A method for at least partially disrupting or removing radioactive deposits formed on a surface of a structure in a nuclear water reactor is disclosed. The method includes identifying the structure, taking the structure out of operational service, isolating the structure, contacting the surface of the structure with an aqueous solution, and adding an effective amount of an elemental metal in solid form to the aqueous solution. The effective amount includes an amount to at least partially disrupt or remove the radioactive deposits formed on the surface of the structure. The method is conducted at ambient temperature. The radioactive deposits include oxide-containing radionuclides deposited on the surface. The surface is a primary side structure in the nuclear water reactor.

A chemical decontamination method includes a dissolution step in which a radioactive insoluble substance containing a metal oxide, the radioactive insoluble substance being adhered to a decontamination object including carbon steel, is dissolved in a decontamination solution and a metal-ion removal step in which the decontamination solution containing the metal ion, the decontamination solution being produced in the dissolution step, is brought into contact with a cation-exchange resin in order to remove the metal ion, the dissolution step including a reductive dissolution step conducted using a decontamination solution containing formic acid, ascorbic acid and/or erythorbic acid, and a corrosion inhibitor.

Provided herein is a method for reducing radiologically-contaminated waste. The method comprises treating radiologically-contaminated surfaces, wherein the radiologically-contaminated surfaces are treated with a surface treatment agent; treating radiologically-contaminated subsurfaces, wherein the radiologically-contaminated subsurfaces are treated with a surface/subsurface treatment agent; consolidating soil waste; employing real-time scanning technology to classify waste, wherein the classifying is based at least in part on a threshold of radiological contamination, and wherein the classified waste is sorted based on the classification; and disposing of the waste via at least one of different disposal routes, based at least in part on the classification.

A method for decontaminating a metal surface exposed to radioactive liquid or gas during operation of a nuclear facility comprises an oxidation step wherein a metal oxide layer on the metal surface is contacted with an aqueous oxidation solution comprising a permanganate oxidant for converting chromium into a Cr(VI) compound and dissolving the Cr(VI) compound in the oxidation solution; and a first cleaning step wherein the oxidation solution containing the Cr(VI) compound is directly passed over an anion exchange material and the Cr(VI) compound is immobilized on the anion exchange material. The method provides for substantial savings of radioactive waste and produces chelate-free waste.

A chemical decontamination reagent containing a reducing agent, a reductive metal ion, and an inorganic acid is provided to remove a radioactive oxide layer on a metal surface. The reagent can dissolve the radioactive oxide layer on the metal surface effectively at a relatively low temperature and enables a simple process of contacting the reagent to the radioactive oxide, thus economically effective in terms of cost and time required for the process. Since the decontamination does not use a conventional organic chelating agent such as oxalic acid, but the reducing agent as a main substance, the residuals of the reducing agent remained after decontamination can be decomposed and removed with an oxidizing agent. Due to the easy decomposition with the chemical decontamination reagent, secondary wastes can be minimized and the radionuclides remained in the decontamination reagent solution can be removed effectively.

The invention relates to methods for mitigating the recontamination of carbon steel surfaces in a nuclear reactor or related water-containing systems and components, which have undergone a decontamination process. The methods include conducting a passivation process of the carbon steel surfaces directly following completion of the decontamination process, prior to the system or component being returned to service. In certain embodiments, a chelating agent is used in the decontamination process and is retained following completion of the process, for use in the subsequent passivation process. The passivation process forms a passivation film that is effective to reduce recontamination of the decontaminated carbon steel surfaces.

The present disclosure relates to the technical field of radioactive waste treatment and provides an electrolyte for electrochemical decontamination and a preparation method and application thereof. The electrolyte for electrochemical decontamination provided in the present disclosure is an aqueous solution including the following solutes: phosphoric acid, oxalic acid, citric acid, tartaric acid, hydrogen peroxide and glacial acetic acid. According to the present disclosure, an electrolyte for electrochemical decontamination that has a good decontamination effect and allows for fast decontamination is obtained by reasonably combining different types of solutes and controlling the levels of the solutes, and resulting secondary waste solution and residues are easy to treat. The electrolyte for electrochemical decontamination is suitable for overall or local electrochemical decontamination of radioactively contaminated stainless steel scrap. In addition, in the electrolyte for electrochemical decontamination provided in the present disclosure, the oxalic acid, the citric acid, the tartaric acid and the glacial acetic acid are organic acids and no N and Cl ions are present, which may be highly advantageous for a glass solidification system for spent decontamination solution. Thus, the resulting waste solution can be treated readily by the glass solidification system.

A method for decontaminating a metal surface exposed to radioactive liquid or gas during operation of a nuclear facility comprises an oxidation step wherein a metal oxide layer on the metal surface is contacted with an aqueous oxidation solution comprising a permanganate oxidant for converting chromium into a Cr(VI) compound and dissolving the Cr(VI) compound in the oxidation solution; and a first cleaning step wherein the oxidation solution containing the Cr(VI) compound is directly passed over an anion exchange material and the Cr(VI) compound is immobilized on the anion exchange material. The method provides for substantial savings of radioactive waste and produces chelate-free waste.

The invention relates to a method of decontaminating a metal surface, wherein the metal surface is located on a component within a nuclear plant, in particular within the cooling system of a nuclear power plant, and is covered with a metal oxide layer containing radioactive substances, and wherein the method comprises a decontamination step in which a metal oxide layer pretreated in an oxidation step is contacted with an aqueous solution of an organic acid to dissolve the metal oxide layer, forming a decontamination solution containing the organic acid as well as metal ions and the radioactive substances, and wherein the decontamination solution is passed over an ion exchanger to immobilize the metal ions and the radioactive substances. An oxidant selected from the group consisting of oxygen, air, hydrogen peroxide and ozone is dosed into the decontamination solution to control the dissolution rate of the metal oxide layer. The method is particularly suitable for large-scale system decontamination and ensures high process stability.

Provided are a chemical decontamination method and a chemical decontamination apparatus capable of preventing deterioration of a metal ion exchange resin and performing decontamination at a low cost in a short time.

The chemical decontamination method of the invention includes: a reduction decontamination step of supplying a reduction decontamination solution to a decontamination target portion and performing reduction decontamination on a surface of a member constituting the decontamination target portion; a hydrogen peroxide decomposition step of decomposing hydrogen peroxide contained in the reduction decontamination solution after the reduction decontamination step; and a metal ion removing step of removing a metal ion contained in the reduction decontamination solution after the hydrogen peroxide decomposition step.