Nuclear Fission Energy in the U.S. Status and Trends in …€¦ · Principles of Energy Generation from Nuclear Fission Fission chain reaction and reactor control Open fuel cycle

Nuclear Fission Energy in the U.S. Status and Trends in Technology

W. Udo Schröder, 2010

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The Diablo Canyon NPPT produces CO2-free electricity at half the state’s (CA) average cost (2¢/kwh)

Nuclear Fission Energy in the U.S.

Status and Trends in Technology


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I. Introduction: Energy Demand and Outlook

II. Principles of Energy Generation from Nuclear Fission

Fission chain reaction and reactor control

Open fuel cycle

III. Strategic Issues for Nuclear Power

IV. New Nukes: Advanced Nuclear Energy Technologies

Gen III and IV reactors

Closed fuel cycle

V. Conclusion: Nuclear Power in a Sustainable Energy Future

Present Energy Demand (U.S.)


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450 Quad Btu/a = 220GJ/a U.S. uses 25% of total global energy demand, 65% imported (Canada, Mexico,.., Middle East) Oil & nat. Gas & Coal 95% Main Energy Uses: •Industry •Transportation (liquid fuels) •Agriculture •Commercial & public •Residential

Renewables 0.2%

Natural Gas 26%

Oil 44%

Coal 25%

Nuclear 2.4%

Hydro 2.6%

IEA 2004

Renewables 2.3% Oil 3%

Coal 49.7% Nuclear

19.3%

Hydro 6.5%

IEA 2004 Other 0.5%

Total

Electricity

Growth potential | bound. cond’s. Nuclear Energy: high power density, scalability, economics

Introduction: America’s Energy Outlook


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Predictions (IEA) 1: World (US) demand up by +50 (28)% (25y: $20T, U.S. >$5T) Now : 450 Quad Btu/a 2030: 680 Quad Btu/a

2: Redistribution Industrial World vs. Developing World 40 Bbloe/a (220 GJ/a) vs. 6 Bbloe/a (34 GJ/a))

Boundary conditions 1: Disappearing resources (IEA) Now, or soon: beyond peak oil > 2050(??) peak gas, unconventional gas (shale) > 2090 peak uranium (235U) ? 2: Mitigate anthropogenic pollution Improve energy efficiency Reduce GHG emissions (fossil fuels) Alternative energy sources (renewables, nuclear) 3: US energy security/independence in global context !?

How to manage significant increases @ Boundary conditions?

(only moderate growth possible, nuclear energy needed)

Nuclear Plants Existent & Under Construction


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Trends in Nuclear Energy Production

Steady increase of nuclear power output over past 20 years. Now equivalent: 24 quads of oil

World (US) 443 (103) reactors 365 (100) GW


World 53 new reactors, US:3-4, > 20 planned, license applications US potential: several new reactors/a (@ $(2-3)B/GWe, 5¢/kWh)




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Open fuel cycle




Closed fuel cycle


Nuclear Rearrangement Energies


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Einstein: equivalence mass = energy E = M·c2

310235 2 9

9

47 47 4 10

1 4 10

M M

fission

M M

combustion

M U mg E g c J

M TNT t E J

M(N,Z) < N·Mn + Z·Mp M B(A=N+Z)

Fe Ni

In assembly of a nucleus B=Mc2 is released to outside

Energy release in fission A2A/2

Nuclear Fuels

fissile

fertile + n

fertile + n

fissile enrichment weapons

Enrichment for fuels 3-4 % fissile Enrichment for weapons >90 % fissile

fissile hot enrichm.weapons


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Energy Generation from nth-Induced Fission

235

147

236 *

236 *

2 2(3) 200

: 287 *fast

thU n FF n MeV

Ex

U

U Brample La n

Converts 0.1% of the mass into energy 1g 235U/day = 1MW 108 x chemical energies

Eff = 168 MeV En tot = 5 MeV Eg = 7 MeV

FF b-decay = 27 MeV Qtotal = 207 MeV

Neutrons per fission: k = 2.5±0.1 k=1 critical (chain rxn) Fission neutrons are fast:

n-energies <En>≈2 MeV

n’s less likely to induce

further 235U fission

Most fission neutrons are lost and/or not useful for further fission Fission fragments = reactor poison, stop chain reaction. k < 1 !!!

