[en] The 106 papers that were received for Theme 1 of the IXth Congress of the ISRM were analysed with regard to content, nature of the papers, methods of analysis and observation methods used by the authors. The general standard of the papers was very high, making the selection process for oral presentation very difficult. It was seen that numerical modeling was the most popular method of analysis and direct measurement the most popular method of observation. A disturbingly high proportion of authors did not describe any observations - this may have been due to restrictions on the space allocated per paper. A trend that appears to be emerging is the combination of rock mechanics with fluid dynamics. More work is required on the effects of time on rock stability. (author)

No abstract available

[en] This paper presents an overview of the safety and design requirements of PBMR fuel, design and performance analyses performed, analyses models and software being developed, and the current program to qualify PBMR fuel for use in the demonstration power plant. PBMR fuel design is based on the German reference fuel design, and will be utilised inside the operating envelope of the original German fuel qualification program. Fuel design, safety functions of the fuel, phenomena that influence fuel performance and fission product release and the design criteria derived from these functions and phenomena are described. Fuel qualification and validation of analyses methods are achieved by evaluations of previous experimental irradiation data and a fuel qualification programme for PBMR type fuel. The performed and planned validation and qualification efforts are presented with some results and issues discussed. The fuel performance analyses methods and legacy software products inherited from the German fuel program are being further developed at PBMR. New models and software are being developed as new requirements such as Monte Carlo design analyses become necessary. (authors)

[en] The innovative fast spectrum experimental facility MYRRHA is being developed at the Belgian Nuclear Research Center SCK-CEN. MYRRHA, a flexible fast spectrum research reactor (50-100 MW(th)), is conceived as an accelerator driven system (ADS) demonstrator, able to operate in sub-critical and critical modes. It contains a proton accelerator of 600 MeV, a spallation target and a multiplying core with MOX fuel, cooled by liquid lead-bismuth. The project started in 1997 and the reactor is forecasted to be fully operational around 2022-2023. The driver fuel for the MYRRHA core is one of its key components. Of special concern is the corrosion behaviour of the cladding materials (15-15Ti or T91 steels) in a lead-bismuth environment with the power profile envisaged for MYRRHA. An overview of the MYRRHA design and the R and D effort ongoing or planned is presented. (author)

[en] The question arose whether the correlation for the pressure drop prescribed for cylindrical pebble bed reactors by the Nuclear Safety Commission (KTA) of Germany could still be applied to the proposed annular configuration of the Pebble Bed Modular Reactor (PBMR) currently being developed in South Africa. An approach is described which uses the extended Brinkman equation for fully developed flow together with the original KTA correlation, to account for the resistance of the pebbles, and an effective viscosity, to account for the effect of the walls. A cylindrical packed bed with the same hydraulic diameter as the annular core was first of all considered. The pressure drops for various Reynolds numbers were calculated using a correlation which accounts for the effect of the wall. The formulation of the correlation for an infinite bed was then used along with the Brinkman equation to determine the appropriate values of the effective viscosity to give the same pressure drops. It was then assumed that the effective viscosities obtained in this way could be applied to the annular configuration of the PBMR. The pressure drop through the annular core was then calculated for various Reynolds numbers employing the effective viscosities in the extended Brinkman equation. It was found that the friction coefficients that could be derived from these pressure drops were in good agreement with the friction coefficients obtained from physical experiments performed on a scale model of the PBMR annular core. It was therefore concluded that the strategy followed could be used with the necessary care to predict the pressure drop through the annular core of the PBMR. (authors)

[en] The Next Generation Nuclear Plant (NGNP) Project is a US-based initiative led by Idaho National Laboratories to demonstrate the viability of using High Temperature Gas-Cooled Reactor (HTGR) technology for the production of high temperature steam and/or heat for applications such as heavy oil recovery, process steam/cogeneration and hydrogen production. A key part of the NGNP Project is the development of a Component Test Facility (CTF) that will support the development of high temperature gas thermal-hydraulic technologies as applied in heat transport and heat transfer applications in HTGRs. These applications include, but are not limited to, primary and secondary coolants, direct cycle power conversion, co-generation, intermediate, secondary and tertiary heat transfer, demonstration of processes requiring high temperatures as well as testing of NGNP specific control, maintenance and inspection philosophies and techniques. The feasibility of the envisioned CTF as a development and testing platform for components and systems in support of the NGNP was evaluated. For components and systems to be integrated into the NGNP full scale or at least representative size tests need to be conducted at NGNP representative conditions, with regards to pressure, flow rate and temperature. Typical components to be tested in the CTF include heat exchangers, steam generators, circulators, valves and gas piping. The Design Data Needs (DDNs), Technology Readiness Levels (TRLs) as well as Design Readiness Levels (DRLs) prepared in the pre-conceptual design of the NGNP Project and the NGNP life cycle requirements were used as inputs to establish the CTF Functional and Operating Requirements (F and ORs). The existing South African PBMR test facilities were evaluated to determine their current applicability or possible modifications to meet the F and ORs of the CTF. Three concepts were proposed and initial energy balances and layouts were developed. This paper will present the results of this CTF study and the ongoing efforts to establish the CTF. (authors)