This included tests to investigate the properties of isotopes such as tritium and determine the neutron capture cross section of elements and compounds that might be used to construct future reactors, or occur in impurities.
12.
Niels Bohr and University of California produced 28 ?g of plutonium in the 60-inch cyclotron there, and found that it had 1.7 times the thermal neutron capture cross section of uranium-235.
13.
Plutonium-240 is a fertile material like uranium-238, becoming plutonium-241 on neutron capture, but plutonium-242 both has a low neutron capture cross section, and would require 3 neutron captures before becoming a fissile nuclide.
14.
In these circumstances of rapid opposing reactions the abundances are not determined by alpha-particle-capture cross sections; rather they are determined by the values that the abundances must assume in order to balance the speeds of the rapid opposing-reaction currents.
15.
The isotope has about the same thermal neutron capture cross section as ( 289.5 ?1.4 vs 269.3 ?2.9 barns ), but only a tiny thermal neutron fission cross section ( 0.064 barns ).
16.
Nuclear transmutation is under consideration as a disposal method, primarily for Tc-99 and I-129 as these both represent the greatest biohazards and have the greatest neutron capture cross sections, although transmutation is still slow compared to fission of actinides in a reactor.
17.
In fact, at extremely low particle energies ( corresponding, say, to thermal equilibrium at room temperature ), the neutron's de Broglie wavelength is greatly increased, possibly greatly increasing its capture cross section, at energies close to resonances of the nuclei involved.
18.
Although the thermal neutron fission cross section ( ? f ) of the resulting is comparable to and, it has a much lower capture cross section ( ? ? ) than the latter two fissile isotopes, providing fewer non-fissile neutron absorptions and improved neutron economy.
19.
In a normal thermal reactor, it has a very low fission product yield, plus its large neutron capture cross section means that most of even the small amount produced is destroyed in the course of the nuclear fuel's burnup; thus, this isotope is not a significant contributor to nuclear waste.
20.
Hafnium diboride also suffers from high susceptibility to material degradation with boron transmutation, but its high melting point of 3380 �C and the large thermal neutron capture cross section of hafnium of 113 barns and low reactivity with refractory metals such as tungsten makes it an attractive control rod material when clad with a refractory metal.
