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The Fission Mechanism And Nuclear Energy
Philipp Büttner 1/19
The Fission Mechanism And Nuclear Energy
Nuclear Power06.12.2011
The Fission Mechanism And Nuclear Energy
Philipp Büttner 2/19
FISSION
1. Fission Mechanism, Spontaneous Fission
2. Neutron-Induced Fission, Chain Reaction
3. Nuclear Energy
The Fission Mechanism And Nuclear Energy
Philipp Büttner 3/19
FISSION
1. Fission Mechanism, Spontaneous Fission
2. Neutron-Induced Fission, Chain Reaction
3. Nuclear Energy
The Fission Mechanism And Nuclear Energy
Philipp Büttner 4/19
Fission Mechanism: fission barrier
spherical nucleus
r1
~
The Fission Mechanism And Nuclear Energy
Philipp Büttner 5/19
Spontaneous Fission: Fissility(derivation: Demtröder 4, p.164)
• surface:• Coulomb:
spontaneous fission:
→ fissility:
→ spontaneous fission: or
example: :
CCCC
SSSS
EEEE
EEEE
0
510
0520
²1
²1
… deformation
00 2 SCSC EEEE
AZ
E
Ex
S
C
50²
2 0
0
Bethe-Weizsäcker-formula
1x 50² AZ
14623892 U
36238
²92
The Fission Mechanism And Nuclear Energy
Philipp Büttner 6/19
50²
,1 AZ
x
25²
,5.0 AZ
x
14623892 U
The Fission Mechanism And Nuclear Energy
Philipp Büttner 7/19
FISSION
1. Fission Mechanism, Spontaneous Fission
2. Neutron-Induced Fission, Chain Reaction
3. Nuclear Energy
The Fission Mechanism And Nuclear Energy
Philipp Büttner 8/19
Neutron-Induced Fission
1934 Enrico Fermi: new elements by impact of neutrons on
Uranium → β-active products1939 F. Straßmann, Lise Meitner, O. Hahn:
- discovered Barium as one of these products => fission:
3n Kr Ba U U n 9236
14456
23992
23892
The Fission Mechanism And Nuclear Energy
Philipp Büttner 9/19
Neutron-Induced Fission
neutrontarget
fissioningnucleus
6.9 5.4 -1.5
6.6 5.7 -0.9
even number of neutrons => => fission by motionless neutrons
5.3 6.0 0.7
4.8 6.5 1.7
odd number of neutrons => => fission by kinetic neutrons
)U( 192
AeE fbE efb EE
U23392 142
23492 U
U23592 144
23692 U
U23492 143
23592 U
U23892 147
23992 U
fbe EE
fbe EE
Plutonium
Uranium
The Fission Mechanism And Nuclear Energy
Philipp Büttner 10/19
Neutron-Induced Fission: Fission Fragments200MeV 43.2 Ba Kr U U 5636
23692
23592 nn
minimum:
maximum:
12
1 AA
32
2
1 AA
The Fission Mechanism And Nuclear Energy
Philipp Büttner 11/19
Chain Reaction
B A X X nn
The Fission Mechanism And Nuclear Energy
Philipp Büttner 12/19
Chain Reaction
• chain reaction:
→ since , a multi-plicative effect canoccur
→ number of neutronswill be multiplied
→ reaction rate incrases
1
The Fission Mechanism And Nuclear Energy
Philipp Büttner 13/19
Chain Reaction: Multiplication Factor
supercritical regime → chain reaction• sub-critical regime → no chain reaction
critical regime → constant reaction
• dependency:- - non fissioning absorbtion- diffusion- …- mass (k=1 => critical mass)
1
1
1
k
,...)3,2,1( 1 iN
Nk
i
i
k
The Fission Mechanism And Nuclear Energy
Philipp Büttner 14/19
FISSION
1. Fission Mechanism, Spontaneous Fission
2. Neutron-Induced Fission, Chain Reaction
3. Nuclear Energy
The Fission Mechanism And Nuclear Energy
Philipp Büttner 15/19
Nuclear Energy
• exothermic nuclear reactions:
– α-decay:
– fission:
• energy release for :
→ … sum of the kinetic energies of the fission fragments
MeV262.4 Th U 234238
Q
fisAZ
AZ
AAZZ QXXX
2
2
1
1
21
21
²)],(),([²),( 22112121 cZAmZAmcZZAAmQ fis
fisQ
MeV200 Ba Kr U 563623692
fisQ
The Fission Mechanism And Nuclear Energy
Philipp Büttner 16/19
Binding energy per nucleon
B/A(240) = 7.6MeV
B/A(120) = 8.5MeV
216MeV
MeV6.7240MeV5.81202
fisQ
The Fission Mechanism And Nuclear Energy
Philipp Büttner 17/19
The Fission Mechanism And Nuclear Energy
Philipp Büttner 18/19
Picture Credits
• http://www.zamandayolculuk.com/cetinbal/nuclearchemistry.htm• A.Junghans• http://frank.mtsu.edu/~phys3110/Syllabus/Examples/CH_11/
EX_11_VII/ex_11_vii.html• W. Demröder: (Springer, Heidelberg, 1998) Kern-, Teilchen- und
Astrophysik 4• http://www3.mpch-mainz.mpg.de/~elbert/geschichte.htm• J.Grehn, J.Krause: (Schroedel Verlag, Hannover, 1998) Metzler Physik• http://clautechonolgyblog.wordpress.com/• http://thushararadioactivity.blogspot.com/• J.L.Basdevant, J.Rich, M. Spiro: (Springer, Heidelberg, 2005)
Fundamentals in Nuclear Physics• http://www.nucleonica.net/wiki/images/d/d4/NuclideChart.pdf
The Fission Mechanism And Nuclear Energy
Philipp Büttner 19/19
References
• J.L.Basdevant, J.Rich, M. Spiro: (Springer, Heidelberg, 2005)Fundamentals in Nuclear Physics – From nuclear structure to cosmology
• W. Demröder: (Springer, Heidelberg, 1998)Kern-, Teilchen- und Astrophysik 4
• Horst Hänsel / Werner Neuman: (Spektrum, Akad. Verl.,Heidelberg, Berlin, Oxford, 1995)Physik – Atome, Atomkerne, Elementarteilchen
• Dr. Arnd Junghans (Helmholtz-Zentrum Dresden-Rossendorf,Institute of Radiation Physics)