Design and licensing of UKAEA IP 2m box

Abstract

Croft Associates Ltd (Croft) was contracted by the United Kingdom Atomic Energy Authority (UKAEA), Winfrith in 2006 to design, manufacture, test and license an intermediate level waste industrial package transport packaging (UKAEA 2 m Box Design no. 3954) for decommissioning waste from the Dragon and steam generating heavy water reactors at Winfrith. The package had to meet the requirements of the existing UK. Nuclear Decommissioning Authority (NDA) (Nirex) 2 m Box specification. The UKAEA 2 m Box is intended for on-site storage at Winfrith and possibly another site for 50 years and subsequent transport to the NDA repository without further processing. The design of the box closure includes a leak testable sealing system which is capable of being replaced at a later date (e.g. before shipment), by the removal of the lid and replacement of seals remote from the box location. Initially the specification for the UKAEA 2 m Box called for rating for gross weight of 40 t, but this was raised to 50 t as it was realised that the efficient use of the capacity of the box would result in a 50 t gross weight. Two prototype 2 m Boxes were produced; one being provided with 100 mm of concrete shielding, and the other being provided without any shielding. The shielded box was filled with simulated waste and a concrete grout cap fitted and the resulting 50 t package was dropped onto the massive target at Winfrith from a height of 300 mm (this being the regulatory test height). The test showed that the box performed as expected; meeting all requirements. In particular: there was no loss of shielding and no effect on the containment system that would reduce its effectiveness.     

Dynamic simulation of cooling stack and cooling circuit for converter gas cooling

Abstract

A dynamic simulation programme for the recooling circuit of converter gas cooling systems has been developed to assist in the design of new plant and efforts to increase the production capacity of existing plant. A suitable choice of independent variables (enthalpy h and pressure p) allows clear mathematical modelling and enhances the numeric performance of the model. The results have been verified by comparison with the operational data from existing steel plants. This simulation programme offers steelmakers the following advantages when seeking an increase in production: recalibration of existing systems and determination of maximum allowable heat input to the cooling circuit; proposals for modification of existing systems to increase the allowable heat input under constraints for optimal investment cost and installation downtime; design of new, low investment cost cooling systems tailored for existing plant infrastructure and local market conditions.     

Industrial treatment processes for recycling of green foundry sands

Abstract

Three treatment processes for the reclamation of green moulding sands coming out from a cast iron foundry located in Northern Italy are considered in this study. A wet mechanical treatment, a dry mechanical treatment and a dry mechanical plus heat treatment are compared to evaluate the efficiency of each process and to point out the best regeneration solution for the recycling of reclaimed sand in foundry operations. The inflow and the outflow samples of each process were characterised by means of particle size analysis and the determination of silica, loss on ignition, acid request, oolitic and some metals contents. A final evaluation of the three processes was performed taking into account the obtained quality of recovered silica sand and the economical aspects; the wet mechanical and the dry mechanical plus thermal treatments are most effective for the recovery of green moulding sands coming out from the considered foundry plant for cold box core production.     

Effect of waste glass and zircon on ceramic properties and microstructure of porcelain tiles

Abstract

The possibility of using waste glass as a flux in porcelain tiles without deterioration in mechanical properties has been assessed. Waste glass was added to a typical porcelain tile body, replacing feldspar by up to 15%. Zircon was also added at 5% in partial replacement of quartz. The prepared batches were fired at temperatures of 1160 to 1240°C with 20 min soaking time. Addition of 5% zircon in the presence of 5% waste glass resulted in unusual mechanical and physical characteristics. Further additions of waste glass enhanced vitrification and consequently some surface and mechanical properties, but worsened modulus of rupture (MOR) and toughness. Generally specimens containing zircon had better physicomechanical properties.     

