Abbreviations -- Abbreviations -- Opening plenary session -- Welcome address -- The CEC Research Action Programme on the Development of Nuclear Fission. -- The CEC Indirect Action Research Programme, Safety of Thermal Water Reactors (1979-1983): Aims, contents and implementation -- Parallel session Research Area A -- The loss of coolant accident (LOCA) and the functioning and performance of the emergency core cooling system (ECCS). -- Session A1 -- Important thermohydraulic aspects during refilling and reflooding of an uncovered LWR core. -- Studies on the effects of blockage upon LWR emergency core cooling systems. -- Session A2 -- Droplet dynamics and heat transfer in dispersed two phase flow. -- An experimental investigation of the effect of clad ballooning on the effectiveness of PWR emergency core cooling -- Out of pile ballooning and bursting tests on Zircaloy cladding rods with direct and indirect heating. -- General Discussion on sessions A1 and A2 -- Session A3 -- 2D effects in the core during the reflooding phase of a LOCA. -- Fluid dynamic effects in the fuel element top nozzle area during refilling and reflooding. -- Study of rewetting and quench phenomena by single pin out-of-pile experiments, with special emphasis on the effect of pin composition. -- Heat transfer to a dispersed two-phase flow and detailed quench front velocity research -- Session A4 -- Rewetting propagation over Zircaloy under bottom flooding conditions. -- The Role of Experiments in The Development and Qualification of Thermalhydraulic.Codes, As Experienced in The Development of The CATHARE Code -- Parallel sessions Research Area B -- The protection of nuclear power plants against external gas cloud explosions -- Session B1 -- Large-scale field trials on dense vapour dispersion. -- Aspects of the dispersion of denser-than-air vapours relevant to gas cloud explosions. -- Session B2 -- Verification of heavy gas models on the basis of large-scale experiments -- Computer processing of visual records from the Thorney Island large scale gas trials. -- Transition from slow deflagration to detonation. -- On the propagation of the pressure pulse due to an unconfined gas cloud explosion. Theoretical analysis. -- Session B3 -- Gas cloud explosions and their effect on nuclear power plant, basic development of explosion codes. -- Validation of blast simulation codes and experimental investigation of flame propagation in the presence of obstacles. -- Characterization of the pressure field induced by the explosions in air of a hydrocarbon-air mixture, with slow deflagration or fast deflagration. -- Experimental investigation of the acceleration of deflagration in wake flow. -- Session B4 -- Calculation of overpressures on the buildings of a power plant due to the passage of a shock wave caused by an accidental explosion. -- Blast wave propagation and the influence of obstacles. -- Calculation of the wall pressure field generated on a group of buildings by an external explosion. -- Recent results of experimental studies on the transition of a deflagration into a detonation and some aspects for the transposition of these results to confined explosions. -- Parallel sessions Research Area C -- The release and distribution of radioactive fission products in the atmosphere following a reactor accident. -- Session C1 -- Review of specific effects in atmospheric dispersion calculations. -- The effects of buildings on low level atmospheric discharges. -- Session C2 -- Predicting lift-off of major self-heating releases under the influence of a building. -- Development of an integral model of a radioactive jet released accidentally from a nuclear reactor. -- Development of a prototype mesoscale computer model, incorporating treatment of topography. -- Finite element three-dimensional formulation of a variational procedure of wind field adjustment over a domain of complex topography. -- Description of a recent nordic mesoscale dispersion experiment over a land-water-land area (the Oresund Experiment). -- Session C3 -- Wind tunnel modelling of turbulent diffusion of pollutant puffs. -- Physical model of the dispersion of a radioactive contaminant in the atmosphere above a "heat island". -- Wind Tunnel Simulation of Atmospheric Dispersion in Stable Conditions at a Real Site. -- Assessment of the dispersion of fission in the atmosphere following a reactor accident under meteorological conditions of low wind speed. -- Session C4 -- Local-scale atmospheric diffusion at a coastal site, in the presence of breeze effect. -- Sensitivity, applicability and validation of bi-Gaussian off-and on-line models for the evaluation of the consequences of accidental releases in nuclear facilities. -- Interlaboratory comparison of SF6 - Determination used within the framework of tracer releases. -- Estimates of uncertainty in dispersion modelling. -- Concluding plenary session -- Overview and conclusions on the results obtained in research Area A: The loss of coolant accident (LOCA) and the functioning and performance of the emergency core cooling system (ECCS). -- Overview and conclusions on the results obtained in research Area B: The protection of nuclear power plants against external gas cloud explosions. -- Overview and conclusions on the results obtained in research Area C: The release and distribution of radioative fission products in the atmosphere following a reactor accident. -- The CEC - Research Action Programme on Reactor Safety (1984-1981) -- Developments in Nuclear Safety Research. -- Concluding panel -- Evaluation of the results of the present Indirect Action Research Programme Safety of LWR. State-of-the-art in LWR Safety Research. Identification of useful topics for future research, with special consideration of Conmnunity programmes. -- Closing address -- List of participants -- Index of authors.