Grants and Contracts Details
Description
The development of a comprehensive understanding of the process of neutron-induced
fission of the actinides is of fundamental importance in many applied areas of nuclear
technology, most notably in the design and operation of reactors and weapons, and in nuclear
waste transmutation. While much is currently known about the basic fission process in these
materials, important gaps remain in our knowledge of the details of fission. For example, it is
known that "high energy" fission neutrons lead to the production of helium in reactors, yet the
neutron yields near 10 MeV currently are not well measured. Various models are used to predict
the distribution of fission neutron energies, but these must be tested against direct measurements.
On the one hand, while the average neutron multiplicity is rather well known, it is much less
certain how the neutrons are distributed in energy. And since a sizable fraction of the neutrons
are emitted below 1 MeV where currently direct measurements do not exist, the average neutron
multiplicity data cannot be used to constrain the high energy region. In short, our rather
incomplete knowledge of the details of fission in uranium and plutonium limits our ability to
understand processes which use these materials in technological application of importance to our
national security and economy.
The basic physics of nuclear fission is understood primarily as a competition between two
energies: the Coulomb energy associated with the distribution of nuclear charge, and the surface
energy of the nucleus as determined, for example, in a liquid drop model. As the nuclear
deformation increases, so too does the surface energy increase. But as the deformation increases,
the Coulomb energy decreases. In a high-Z nucleus where these two terms are of a similar
magnitude, the net result is to produce a potential barrier to fission which is typically on the
order of only about 6 MeV. In a heavy odd-N target nucleus, the pairing energy associated with
the capture of a slow neutron is sufficient to allow fission to occur with high probability, while
Status | Finished |
---|---|
Effective start/end date | 1/11/10 → 6/30/13 |
Funding
- Department of Energy: $450,000.00
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