236U*

fission fragment

fission fragment

n

n

n


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Thermal-n Induced Fission Chain Reaction

Leo Szilard 1938

Neutron multiplication through fission k=2.4, minus losses (capture, leaking,..), effective k < 2.4.

One n used in fission effective multiplication k-1:

1

11

( ) (0)

nn

k tn n

dNk N

dt

N t N e

k >1: avalanche of n = time betw. generations ( ~ 40s in reactors ~ ns in explosives)

eff prompt delayedk k k

Characteristic period: ( 1)eff

Tk

keff≈1

e.g.,keff=1.03

Reactor Control

Most fission neutrons are lost and/or not useful for further fission Fission fragments = reactor poison, stop chain reaction. k < 1 !!!


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Neutron Moderation

Fast Neutrons from Fission

Fission neutrons too energetic, “thermalize” to maximize sf for 235U

multiple elastic scattering (“moderation”) moderator: small scapt !

A=238

A=65

A=12

A=1

Need:2 MeV 0.025 eV/2MeV= 10-8

Need to “miss” 238U capture resonances (2eV< En <10keV)

H2O, D2O, Be, C(graphite), prevent leakage

moderator

n-reflector

U U U

d<lfast

Slow down

H, D are best moderators

moderator

H can capture neutrons: H+nth D+2.2 MeV


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Fission and n-Capture Probabilities

Neutron Kinetic Energy (eV)

Neutr

on C

aptu

re a

nd F

issio

n C

ross S

ection (

b)

235U

238U

natU: 99.3% 238U, 0.7% 235U

Fission cross sections 238U: sf ~ 1 b for En > 1 MeV ≈ 0 b for En < 1 eV dominating: scattering (~8b) + capture

235U: sf ~ 1-2 b for En > 1 MeV ~ 103 b for En < 1 eV dominating: (n, f) fission

Observed fission due to (0.7%) 235U

isotopically enrich 235U (4% for light-water reactors)

How to induce a self-sustaining fission reaction? Recycle and slow down fission neutrons!

Quantum Mech. “resonance”

Slowing-down (moderation) of fission neutrons by elastic scattering on moderator nuclei (H, C,…)

“cross section” Probability

99.3%

0.7%

Slow down

Principle Boiling Water Reactor


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Nuclear Power Plant 1-2GW


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Passive safety: Pressure reactor vessel ~1’ thick steel, pressure tubes, Reactor containment building with several 3-4 foot thick concrete walls, concrete + water shielding on top of reactor vessel, gravitation replaces mechanical pumps.

Fail-safe operation Negative Reactivity Negative feedback loops: Reaction subsides when • coolant gets too hot or disappears (less dense, less moderation) • fuel gets too hot (n capture increases) • control rods are not moved out

2-3 B$/NPPt

Nuclear Fuel Storage & Transport


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Progress Energy

W. Udo Schröder, 2010 ECE_New Nukes 17

US Now

Radiotoxicity of Spent Nuclear Fuel


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Radio toxicity vs. time after shutdown, of spent fuel from

•pressurized water uranium reactor (PWR),

• U/Pu breeder, and

• Th/U fuel cycle.

FP indicates the faster decay of fission products.

Multiple reprocessing, less residuals.

Reprocessing involves robotics because of Tl gamma radiation

not for extremists’ garage!

(David, Nifenecker, 2007)

Natural uranium




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Fuel cycle




Closed fuel cycle



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1. Operational reactor safety ………………………………….

2. Resource limits of nuclear fuel (235U/Pu, Th,…) …

3. Safe capture, storage and sequestration of

radiotoxic nuclear waste …………………………………….

4. Proliferation resistance (nations, individuals) ……

5. Economy (Capital plus fuel costs) ……………………….

6. R&D requirements ……………………………………………….

7. Capability for rapid deployment

8. Public perception ………………………………………………….

√

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√

√

(√)

(√)

(√)

Status

Fatalities in Energy Production (1969-2000)


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Paul Sherrer-Institute/Switzerland. Omitted: large hydro disasters Shimantan and Banqiao (China 1976: 26,000†).