Improvement of the Fatigue Properties of Investment-cast Steels as a Result of HIPing

Abstract

Two alloys, a ferritic stainless steel, 17/4PH, and a 3% CrMo low alloy steel, CLA3, were produced as investment-cast bars, processed in air. For each alloy, half the number of bars were heat-treated and machined to provide rotating bend fatigue test pieces. The others were HIPed and heat-treated before preparation of the test pieces. Tensile tests and a limited metallographic examination were carried out. The results show that HIPing gives considerable improvements in tensile ductility and fatigue strength, as judged by the Fatigue Endurance Ratio (FER). For the 17/4 PH alloy, a FER of 0.42 was obtained, whilst for the CLA3 alloy, the FER was 0.47, each about 90% of the wrought state value. HIPing also reduced the scatter in the test results. For interest, the results are compared with those obtained during a recent NEL/BICTA project.     

Formulation of caesium based and caesium containing geopolymers

Abstract

Cement encapsulation is widely used as a low- and intermediate level radioactive waste immobilisation process. Among these wastes, caesium ions are poorly immobilised by Portland cement based materials. This work consists of an experimental investigation into the ability of geopolymers to effectively encapsulate this chemical species and to determine the impact of caesium incorporation on the geopolymer properties. Geopolymers were synthesised with several compositions based on the activation of metakaolin with an alkali hydroxide solution containing caesium. The setting time, mineralogy, porosity and mechanical properties of the samples were examined for one month. Leach tests were conducted during the same period to determine the immobilisation efficiency. The results depend to a large extent on the composition of the activation solution in terms of soluble silica content and alkali used. These parameters determine both the degree of condensation and the geopolymer composition.     

Mechanical design assessment approaches of actual spent fuel and HLW transport package designs

Abstract

In recent years, BAM Federal Institute for Materials Research and Testing finalised the competent authority assessment of the mechanical and thermal package design in several German approval procedures of new spent fuel and high level waste package designs. The combination of computational methods and experimental investigations in conjunction with materials and cask components testing is the most common approach to mechanical safety assessment. The methodology in the field of safety analysis, including associated assessment criteria and procedures, has evolved rapidly over the last years. The design safety analysis must be based on a clear and comprehensive safety evaluation concept, including defined assessment criteria and constructional safety goals. In general, for new package designs, the implementation of experimental package drop tests in the approval process should be obligatory. Additionally, pre- and post-test calculations as well as components or material testing could be important. The extent to which drop tests are necessary depends on the individual package construction, the materials used and identified safety margins in the design.     

Tribological behaviour of glass fibre bundles reinforced epoxy gradient composites

Abstract

The short fibre bundles separated from the machining waste of a printed circuit board manufacturing plant were used in preparing functionally graded composites using polysulphide modified epoxy resin. Glass fibre bundles were thouroughly mixed with epoxy, which is getting polymerised with time and centrifugal force was applied to achieve graded dispersion of glass fibre bundles. The centrifugation time was varied to obtain different gradient profiles. Optical microstructures confirmed the graded dispersion of glass fibres bundles in the epoxy matrix. Increase in distance towards the centrifugation force direction increases the glass fibre concentration. Gradient characteristics in the composite have been observed in wear and friction measurements, which were conducted using a pin-on-disc machine. Worn surfaces of samples were analysed with the help of SEM. Both sliding (adhesive) and abrasive wear rates of glass fibre reinforced epoxy gradient composites reduced with increasing centrifugation time. Reduction in wear rate in glass fibre epoxy gradient composites has been attributed to the better interface bonding between epoxy coated fibre bundles and the epoxy matrix and hardening property of glass fibre. It has been found that capability to sustain pressure limit increased from 0·59 to 0·79 MPa on centrifuging the sample upto 2 min and reached to 1·19 MPa with increasing the centrifugation time to 30 min.     

Ten years of transport of vitrified high level waste (HLW) from Areva La Hague

Abstract

Areva has extensive experience in reprocessing irradiated fuel from both gas cooled and water cooled reactors and has legal obligations to return residues to respective foreign owners, usually in the form of vitrified waste. Such returns are subject to appropriate quality assurance controls. Appropriate transport flasks have been designed and certified. Transport operations are routinely conducted to Belgium, Germany, Japan, Switzerland and the Netherlands. The present paper reviews the experiences over a ten year period from 1995 to 2005.