ABSTRACT
An oxidative process using hydrogen peroxide for the dissolution of metallic antimony, stripping of the dissolved antimony ions, and the compatibility of the oxidative process with the structural materials present in the coolant systems of nuclear reactors have been investigated. This process has direct application for the removal of antimony activity and thereby reducing the radiation exposure hazard to the operating personnel. The rate of dissolution of metallic antimony increased in the presence of hydrogen peroxide. The re-deposition of dissolved antimony on the oxide coated carbon steel coupons was ≤0.02 mg/cm2. Three substrates investigated, namely, strong base anion exchange resin and two chitosan-TiO2 based substrates, for the removal of dissolved antimony were equally efficient. The process could dissolve antimony without any significant re-deposition on the oxide coated carbon steel surface and could dissolve antimony incorporated in the oxide film of zircaloy. Corrosion compatibility of relevant alloys, namely, carbon steel, incoloy-800, Zr2·5Nb and monel-400, at pH 10.2 and 9.0, showed that only monel-400 underwent pitting type of attack at pH 10.2.
ABSTRACT
Gadolinium as gadolinium nitrate is used as neutron poison in the moderator system for regulating and controlling the power generation of Pressurized Heavy Water Reactors (PHWR) and proposed to be used in Advanced Heavy Water Reactors (AHWR) owing to its high neutron absorption cross section. Removal of the added gadolinium nitrate (Gd3+ and NO3-) from the system after its intended use is done using ion exchange resins. In the present investigation, attempts have been made to optimize the ion exchange process for generation of low radioactive waste and maximize utilization of the ion exchange resins by employing different types of resins and different modes of operation. The investigations revealed that use of mixed bed (MB) resin column consisting of Strong Acid Cation (SAC) resin and Strong Base Anion (SBA) resin followed by SAC resin column is efficient in removing the Gd3+ and NO3- from the system besides maintaining the pH of the moderator system in the desirable regime, where gadolinium does not get precipitated as its hydroxide.
ABSTRACT
Permanganate and nitrilotriacetic acid (NTA) based dilute chemical formulations were evaluated for the dissolution of uranium dibutyl phosphate (U-DBP), a compound that deposits over the surfaces of nuclear reprocessing plants and waste storage tanks. A combination of an acidic, oxidizing treatment (nitric acid with permanganate) followed by reducing treatment (NTA based formulation) efficiently dissolved the U-DBP deposits. The dissolution isotherm of U-DBP in its as precipitated form followed a logarithmic fit. The same chemical treatment was also effective in dissolving U-DBP coated on the surface of 304-stainless steel, while resulting in minimal corrosion of the stainless steel substrate material. Investigation of uranium recovery from the resulting decontamination solutions by ion exchange with a bed of mixed anion and cation resins showed quantitative removal of uranium.
