Safety of Thermal Water Reactors : Proceedings of a Seminar on the Results of the European Communities' Indirect Action Research Programme on Safety of Thermal Water Reactors, Held in Brussels, 1–3 October 1984

The European Community's Indirect Action Research Programme on the Safety of Thermal Water Reactors had as main obj ectives to execute useful fundamental research, complementary and confirmatory to on-going work in national programmes, and to improve collaboration and exchange of inform­ ation between laboratories in the Member States. The Seminar was aimed to report on work performed during the last five years and to identify useful further research areas with a tentative assessment of the state of the art for future work in certain issues of LWR-safety. The results obtained in 33 research projects executed in different national laboratories of the European Community were presented, evaluated and discussed, together with a number of invited papers on topics related to the research programme. Topics covered mainly within 3 distinct research areas or sub-programmes: Research Area A: The loss of coolant accident (LOCA) and the func­ tioning and performance of the emergency core cooling system (ECCS). Fundamental work on thermalhydraulics and heat transfer during refill and reflood of an uncovered core after a LOCA. Research Area B: The protection of nuclear power plants against external gas cloud explosions. Study of the impact on plant structure and systems of external explosions of dense combustible gas clouds due to accidental releases of hydro­ carbons in the vicinity of the plant. Research Area C: The release and distribution of radioactive fission products in the atmosphere following a reactor accident. Front Matter....Pages i-xi Introduction....Pages 1-1 Abbreviations:....Pages 3-4 Front Matter....Pages 5-5 Welcome Address....Pages 7-7 The CEC Research Action Programme on the Development of Nuclear Fission Energy....Pages 9-18 The CEC Indirect Action Research Programme, Safety of Thermal Water Reactors (1919–1983)....Pages 19-20 Front Matter....Pages 21-21 Important thermohydraulic aspects during refilling and reflooding of an uncovered LWR core....Pages 23-36 Studies on the Effects of Blockage Upon LWR Emergency Core Cooling Systems....Pages 37-47 Droplet Dynamics and Heat Transfer in Dispersed Two Phase Flow....Pages 51-64 An Experimental Investigation of the Effect of Clad Ballooning on the Effectiveness of PWR Emergency Core Cooling....Pages 65-78 Out of Pile Ballooning and Bursting Tests on Zircaloy Cladding Rods with Direct and Indirect Heating....Pages 79-96 General discussion concerning on Sessions A1 and A2....Pages 97-99 2D Effects in the Core During the Reflooding Phase of a Loca....Pages 103-113 Fluid Dynamic Effects in the Fuelelement Top Nozzle Area During Refilling and Reflooding....Pages 115-124 Study of Rewetting and Quench Phenomena by Single Pin Out-of- Pile Experiments, with Special Emphasis on the Effect of Pin Composition....Pages 125-134 Heat Transfer to a Dispersed Two-Phase Flow and Detailed Quench Front Velocity Research....Pages 135-149 Rewetting Propagation Over Zircaloy Under Bottom Flooding Conditions....Pages 153-163 The Role of Experiments in the Development and Qualification of Thermalhydraulic Codes, as Experienced in the Development of the Cathare Code....Pages 165-176 Front Matter....Pages 201-201 Large-Scale Field Trials on Dense Vapour Dispersion....Pages 179-189 Aspects of the Dispersion of Denser-Than-Air Vapours Relevant to Gas Cloud-Explosions....Pages 191-200 Verification of Heavy Gas Models on the Basis of Large Scale Experiments....Pages 203-212 Front Matter....Pages 201-201 Computer Processing of Visual Records from the Thorney Island Large Scale Gas Trials....Pages 213-221 Transition from Slow Deflagration to Detonation....Pages 223-240 On the Propagation of the Pressure Pulse Due to an Unconfined Gas Cloud Explosion. A Theoretical Analysis....Pages 241-251 Gas Cloud Explosions and their Effect on Nuclear Power Plant Basic Development of Explosion Codes....Pages 255-268 Validation of Blast Simulation Codes and Experimental Investigation of Flame Propagation in the Presence of Obstacles....Pages 269-280 Characterization of the Pressure Field Induced by the Explosions in Air of a Hydrocarbon-Air Mixture, with Slow Deflagration or Fast Deflagration....Pages 281-291 Experimental Investigation of the Acceleration of Deflagration in Wake Flow....Pages 293-304 Calculation of Overpressures on the Buildings of Power Plant Due to the Passage of a Shock Wave Caused by an Accidental Explosion....Pages 307-317 Blast Wave Propagation and the Influence of Obstacles....Pages 319-328 Calculation of the Wall Pressure Field Generated on a Group of Bluidings by an External Explosion....Pages 329-340 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....Pages 341-350 Front Matter....Pages 351-351 Review of Specific Effects in Atmospheric Dispersion Calculations....Pages 353-367 The Effects of Buildings on Low-Level Atmospheric Discharges....Pages 369-382 Predicting Lift-Off of Major Self-Heating Releases under the Influence of a Building....Pages 385-397 Development of an Integral Model of a Radioactive Jet Released Accidentally from a Nuclear Reactor....Pages 399-404 Development of a Protoype Mesoscale Computer Model Incorporating Treatment of Topography....Pages 405-414 Finite Element Three-Dimensional Formulation of a Variational Procedure of Wind Field Adjustment Over a Domain of Complex Topography....Pages 415-426 Description of a Recent Nordic Mesoscale Dispersion Experiment Over a Land-Water-Land Area (The Øresund Experiment)....Pages 427-438 Wind Tunnel Modeling of Turbulent Diffusion of Pollutant Puffs....Pages 441-450 Physical Model of the Dispersion of a Radioactive Contaminant in the Atmosphere above a Heat Island....Pages 451-456 Front Matter....Pages 351-351 Wind Tunnel Simulation of Atmospheric Dispersion in Stable Conditions at a Real Site....Pages 457-468 Assessment of the Dispersion of Fission Products in the Atmosphere following a Reactor Accident under Meteorological Conditions of Low Wind Speed....Pages 469-479 Local Scale Atmospheric Diffusion at a Coastal Site in the Presence of Breeze Effect....Pages 483-495 Sensitivity, Applicability and Validation of Bi-Gaussian Off- and On-Line Models for the Evaluation of the Consequences of Accidental Releases in Nuclear Facilities....Pages 497-505 Interlaboratory Comparison of SF 6 Determination used within the Framework of Tracer Releases....Pages 507-512 Estimates of Uncertainty in Dispersion Modelling....Pages 513-526 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)....Pages 529-538 Overview and Conclusions on the Results Obtained in Research Area B: The Protection of Nuclear Power Plants Against External Gas Cloud Explosions....Pages 539-545 Overview and Conclusions on the Results Obtained in Research Area C: The Release and Distribution of Radioactive Fission Products in the Atmosphere following a Reactor Accident....Pages 547-558 The CEC Research Action Programme on Reactor Safety (1984–1987)....Pages 559-569 Developments in Reactor Safety Research....Pages 571-581 Concluding Panel....Pages 583-605 Closing Address....Pages 607-607 Back Matter....Pages 609-613