded to seal the tube
...
” The fuel rods are bundled together into
“fuel assemblies” or “fuel elements
...


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Nuclear Power for Electrical Generation

REACTOR FUEL ASSEMBLIES
Both boiling water reactor and pressurized water reactor fuel assemblies consist of the same major
components
...
The fuel assembly drawing on page 1-11 shows these major components (pressurized water
reactor fuel assembly)
...
The fuel rods are approximately 12 feet long and contain
a space at the top for the collection of any gases that are produced by the fission process
...

The spacer grids separate the individual rods with pieces of sprung metal
...

Some spacer grids may have flow mixing vanes that are used to promote mixing of the coolant as it
flows around and though the fuel assembly
...
The
lower fitting (or bottom nozzle) will direct the coolant flow to the assembly through several small holes
machined into the fitting
...
The upper end fitting will also have a connecting point for the refueling
equipment to attach for the moving of the fuel with a crane
...
The
guide tubes will be welded to the spacer grids and attached to the upper and lower end fittings
...

The upper end of the control rod will be attached to a drive shaft, which will be used to position the rod
during operations
...


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Reactor Concepts Manual

Nuclear Power for Electrical Generation

HOLD DOW N SPRING

ROD CLUSTER CONTROL
TOP NOZZLE

FUEL ROD

CONTROL ROD

THIMBLE TUBE
GRID

MIXING VANES

BULGE JOINTS

DASHPOT REGION

GRID SPRING

DIMPLE

THIMB LE SCREW

BOTTOM NOZZLE

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Nuclear Power for Electrical Generation

At the nuclear power plant, the fuel assemblies are inserted vertically into the reactor vessel (a large steel
tank filled with water with a removable top)
...
”

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Reactor Concepts Manual

Containment/Drywell

Nuclear Power for Electrical Generation

Reactor
Vessel
Steam
Line

Turbine Building

Throttle
Valve

Steam Dryer
&
Moisture
Separator

Electrical
Generator

Turbine

Reactor Core

Condenser

Jet Pump
To/From
River
Recirculation
Pump
Pump
Containment Suppression Chamber

There are two basic types of reactor plants being used in the United States to produce electricity, the
boiling water reactor (BWR) and the pressurized water reactor (PWR)
...
Inside the reactor vessel, a
steam/water mixture is produced when very pure water (reactor coolant) moves upward through the core
absorbing heat
...
The steam/water mixture leaves the top of the
core and enters two stages of moisture separation, where water droplets are removed before the steam
is allowed to enter the steam line
...
The unused steam is exhausted to the
condenser where it is condensed into water
...
The recirculation pumps and the jet
pumps allow the operator to vary coolant flow through the core and to change reactor power
...
Boiling water reactors comprise about one-third of the power reactors in the United States
...
The pressurizer keeps the water that is flowing
through the reactor vessel under very high pressure (more than 2,200 pounds per square inch) to prevent
it from boiling, even at operating temperatures of more than 600EF
...

Pressurized water reactors were manufactured in the United States by Westinghouse Electric Corporation
(Pittsburgh, Pennsylvania), Babcock and Wilcox Company (Lynchburg, Virginia), and the Combustion
Engineering Company (Windsor, Connecticut)
...

The only high temperature gas-cooled reactor (HTGR) in the United States was the Fort St
...
The plant was manufactured by General Atomic Company of La Jolla, California
...


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Nuclear Power for Electrical Generation

Other
(biomass fuels, wood, wind,
photovoltaic, and solar)
(<1%)

Petroleum
(2%)

Gas
(10%)

Nuclear
(22%)

Coal
(55%)

Hydroelectric
(10%)

Electrical Production by Type
Commercial nuclear power plants generate approximately 22% of the electricity produced in the United
States
...

For comparison purposes, nuclear generation accounts for the following of the total electrical production
in some other countries: 75% in France, 46% in Sweden, 43% in Ukraine, 39% in south Korea, 30%
in Germany, and 30% in Japan
...
This compares with 16% for France, 13% for Japan, 7% for
Germany, 5% for Russia, and 4% for South Korea and United Kingdom
...
Of the 104
plants, 48 were built by Westinghouse, 35 by General Electric, 14 by Combustion Engineering, and 7
by Babcock & Wilcox
...


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Nuclear Power for Electrical Generation

STEAM

ELECTRIC
GENERATOR

MAIN
TURBINE

MAIN
CONDENSER

CONDENSATE
PUMP
CIRCULATING
WATER PUMP

To operate properly, all steam plants, whether nuclear or fossil-fueled, need a circulating water system
to remove excess heat from the steam system in order to condense the steam, and transfer that heat to
the environment
...
Steam exiting the plant’s turbine is very
rapidly cooled and condensed into water when it comes in contact with the much cooler tubes
...
Because a condenser operates at a vacuum, any tube leakage
in this system will produce an “inflow” of water into the condenser rather than an “outflow” of water
to the environment
...
)

INTAKE
CIRCULATING
WATER PUMP

Power plants located on the ocean (or other large bodies of water) will often discharge their circulating
water directly back to the ocean under strict environmental protection regulations
...
The expected temperature increase from circulating water inlet
to outlet is about 5 to 10 degrees Fahrenheit
...
One type of cooling tower is the forced draft cooling tower
...
Several large electrical fans,
located at the top of the cooling tower, provide forced air circulation for more efficient cooling
...
Rather, the natural tendency of hot air to rise
removes the excess heat as the circulating water splashes down inside the cooling tower
...


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Reactor Concepts Manual

Nuclear Power for Electrical Generation

Cold Dry Air

35
30
Grams of
Water per
Cubic
Meter
of Air

25
20
0%
10

15

VE
TI
LA
RE

TY
DI
I
UM
H

Warm
Wet
Air

10
5
30

50

70

90

EF

The “steam” vented from the top of a cooling tower is really lukewarm water vapor
...
As the warm, wet air from inside the cooling tower contacts the cooler, dryer air
above the cooling tower, the water vapor which cannot be held by the cooler air forms a visible cloud
...
The released cloud of vapor will
only be visible until it is dispersed and absorbed by the air
...


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Reactor Concepts Manual

Nuclear Power for Electrical Generation
PRESSURIZED WATER REACTOR PLANT LAYOUT

CONTAINMENT BUILDING

REACTOR
COOLANT SYSTEM

MSR
ELECTRIC
GENERATOR

S/G
P
Z
R

HP

LP
COOLING TOWER

MAIN
TURBINE

MAIN
CONDENSER
CO R E

RHR
HX

RCP

RHR
PUMP

MAIN FEED
PUMP

AUXILIARY BUILDING

CONTAINMENT
SUMP

FW
HTR

CONDENSATE
PUMP

CIRC
...


Depending upon the plant location and environmental regulations, there may or may not be a cooling
tower to remove the excess heat from the facility
...


Depending upon the plant location, there may or may not be a cooling tower to remove excess heat from
the facility

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