The Nuclear Energy Alternative
How does it work?
The Nuclear Fuel Cycle
Alternative Fuel Cycles
Legacies
Mr. Nicholas [email protected]
Nuclear Power Generation
Reactor (primary loop) Steam Generator (Secondary Loop) Condenser (Tertiary Loop)
Reactor Coolant System – 4 Loop PWR
Reactor Vessel
Height - 43’ Width – 15’Weight - 435 Tons
Active fuel region:
193 assemblies
3.5% enriched U-235
Fission Process
Thermal “Uranium-235” Fission Fission Products Fast Neutrons Neutron + Energy
Key Components of the Reactor Design
• Neutron Energy • Fission atom (fuel)• Probability of Fission f(E)n, fuel
• Moderator• Coolant• Products of Reactions
Neutron Energy Distribution from Fission
Neutron Energy ( 1 eV = 1.602 x 10-19 joules)
FISSILE AND FISSIONABLE NUCLIDES PRESENTIN LIGHT WATER REACTORS
Nuclide
Thermal NeutronMicroscopic
Cross Sectionfor Fission (barns)
Fissile orFissionable
585 FissileU23592
5 10-6 FissionableU23892
750 FissilePu23994
0.05 FissionablePu24094
1010 FissilePu24194
< 0.2 FissionablePu24294
One barn = 1 x 10 – 24 cm2
How do we characterize:
Probability of fission?
Cross section (target area for incident particle)
Thermal region
How do we slow down (thermalize) the fission spectrum neutrons?
2 MeVNEUTRON
Ef
Ei
COLLISION
0.025 eVNEUTRON
BIRTH ATHIGH ENERGY
ENERGY LOSSESUPON COLLISION
2 MeV
AVERAGETHERMAL ENERGY
NEUTRON ENERGY
TIME
f
i
E
Eln
= logarithmic energy decrement
Ei = initial energy level of neutron
Ef = final energy level of neutron
H2O 0.948 0.66 103
MATERIAL COLLISIONSTOTHERMALIZE
s a
MODERATINGRATIO
x
s s
MICROSCOPICCROSS SECTION(BARNS)
D2O 0.570 0.001 13.6
Be 0.209 0.0092 7.0
C 0.158
19
35
86
114 0.003 4.8
148
7752
159
253
COMPARISON OF MODERATORS
KINETIC ENERGY OFFISSION FRAGMENTS
165 MeV
INSTANTANEOUS
KINETIC ENERGY OFFISSION NEUTRONS
5 MeV
INSTANTANEOUSGAMMA RAYS
7 MeV
DELAYEDKINETIC ENERGY OFBETA PARTICLES
7 MeV
DECAY GAMMA RAYS 6 MeVNEUTRINOS 10 MeV
TOTAL ENERGY RELEASED 200 MeV
FISSION ENERGY
TRACK LENGTH DESCRIPTION OF NEUTRON FLUX
1 CUBICCENTIMETER
NEUTRONDENSITY
NEUTRONVELOCITY (Energy)
NEUTRONFLUX
seccm
NEUTRONS
sec
cm
cm
NEUTRONS23
NEUTRON FLUX
nn
n
n
n
1 SQUARECENTIMETER
nn
Neutrons cm2 sec
Where:
Reaction Rate (Fission)
R = reaction rate(reactions/cm3 sec)
N = atomic density of the fuel (atoms/cm3)
= microscopic cross section (cm2)
f = neutron flux(neutrons/cm2 sec)
R = N f
Where:
REACTOR POWER
P = thermal power output (MWt)
G = thermal energy produced per fission(3.2 10-17 MWt sec/fission)
N = atomic density (fuel atoms/cm3)
sf = microscopic fission cross section (cm2)
V = fuel volume in the core (cm3)
f = neutron flux(neutrons/cm2 sec)
P = G N sf V f
THE SIX FACTOR REACTOR NEUTRON LIFE CYCLE
U-235 FUELMODERATOR
435NEUTRONSFROMTHERMALFISSION
START CYCLEHERE
965THERMALNEUTRON
1384 FASTNEUTRONS
1017THERMALNEUTRONS
1038THERMALNEUTRON
1442 FASTNEUTRONS
1400 FASTNEUTRONSBORN
1400 FASTNEUTRONS
346RESONANCELOSSES
21THERMAL NEUTRONLEAKAGE 52
THERMAL NEUTRONSABSORBED BY NON-FUEL ATOMS
58FAST NEUTRONLEAKAGE
U-235238239
NEUTRONSFROMFAST FISSION
42
p fLth
Lf
e
h
fpk th f eff LL
Moderator
Control Rods
Prompt and DelayedNeutrons
Nuclear Power Generation
Reactor (primary loop) Steam Generator (Secondary Loop) Condenser (Tertiary Loop)
The Existing Nuclear Fuel Cycle
Interim Dry Cask Storage Geologic RepositorySpent Fuel Rods
Mining
US Mines located in the SW
Uranium mines operate in 20 Countries
Half of the world’s supply comes from six operating mines
Current mining practice results in minimal ecological disturbance
Uranium slurry extracted from mines is filtered and then injected with sulfuric acid. Uranium Oxides are a precipitate of the Solution. The precipitate is filtered again and then dried to produce “yellow cake”powder (U3O8)
Purified U3O8 from the dry process and purified uranium oxide UO3 from the wet process are then reduced in a kiln by hydrogen to UO2:U3O8 + 2H2 ===> 3UO2 + 2H2O deltaH = -109 kJ/mole or UO3 + H2 ===> UO2 + H2O deltaH = -109 kJ/mole This reduced oxide is then reacted in another kiln with gaseous hydrogen fluoride (HF) to form uranium tetrafluoride (UF4), though in some places this is made with aqueous HF by a wet process:UO2 + 4HF ===> UF4 + 2H2O deltaH = -176 kJ/mole The tetrafluoride is then fed into a fluidised bed reactor or flame tower with gaseous fluorine to produce uranium hexafluoride, UF6. Hexafluoride ("hex") is condensed and stored.UF4 + F2 ===> UF6 Removal of impurities takes place at each step.
