Study On Redox Reaction Of Low Carbon Steel Corrosion Product With Pu

In this paper,the oxidation-reduction reaction between corrosion products of mild steel and Pu in packaging containers has been studied under the condition of groundwater environment for high-level radioactive waste repository.The author aims to obtain constants of kinetics equations and reaction of the oxidation-reduction between the corrosion products and Pu and impact characteristics.Therefore,technical parameters will be provided for safety evaluation of geological disposal of high-level radioactive waste.The background of this study is based on the following facts.Because disposal repositories suffer from the natural or artificial effects in the long-term disposal process?possibly tens of thousands of years?for high-level radioactive waste,engineering barrier layer is destroyed,nuclear waste containers are eroded by the underground water and nuclear waste leaked and transferred.To make a study on the oxidation-reduction reaction of Pu by corrosion products,electrochemical laboratory is applied to simulate the corrosion process of mild steel storage tanks in groundwater environment.The distribution of Pu species in corrosion solutions and groundwater is simulated with the help of PHREEQC software.Then,the paper discusses adsorption mechanism and the effect process of kinetics of Pu caused by corrosion solution and groundwater solution.This paper will provide guidance for Pu's barrier technology in geological environment.It will develop a scientific significance for the safe disposal of nuclear waste.The main research contents and conclusions are listed as follows:?1?Electrochemical methods are used to obtain the corrosion potential of low-carbon steel in solution.Corrosion products are obtained by corroding low-carbon steels through corrosion potentials.The solution under different conditions will have a certain influence on the corrosion potential and corrosion potential density of low carbon steel.By XRD analysis of corrosion products,the corrosion products of low carbon steel are mainly?-FeOOH,Fe₃O₄,and a small amount of Fe₂?OH?₂CO₃ is produced in groundwater environment and HCO₃^-environment.?2?Using PHREEQC software,the distribution of Pu species under specific conditions was simulated,and the distribution of species distribution under different conditions was compared.Simulation studies have found that different pH groundwater solutions and corrosion solutions have a certain influence on the species distribution of Pu,mainly represented by the trivalent PuSO₄⁺and Pu?SO₄?₂^-in the acidic solution,and Pu in the neutral environment.In the presence of?OH?₃⁺,the combination of OH-and Pu in an alkaline solution produces a large amount of Pu?OH?₄.?3?The content of Pu?III?,Pu?IV?and Pu?V,VI?in solution was obtained by extraction with TTA-xylene.Through the preparation of Pu single valence state,the method of extraction verification proves that the extraction method is feasible and effective at more than 90%.According to the Pu extraction in groundwater solution,Pu is mainly in the form of Pu?IV?,and Pu?V?and Pu?VI?are produced in small amounts after a certain period of time.Pu in groundwater corrosion solution mainly exists in Pu?III?and Pu?IV?states.The kinetic equation of Pu?IV?in the corrosion solution was calculated by extracting the groundwater corrosion solution at different pH.?4?The adsorption properties of Pu in two kinds of backfill materials were found through groundwater corrosion solution,groundwater solution and single ion solution.GMZ bentonite and Alashan clay contain large amounts of Al₂O₃ and SiO₂.When the two compounds are in contact with water,the solution forms hydroxyl functional groups on the surface of the medium such as?Si-OH,and=Al-OH.These functional groups react with the Pu in the solution in an acidic or alkaline environment,and the surface states of Pu are different.The different bonding modes of Pu and functional groups lead to the influence of geological media on the adsorption of Pu.In summary,the concentration of ions in groundwater solution will have a significant impact on the migration of Pu in geological media.When certain ions in the solution are too high,Pu is not easily adsorbed by geological media,and Pu easily migrates with groundwater.diffusion.