Highly enhanced foams for stability and decontamination efficiency with a fluorosurfactant, silica nanoparticles, and Ce(IV) in radiological application

Abstract The stability and decontamination efficiency of foams containing a fluorosurfactant, stabilizer, and the chemical reagents HNO3 and Ce(IV) for the decontamination of Fe-Cr oxide layers containing 60Co radio-nuclides were tested to find their optimum formulation. The stability of foams containing 2 M HNO3 and 0.5 M Ce(IV) with 1 wt% silica nanoparticles (NPs) is higher for Zonyl TBS (an anionic fluorosurfactant) than for other surfactants such as SDS (anionic) and CTAB (cationic). This result indicates that Zonyl TBS is more suitable for the harsh conditions required for the use of the oxidant Ce(IV) and silica NPs. After three repetitions of the decontamination test, performed by re-injecting air into the decontamination foam, approximately 73% of 60Co was removed from the corroded specimen (SUS 304) by the foam containing 1% v/v Zonyl TBS, which is close to the value obtained with the chemical solution alone, i.e., 80%. In addition, de-contamination foam decreased the generated secondary wastes by 80%, because the decontamination foam contains only 70 ml of chemical reagent solution and 280 ml of gas, compared to use of 350 ml of chemical reagent solution. Moreover, the results indicate that the use of silica NPs and the TBS surfactant enhances foam stability, particularly because of the resistance to harsh conditions of the surfactant due to its low pK a and strong C-F bonding.