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Nuclear Science and Engineering
Fusion Science and Technology
Notes on fusion
The ST25-HTS tokamak.
Governments around the world have been interested in fusion for more than 70 years. Fusion research was largely secret until 1968, when the Soviets unveiled exciting results from their tokamak (a magnetic confinement fusion device with a particular configuration that produces a toroidal plasma). The Soviets realized that tokamaks were not useful as weapons but could produce plasma in the million-degree temperature range to demonstrate Soviet scientific and technical prowess to the world.
Following this breakthrough, government laboratories around the world continued to pursue various methods of confining hot plasma to understand plasma physics under extreme conditions, getting closer and closer to the conditions necessary for fusion energy production. Tokamaks have been by far the most successful configuration. In the 1990s, the Tokamak Fusion Test Reactor at the Princeton Plasma Physics Laboratory produced 10 MW of fusion power using deuterium-tritium fusion. A few years later, the Joint European Torus (JET) in the United Kingdom increased that to 16 MW, getting close to breakeven using 24 MW of power to heat the plasma.
Jason J. Song, Paul K. Chan, Hugues W. Bonin, Stéphane Paquette
Nuclear Technology | Volume 195 | Number 3 | September 2016 | Pages 310-328
Technical Paper | dx.doi.org/10.13182/NT16-1
Articles are hosted by Taylor and Francis Online.
Trace amounts of burnable neutron absorbers (BNAs) were used to tailor the reactivity of the 37-element, natural uranium (NU) fuel bundle used in CANDU reactors. The BNAs of interest included Gd2O3 and Eu2O3, which were added to the fuel in variable quantities and combinations. The fuel lattice was modeled using the WIMS–AECL 3.1 code, and core simulations were conducted using the Reactor Fuelling Simulation Program (RFSP). The fuel model assumes an equivalent and uniform distribution of BNAs in the CANLUB layer of each fuel element.
The incorporation of BNAs is designed to improve CANDU reactor operating margins during on-power refueling by eliminating the fueling transient (FT) and reducing the magnitude of the plutonium peak (PP) that is characteristic of NU fuels. By adding an optimal combination of “fast-burning” and “slow-burning” BNAs, the FT and PP can be selectively reduced, and a significantly flatter trend in the burnup-dependent evolution of fuel reactivity can be achieved.
The results of the study indicate that by adding ~150 mg [~8 parts per million (ppm)] of Gd2O3 and ~300 mg (~15 ppm) of Eu2O3 per fuel bundle, the best gain in the operating margins of a 2650-MW(thermal) (480-channel) model CANDU reactor can be achieved. Based on the simulation of refueling events, it was shown that the magnitude of average postrefueling channel power ripples can be reduced by an average of 100 kW and a maximum of 220 kW for powers observed immediately after refueling. This reduction in postrefueling powers was also shown to allow the average liquid zone controller level to decrease from ~48% to 10%. This decrease implies a potential relief on overpower protection (an operating margin).