  Numerous particle physics experiments utilize gadolinium (Gd), a rare earth
element with the most significant neutron capture cross-section among all
elements, to detect anti-neutrinos via inverse beta-decays or to remove
neutron-induced background events. For example, to load Gd into water Cherenkov
detectors, $\mathrm{{Gd_{2}(SO_{4})_{3}\cdot 8H_{2}O}}$ is dissolved and rare
event search experiments are required to screen for radioactive impurities in
$\mathrm{{Gd_{2}(SO_{4})_{3}\cdot 8H_{2}O}}$ before dissolution. This study
developed a new method to rapidly measure the radium-226($\mathrm{^{226}Ra}$)
concentration in $\mathrm{{Gd_{2}(SO_{4})_{3}\cdot 8H_{2}O}}$. This method
requires only three days to measure a batch of samples, as opposed to the usual
method using high-purity germanium detectors, which takes approximately 20 days
after arrival. The detection limit for the measurement of $\mathrm{^{226}Ra}$
is 0.32 mBq/kg. This method has been already used for
$\mathrm{{Gd_{2}(SO_{4})_{3}\cdot 8H_{2}O}}$ screening at the Super-Kamiokande
Gd(SK-Gd) project, and it can be applied to future experiments.
