Stable power processes are never guaranteed. An assortment of unstable behaviors wrecks power apparatus, including mechanical vibration, malfunctioning control apparatus, unstable fluid flow, unstable boiling of liquids, or combinations thereof. A necessary condition for stable reactor power is that the reactor distortion accompanying a temperature rise decreases the reactivity, thus slowing an...

Thorium fueled Accelerator Driven Subcritical Reactors have been proposed as a more comprehensive alternative to conventional nuclear reactors for both energy production and for burning radioactive waste. Several new classes have been added by the authors to the GEANT4 simulation code, an extension which allows the state-of-the-art code to be used for the first time for nuclear reactor critical...

Neutrons are sourced from the SAFARI-1 nuclear research reactor operated by Necsa. Necsa is located at Pelindaba in the Northwest Province of South Africa, which is 30 km west of Pretoria. The South African Neutron Radiography (SANRAD) facility is located on the beam port floor of the SAFARI-1 nuclear research reactor hall and sources neutrons from beam port No. 2. The facility has neighbouring...

Geomagnetic field reversals and changes in intensity are understandable from an energy standpoint as natural consequences of intermittent and/or variable nuclear fission chain reactions deep within the Earth. Moreover, deep-Earth production of helium, having (3)He/(4)He ratios within the range observed from deep-mantle sources, is demonstrated to be a consequence of nuclear fission. Numerical s...

In this work we present an accurate parameterization of the anti-neutrino flux produced by the isotopes 235U, 239Pu, and 241Pu in nuclear reactors. We determine the coefficients of this parameterization, as well as their covariance matrix, by performing a fit to spectra inferred from experimentally measured beta spectra. Subsequently we show that flux shape uncertainties play only a minor role ...

nuclear cross sections that determine core multiplication strongly depend on core temperature (e.g., the doppler, moderator density effects etc). on the other hand, since this heat is generated by the neutron flux in the reactor core, the temperature distribution in the core will depend heavily on its neutronic behavior. fuel centerline temperature could be the limiting constraint on reactor po...

In the first half of the 20 century nuclear fusion and fission were both seen as processes that could potentially be harnessed as a powerful energy source. Research into fusion began in the 1920’s, but it was too technically challenging to make a working fusion reactor. Fission developed much more successfully during the Second World War, when North America’s Manhattan Project attempted to use ...

Nuclear accidents that lead to melting of a reactor core create heterogeneous materials containing hundreds of radionuclides, many with short half-lives. The long-lived fission products and transuranium elements within damaged fuel remain a concern for millennia. Currently, accurate fundamental models for the prediction of release rates of radionuclides from fuel, especially in contact with wat...