Key experiments in nuclear and particle physics
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
Lecture 3
Nuclear fission, nuclear energy and transuranic elements
• Prelude
• Nuclear fission
• Transuranic elements
• Nuclear energy (reactors and bombs)
Prelude to fission
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• neutron discovery leads to the right model of the nucleus
(D. Ivanenko, W. Heisenberg, 1932)
• F. Joliot, I Curie discover artificial radioactivity (1934; Nobel Prize Chemistry
1935)
e+ radioactivity of Al, B, Mg under α (Po) exposure (half-lives of several min30P+n; 30P→30Si+e++ν
utes) 27
Al+α=
13
15
15
14
about 1 disintegration for a million α particles
• Fermi realized that with neutrons it can be more advantageous (obtained radioactivity on F) ...and (n,α), (n,p), (nγ) reactions (Nobel Prize 1938)
• Fermi: n on U produced radioactivity (1934), but it was thought (because of
absence of elements heavier than Pb) that the reaction was 238U(n,γ)238U,
238U→23993
• Fermi: slowing down of neutron by paraffin (due to elastic collisions)
Discovery of fission
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• O. Hahn, F. Strassmann (1938; Nobel Prize Chemistry Hahn 1944)
identified Ba, La, Ce among the products of n bombardment of U
• O. Frisch and L. Meitner understood that they come from fission of U
(was suggested by I. Noddack in
1935 for Fermi’s experiments)
Frisch also saw the large pulses in
an ionization chamber
about 200 MeV is released in a fission event
Discovery of fission
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
Hahn and Strassmann’s laboratory (originally in 3 rooms)
Deutsches Museum München, http://www.deutsches-museum.de/
Nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
E=mc2
first seen by Cockroft and Walton (1932)
p(770 keV)+7Li=α+α+(14.3±2.7) MeV
Fast developments
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• Bohr realized that 235U is the isotope (0.7%) that fissions with slow neutrons,
while 238U fissions with fast (>1 MeV) neutrons
• it was realized that a chain reaction can occur (Szilard)
leading to an energy source or to a
bomb
Oct. 1939: famous letter to US
president (Einstein-Szilard)
Dec. 1939: Heisenberg handed in
a report on a U bomb possibility
March 1940: Frisch-Peierls memorandum (first practical outline of
an atomic bomb ...1 kg 235U)
Transuranic elements
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• E. McMillan and P. Abelson identify Neptunium (239Np), 1940
• E. Segré et al. produce Plutonium (239Pu) and show that it could be used as
nuclear fuel (1941)
• Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr (Actinides)
• superheavy elements
Rf, Db, Sg ...and, discovered at GSI Darmstadt: Bh, Hs, Mt, Ds, Rg, Cn
Cn: discovered in 1996, named in 2010:
70Zn+208Pb→278Cn∗→ 277Cn+n
30
82
112
112
more discovered up to Z=119
Nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• The nuclear reactor (pile) proposed by Fermi and Szilard (graphite as n
moderator)
• Fermi builds a nuclear reactor to produce Pu (Chicago Pile-1), Dec. 1942
• The Manhattan Project starts (1942): enriching 235U and Pu production
• First atomic bomb test (“Trinity”, New Mexico, Alamogordo)
16 ms after detonation (about 250 m diameter); 6.2 kg Pu (≃18 kt TNT)
Peaceful nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
• power, research, breeder reactors
• majority of nuclear reactors work with enriched 235U (3%) and light water
(natural 235U and heavy water too)
• nuclear power provides 10% of world electricity
US: 19% (101 GW), EU: 30% (France 80%)
• unused fuel (reprocessing done in Britain, France, Russia; France reprocesses
28% of used fuel)
• it does generate radioactive waste, about 10000 tons/year
(stored on 430 locations around the world)
... a solution is to perform transmutation of long-lived isotopes, see
https://www.dpg-physik.de/veroeffentlichung/physik konkret/pix/Physik Konkret 14.pdf
• NB: radiation from coal power plants is ∼100 times larger than from power
reactors
Peaceful nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
percentage of electricity from nuclear power
http://www.eia.gov
Peaceful nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
http://www.eia.gov
Peaceful nuclear energy
A. Andronic - TU Darmstadt — Fachbereich Physik — SS 2013
http://www.eia.gov
1 Btu =1055 J = 0.293 Wh