2. Use of reactors
• Electricity production
• Heat production
• Research into a large range of fields
• Production of Radioisotopes for medicine
• Production of material (plutonium) for nuclear weapons
!Some reactors are designated research and medicine only and do not produce any
electricity
3. Nuclear Energy Explained: How does it work? ⅓
https://youtu.be/rcOFV4y5z8c
3 Reasons Why Nuclear Energy Is Terrible! ⅔
https://youtu.be/HEYbgyL5n1g
3 Reasons Why Nuclear Energy Is Awesome! 3/3
https://youtu.be/pVbLlnmxIbY
How Many People Did Nuclear Energy Kill? Nuclear Death Toll
https://youtu.be/Jzfpyo-q-RM
4. Conceptual Design Selection Criteria:
Conventional Nuclear Technology
Pros
• High power-density source
• Availability of massive amounts of
energy
• No green house emissions
• Minimal transportation costs
• Low $/kW baseload supply
Cons
• Safety fears
• High capital costs
• Proliferation & terrorist target
• Long term waste disposal
• Uranium sustainability
• Unsightly, bad reputation
~1/3 of CO2 comes from
electricity production
Inherently nuclear power
produces essentially no CO2
5. Where largest global problem actually resides…
Address
huge
losses
Improve
desirable
sources
Phase out
poor sources
for electricity
More electrical energy
diverted to electric
transportation options
Conservation has its
limits here
6. Number of reactors
• 449 operational reactors in April 2018 (electrical capacity of 394 GW)
– 34 of these are for research only
• Additionally, there are 58 reactors under construction (63 GW)
• 154 reactors planned (157GW)
• Over 300 more reactors are proposed
7. Natural Reactors
• Only one known site in the world Oklo
• 2 billion years old.
• No longer active
• Found because people thought
uranium had possibly been stolen.
• https://www.youtube.com
/watch?v=yS53AA_WaUk
8. Research reactors
• The neutrons produced by a research reactor are used for neutron scattering, non-
destructive testing, analysis and testing of materials, production of radioisotopes,
research and public outreach and education. Research reactors that produce
radioisotopes for medical or industrial use are sometimes called isotope reactors.
• They operate at lower energies and temperatures.
• Are not used to produce electricity
• They tend to use higher purity uranium (20-93%)
• Australia’s only nuclear reactor OPAL (in Lucas Heights) is a research reactor.
9. Types of reactors
• Solid fuel reactors
– UOX – uranium oxide pellets
– MOX – a mixture of plutonium and depleted uranium
– Thorium – Not used in current reactors but may be a good alternative
• Liquid fuel reactors
– Molten salt – nuclear fuel is dissolved in a molted salt (~700-1000degC)
• There are many others but are not as common or have specific purposes
10. Pressurized Water Reactor (PWR)
http://www.eas.asu.edu/~holbert/eee460/pwrdiag.gif
A common type of Light Water Reactor (LWR)
11. Advantages
• PWR reactors are very stable due to their tendency to produce less power as
temperatures increase; this makes the reactor easier to operate from a stability
standpoint.
• PWR turbine cycle loop is separate from the primary loop, so the water in the
secondary loop is not contaminated by radioactive materials.
• PWRs can passively scram the reactor in the event that offsite power is lost to
immediately stop the primary nuclear reaction. The control rods are held by
electromagnets and fall by gravity when current is lost; full insertion safely shuts
down the primary nuclear reaction.
• PWR technology is favoured by nations seeking to develop a nuclear navy; the
compact reactors fit well in nuclear submarines and other nuclear ships.
12. Disadvantages
• The coolant water must be highly pressurized to remain liquid at high
temperatures. This requires high strength piping and a heavy pressure
vessel and hence increases construction costs.
• Additional high pressure components such as reactor coolant pumps,
pressurizer, steam generators, etc. are also needed. This also increases
the capital cost and complexity of a PWR power plant.
