New Laser Decontamination Technique for Radioactively Contaminated Metal Surfaces using Acid-Bearing Sodium Silicate Gel

Abstract

A new laser decontamination method utilizing a gel made from a sodium silicate solution and an acid was developed for removing radioactive nuclides embedded in surface oxide layers of metal waste. Decontamination tests were carried out using both simulated contaminated samples and pipe specimens cut from the primary coolant system of the Japan Power Demonstration Reactor. In the case of surface oxide layers consisting mainly of iron oxide, more than 99% of the radioactive contamination was removed after two to three decontamination runs. In order to ascertain the role of laser irradiation on chemical reactions, chemical states of O and Fe in the oxide layer before and after decontamination were analyzed by X-ray photoelectron spectroscopy. It was found that the oxide layer was dissolved into the acid-containing gel, and this dissolution was extensively promoted by laser irradiation.

KEYWORDS:

• decontamination
• laser
• radioactive metal waste
• surface oxide layer
• sodium silicate gel
• chemical state
• X-ray photoelectron spectroscopy