Investigation into the safety case of the MEGAPIE target in the spallation neutron source SINQ Pressure development in the beam line of the facility in case of the hypothetical accident 'Breach of the beam windows on target container and safety hull' / Untersuchung zum Sicherheitskonzept des MEGAPIE Targets in der Spallations-Neutronenquelle SINQ Druckentwicklung im Strahlrohr der Anlage in dem angenommenen Stoerfall ''Bruch der Strahlfenster an Targetbahaelter und Sicherheitshuelle''

H. Jacobs; forschungszentrum karlsruhe; forschungszentrum karlsruhe

The MEGAPIE target is being developed as liquid metal target for the Spallation Neutro Source SINQ at the Paul Scherrer Institute at Villigen, Switzerland. The present report analyses the hypothetical accident 'failure of the beam windows of target and safety hull.' During such an accident, the liquid potassium-bismuth alloy from the target would come into contact with the liquid water (D_2O) from the safety hull. The question arises whether this contact can lead to pressures that could lead to damage of the beam line. The critical initial phase of this accident is analysed with the help of the transient thermo-hydraulic code MATTINA which is being developed at Forschungszentrum Karlsruhe for the analysis of steam explosions that might occur during severe accidents in light water reactors. According to the calculations performed the pressure will remain below 1 MPa (10 bar) on short-term, e.g. during the first 10 sec. This remains true on the long run if the liquid metal moves a long distance downward, as foreseen. If, however, the flow of the liquid metal should be hindered severely by the collimator, up to about 2 MPa (20 bar) might be reached. Also, water could penetrate into the target container while it is emptying and cause pressure spikes up to about 2 MPa (20 bar). Pressures beyond 2 MPa (20 bar) will not occur. Most probably the pressures that might be reached on the long term are much lower because condensation on cold structures would play an important role. This phenomenon could here not be treated quantitatively. (orig.) / SIGLE / Available from TIB Hannover: ZA 5141(6673) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische Informationsbibliothek / DE / Germany

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