Ultrahigh Water Permeance of Reduced Graphene Oxide Membrane for Radioactive Liquid Waste Treatment

Membrane methods exhibit great potential for application in radioactive liquid waste treatment. In this work, we prepared a reduced graphene oxide using the amino-hydrothermal method (AH-rGO) that exhibited effective rejection rates of 99.9% for CoCl2, ZnCl2, NiCl2, and radionuclide 60Co solutions with an ultrahigh water permeance of >71.9 L m−2 h−1 bar−1. The thickness of the AH-rGO membranes affects the water permeance, as the membrane with a thickness of ≈250 nm has the highest water permeance of up to 125.1 L m−2 h−1 bar−1 with the corresponding rejection rate of 86.8%. Importantly, this is the most permeable membrane with a satisfactory level of the rejection rate for typical radioactive ions of Co2+, Zn2+, and Ni2+. Moreover, the AH-rGO membranes presented excellent stability. These findings demonstrate the potential of reduced graphene oxide (rGO) membranes for radioactive liquid waste treatment.

Treatment of Radioactive Liquid Waste Using Bentonite

Radioactive liquid waste contaminated with cesium-137 found in the radiochemistry laboratories at Tuwaitha site, south of Baghdad, was treated in this work. Bentonite was used as a sorbent material for the removal of radioactive cesium-137 from liquid waste by ion exchange method. The results indicated that the best removal efficiency obtained was 95.13% with experimental conditions of 2 h mixture time, 0.04 g sorbent mass, and pH=10 for the radioactive liquid. It was found that the experimental results match well with Langmuir and Freundlich models, with better matching with the latter.

Management of hospital radioactive liquid waste: treatment proposal for radioimmunoassay wastes

<abstract> <p>Radioactive liquid wastes are produced at hospitals from diagnostic and therapeutic applications of radionuclides. The most usual management of these wastes is temporary storage at the hospital for radioactivity decay and, then, discharge into sewage if not other pollutants are present in waste, always after authorization of the corresponding institution. In some cases, radioactive wastes have other hazards, such as chemical or biological ones, which can be more dangerous than radiological hazard, and do not allow direct discharge into sewage in spite of decaying activity below the clearance level. Therefore, these wastes have to be treated and condition before discharge in spite of activity decay below discharge limit. This is the case of liquid wastes from radioimmunoassay (RIA), a laboratory technique that allows to determine human substances in very low concentrations (below 10^-12 g/mL), like hormones, using ¹²⁵I as radionuclide. This study summarizes the usual management of radioactive liquid wastes from hospitals, including conventional and recent treatments applied. Furthermore, based on experimental results obtained with real RIA wastes, this work exposes a proposal of treatment with ultrafiltration and reverse osmosis membranes, and determines the most suitable application of this treatment according to radiological and operational considerations.</p> </abstract>

Monte Carlo Simulation and Experimental Validation for Radiation Protection with Multiple Complex Source Terms and Deep Penetration for a Radioactive Liquid Waste Cementation Facility

A new radioactive liquid waste cementation facility was under commissioning recently in the Institute of Nuclear and New Energy Technology of Tsinghua University, which is designed to simultaneously process multiple intermediate-level radioactive waste drums. Therefore, the multiple volume sources and the scattering effect becomes a key issue in its radiation protection. For this purpose, the Monte Carlo program FLUKA code and experimental measurement were both adopted. In the FLUKA simulation, five different scenarios were considered, i.e., one drum, two drums, four drums, six drums, and eight drums. For the multiple volume sources, the source subroutine code of FLUKA was rewritten to realize the sampling. The complex shielding also leads to a deep penetration problem; hence, the optimization algorithm and variance reduction techniques were adopted. During the measurement, two scenarios, outdoor and indoor, were carried out separately representing the dose field when only one drum is considered and when the scattering effect is considered. A comparison between the experiments and calculations shows very good agreement. From both of the Monte Carlo simulation and the experimental measurement, it can be drawn that, in the horizontal direction, with the increase of the drum number, the dose rate increases very little, while in the vertical direction, the increase of the dose rate is very obvious with the increase of the drum number. The complicated source term sampling methods, the optimization algorithm and variance reduction techniques, and the experimental verification can provide valuable references for the similar scattering problem in radiation protection and shielding design.