2006 U.S. coal mines : 42† (equivalent 1 Chernobyl nuclear accident/a)

LNG

Chernobyl/ Ukraine 1986: 45 Ŧ

Pollution Footprints of Energy Technologies


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GHG (fossile): CH4, CO2, NOx, SOx, H2O Other (fossile): Particles PM2.5, Metals (coal, oil): (Be,…., Hg, U, Th) Chemical toxins (Solid-state PV) Radiotoxins (99% from coal, airbn: 80-100 t U/a nuclear fuel residues: Fiss Frgm, Min Actind, localized + decays)

High power density small environmental footprint Nuclear

Nuclear Fuel Resources


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World (US) 443 (103) reactors 365 (100) GW U use: 67 kt/a World reserves: 5 Mt known (15 est.) Once-through cycle:200 years Reprocessing: ~103 years US:174 t weapons grade U for fuel mix Th use: little so far World reserves >15 Mt ~103 a with reprocessing. Gen IV breeder reactors, Thorium reactors, molten salt reactors



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Multiple reprocessing, less residual waste.

Transmute/incinerate transactinides and FF solves waste issue

Store very small amounts of HL waste for ~100 years small geological depository, problem disappears in time.


Natural uranium

Deployment Potential


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Past performance: Construction dates of reactors still operating (GWe vs. year). 1985: France built (completed) 2.5 GW/a Construction time now 2 years/NPPT Japan, Korea, China Operator manpower

D. McKay: Sustainable energy without the hot air, 2009

Can we double nuclear capacity over 25 years? 100 GW/25y=4 GW/a = (2-3)NPPT/a requires $(8-10)B/a = 12,000 construction workers continuously. + 2500 operators/a

Capital Requirements


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Can we afford to invest long-term $10 B/a into nuclear energy infrastructure? (Can we afford not to??) Economic necessity, global growth high-tech industry

No strategic problem, except political and regulatory

Economics of scale for standardized, modular NPPT

Loan guarantees

Combined licensing for construction and operation

Limit number of standardized, safe reactor designs

Mass fabrication of modular designs (combine for size)

Integrated self-contained modules (on site disposal)

Strategic Issue: Nuclear Proliferation


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“ At present, nine countries have developed and possess nuclear weapon stockpiles, each in the proclaimed interest of national security. In fact, for a nuclear-armed country the presumed retaliation for a first-strike nuclear attack on another nuclear country is a strong deterrence of such use and of war-like conflict resolution in general. And perhaps for these reasons, despite much international tension and a number of armed conflicts, in 63 years the U.S. has remained the only nation that has ever engaged in nuclear warfare. This action was taken in an epoch when nuclear retaliation was not an option for an adversary. “

Nuclear power plants in a specific country is neither necessary nor sufficient for the production of nuclear weapons.

Threat from individuals, not nation states. Illicit trade in weapons-grade 235U or 239Pu. Weaponized 235U or 239Pu: > 95% enriched Need ~ (10-20) kg for one bomb. Reactor materials: low-enriched mix of isotopes




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Fuel cycle




Closed fuel cycle


Timeline of Advanced Reactors/Fuel Cycles

GNEP framework (now includes U.S., U.K.)

2030: Gen IV designs studied, modelled, tested:

• Very high-temperature reactors (VHTR)

• Sodium-cooled fast reactors (SFR)

• Reactors cooled by supercritical water

(SCWR)

• Lead-cooled fast reactors (LFR)

• Gas-cooled fast reactors (GFR)

• Molten-salt reactors (MSR)

Already testing Gen IV: France, Japan, S-Africa, China, India


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• Operational reactor safety;

• Resource limits of nuclear fuel

(235U/Pu);

• Safe capture, storage, sequest-

ration of radiotoxic waste;

• Prevention of proliferation of

nuclear materials for weapons;

• Economy of nuclear energy.

