Integrated waste management and R&D at the National Nuclear Laboratory

Integrated waste management is a strategy adopted in the UK to minimise the waste arising from nuclear operations. The application of the waste hierarchy, that prioritises waste prevention, minimisation, reuse and recycle in preference to waste disposal is central to the minimisation of waste and ultimately the development of a circular economy. This paper describes the waste hierarchy approach and illustrates through examples, how R&D at NNL is supporting this approach and developing and demonstrating new technology to underpin its application to environmental restoration and clean energy programme

Towards the decontamination of plutonium contaminated bricks:Creation of a cerium-based simulant contamination system

There is a need for the decontamination of a number of plutonium-contaminated bricks encountered in a legacy BUTEX reprocessing plant on Sellafield site in the UK. Documentary review has indicated that the source of the contamination was a 8 mol dm -3 nitric acid process stream containing 10 mmol dm -3 of Pu in either the (III) or (IV) oxidation state. Here we have sought to emulate the behaviour of Pu(III) by treatment of fired clay brick surfaces with a solution of 10 mmol dm -3 Ce(III) nitrate in 8 mol dm -3 nitric acid. XRD, porosimetry and EDX measurements of the untreated bricks reveal them to be comprised of low porosity silica and aluminosilicate phases with a surface layer of a low-Si content Al-C-N oxide derived from the atmosphere of the kiln in which the bricks were fired. Depth profiling after an initial 6 week acid soak reveals that the acid penetrates <10 mm into the brick. SEM/EDX analysis reveals that acid treatment significantly roughens the brick surface due to dissolution the above described Al-C-N oxide layer. The EDX data also shows that virtually no Ce is retained as tenacious contamination at the brick surface; this may be due to a either a mass action/kinetic effect or taken to indicate that trivalent Ce(III) is less likely to absorb at the crystalline silica/aluminosilicate surface of the brick than its more easily hydrolysable tetravalent equivalent. Preliminary higher-resolution EDX analysis indicates that small quantities of Ce(III) can be detected in pores or cracks on the surface of acid-treated brick samples. This suggests that Ce(III) may be non-tenaciously sequestered into surface defects - and that a simple salt wash may be sufficient to remove it. Based on the above observations, potential decontamination strategies are discussed and future studies outlined

Strategic Options For The Management Of Waste Irradiated Graphite -9456

ABSTRACT World-wide there are over 230 000 tonnes of irradiated graphite that will ultimately require the identification of treatment, management and/or disposal options. This legacy has arisen predominantly from the use of graphite moderated reactors for base-load generation. The UK is one of several countries that have an irradiated graphite waste legacy; some of these countries have combined to address this future waste management problem. This paper describes how this consortium (CARBOWASTE) will evaluate and analyse graphite management options

Inferring Social Ties in Academic Networks Using Short-Range Wireless Communications

International audienceWiFi base stations are increasingly deployed in both public spaces and private companies, and the increase in their density poses a significant threat to the privacy of connected users. Prior studies have provided evidence that it is possible to infer the social ties of users from their location and co-location traces but they lack one important component: the comparison of the inference accuracy between an internal attacker (e.g., a curious application running on a mobile device) and a realistic external eavesdropper in the same field trial. In this paper, we experimentally show that such an eavesdropper is able to infer the type of social relationships between mobile users better than an internal attacker. Moreover, our results indicate that by exploiting the underlying social community structure of mobile users, the accuracy of the inference attacks doubles. Based on our findings, we propose countermeasures to help users protect their privacy against eavesdroppers

The influence of oxidation on space charge formation in gamma-irradiated low density polyethylene

The research presented in this paper investigates the role of oxidation in the formation of space charge in gamma-irradiated low-density polyethylene after being electrically stressed under dc voltage. Polyethylene plaques both with and without antioxidant were irradiated up to 500kGy using a 60Co gamma source and space charge distributions were measured using the piezoelectric induced pressure wave propagation method. It has been found that a large amount of positive charge evolved adjacent to the cathode in the sample without antioxidant and was clearly associated with oxidation of the near surface. The amount of charge formed for a given applied stress, increased with the dose absorbed by the material. On the other hand space charge in a sample containing antioxidant under the same applied electric stress was negligible even in the sample exposed to 500kGy. The Main process to form space charge is via charge injection rather than charge separation in the sample without antioxidant