• Natural uranium is only 0.7% uranium-235, the isotope necessary for
thermal reactors. This makes it necessary to enrich the uranium fuel,
which significantly increases the costs of fuel production.
• Only a low percentage of the fuel is actually used.
• Because water acts as a neutron moderator, it is not possible to build
a fast neutron reactor with a PWR design. A reduced moderation
water reactor may however achieve a breeding ratio greater than
unity, though this reactor design has disadvantages of its own.
15. Generation IV Reactors
neutron
spectrum
(fast/
thermal)
coolant
temperature
(°C)
pressure* fuel fuel cycle
size(s)
(MWe)
uses
Gas-cooled
fast reactors
fast helium 850 high U-238 +
closed, on
site
288
electricity
& hydrogen
Lead-cooled
fast reactors
fast Pb-Bi 550-800 low U-238 +
closed,
regional
50-150**
300-400
1200
electricity
& hydrogen
Molten salt
reactors
epithermal
fluoride
salts
700-800 low UF in salt closed 1000
electricity
& hydrogen
Sodium-
cooled fast
reactors
fast sodium 550 low
U-238 &
MOX
closed
150-500
500-1500
electricity
Supercritical
water-cooled
reactors
thermal or
fast
water 510-550 very high UO2
open
(thermal)
closed (fast)
1500 electricity
Very high
temperature
gas reactors
thermal helium 1000 high
UO2
prism or
pebbles
open 250
hydrogen
& electricity
* high = 7-15 Mpa
+ = with some U-235 or Pu-239
** 'battery' model with long cassette core life (15-20 yr) or replaceable reactor module
http://www.world-nuclear.org/info/inf77.html
16. Fast Breeder Reactors
• U-238 captures a neutron and transmutes to Pu-239
• Pu-239 is fissile like U-235
• Increases efficiency of uranium use >50x
• Could use up depleted uranium stockpiles & plutonium from
dismantled weapons
http://www.atomeromu.hu/mukodes/tipusok/gyorsreak-e.htm
18. Fast Breeder Reactors
•It was expected that uranium would be scarce and high-grade deposits would quickly become depleted if fission
power were deployed on a large scale; the reality, however, is that since the end of the cold war, uranium has been
much cheaper and more abundant than early designers expected.[60]
•It was expected that breeder reactors would quickly become economically competitive with the light-water reactors
that dominate nuclear power today, but the reality is that capital costs are at least 25% more than water-cooled
reactors.
•It was thought that breeder reactors could be as safe and reliable as light-water reactors, but safety issues are cited
as a concern with fast reactors that use a sodium coolant, where a leak could lead to a sodium fire.
•It was expected that the proliferation risks posed by breeders and their “closed” fuel cycle, in which plutonium
would be recycled, could be managed. But since plutonium-breeding reactors produce plutonium from U238, and
thorium reactors produce fissile U233 from thorium, all breeding cycles could theoretically pose proliferation risks.[61]
However U232, which is always present in U233 produced in breeder reactors, is a strong alpha-emitter, and would
make weapon handling extremely hazardous and the weapon easy to detect.[62]
• There are some past anti-nuclear advocates that have become pro-nuclear power as a clean source of electricity
since breeder reactors effectively recycle most of their waste.
19. Thorium
Thorium is one candidate to replace uranium in
nuclear reactors.
Currently thorium is a potential waste product
from rare earth metal ore refining.
Many of these ores can't be refined due to the
issue of disposing the excess thorium.
Rare earth metals are used in many industrial
and commercial products.
20. Thorium reactors
Thorium-232 is not fissile but
it is fertile.
It needs to be struck by a
neutron to start a decay and
fission chain.
