Improved Design of Nuclear Reactor Control System

Application/instrumentation: Improved Design of Nuclear Reactor Control System
Developed at: Oak Ridge National Laboratory, Holifield Radioactive Ion Beam Facility (HRIBF)
Developed in: 2004-present (multiple developments, some continuing
Result of NP research: Understanding the ashes of supernovae - Beta-delayed neutron emission. Spectroscopy of very neutron-rich nuclei near the N=50 and N=82 closed neutron shells.
Application currently being supported by: Developments continue with support from basic research funding
Impact/benefit to spin-off field: Particularly useful for the design of more efficient nuclear reactors

The Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory produces intense beams of neutron-rich radioactive nuclei. The study of decay properties of these nuclei provides insights into the processes which occur in very neutron-rich environments, such as supernovae explosions.

The first experiments used beams of copper (Cu) and gallium (Ga) isotopes. These nuclei are more than 10 neutrons heavier than their nearest stable isotope.

Rendering of a Supernova

The beta decay of these extremely neutron-rich nuclei results in the emission of neutrons and thus, alters the normally expected decay sequence. This change of nuclear mass affects the isotopic abundances observed following the explosion of a star, i.e. a supernova. Supernovae are believed to be sites of the rapid-neutron capture process (r-process) which creates approximately half of the neutron-rich atomic nuclei that are heavier than the element iron. Thus, scientists can effectively study the “ashes” of stellar cataclysmic events in the laboratory like the one depicted in Fig. 1 [1].

What is interesting is that data show [2] beta-delayed neutron branching ratios that are 2-4 times higher than previously reported. The precision of the data as well as the ability to study a sequence of isotopes also allowed scientists to explain changes in the structure of the neutron-rich Cu isotopes. These same studies also allow better design and operation of nuclear reactor control systems [3].

Fission of very heavy nuclei is a traditional source of neutron-rich isotopes. The energy released during the neutron-induced fission of nuclear fuels is used for energy production in power reactors. The process of beta-n emission from fission products contributes to the total number of neutrons inducing fission process in nuclear fuel. The uncertainties in beta-delayed neutron data may result in undesirable conservatism in the design and operation of nuclear reactor control systems. Since the construction costs of nuclear reactors is substantial, optimized control systems allow for improved efficiencies. In particular, new trends in reactor technologies (Advanced Fuel Cycle, Hybrid Accelerator-Reactor systems) are requiring verification of the available data as well as new measurements.


[1] Composite image of G292.0+1.8 from the Chandra X-ray Observatory website; Image credit: X-ray: NASA/CXC/Penn State/S.Park et al.; Optical: Pal.Obs. DSS.

[2] J. A. Winger et al., submitted to Physical Review Letters

[3] D'Angelo, Progress in Nucl. Energy, Vol. 41, 1, 2002.