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Stable
isotope
(none)
Relative
atomic mass
Mole
fraction
Promethium isotopes in industry
The beta-particle-emitting 147Pm is used in the nuclear fuel industry to measure the thickness of
the inner surface layer of graphite in the cladding tube where the nuclear fuel rod is placed in a
nuclear fuel reactor (Figure 1). The graphite serves as a protective layer against mechanical
contact between the nuclear fuel rod and the Zircaloy cladding (fuel-rod holding tube) and as a
diffusion barrier against fission products. By placing a layer of 147 Pm along the inner surface of
the cladding before the graphite, the long half-life of 147Pm and constant beta-particle emission
provide a reliable and simple technique to measure the thickness of the graphite along the inner
surface of the tube (called the beta-ray backscatter technique) [435-437].
The beta decay property of 147 Pm makes this radioisotope an ideal candidate for
nuclear batteries (beta voltaics). Long-lived power supplies for remote and sometimes hostile
environmental conditions are needed for space and sea missions, and nuclear batteries can
uniquely serve this role. A nuclear battery using beta voltaics can have an energy density
(quantity of energy per unit mass) near a thousand watt-hours per kilogram with 21 percent
efficiency, which is much greater than the best chemical batteries [435, 437, 438].
Fig. 1: The beta-ray backscatter technique requires a layer of 147Pm between the cladding and the
graphite layer to measure the thickness of the graphite along the inner surface of the cladding
tube. (Modified from [307]).
Glossary
atomic number (Z) – The number of protons in the nucleus of an atom.
beta decay (β-decay) – radioactive decay process resulting in emission of a beta particle of
either positive or negative charge (an electron or positron). [return]
electron – elementary particle of matter with a negative electric charge and a rest mass of about
9.109 × 10–31 kg.
element (chemical element) – a species of atoms; all atoms with the same number of protons in
the atomic nucleus. A pure chemical substance composed of atoms with the same number of
protons in the atomic nucleus [703].
fission – the spontaneous (or induced by particle collision) splitting of a heavy nucleus into a
pair (only rarely more) of nearly equal fission fragments (fission products) generally with some
neutrons. Fission is accompanied by the release of a large quantity of energy. [return]
gamma rays (gamma radiation) – a stream of high-energy electromagnetic radiation given off
by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher
than those of X-rays; thus, gamma rays have greater penetrating power.
half-life (radioactive) – the time interval that it takes for the total number of atoms of any
radioactive isotope to decay and leave only one-half of the original number of atoms. [return]
isotope – one of two or more species of atoms of a given element (having the same number of
protons in the nucleus) with different atomic masses (different number of neutrons in the
nucleus). The atom can either be a stable isotope or a radioactive isotope.
neutron – an elementary particle with no net charge and a rest mass of about 1.675 × 10–27 kg,
slightly more than that of the proton. All atoms contain neutrons in their nucleus except for
protium (1H).
nuclear battery – a device that uses radioactive decay to generate electricity. [return]
positron – the antimatter counterpart of the electron, with a mass identical to that of the electron
and an equal but opposite (positive) charge.
proton – an elementary particle having a rest mass of about 1.673 × 10–27 kg, slightly less than
that of a neutron, and a positive electric charge equal and opposite to that of the electron. The
number of protons in the nucleus of an atom is the atomic number.
radioactive decay – the process by which unstable (or radioactive) isotopes lose energy by
emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma
radiation, neutrons or protons to reach a final stable energy state.
radioisotope (radioactive isotope) – an atom for which radioactive decay has been
experimentally measured (also see half-life). [return]
stable isotope – an atom for which no radioactive decay has ever been experimentally measured.
voltaics – of, relating to, or producing direct electric current by chemical action (as in a battery)
[719]. [return]
X-rays – electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers—
shorter than those of UV rays and typically longer than those of gamma rays.
References
307. Whatisnuclear.com. Nuclear Reactors. Whatisnuclear.com. 2014 Feb. 26.
http://www.whatisnuclear.com/articles/nucreactor.html
435. J. K. Shultis, and Faw, R. E. Fundamentals of Nuclear Science and Engineering. Marcel
Dekker, Inc., New York (2002).
436. M. Kumar, Udhayakumar, J., Nuwad, J., Shukla, R., Pillai, C.G.S., Dash, A., and
Venkatesh, M. Applied Radiation and Isotopes. 69 (3), 580 (2011).
10.1016/j.apradiso.2010.11.026
437. R. P. Taleyarkhan. Atoms For Peace: an International Journal. 2 (4), 381 (2009).
10.1504/AFP.2009.02787
438. G. N. Yakubova. In Nuclear, Plasma, and Radiological Engineering. University of
Illinois Champaign-Urbana (2010).
703. I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold
Book"). Blackwell Scientific Publications, Oxford (1997).
719. Merriam-Webster. voltaics. Merriam-Webster. 2016 June 22. http://www.merriamwebster.com/dictionary/voltaics