Calculations are reported for ambient dose equivalent rates [Ḣ*(10)] at 1 m height above the ground surface before and after remediating radiocesium contaminated soil at wide and open sites. The results establish how the change in Ḣ*(10) upon remediation depends on the initial depth distribution of radiocesium within the ground, on the size of the remediated area and on the mass per unit area of remediated soil. The remediation strategies considered were topsoil removal (with and without recovering with a clean soil layer), interchanging a topsoil layer with a subsoil layer, and in situ mixing of the topsoil. The results show the ratio of the radiocesium components of Ḣ*(10) post-remediation relative to their initial values (residual dose factors). It is possible to use the residual dose factors to gauge absolute changes in Ḣ*(10) upon remediation. The dependency of the residual dose factors on the number of years elapsed after fallout deposition is analyzed when remediation parameters remain fixed and radiocesium undergoes typical downward migration within the soil column.
A. Malins, H. Kurikami, A. Kitamura & M. Machida
Health Physics 111 (4), 357-366 (2016)