[en] A system for the ultimate disposal of high-level waste is proposed which involves the separation of the transuranic component from the remaining nuclear ash. The transuranics, which comprise only 100 cm³ per tonne of nuclear fuel, are enclosed in stainless steel and then gold plated to a thickness of 1 mm to prevent chemical interaction with the environment. Further layers of copper, cadmium, lead, and asphalt are added before disposal at great depth in the ground. The nuclear ash component is vitrified in fireproof steel and stored in rock chambers, the decay heat keeping the containers dry and rust-free for the 500 to 600 years needed for the nuclear ash to become harmless. (author)

No abstract available

[en] The unique design of the AGR system requires a specialized fuel design. The design solution of a thin weak can with high density stable fuel and a hollow pellet is described together with the powder and pellet production processes. Production starts with the BNFL Integrated Dry Route single stage dry process for the conversion of UF₆ to UO₂ which is followed by the production of free flowing granules from a spray dried slurry of UO₂ and binder-lubricant. The performance of this fuel in the four AGR stations is described together with the first Post Irradiation Examination results. To improve fuel utilization in the future, it will be necessary to steadily increase rating and burn-up, so to meet this situation an improved design of fuel element with higher strength cladding and gas retentive fuel is being irradiated as part of the experimental programme. (author)

[en] The increasing size of nuclear power plants and the need whenever possible to reduce the number of weldments in the core area had led to a progressive increase in the size of individual components in light water reactors. Improvements in production methods are outlined and reference is made to the role of minor alloying elements on properties, particularly under neutron irradiation conditions. Developments in the welding of heavy sections and in cladding with austenitic materials are described. Stress-relief cracking in the heat-affected zones of joints and under weld cladding is now better understood and can be avoided by the use of modified welding procedures and/or a change of base steel composition from SA 508 Class 2 to SA 508 Class 3. Ultrasonic testing has been widely used in and further developed for inspection of components for the nuclear industry. Newer techniques of non-destructive testing are discussed with particular reference to acoustic holography and sound-emission analysis. (author)

[en] The FORATOM Working Group on Quality Assurance, formed in 1976 has been comparing National Codes and Standards, first by considering definitions, following with a detailed evaluation of Regulatory Requirements, and concluding with an assessment of Quality Assurance Programme Standards used for procurement. Details of its considerations are given and the following recommendations are made: that IAEA or ISO should be asked to prepare a set of internationally acceptable definitions for their member countries to adopt; that IAEA should restructure its Code of Practice into 18 criteria for all FORATOM countries to adopt; and that the ISO draft Standard on Quality Assurance for Nuclear Power Plants be adopted by all member countries as soon as it is issued in final form. (U.K.)

[en] The theory underlying the Harwell time-of-flight technique is discussed in terms of the modelling used to understand the technique and optimize its application. Detailed results are presented for amplitudes from crack-like defects and are related to those from a 3 mm dia. flat-bottomed hole. The effects of cladding and the corrections involved to account for it are described. Corrections required for curved surfaces or volumetric defects are discussed. Mention is also made of rough, contaminated defects. (author)

[en] Many components of fast fission and fusion reactors are subjected to high temperature irradiation damage. Physical and technological aspects of these damage processes for both fissile and non-fissile materials are reviewed and progress, with particular reference to work over recent years at AERE Harwell, towards the successful modelling of microstructural evolution in such materials is identified. (author)

[en] In the event of the loss of integrity of a nuclear power plant, complex thermo-hydraulic problems may be encountered in both the primary and secondary circuits. The analysis of such complex transient problems requires both a rigorous mathematical model and reliable input information in terms of items such as friction factors, slip ratios and heat transfer coefficients to the equations describing it. This Paper describes the mathematical formulation of the governing equations and some of the constitutive laws in the two-phase regions of a downcomer tube of a forced circulation Freon test rig. Two suitable numerical schemes are employed to solve the one-dimensional equations system describing the transient flow in the tube, caused by a depressurization in the main circuit of the rig. Comparison between the experiments and the predictions are made on the downcomer section of the test rig where the flash evaporation effects are most apparent. The results show reasonably good agreement when the effects of phase slip and thermal non-equilibrium are introduced. (author)

[en] An important design feature of AGRs is the facility to refuel routinely while on-load. Safety cases are being developed to demonstrate that the equipment provided enables safe routine on-load refuelling. This paper briefly describes the equipment, sets out the main elements of the safety case, and discusses measures by which the benefits of on-load refuelling may be further enhanced. (U.K.)

[en] Projection of future waste arisings are an essential complement to a knowledge of existing waste stocks. The joint project funded by the DOE and NIREX has resulted in a detailed inventory being developed which will allow these projections to be undertaken to 2010 and for the future up to the year 2030. One of the major items in the strategy development is the identification of all radioactive waste streams (current and projected) and the associated time scales. The data representing the UK radioactive waste inventory is stored and handled by a computer code, DATABASE, developed for the DOE by the UKAEA. The models of storage, conditioning, packaging, transport and disposal operations in a waste management system is achieved by use of the code SIMULATION2, also developed for the DOE by the UKAEA. (author)