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Encyclopedia of Physical Science and Technology EN001F-11 May 7, 2001 12:19

216 Actinide Elements

TABLE I (continued )
Most
Atomic Source or Isotope first stable
number Element Symbol Investigators synthesis discovered isotope Source of name

100 Fermium Fm Workers at Berkeley, Discovered in the 255 Fm 257 Fm Enrico Fermi
Argonne, and fallout of the first
Los Alamos (1952) thermonuclear
explosion as a result
of uranium
bombardment
with fast neutrons:
238 1
92 U + 17 n →
0
255 −8β − 255 Fm
92 U −→ 100
101 Mendelevium Md A. Ghiorso, Bombardment of 256 Md 258 Md Dimitri Mendeleev
B. H. Harvey, einsteinium with
G. R. Choppin, helium ions:
4
S. G. Thompson, 253 Es + He
99 2
1
G. T. Seaborg (1955) → 256 Md + n
101 0
102 Nobelium No E. D. Donets, Bombardment of 254 No 259 No Alfred Nobel
V. A. Shegolev, americium with
V. A. Ermakov (1966) nitrogen ions:
15
243 Am + N
95 7
1
→ 254 No + 4 n
102 0
103 Lawrencium Lr Workers at both Bombardments of ( 258 Lr) 262 Lr Ernest Lawrence
Berkeley and actinide targets
Dubna (1961–1971) with heavy ions
III. APPLICATIONS OF ACTINIDES cial, and international problems. Technical problems are
related to the safe operation of nuclear reactors, reprocess-
The practical importance of the actinide elements derives ing, and waste disposal, to the prevention of environmen-
mainly from their nuclear properties. The principal appli- tal contamination with radioactive and toxic substances,
cation is in the production of nuclear energy. Controlled and to the prevention of the diversion of plutonium for an
fission of fissile nuclides in nuclear reactors is used to uncontrolled manufacture of nuclear weapons. All these
provide heat to generate electricity. The fissile nuclides technical and technological problems are soluble, but the
233 235 239 future of nuclear energy depends also on the solution of
U, U, and Pu constitute an enormous, practically
inexhaustible, energy source. other problems of acute global concern.
Several actinide nuclides have found other applications.
Heat sources made from kilogram amounts of 238 Pu have
been used to drive thermoelectric power units in space IV. ACTINIDE METALS
vehicles. In medicine, 238 Pu was applied as a long-lived
A. Preparation of Actinide Metals
compact power unit to provide energy for cardiac pace-
makers and artificial organs. 241 Am has been used in neu- All of the actinide elements are metals with physical
tron sources of various sizes on the basis of the (α,n) reac- and chemical properties changing along the series from
tion on beryllium. The monoenergetic 59-keV γ radiation those typical of transition elements to those of the lan-
of 241 Am is used in a multitude of density and thickness thanides. Several separation, purification, and preparation
determinations and in ionization smoke detectors. 252 Cf techniques have been developed considering the differ-
decays by both α emission and spontaneous fission. One ent properties of the actinide elements, their availability,
gram of 252 Cf emits 2.4 · 10 12 neutrons per second. 252 Cf and application. Powerful reducing agents are necessary
thusprovidesanintenseandcompactneutronsource.Neu- to produce the metals from the actinide compounds. Ac-
tron sources based on 252 Cf are applied in nuclear reactor tinide metals are produced by metallothermic reduction of
start-up operations and in neutron activation analysis. halides, oxides, or carbides, followed by the evaporation
Nuclear energy and the application of actinide elements in vacuum or the thermal dissociation of iodides to refine
in other fields may promise mankind a prosperous future; the metals.
however, whether the promise becomes a reality depends The metallothermic reduction of halides was the first
on the solution of numerous technological, economic, so- method to be successfully applied. Actinium metal can