21. Uranium Fuel Cycle vs. Thorium
1000 MW of electricity for one year
250 tons
Natural uranium
35 tons
Enriched Uranium
(Costly Process)
215 tons
depleted uranium
-disposal plans uncertain
Uranium-235 content is
“burned” out of the fuel;
some plutonium is formed
and burned
35 tons Spent Fuel
Yucca Mountain
(~10,000 years)
• 33.4 t uranium-238
• 0.3 t uranium-235
• 0.3 t plutonium
• 1.0 t fission products
1 ton
Natural Thorium
Thorium introduced into
blanket of fluoride reactor;
completely converted to
uranium-233 and “burned”
1 Ton
Fission products;
no uranium,
plutonium, or
other actinides
Within 10 years, 83%
of fission products are
stable and can be
partitioned and sold.
The remaining 17%
fission products go to
geologic isolation for
~300 years.
800,000 tons Ore
200 tons Ore
22. Advantages
• Thorium is three times as abundant as uranium. Estimates that one ton of thorium can
produce as much energy as 200 tons of uranium, or 3,500,000 tons of coal.[25]
• It is difficult to make a practical nuclear bomb from a thorium reactor's byproducts. It
produces less plutonium and some isotopes cause significant issues with nearby
electronics.
• There is much less nuclear waste—up to two orders of magnitude less, The
radioactivity of the resulting waste also drops down to safe levels after just a one or a
few hundred years, compared to tens of thousands of years needed for current nuclear
waste to cool off.[23]
• "once started up [it] needs no other fuel except thorium because it makes most or all
of its own fuel."[4] This only applies to breeding reactors, that produce at least as much
fissile material as they consume. Other reactors require additional fissile material, such
as uranium-235 or plutonium.[17]
• Thorium fuel cycle is a potential way to produce long term nuclear energy with low
radio-toxicity waste.
• Since all natural thorium can be used as fuel no expensive fuel enrichment is
needed.[23] However the same is true for U-238 as fertile fuel in the uranium-plutonium
cycle.
• Mining thorium is safer and more efficient than mining uranium.
23. Disadvantages
• Breeding in a thermal neutron spectrum is slow and requires extensive
reprocessing. The feasibility of reprocessing is still open.[30]
• Significant and expensive testing, analysis and licensing work is first required,
some state that it would "require too great an investment and provide no clear
payoff"
• There is a higher cost of fuel fabrication and reprocessing than in plants using
traditional solid fuel rods.[17][28]
• Thorium, when being irradiated for use in reactors, will make uranium-232, which
is very dangerous due to the gamma rays it emits.
24.
25. Advantages
• Inherently safe design.
– LWR's have no fundamental "off switch", but once the initial
criticality is overcome, an MSR is comparatively easy and fast to
turn off by letting the freeze plug melt.
– A low-pressure MSR lacks a LWR's high-pressure radioactive steam
and therefore do not experience leaks of radioactive steam and
cooling water, and the expensive containment, steel core vessel,
piping and safety equipment needed to contain radioactive steam.
• The fuel's liquid phase might be pyroprocessed to separate fission
products (nuclear ashes) from actinide fuels. This may have advantages
over conventional reprocessing, though much development is still
needed.
• Some designs can "burn" problematic transuranic elements from
traditional solid-fuel nuclear reactors.
• An MSR can react to load changes in less than 60 seconds (unlike many
"traditional" solid-fuel nuclear power plants that suffer).
26. Disadvantages
• Little development compared to most Gen IV designs .
• Required onsite chemical plant to manage core mixture and remove
fission products.
• Required regulatory changes to deal with radically different design
features.
• MSR designs rely on nickel-based alloys to hold the molten salt. Alloys
based on nickel and iron are prone to embrittlement under high neutron
flux.
• Corrosion risk of metal pipes and enclosures
• As a breeder reactor, a modified MSR might be able to produce
weapons-grade nuclear material.[71]
• The MSRE and aircraft nuclear reactors used enrichment levels so high
that they approach the levels of nuclear weapons. These levels would be
illegal in most modern regulatory regimes for power plants.
• Neutron damage to solid moderator materials can limit the core lifetime
of an MSR that makes moderately fast neutrons.
