Nuclear Energy

1
Nuclear Energy
2
Nuclear Energy

• How does a nuclear reactor work?
• Is it a major energy source worldwide?
• Is it Green?
• Problems
• Waste Disposal
• Accidents
• Future
• Research
• Generation IV

3
Nuclear Energy Plant

• Nuclear Fission
• 235U n ? 236U ? 92Kr 141Ba g 3n
• Chain Reaction
• Controlled by control (graphite) rods and water
  coolant
• Heat from reactor is cooled by circulating
  pressurized water
• Heat exchange with secondary water loop produces
  steam
• Steam turns turbine generator to produce
  electricity

4
Present Nuclear Energy

• 100 plant produce about 20 of the electricity
  in US
• 431 plants worldwide in 31 countries produce
  about 17 of the worlds electricity
• Environmental Impact
• No Greenhouse gases
• Completely contained in normal operation
• Spent fuel issue

5
Waste Disposal

• Waste kept at plant, but running out of room.
• Site chosen in Nevada for nuclear waste.
• Research on safe transportation
• Nuclear proliferation fuel is very dilute and
  not easily converted to weapons grade
• Stored in very heavy casings (difficult to steal)

6
Accidents

• Nuclear Meltdown
• Fukushima Daiichi
• Chernobyl
• Three Mile Island
• Environmentalist watch dogs note other near
  misses in recent years

7
Fukushima - 2011

• 6 Power plants on site
• 9.0 earthquake , followed by a 45 ft tsunami
• Flooded power plant
• 1/10 radiation that was released in Chernobyl
  accident

8
More info

• Reactor 4 had been defueled at time of shutdown
  and Reactors 5 and 6 were in shutdown mode for
  routine maintenance
• The tsunami destroyed the connection to the grid
• The tsunami flooded the pumps, shorting them out
• Reactors 1-3 experience complete meltdown

9
more

• Tokyo in 2008, an IAEA expert warned that a
  strong earthquake with a magnitude above 7.0
  could pose a "serious problem" for Japan's
  nuclear power stations.
• In the late 1990s to comply with new regulatory
  requirements, three additional backup generators
  for reactors Nos. 2 and 4 were placed in new
  buildings located higher on the hillside. All six
  reactors were given access to these generators,
  however the switching stations that sent power
  from these backup generators to the reactors'
  cooling systems for Units 1 through 5 were still
  in the poorly protected turbine buildings. All
  three of the generators added in the late 1990s
  were operational after the tsunami. If the
  switching stations had been moved to inside the
  reactor buildings or to other flood-proof
  locations, power would have been provided by
  these generators to the reactors' cooling
  systems.
• Hydrogen Explosions Zr 2 H2O ? ZrO2 2 H2
• Sea water

10
Chernobyl (1986)

• A planned test gone horribly wrong
• The test
• See if turbine generator could power the water
  pumps that cool the reactor in the event of a
  loss of power
• Crew shut off power too rapidly, producing a Xe
  isotopes that poisons the reactor
• In response the rods were lifted to stimulate
  reaction
• The lower cooling rate of the pumps during the
  experiment led to steam buildup that increase
  reactor power
• Temperature increased so rapidly, that rod
  insertion could not be performed in time to stop
  meltdown
• Roof blew off, oxygen rushed in a caused fire
  that spread radioactive material over a large area

11
Blame

• Management communication
• A bizarre series of operator mistakes
• Plant design, poor or no containment vessels
• Large positive void coefficient (steam bubbles in
  coolant)
• Poor graphite control rod design
• Poorly trained operators
• Shut off safety systems
• Helicopter drops
• Coverup

12
Consequences

• Deaths of plant and workers
• Medical problems (short and large term)
• Thyroid cancer
• Contaminated soil as far as Great Britain
• Billions of

13
Comparison

• A key difference between the Fukushima accident
  and the Chernobyl accident was that the Chernobyl
  explosion shattered the fuel and flung it out of
  the reactor building, while at Fukushima there
  was no steam explosion driven by the release of
  fission energy.

14
Three Mile Island

• Partial meltdown
• No radiation escaped
• Caused fear of nuclear power and cost in terms
  of clean up
• Operator error and lack of safety backups in
  design
• In some ways the accident showed how the kind of
  catastrophic disaster at Chernobyl is avoidable

15
types

• Generation I retired one of a kinds
• In operation Gen II and Gen III
• Gen II was a large design changes
• Gen III and Gen II, upgraded with many safety
  features along the way
• Gen III plus (passive safety systems)
• Gen IV, 30 yrs away

16
Gen IV

• Very High Temperature Reactor
• Advance Nuclear Safety
• Address Nuclear Nonproliferation and Physical
  Protection Issues
• Are Competitively Priced
• Minimize Waste and Optimize Natural Resource
  Utilization
• Compatible with Hydrogen Generation

17
Gen IV Roadmap - 2002

• Solicited design models
• Chose six design models to base future research
• Out of these six, the DOE has relatively recently
  selected two for further investment
• Very-High Temperature Reactor (VHTR)
• Sodium-Cooled Fast Reactors (SFR)

18
Very-High Temperature Reactor

• Reach temperatures gt 1000 C
• Drive water splitting for hydrogen production 2
  M m3
• 50 efficiency for producing electricity
• Heat and power generation
• Fuel recycling/reprocessing
• Fuel coating requirements, absorbers, ceramic
  rods, vessel materials, passive heat removal
  systems

19
Show pic
20
Actinide management

• To support effective actinide management a fast
  reactor must have a compact core with a minimum
  of materials which absorb or moderate fast
  neutrons. This places a significant heat transfer
  requirement on the coolant.

21
Sodium-Cooled Fast Reactors

• Old technology
• Management of waste
• Low system pressure, high thermal conductivity,
  large safety margins.
• Burns almost all of the energy in uranium, as
  opposed to 1 in todays plants
• Smaller core with higher power density, lower
  enrichment, and lower heavy metal inventory.
• Primary system operates at just above atmospheric
  pressure
• Secondary sodium circulation that heats the water
  (if it leaks, no radiation release)
• Demonstrated capability for passive shutdown and
  decay heat removal.