The Nuclear Energy Alternative How does it work? The Nuclear Fuel Cycle Alternative Fuel Cycles...

The Nuclear Energy Alternative

How does it work?

The Nuclear Fuel Cycle

Alternative Fuel Cycles

Legacies

Mr. Nicholas Lizzonslizzo@gmail.com

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