Transcript Physics 201 - University of Virginia

PHYS 1110
Lecture 24
Professor Stephen Thornton
November 29, 2012
Reading Quiz
Which of the following has the lowest
death rate per unit of electrical energy
generated?
A)
B)
C)
D)
gas
coal
nuclear
hydro
Reading Quiz
Which of the following has the lowest
death rate per unit of electrical energy
generated?
A)
B)
C)
D)
gas
coal
nuclear
hydro
Remaining schedule:
Tuesday, Dec. 4: HW 7 on Ch. 10 due
Quiz on Chs. 9 and 10
Thursday, Dec. 6: HW 8 on Ch. 11 due
Divide up into groups and discuss the
following, then make reports.
• Mining
• Conversion
& Enrichment
• Fuel
• Reprocessing
• Waste
Schematic of CANDU power reactor.
The first new power reactor beginning construction in the
United States since 1977 is near Waynesboro, Georgia at Plant
Vogtle. The two AP1000 units are being constructed by Southern
Nuclear and are expected to be completed in 2016 and 2017. The
Watts Bar 2 nuclear reactor in Tennessee was about 80% complete
when construction was stopped on it in 1988. Construction
resumed in 2007, and it is expected to be the first new nuclear
reactor to be completed in more than a decade in the US. But it has
gone over budget and behind schedule. It is now hoped that it will
be finished by the end of 2015.
As of October 2012 there were 64 nuclear reactors under
construction in 13 countries, most of them in Asia, 26 in China, 10
in Russia, 7 in India. There are currently 434 operable nuclear
reactors, capable of producing 373 GWe. The 64 under
construction will add another 64 GWe, and many of the new ones
will be Gen III.
Gen IV Reactors
• Nuclear waste that is radioactive for a few
hundred, rather than thousands, of years.
• More energy yield (by 100-300) than existing
nuclear fuel.
• Ability to consume current nuclear waste to
produce electricity.
• Enhanced operational safety.
• Reduced capital costs.
Look over goals: 2 sustainability, 2 economic, 3
safety and reliability, 1 proliferation resistance
Generation IV Proposed Reactor Systems
Temp 0C Fuel
Cycle
900 to
open
1000
Size (MWe)
sodium
550
closed
thermal/
fast
water
510-625
open/
closed
30-150,
300-1500,
1000-2000
300-700
1000-1500
fast
helium
850
closed
1200
LFR (Lead-cooled fast fast
reactor)
lead
480-800
closed
MSR (Molten salt
reactor)
fluoride
salts
700-800
closed
20-180,
300-1200,
600-1000
1000
System
Neutron
Spectrum
thermal
Coolant
SFR (Sodium-cooled
fast
reactor)
SCWR (Supercritical
watercooled reactor)
fast
GFR (Gas-cooled fast
reactor)
VHTR
(Very high temperature
gas reactor)
epithermal
helium
250-300
Quiz
Which of the following countries (or
unions, areas) has the most nuclear
reactors under construction?
A)
B)
C)
D)
E)
China
European Union
United States
South America
India and Pakistan
Quiz
Which of the following countries (or
unions, areas) has the most nuclear
reactors under construction?
A)
B)
C)
D)
E)
China
European Union
United States
South America
India and Pakistan
Quiz
How many nuclear reactors are currently
operating throughout the world?
A)
B)
C)
D)
E)
less than 100
100 to 200
200 to 300
300 to 400
over 400
Quiz
How many nuclear reactors are currently
operating throughout the world?
A)
B)
C)
D)
E)
less than 100
100 to 200
200 to 300
300 to 400
over 400
Quiz
What is an example of a supercritical
reaction?
A)
B)
C)
D)
E)
a reaction that produces
a fusion bomb
a fission bomb
a reaction caused by a slow neutron
a reaction caused by a fast neutron
Quiz
What is an example of a supercritical
reaction?
A)
B)
C)
D)
E)
a reaction the produces
a fusion bomb
a fission bomb
a reaction caused by a slow neutron
a reaction caused by a fast neutron
Quiz
Which of the following is not a cause of
the nuclear renaissance of the 2000s?
A)
B)
C)
D)
E)
economics
security of fuel supply
low cost of natural gas
increasing energy demand
climate change
Quiz
Which of the following is not a cause of
the nuclear renaissance of the 2000s?
A)
B)
C)
D)
E)
economics
security of fuel supply
low cost of natural gas
increasing energy demand
climate change
Small nuclear reactors
•
cheaper to construct and run than larger reactors.
•
placed in remote areas not having sufficient electrical grids. 100,000 people.
•
used in places like third-world or remote island countries.
•
can be used for specialized purposes like desalination or hydrogen production.
•
do not have to be custom designed.
•
can be factory built and delivered as needed.
•
have short construction times and can even be “shelf” ready.
