Quantifying gadolinia burnable absorber rods for APR1400 nuclear reactor core
image credit: reactor core and fuel assembly (image from google)
- Oct 9, 2020 10:25 am GMTOct 9, 2020 5:30 am GMT
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by Mark Gino Aliperio
Burnable absorbers (BA) are materials that have a high neutron absorption cross-section that are converted into materials of relatively low absorption cross section as the result of radiative capture. Due to the burnup of the absorption material, the negative reactivity of the burnable absorber decreases over core life. Ideally, these absorbers should decrease their negative reactivity at the same rate the fuel’s excess positive reactivity is depleted. In PWRs burnable absorbers are used to decrease initial concentration of boric acid (also to decrease BOC MTC) and to decrease relative power of fresh fuel assemblies. Fixed burnable absorbers are generally used in the form of compounds of boron or gadolinium, shaped into separate lattice pins or plates, or introduced as additives to the fuel. Since they can usually be distributed more uniformly than control rods, they are less disruptive to the core power distribution.