Advanced Reactors: Pebble-Bed HTR


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He (inert gas) cooled T 9500C

C-moderator/reflector Continuous throughput replacement of “pebble” fuel elements Strongly negative reactivity. Core has high surface/volume ratio, low power density. Fail-safe operation.

S-Africa, China: Modular (@250MW)

Advanced Reactors: Pebble-Bed HTR


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He (inert gas) cooled T 9500C

C-moderator/reflector Continuous throughput and replacement of “pebble” fuel elements Strongly negative reactivity. Core has high surface/volume ratio, low power density. Fail-safe operation.

Modular reactor batteries (@250MW) Built in S-Africa, China

Modular Pebble Bed Reactor Fuel Pebbles


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Small UO2 spheres embedded in graphite matrix, silicon carbide/graphite shells

Proliferation resistant difficult reprocessing

Small Modular Reactors


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Prefabricated (GE A-1000 conventional PWR comes in 300 parts) Few standardized reactor designs. Autonomous operation: without human interference, self-fuelling (traveling wave) U or Th fuel Babcock-Wicox modular reactor Could run on Th Hyperion 200 MW U/He


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Transmutation of Spent Nuclear Fuel in ADS

Spallation: n multiplication incineration of waste generates E Advanced (ADS) reactor development under GNEP program

Yucca Mountain = overkill Much more than needed with reprocessing


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Fuel Breeding 239Pu/233U Breeding

238 239 239 492 9323min 2.4

23994

1 22.4 10

t d

U Pu Cycle n n

U n U auNp Pb b

Technologically understood, several working research/test reactors

Fast (neutron spectrum) U reactor: n-capture without fission

239 24094 9

240 24944

194| Pu nP uP Puu n

Isotope mix: Not useful for nuclear fuel/weapons extensive isotope separation

Continued n capture/b decay

Need many neutrons: source is unimportant ! (Use waste or heavy materials like Pb, Bi,….)

Prevent additional n capture


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232Th/233U Fuel Breeding

Technologically understood, several working research/test reactors

Fast (neutron spectrum) U reactor: n-capture without fission

b

b b

234 234 591 926

232 233 233 590 90 9122min 2

29271 2

33

2.5 10

1.6 10

h

t d

Th U Cycle Pa U a

n n

Th n Th P Ua a

India builds Th reactor fleet large Th resources, small waste problem.

(Mumbay test reactor). Also France, Russia

Isotope mix: Not useful for nuclear fuel/weapons extensive isotope separation

Prevent additional n capture


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Nuclear Transmutation of Fission Products

99 100 100

15.8

129 130 130

12.4

s

h

Tc n Tc Ru

I n I Xe

b

b

stable isotopes

Transmutation of actinides: n-induced fission of Pu, Np, Am, Cm radioactive and nonradioactive fission

products (most with half-lives < 30 a ).

Transmutation of fission products carried out by specific nuclear reactions induced by neutrons, protons, photons, light nuclei, e.g., resonant n-capture. Need high n flux Fn~1016/s·cm2 C.D. Bowman et a., NIM A320, 336 (1992) H. Nifenecker et al., Accelerator Driven Subcritical Reactors, IOP Bristol, 2003



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Multiple reprocessing, less residual waste.

Transmute/incinerate transactinides and FF solves waste issue

Store small amounts of HL waste for ~100 years small geological depository


Natural uranium

Conclusion: Nuclear Power in a Sustainable Future


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Develop and Employ Advanced Nuclear Power in the US:

• Continue to improve the safety of nuclear reactors and processing plants.

• Test/construct advanced modular nuclear reactors @ sites of existing plants.

• Test/construct advanced burner/transmuter reduce radiotoxic waste.

• Import/develop closed nuclear fuel cycle technologies.

• Develop/test proliferation-safe reprocessing methods (e.g., UREX+).

• Test/develop a closed Th/U breeder fuel cycle.

• Develop ADS systems, high current accelerator technology.

• Develop the chemistry of molten salt mixtures, molten salt test reactor.

• Expand the radio-chemistry of actinides, transactinides and fission products.

• Operating a semi-permanent nuclear waste depository, flexible strategy.

• Train personnel in nuclear and radiation technologies !