•
can be returned to specialized facilities for decommissioning.
•
do not necessarily need to be cooled by water and, therefore, placed near large
bodies of water. They can be cooled by air, gas, low-melting point metals.
The Westinghouse SMR
design is a 225 MWe
integral PWR with all its
primary components
located inside the reactor
vessel. It utilizes passive
safety systems and many
other components that
Westinghouse has
gleaned from its many
years of producing
nuclear reactors
including its recent
AP1000, on which the
SMR is based.
Left: schematic of Babcock & Wilcox mPower reactor.
Right: underground containment structure for two
mPower reactors.
The NuScale Reactor is a 45
MWe advanced light water
reactor. Its passive cooling
systems use natural circulation
to maximize safety. The reactor
vessel sits within a containment
vessel inside a water filled pool
that is built below grade. It uses
a convection process (no
pumps) to circulate water
through the containment vessel.
The reactor system can be
operated solely for heat
generation (160 MWt) for
industrial applications, district
heating, or for use in the
production of synthetic fuels.
The Chinese HTR-PM is a 210 MWe high temperature, gas-cooled
reactor. Helium gas is used to cool the reactor core, and graphite is
the moderator. The fuel is ceramic coated kernels (called pebble bed
module) and uranium, thorium, and platinum call all be used. The
fuel kernels are small, 200-600
in diameter. A previous
prototype reactor, HTR-10, was a smaller 10 MWe, and it was
extensively tested at Tsinghua University in Beijing after it reached
full power in 2003. It continues to operate today as a research
reactor. Such a reactor has several safety features that make it
attractive. For example, the HTR-10 underwent several tests to test
its safety features: loss of offsite power, main helium coolant
shutdown, loss of main heat sink, and withdrawal of all control rods.
The current HTR-PM was designed by Tsinghua University and is
under construction at Rongcheng, Shandong Province. The plan is
to use two modules to reach 210 MWe, and customers may purchase
multiple modules.
The TerraPower Travelling Wave Reactor (TWR) The concept
is that the reactor can breed its own fuel inside the reactor from natural or
depleted 238U. It only needs a small amount of enriched 235U to begin the
process. Thereafter neutrons produced by fission are in turn absorbed by 238U
and in turn decay, eventually producing the fissile material 239Pu.
The TWR nuclear core does not move. We show a schematic of the
“breed and burn” concept below. The reaction started on the far left
with enriched 235U and the breeding and fission areas are moving slowly
to the right, thus the traveling wave.
Fast breeder reactors and fusion reactors.
A fast breeder reactor (FBR) is a nuclear reactor that utilizes
fast neutrons to produce more fissile material than it consumes.
Remember nuclear fission normally produces fast neutrons that
have to be slowed down or thermalized by a moderator.
Reactions like the previous produce 239Pu from fast neutrons
interacting with the highly abundant uranium isotope 238U.
The extra 239Pu produced could be used to start another nuclear
reactor. There was considerable interest in fast breeder
reactors about 50 years ago, because of the fuel economy, and
there was concern about lack of uranium reserves. There
currently seems to be enough uranium reserves to last for
decades, and there does not seem to be difficulty in finding
new reserves when needed. Uranium enrichment using
centrifuges and eventually lasers is much more economical
than the older gaseous diffusion process.
Deaths from energy related accidents per
unit of electricity generated.
The primary concern about nuclear reactors is if a large
amount of radioactive fission products were dispersed over a wide
area, where the radiation material could contaminate the soil and
vegetation and be ingested by humans and animals. It is impossible,
however, for a commercial nuclear reactor to detonate like a nuclear
bomb, because the fuel is not highly enriched enough and it cannot
be forced to a high enough density.
Except for the Chernobyl disaster, no nuclear workers or members of
the public have ever died due to radiation received due to a
commercial nuclear reactor event. There have been at least ten
accidents in military and experimental reactors. Only one resulted in
significant radiation release. There is also a significant difference in
safety between well-developed countries in the OECD and nonOECD countries. Hydropower has caused many more
fatalities/TWy, followed by coal and then natural gas. Nuclear is a
factor of more than 200 safer than hydropower.
Attacks on Nuclear Facilities
Year
Event______________________________
1980
1981
1984-87
1991
Iran bombed a nuclear complex in Iraq
Israel destroyed a nuclear research facility in Iraq
Iraq bombed a nuclear plant in Iran six times
USA bombed three nuclear reactors and an
enrichment facility in Iraq
Iraq launched Scud missiles at an Israeli nuclear
power plant
Israel bombed a Syrian nuclear reactor under
construction.
Israel/United States will bomb Iranian nuclear
facilities
2007
2008
2013-14
There are a number of ways in which a nuclear
reactor can fail. The primary concern is a loss of coolant,
which may cause the fuel to melt or cause the containment
vessel to overheat and melt. This event is called a nuclear
meltdown. The Generation IV reactors presently being
considered and designed hope to completely alleviate this
concern.
