Page 19 - Radiochemistry and nuclear chemistry

Radiochemistry and Nuclear Chemistry

1925 - 1927 Important improvements of the Bohr atomic model: Pauli exclusion principle, Schrrdinger
wave mechanics, Heisenberg uncertainty relationship.
1928 Geiger and Mfiller construct the first GM tube for single nuclear particle measurements.
1931 van de Graaff develops an electrostatic high voltage generator for accelerating atomic ions
to high energies.
1931 Paul/postulates a new particle, the neutrino, to be formed in B-decay.
1932 Cockcroft and Walton develop the high voltage multiplier and use it for the first nuclear
transformation in the laboratory with accelerated particles (0.4 MeV tH + 7Li --- 2 4He).
1932 Lawrence and Livingston build the first cyclotron.
1932 Urey discovers deuterium and obtains isotopic enrichment through evaporation of liquid
hydrogen.
1932 Chadwick discovers the neutron.
1932 Andersson discovers the positron, e + or 13 +, through investigation of cosmic rays in a cloud
chamber.
1933 Urey and Ritteaberg show isotopic effects in chemical reactions. ~ +
1934 Joliet and I. Curie discover artificial radioactivity: 4He + 27AI --- ~Op + n; 3Ol)___ > 30Si"
1935 DeHevesy develops neutron activation analysis. 2.5 min
1935 Yukawa predicts the existence of mesons.
1935 Weizs~ker derives the semiempirical mass formulae.
1937 Neddermeyer and Andersson discover/z-mesons in cosmic radiation using photographic
plates.
1938 Bethe and We/zsaeker propose the first theory for energy production in stars through
nuclear fusion: 3 4He -- 12(2.
1938 Hahn and Strassman discover fission products after irradiation of uranium with neutrons.
1938-1939 Meitner and Frisch interprets the discovery by Hahn and Strassman as fission of the U-
atom by neutrons; this is almost immediately confirmed by several laboratories in Europe
and the USA.
1938-1939 F. Joliet, yon Halban, Kowarski and F. Perrin in France apply for patents for nuclear
chain reacting energy producing devices and starts building a nuclear reactor; the work is
interrupted by the war.
1940 McMillan, Abelson, Seaborg, Kennedy, and Wahl produce and identify the first
transuranium elements, neptunium (Np), and plutonium (Pu), and with Segr~ discover that
239pu is fissionable.
1940 Scientists in many countries show that ~SU is fissioned by slow neutrons, but ~l'h and
~U only by fast neutrons, and that each fission produces two or three new neutrons while
large amounts of energy are released. The possibility of producing nuclear weapons and
building nuclear power stations is considered in several countries.
1942 Fermi and co-workers build the first nuclear reactor (critical on December 2).
1944 First gram amounts of a synthetic element (Pu) produced at Oak Ridge, USA. Kilogram
quantities produced in Hanford, USA, in 1945.
1944 McMill~n and Veksler discover the synchrotron principle which makes it possible to build
accelerators for energies > 1000 MeV.
1940-1945 Oppenheimer and co-workers develop a device to produce fast uncontrolled chain reactions
releasing very large amounts of energy. First test at Alamogordo, New Mexico, USA, on
July 16, 1945 produces an energy corresponding to 20,000 tons of TNT; this is followed by
the use of atomic bombs on Hiroshima (Aug. 6, 1945) and on Nagasaki (Aug. 9, 1945).
1944-1947 Photo-multiplier scintillation detectors are developed.
1946 Libby develops the 14C-method for age determination.
1946 First Soviet nuclear reactor starts.
1949 Soviet tests a nuclear bomb.
1950 A nuclear shell model is suggested by Mayer, Haxel, Jem~a and Suess.
1951 The first breeder reactor, which also produces the first electric power, is developed by
Argonne National Laboratory, USA, and built in Idaho.
1952 The United States test the first device for uncontrolled large scale fusion power (the
hydrogen bomb).