[1C14-18] Concrete 3

[1C14] Study on the Radionuclide Contamination Mechanisms of Concrete and the Estimation of Distribution of Radionuclides

(21) Estimation of the penetration depth of radioactive cesium in concrete exposed to contaminated cooling water

Keita Himori¹, Kazuo Yamada², *Tsuneki Ichikawa^1,2, Hideyuki Hokora³, Yasumasa Tojo¹ (1. Hokkaido Univ, 2. NIES, 3. Taiheiyo Consultant)

Keywords:concrete, contaminated cooling water, radioactive cesium, penetration depth, diffusion equation, ionic adsorption

The penetration profiles of Cs in concrete exposed to aqueous solutions of Cs ions were measured with EPMA and autoradiography for estimating the penetration depth of ¹³⁷Cs in concrete exposed to contaminated cooling water from broken nuclear reactors. The profiles compared well with the solutions of the Nernst-Planck diffusion equation under the assumption that Cs ions diffused in the pore solution of concrete while being immobilized by ionic adsorption on the aggregates. The equation reproduced the effect of coexisting ions on the observed diffusion profile. Although the accuracy of the measurements, 1/1,000 of the maximum Cs concentration, was not enough for determining the thickness of the region with impermissible ¹³⁷Cs concentration, the equation was able to determine the thickness. The Fick's simple diffusion equation underestimated the thickness.