Effects of Aging and Decontamination Pressure on the Penetration of Radionuclides into Concrete - 18418

Radionuclide penetration into concrete was investigated as function of time and pressure of an applied water spray. Depth profiles of three radionuclides into a concrete surface over the time periods of 20-24 hours, 9 days, and 90 days were found by grinding the surface. The profiles were starkly different between the radionuclides, as Eu-152 deposited close to the surface and did not penetrate further over time while the depth of Cs-137 increased with time. Such differences suggest that response time during a remediation effort is more important for Cs-137 decontamination compared to Eu-152. The depth profiles were also used to assess the water pressure that was needed to remove contamination. Static tests, where the surface was soaked in 0.5 M KCl, accessed up to 80 μm into the surface, while ablation through high pressure washing removed approximately 10-20 μm of the surface. Similar grind profiles were then collected on decontaminated coupons, displaying that high pressure washing drove Sr-85 into the surface, decreasing the removal of the nuclide. As such, radionuclide specific decontamination may be required because of the varied response times and pressures effects for each radionuclide. (authors)