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NUCLEAR FUEL CYCLE: Nuclear Source Characterization T. Downar Nuclear Engineering Purdue University March, 2005 THE NUCLEAR FUEL CYCLE

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Nuclear fuel cycle nuclear source characterization l.jpg
NUCLEAR FUEL CYCLE:Nuclear Source Characterization

T. Downar

Nuclear Engineering

Purdue University

March, 2005


The nuclear fuel cycle l.jpg
THE NUCLEAR FUEL CYCLE

  • The Nuclear Fuel Cycle consists of sequence of steps in which uranium ore is mined, milled, enriched, and fabricated into nuclear fuel and then irradiated in a reactor for several years.

  • The entire fuel cycle lifetime from mining to discharge is about 8 years.


Fuel cycle economics l.jpg
Fuel Cycle Economics

  • Transaction Cost:mills/kwhr(e)

    • Ore 1.00

    • Conversion0.15

    • Enrichment1.10

    • Fabrication1.60

    • Disposal1.00

    • Misc0.25

  • Total5.10


Nuclear energy costs l.jpg
Nuclear Energy Costs

  • Fuel Cycle 0.5 cents/ kwhr(e)

  • “Busbar” Cost* ~5.0 cents/ kwhr(e)

  • Total annual Value of electricity from typical nuclear plant:

    1000E3KW x 8760hr x 0.90 x 0.05 = 394E6dollars

  • Value of annual fuel loading in a nuclear plant

    0.5E6 dollars/fuel assembly x 64 assemblies = 32E6dollars


Nuclear electricity cost model l.jpg
Nuclear Electricity Cost Model

  • Fuel Cycle Cost: ef

    • i=fuel cycle transaction (e.g. enrich, fabrication, etc)

    • C=Cost for transaction “i”

    • M=Mass of fuel for transaction “i”

    • F=Financing Factor

  • Busbar Cost: eb

    • L=Capacity Factor

    • A=capital costs

    • I=construction costs

    • O=operating costs

    • K=plant power rating

  • System energy costs: es

    • er = replacement energy costs


The nuclear fuel cycle7 l.jpg
THE NUCLEAR FUEL CYCLE

  • After irradiation the fuel is cooled in the spent fuel pit for several years and then moved to dry cask storage on the reactor site.

  • Current plans are to open the YUCCA Mountain high level waste repository in 2015 


Spent nuclear fuel pool l.jpg
Spent Nuclear Fuel Pool

  • Keep spent fuel rods under at least 20 feet of water to provide adequate shielding from the radiation for anyone near the pool

  • Spent Fuel Pools were designed as TEMPORARY storage for fuel while short lived isotopes decay (<1 yr)


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Nuclear Plant Schematic

Containment (Hardened Structure)

Fuel Building(Soft Structure)



Long lived radioactive isotopes in discharged nuclear fuel l.jpg
Long Lived Radioactive Isotopes in Discharged Nuclear Fuel

  • Fission Products

    • Over 60 isotopes

    • 7 isotopes have significant gamma decay during first 20 years that can be useful to identify the source: Zr95, Nb95, Ru103, Cs134, Cs137, Ce141, Ce144

  • Actinides

    • Over 20 isotopes

    • The gamma rays generated by Actinides have lower energy


Fission product build up in a nuclear reactor l.jpg

Parent 1

Parent 2

Fission

Decay

2

Yield

Yk

Decay

1

Capture Neutron σk

Capture Neutron σj->k

Iso. j

Iso. k

Decay

k

Fission Product build up in a Nuclear Reactor

  • Nuclide balance:

  • Governing Equation:

  • Half Life:


Fission product decay chains l.jpg

0.8%

95mNb

86.6h

94.6%

99.7%

103mRh

56.12m

95Zr

64d

103Ru

39.35d

94.5%

134Cs

2.026y

95Nb

35d

103Rh

99.2%

5.4%

0.3%

1.4%

144mPr

7.2m

141Ce

32.5d

137mBa

2.552m

144Ce

284.3d

137Cs

30.17y

154Eu

8.8y

144Pr

17.28m

137Ba

98.6%

106Ru

368.2d

103mRh

29.9s

Fission Product Decay Chains

  • Red isotopes have short half lives, they decay out within one year

  • Blue isotopes have gamma decays in longer period

  • Other isotopes are either stable, such as 103Rh, or very short half lives.