The three primary objectives of nuclear safety systems in an
accident or unexpected event are
• to shut down the reactor
• to maintain it in a safe, shutdown stable condition, and
• to prevent the release of radioactive waste during accidents
or unexpected events.
Nuclear power plants, according to extensive studies,
should be able to sustain a terrorist attack against them like the one
that occurred in September 2001 against New York City’s World
Trade Center and the Pentagon in Washington, DC.
There is general agreement that human error is perhaps the greatest
concern. Safety culture in the workplace is extremely important, but
there is evidence that operational practices are not easy to change.
Many experts warn that the Fukushima nuclear disaster is a wakeup
call that should force a reevaluation of nuclear safety, and there is
evidence that is happening. Humans are prone to error, and operators
must guard against complacency and avoid overconfidence. Experts
argue that the single biggest internal factor in nuclear plant safety is
the culture of security among regulators, operators and the
workforce.
Divide up into groups, discuss, and make a report:
1)
2)
3)
4)
Economics of nuclear reactors
Proliferation
Nuclear waste, environmental issues, pros and cons
Future – start after cons
Projections of Global Nuclear Generation Capacity through
2030 by the International Atomic Energy Agency (2008).
One low and one high projection.
Installed nuclear
generating capacity in
2011 and estimated for
2020 and 2035.
Source: OECD Nuclear
Energy Agency and the
International Atomic
Energy Agency.
Quiz
Which of the following commercial
nuclear reactors are most numerous?
A)
B)
C)
D)
E)
Gen I
Gen II
Gen III
Gen III+
Gen IV
Quiz
Which of the following commercial
nuclear reactors are most numerous?
A)
B)
C)
D)
E)
Gen I
Gen II
Gen III
Gen III+
Gen IV
Quiz
Which of the following commercial
nuclear reactors are now in operation?
A)
B)
C)
D)
E)
Only Gen I
Only Gen II
Only Gen III
Mostly Gen I and II
Mostly Gen II and III
Quiz
Which of the following commercial
nuclear reactors are now in operation?
A)
B)
C)
D)
E)
Only Gen I
Only Gen II
Only Gen III
Mostly Gen I and II
Mostly Gen II and III
Quiz
How many nuclear reactors are currently
under construction in the United States?
A)
B)
C)
D)
E)
None
1
2
3
5 or more
Quiz
How many nuclear reactors are currently
under construction in the United States?
A)
B)
C)
D)
E)
None
1
2
3
5 or more
Quiz
Which of the following is not characteristic of a
Small Nuclear Reactor?
A) Can be factory built and delivered as needed
B) Can be left in place after decommissioning
C) Can be used in specialized places like islands
or for Disney World.
D) Standard, not custom, designed
E) Do not necessarily need water for cooling
Quiz
Which of the following is not characteristic of a
Small Nuclear Reactor?
A) Can be factory built and delivered as needed
B) Can be left in place after decommissioning
C) Can be used in specialized places like islands
or for Disney World.
D) Standard, not custom, designed
E) Do not necessarily need water for cooling
Chapter 11
Energy Transmission and
Storage
Electricity Generation Electricity is normally generated at values
of 1000s of volts, but that is not ideal to transmit, so we first have to
use transformers to increase the voltage.
Electric Power Transmission We will explain in this chapter why
it is best to transmit electricity at values of 500,000 volts or higher.
After being transformed at the power plant, the electricity is
carefully connected to transmission lines which carry it sometimes
long distances, even across international borders like from Canada
to the United States or from France to Italy. The high voltage lines
send the electricity to an electrical substation.
Electric Power Distribution Once the electricity reaches a
substation normally owned by the local utility, the voltage is
reduced substantially before being delivered to a local transformer
when the voltage is reduced again before being delivered to the
customer.
2
2
P
P R
Ploss = I R = 2 R =
V
V2
2
For a given transmitted power P and resistance
R of the transmission line, we minimize the
power loss by using the highest possible
voltage V. That is why overhead transmission
lines have voltages above 100 kV. Values
include 230, 345, 500 and 765 kV.
Transmission lines – electrical grid
Electrical energy must be generated as needed; a complex
control system is required to match the electrical
generation with the demand. The normal supply is
provided by the base load, which consists of power
plants like nuclear, coal, wind, and solar that cannot be
turned on and off quickly. When the demand exceeds the
supply, generating plants must be brought online for more
supply. When the demand far exceeds the supply, then
serious problems can occur, and generating plants and
transmission shut down. This causes blackouts which
have occurred in the US Northeast in 1965, 1977, 1996,
2003, and 2011. Sometimes rolling blackouts are
engineered to prevent more widespread blackouts.