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55th annual Nuclear News Buyers Guide now available
For American Nuclear Society members and Nuclear News subscribers, the 2024 Buyers Guide is now available in the ANS Digital Nuclear Library. The print version will be mailed along with the May “Capacity Factors/Nuclear Security” issue of Nuclear News magazine.
The corresponding ANS online Buyers Guide database is available year-round to all readers—updated with the latest products, services, and suppliers contact information for more than 600 nuclear-related companies.
Jason J. Song, Paul K. Chan, Hugues W. Bonin, Stéphane Paquette
Nuclear Technology | Volume 195 | Number 3 | September 2016 | Pages 310-328
Technical Paper | 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).