[en] This paper describes the development of the CONTAIN-code to enable appropriate analysis of severe accident consequences in an LMFBR containment. The author presents the experiment chosen for CONTAIN verification

[en] The Vltava river is the source of water for the power plant and the recipient of its waste water. The sewerage system of the power plant is described, divided into 5 independent parts by the source of the discharge. The discharge of water with maximal permitted content of radionuclides would increase the dose rate in the river by less than 3% which is less than the fluctuation of the background. The question is discussed of tritium in waste waters as are possible pathways of its escape into the environment. Tritium-containing water from the primary circuit will be discharged into spray pools. The table shows project specific activities of important radionuclides in technological waste waters and the respective dose rates in the water from gamma radiation (M.D.). 1 tab., 5 refs

[en] An evaluation of coolant aerosol influence on heat capacity and density of room atmospheres has been performed by extension of the CONTAIN-code. Comparison of results with measured data from the HDR-experiment T31.6 gave some influence - especially on natural circulation flow - when two phase blowdown dominates. Later during pure steam blow the influence both on temperature and on flow is minor. Unfortunately the turbulences in the break room and the poor ability of CONTAIN to model this situation due to the lack of a model for turbulent deposition strongly overestimate the flow development. The realized extension of the CONTAIN-modelling will be of some more significance for the analysis of temperature and flow behaviour in a containment resulting from a boiling coolant pool for example for LMFBRs. (author)

[en] The accident loading of the SNR-300 containment is different from that of an LWR due to the different containment concept, sodium as coolant, which can cause energetic reactions, additional design measures against loads resulting from an HCDA. Accidental release of sodium, radioactive materials and/or decay heat result in pressure and temperature rise in the containment. Due to the temperature rise of the concrete structures stress and deformation analysis is often necessary. Heated concrete releases water or steam which has to be separated from the Na-leakage by a steel lining and by a system to avoid chemical reactions with additional energy and gas release. The additional assumption of safety system failures as the core catcher, the steel lining, the reventing system, the energy supply, the barriers between inner and outer containment alone or still in combination for risk analysis can lead to physical and chemical phenomena as sodium fires, water release from heated concrete, sodium-water reactions, sodium boiling, core concrete interactions or sodium-concrete interactions. An acceptable best estimate evaluation of the resulting loads and concequences can only be realized by application of computer codes as CONTAIN or CACECO, which mostly respect the coupling of all involved phenomena. (orig.)

[en] The CACECO- and the CONTAIN-results for a detailed thermodynamic analysis of a HCDA show the same tendencies and most results meet acceptable. A direct modeling of natural circulation in the inner containment would reduce the differencies even when the CONTAIN modeling for heat transfer by radiation is not as extended as for CACECO. (orig./HP)

[en] During the discussion of the SNR-300 concept, the feasibility of the secondary containment system was assessed. The secondary containment consists of the inner containment enveloping the primary sodium circuits and the outer containment enclosing the secondary heat transfer system, reactor service installations, fuel handling equipment, etc. In addition to the more conventional accidents up to loss-of-coolant accidents for the SNR-300 the consequences of a hypothetical accident with resulting core-melt-down had to be taken into account for the design of the containment system. The decay heat removal from the molten core is performed by the external core catcher cooling system and by natural convection via the compartments of the inner containment. The latter path of the heat results in thermal loads for the containment walls. (orig.)

[en] Severe accident analysis for LMFBR-containments has to consider various phenomena influencing the development of containment loads as pressure and temperatures as well as generation, transport, depletion and release of aerosols and radioactive materials. As most of the different phenomena are linked together their feedback has to be taken into account within the calculation of severe accident consequences. Otherwise no best-estimate results can be assured. Under the sponsorship of the German BMFT the US code CONTAIN is being developed, verified and applied in GRS for future fast breeder reactor concepts. In the first step of verification, the basic calculation models of a containment code have been proven: (i) flow calculation for different flow situations, (ii) heat transfer from and to structures, (iii) coolant evaporation, boiling and condensation, (iv) material properties. In the second step the proof of the interaction of coupled phenomena has been checked. The calculation of integrated containment experiments relating natural convection flow, structure heating and coolant condensation as well as parallel calculation of results obtained with an other code give detailed information on the applicability of CONTAIN. The actual verification status allows the following conclusion: a caucious analyst experienced in containment accident modelling using the proven parts of CONTAIN will obtain results which have the same accuracy as other well optimized and detailed lumped parameter containment codes can achieve. Further code development, additional verification and international exchange of experience and results will assure an adequate code for the application in safety analyses for LMFBRs. (orig.)

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No abstract available

[en] Published in summary form only