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.     

Development of intermediate temperature SOFC using LaGaO3 based oxide film

Abstract

The effect of the NiO–Fe₃O₄ (NiFeO)/Ce_0·8Sm_0·2O_2-δ (SDC) ratio on the microstructure and electrochemical activity of cermet substrates was systematically investigated. Dense NiFeO–SDC substrates, which are suitable for the deposition of thin oxide films for example, La_0·9Sr_0·1Ga_0·8Mg_0·2O_3-δ (LSGM) tend to be porous and applicable as anodes in intermediate temperature solid oxide fuel cells (IT SOFC). The porosity and electrical conductivity of the reduced substrates were evaluated with increasing NiFeO ratios. The lowest anode overpotential was measured in a substrate with a NiFeO/SDC ratio of 6:4, especially at a high current density. In a reduced substrate with this composition, continuous frames of SDC and NiFe alloy can be formed simultaneously, thus leading a longer triple phase boundary.     

A Constant Propagation Algorithm for Explicitly Parallel Programs

In this paper, we present a constant propagation algorithm for explicitly parallel programs, which we call the Concurrent Sparse Conditional Constant propagation algorithm. This algorithm is an extension of the Sparse Conditional Constant propagation algorithm. Without considering the interaction between threads, classical optimizations lead to an incorrect program transformation for parallel programs. To make analyzing parallel programs possible, a new intermediate representation is needed. We introduce the Concurrent Static Single Assignment (CSSA) form to represent explicitly parallel programs with interleaving semantics and synchronization. The only parallel construct considered in this paper is cobegin/coend. A new confluence function, the -assignment, which summarizes the information of interleaving statements between threads, is introduced. The Concurrent Control Flow Graph, which contains information about conflicting statements, control flow, and synchronization, is used as an underlying representation for the CSSA from.     

A Tree-Based Alternative to Java Byte-Codes

Despite the apparent success of the Java Virtual Machine, its lackluster performance makes it ill-suited for many speed-critical applications. Although the latest just-in-time compilers and dedicated Java processors try to remedy this situation, optimized code compiled directly from a C program source is still considerably faster than software transported via Java byte-codes. This is true even if the Java byte-codes are subsequently further translated into native code. In this paper, we claim that these performance penalties are not a necessary consequence of machine-independence, but related to Java's particular intermediate representation and runtime architecture. We have constructed a prototype and are further developing a software transportability scheme founded on a tree-based alternative to Java byte-codes. This tree-based intermediate representation is not only twice as compact as Java byte-codes, but also contains more high-level information, some of which is critical for advanced code optimizations. Our architecture not only provides on-the-fly code generation from this intermediate representation, but also continuous re-optimization of the existing code-base by a low-priority background process. The re-optimization process is guided by up-to-the-minute profiling data, leading to superior runtime performance.     

Cyclic voltammetric studies on zinc transition metal alloy electrodeposition

Abstract

Cyclic voltammetric studies were carried out on zinc transition metal alloy films to identify the phases formed during alloy deposition. The deposition of zinc was found to involve stepwise reduction of divalent zinc ions. The formation of monovalent zinc ion was found to be slow. The zinc alloy systems were found to be anomalous, resulting in a higher content of zinc in the film. Dissolution of zinc from the alloy was observed. The dissolution was found to occur in intermediate phases rich in zinc.