[en] A definition of reactor safety and its role within EDF is followed by an outline of the organisation set up in France and the main procedures which EDF must respect in order to obtain the necessary authorisations. The basic principles obeyed by safety are then given. Concrete examples are used to illustrate the rules governing the sizing of plants in normal and accidental operation. The different lines of thought embarked on to improve existing knowledge and the sets of hypotheses now used are presented in conclusion

[en] The facility for blowdown experiments at the Scalbatraio Center of the Pisa University and the experimental program are briefly described. The results of the tests have been compared with the output of calculations performed with RELAP-3 code. A large number of computer runs have been made varying bubble-gradient parameter, bubble velocity and contraction coefficient of leak for evaluate code's sensibility and correlate the main blowdown parameters with different test conditions

[en] The contributions to this topic are dealing, in a broad overview, with important aspects of Nuclear Emergency Preparedness and Response, like the influence of the new ICRP recommendations number 103 and number 109 on emergency preparedness and on planning for response, possible problems in installing and operating emergency care centres, experience from exercises as well as the training of response personnel in Austria and Germany. Finally, measures in emergency preparedness with regard to a dirty bomb attack are reported by means of an INEX-4-exercise in Switzerland. (orig.)

[en] In order to supply solution fuel to STACY (Static Experiment Critical Facility) and TRACY (Transient Experiment Critical Facility) in the NUCEF (Nuclear Fuel Cycle Safety Engineering Research Facility), large amounts of enriched uranyl nitrate solution fuel have been prepared at the fuel treatment system. During financial year 1994-2000, 635 kg of enriched uranium oxide were dissolved after optimizing the operation condition for dissolver by preliminary tests to prepare 10% and 6% enriched uranyl nitrate solution fuel. During financial year 1995-2003, large amounts of uranyl nitrate solution after critical experiments were concentrated and distilled for acid removal at uranium evaporator. The method for removing nitric acid from the solution fuel was established by preliminary evaporator tests. This report presents results of these preliminary test and operation. (author)

[en] Prospects to the development of gaseous nitrogen injection unit as a precaution to the prevention of sodium combustion in the FBR Monju reactor are performed. Concepts and calculations for the elaboration of the system are demonstrated, results of experiments for the verifications of the dependence between oxygen concentration and sodium combustion are systematized. Efficiency of the nitrogen injection was estimated during the analysis of the combustion at different nitrogen flow. The need for the maintenance of low oxygen concentration on the prolonged injection is noted

[en] Changes of fuel element design and modifications of the operational conditions have to be tested in experiments and pilot projects for nuclear safety. Experimental design is an useful statistical method minimizing costs and risks for this procedure. The main problem of our work was to investigate the connection between failure rate of fuel elements, sample size, confidence interval, and error probability. Using the statistic model of the binomial distribution appropriate relations were derived and discussed. A stepwise procedure based on a modified sequential analysis according to Wald was developed as a strategy of introduction for modifications of the fuel element design and of the operational conditions. (author)

[en] General statements may be made on the behavior of single-component and multi-component aerosols in the Nuclear Safety Pilot Plant vessel. The removal processes for U₃O₈, Fe₂O₃, and U₃O₈ + Fe₂O₃ aerosols are enhanced in a steam-air atmosphere. Steam-air seems to have little effect on removal of concrete aerosol from the vessel atmosphere. A steam-air environment causes a change in aerosol shape from chain-agglomerate to basically spherical for U₃O₈, Fe₂O₃, and U₃O₈ + Fe₂O₃ aerosol; for concrete the change in aerosol shape is from chain-agglomerate to partially spherical. The mass ratio of the individual components of a multi-component aerosol seems to have an observable influence on the resultant behavior of these aerosols in steam. The enhanced rate of removal of the U₃O₈, the Fe₂O₃, and the mixed U₃O₈ + Fe₂O₃ aerosols from the atmosphere of the NSPP vessel by steam-air is probably caused by the change in aerosol shape and the condensation of steam on the aerosol surfaces combining to increase the effect of gravitational settling. The apparent lack of an effect by steam-air on the removal rate of concrete aerosol could result from a differing physical/chemical response of the surfaces of this aerosol to condensing steam

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[en] The pilot conditioning plant at Gorleben, Germany, is designed as a multi-purpose plant. Its primary task is the conditioning of spent fuel assemblies into a form suitable for final disposal. As a pilot plant, it allows furthermore for the development and testing of various conditioning techniques. In terms of international safeguards, the pilot conditioning plant is basically considered an item facility. Entire fuel assemblies enter the plant in transport casks, whereas bins filled with fuel rods or canisters containing cut fuel rods leave the facility in final disposal packages (e.g. POLLUX). Each POLLUX final disposal package content is uniquely correlated to a definite number of fuel assemblies which have entered the conditioning process. For this type of facility, containment/surveillance (C/S) should take over the major role in nuclear material safeguards. This paper discusses the safeguards at the Gorleben plant