    • The gamma decay from very short half life isotope can be taken count with their parent isotopes




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Inventory of Nuclear Fuel

United States

  • 103 nuclear power plants

  • 22% of electrical power

    World

  • 438 nuclear power plants (33 under construction)

  • 17% of electrical power

  • 30 countries use nuclear power

  • 16 countries produce more than 25% of electrical power using nuclear energy



Proliferation of nuclear materials l.jpg
Proliferation of Nuclear Materials

  • Worldwide there exists on the order of a million metric tons of nuclear material from the commercial nuclear industry alone (400 plants x 50 tons/year x >20 years).

  • When combined with military waste and medical isotopes, the potential data base to catalogue the complete inventory of nuclear materials can not be accessed in “real time”


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Motivation for Radiation Source Characterization

  • The decision making for response to the detonation of a “Dirty Bomb” requires methods that can rapidly characterize and identify the origin of the nuclear materials used in the bomb.

  • If the material is from nuclear spent fuel, three parameters are important to identify the origin of the source:

    • Cooling time: time after it is discharged from the reactor

    • Burnup: the amount of fuel used up in the reactor

    • Reactor type: whether it comes from a PWR (Pressured Water Reactor) or a BWR (Boiling Water Reactor)


Pwr vrs bwr l.jpg
PWR vrs BWR

Are the nuclide inventories sufficiently different between these two types of reactors to enable distinguishing whether proliferated nuclear source came a PWR or a BWR?

PWR (1/8) Assembly BWR Assembly


Fission product densities in pwr as a function of fuel irradiation time burnup l.jpg
Fission Product Densities in PWR as a Function of Fuel Irradiation Time (Burnup)


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Difference in Fission Product Inventory in BWR and PWR


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Actinide Difference Between BWR and PWR


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Radiation Detection Equipmentwww.canberra.com

  • Commercial “Field” Detection Equipment

    • Inspector1000 Handheld Radiation Identifier

    • Inspector2000 Portable Spectroscopy Workstation

      • Multichannel Analyzer

      • Nuclide Identification / Activity

  • The technology exists to rapidly characterize a nuclear source by isotope and activity

  • How do we identify the origin of the nuclear source?


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Artificial Neural Networks (ANN)

  • Artifical Neural Networks (ANN) have been well established as accurate and efficient tools for a wide variety of practical applications.* In the work here we will train neural networks using isotopics data from all known possible sources of radionuclides.

  • Sufficient differences exist in the radioactive decay of the nuclides and in the irradiation spectrum of the various nuclear power plants in the world that there should be sufficient differences in the characteristics of the nuclear materials and their radiation fingerprint.

    * [Tsoukalas, 1997] Tsoukalas, Uhrig “Fuzzy and Neural Approaches in Engineering,” Wiley, 1997.


Nuclear source characterization identification with anns l.jpg

Mdiecal

Military

BWR

PWR

Nuclear Source Characterization/ Identification with ANNs

Hand-held

Detector

GammaSpectra

Pattern Transformation

Neural Networks Pattern Recognition

Decision

Making


Artificial neural networks ann31 l.jpg
Artificial Neural Networks (ANN)

  • A hierarchical approach is used to isolate the origin of the source.

    • For example, at the highest level, the ANN will be trained to identify whether the nuclear materials came from a commercial reactor, a military waste site, medical facility, etc.

    • At the next level, the ANN will be trained to identify the specific type of commercial power reactor (e.g. pressurized vrs boiling water reactor) and then to identify the specific plant by using information on the plant operating history.


A typical run of the neural network l.jpg

Ru106/Cs137

Cs134/Cs137

Ce141/Cs137

Ce144/Cs137

Eu154/Cs137

A Typical Run of the Neural Network

-1: PWR

+1: BWR

?

=

GwD/T

Year

Ratios as Inputs

Trained Neural Net

Neural Net Output

Desired Target


Summary l.jpg
Summary

  • The ANN approach is an advanced analysis algorithm that can be integrate with any hand-held gamma detector and is capable of identifying commonly seen isotopes.

  • It provides forensic clues of sources’ origins: medical uses, industrial or nuclear spent fuel. For nuclear spent fuel, it further provides possible type of reactor: BWR, PWR, etc.

  • The required resources (CPU time and memory storage) are nominal and can be easily integrated with any hand-held device to provide information in real time on the scene.

  • It relies on advanced software technologies and the implementation is very low cost and operates automatically without human operators’ interferences.


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