U3O8 is converted to gaseous UF6
Gaseous UF is used to separate the heavierisotopes of uranium from the lighter ina series of high speed centrifuges.
The gas extracted from the center of the centrifuge is enriched in 235U
UF – a powder at room temperature, is shipped to a fuel fabrication Facility and converted to UO2 powder
Density of UO2 = 10.97 g / cm3 , Length of active fuel = 12 feet
SPENT FUEL STORAGE• 55 of 103 US LWRs now using “DRY CASK STORAGE” to store
spent fuel.• The Department of Energy was supposed to provide a
national storage facility by the mid 1990’s. Yet to materialize • Dry Cask Storage is a method of removing spent fuel from
spent fuel pools and storing it in a steel and concrete cask.• Each “Cask” holds 32 Fuel assemblies and is stored on a
concrete pad.
Repository
The Existing Nuclear Fuel Cycle
Interim Dry Cask Storage Geologic RepositorySpent Fuel Rods
Mill tailings include depleted Uranium
Depleted Uranium
Actinides, including Uranium, Thorium, Plutonium
• Neutron Energy Fast, Epithermal, Thermal
• Fission atom (fuel) Actinides• Probability of Fission f(E)n, actinide
• Moderator LW, HW, C, Be• Coolant LW, Liquid Metals, Gases• Products of Reactions Fission Products (Waste)
Actinides (Fuel)
Reactor Types
Nuclear power plants in commercial operationReactor type Main Countries Number GWe Fuel Coolant ModeratorPressurised Water Reactor (PWR) US, France, Japan, Russia, China 273 253 enriched UO2 water waterBoiling Water Reactor (BWR) US, Japan, Sweden 81 76 enriched UO2 water waterPressurised Heavy Water Reactor 'CANDU' (PHWR) Canada 48 24 natural UO2 heavy water heavy waterGas-cooled Reactor (AGR & Magnox) UK 15 8 natural U (metal), CO2 graphite
enriched UO2Light Water Graphite Reactor (RBMK & EGP) Russia 11 + 4 10.2 enriched UO2 water graphiteFast Neutron Reactor (FBR) Russia 2 0.6 PuO2 and UO2 liquid sodium none
TOTAL 434 372
billion kWh Percent
Electric Units
Output
Argentina 5.7 4.4 3
Armenia 2.2 29.2 1
Belgium 40.6 52 7
Brazil 13.8 2.8 2
Bulgaria 13.3 30.7 2
Canada 94.3 16 19
China 104.8 2.1 21
Czech Republic 29 35.9 6
Finland 22.7 33.3 4
France 405.9 73.3 58
Germany 92.1 15.4 9
Hungary 14.5 50.7 4
India 30 3.4 21
Iran 3.9 1.5 1
Japan 13.9 1.7 48
Korea RO (South) 132.5 27.6 23
Mexico 11.4 4.6 2
Netherlands 2.7 2.8 1
Pakistan 4.4 4.4 3
Romania 10.7 19.8 2
Russia 161.8 17.5 33
Slovakia 14.6 51.7 4
Slovenia 5 33.6 1
South Africa 13.6 5.7 2
Spain 54.3 19.7 7
Sweden 63.7 42.7 10
Switzerland 25 36.4 5
Ukraine 78.2 43.6 15
United Kingdom 64.1 18.3 16
USA 790.2 19.4 100
WORLD** 2359 c 11 436
LWR Uranium Recycle without plutonium recovery
30% to 50% improvementin energy extracted
LWR Uranium Recycle with plutonium recovery
Fuel Cycle Design Imperatives Determine Fuel Cycle Implementation
• Minimization of HLW
• Proliferation Concern
• Radiological Accident Dimension (Design Basis and Beyond)
• Energy Output
• Carbon Footprint (vs. alternatives in energy mix)
Legacies
• Waste• Proliferation & weapons potential• Fuel• Proven designs / processes / materials• Human performance methods (60 to 91%)• Lessons Learned
App R, Physical Train Separation, Access for Emerg Psnl
Training, Staffing, I&C, NUREG 0636, RG 1.97, INPO, Human Factors, Emergency Prep
Removal of mid scale failure modes, Auto IB transfer
Natural Circ Cooldown Parametersand Training
BWR Scram discharge volume & ATWS improvements
ATWS procedures, breaker maintenance and designRod misalignment specs and procedures
Focus on failure modes in design / installation of mods
Improved criticality monitoring and approach to criticaility proceduresMOV PMs, ABFP mods
IPTE focus, WANO created
FAC inspection s and PM
Nuclear Generation Part of the Mix?
• One hundred US facilities provide 20% US electric power (780 Billion kWh)• Power generation 24/7 as base load provides grid stability & reliability• One fuel pellet = 17,000 cubic feet of natural gas, one ton of coal• Current HLW volume = one football field, 21 feet deep• Russian Federation weapons supplied 500 tons of US uranium supply (20,000
weapons)• $40 million in wages, 500 jobs per 1000 MW v. 50 jobs for wind or natural
gas• Carbon emission, including mining, construction, fuel fabrication = 17 tons of
CO2 equivalent per GWh (geothermal = 15, wind = 14)• Only type of electric generation with required emergency plans and support
facilities• Current reactor designs could provide 100% (2014 level) of electric supply
for 800 years – without mining an additional gram of uranium