Promising and potent: Advanced nuclear power, redirection of electricity generation mainly to nuclear. Develop synfuels from coal/nat. gas. Need massive renewal of energy infrastructure


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Auxiliary slides following

Useful Figures for Illustration

Fuel: Pu-239. E in 1 lb of Pu-239 =2,000,000 lbs of coal

US: 104 nuclear reactors in operation (20% electricity). Total spent fuel discharged= 2,000 tons/a 95% = U-238, 4% (80 t) FF (waste), 1% is transuranics (TRU). Of the 1% TRU, 90% is Pu, which can be recycled as fuel. Remaining 10% (0.1% of the total) is Np, Am, and Cm = “waste” can be recycled in a fast reactor Actual waste (FF) per year: 4% of 2,000 tons = 160,000 lbs. =0.2 grams per person per year. If 100% electricity from nuclear power for entire lifetime,

nuclear waste = one coffee cup. Compare: carbon footprint of 20 tons of CO2 per year.


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The half-lives of the numerous fission products vary from a fraction of a second to many years. It takes about 500 years for the fission products to decay to same level of radioactivity as the natural uranium we started with.


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bDelayed Neutrons

87% of fission energy (≈200 MeV) promptly in fission ≤ 10-14 s 13% emitted in b-decays of fission fragments, range of life times delayed emission of b, b, ne, g, n

0.65% of neutrons from 236U fission are delayed (occur after fission)

essential for sustaining chain rxn + control function

bdelayed neutron <> ≈ 80 s

86Kr+n

87Kr

87Br

b 2%)

b

b

87Rb

87Sr

b

98%)

(55.6 s)

(76 m)

(5·1010a)

Example

k<1 keff≈1 Effective neutron multiplication factor, but not all “survive” Most have “wrong” energy for 235U chain rxn

Reactor Control and Safety


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“Reactivity“ = (keff-1)/keff Reduce by n absorbers Cd, B (control rods, moderator) Automatic: fission products= “reactor poisons“

In BWR/PWR: Doppler Effect: broadening of resonance and n spectrum leads to increased n-capture by 238U d/dT < 0

Density Effect: hot moderator expands, lower density longer mean free path, less moderating efficiency d/dT < 0

Dilatation Effect: hot moderator delays slowing down d/dT < 0

U U U

Cd Control Rods

Temperature dependent reactivity coefficient d/dT<0 Negative reactivity desirable.

d/dT = -(0.5-1)x10-4/0C PWR

d/dT = - 1x10-3/0C Breeder, EA

Storage of Used Fuel Elements

Spent fuel is stored under water for at least 5 years to allow the fuel to cool (water is also an excellent shielding material). After that the fuel can be transferred to dry storage casks, which use steel and concrete for shielding. Six inches of concrete will stop more than 90% of the radiation from the spent fuel. A typical cask has about 3 inches of steel (for gamma shielding) and almost 3 feet of heavily reinforced concrete (for both gamma and neutron shielding).


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New “Traveling Wave” Micro Reactors


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integrated, self-contained, autonomous units

LFTR On-Line Processing


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Molten Salt Thorium Reactor Principle


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W. Udo Schröder, 2010 ECE_New Nukes 50


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Open Fuel Cycle

weapons Pu MOX fuels

Advanced Closed Fuel Cycle


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Aqueous nuclear fuel reprocessing scheme. Spent fuel rods are cut open and dissolved chemically. Isotopic separator provides different streams for uranium, actinides and fission products. U and Pu recast into fuel elements for another reactor cycle. Fission products and some transactinides are vitrified and stored in long-term repository.

Public Misconception: Size


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70 MW floating nuclear power plant (planned Rosenergoatom)

“One problem with NPP is that they only come in one size, XL”

Balakova 1- 4 PWR @0.95GW Moscow/Russia

In fact: NPPs come in many sizes, S: few MW research reactors M: 50 MW submarines, carriers L: 250 MW modular (pebble bed) XL:1-2GW large commercial

Friedman

Documents

Nuclear Fission Energy in the U.S. Status and Trends in …€¦ · Principles of Energy Generation from Nuclear Fission Fission chain reaction and reactor control Open fuel cycle