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One of the most important concerns for NET is the residual power stored in the structures of the plasma facing components which is essentially due to decay heat from activated materials. In the case of LOFA (Loss of Flow Accidents) in the cooling circuits, the residual power must be removed to avoid major hazards to the workers and the environment. The most common envisageable accident scenarios are the LOFA in one single cooling circuit (pumping fault), or the LOFA in the whole reactor (power black-out), both followed by an automatic plasma shut- down. A model of heat transfer by conduction and radiation between plasma facing components was set up and a preliminary analysis of the thermal consequences of the accidents was carried out. It is shown that no major hazards should be expected for a LOFA in a single circuit, while the power black-out could lead to severe consequences. To improve the natural capability of the system, a preliminary design of the Inboard First Wall (IFW) cooling circuit was carried out in such a way that the thermosyphon effect came into play. A thermohydraulic transient analysis related to the IFW circuit was performed. The data of this circuit were adjusted for the removal of the residual power of the whole reactor. The results show that water boiling in the IFW and significant pressure peaks can be avoided. Extrapolating these results to other independent cooling circuits of the plasma facing components, it follows that, in all cases of LOFA, the residual power can always be removed by means of natural mechanisms, so making the reactor inherently safe for the class of accidents analysed. The conditions for obtaining these very important results are good radial conduction/radiation heat transmission and a proper design of the plasma facing component circuits in such a way that a thermosyphon effect is allowed.

Additional information

Authors: FENOGLIO F, Turin Polytechnic, Dipartimento di Energetica, Turin (IT);RENDA V, JRC Ispra (IT);PAPA L, JRC Ispra (IT);SORIA A, DENIM-ETSII, Universidad Politécnica, Madrid (ES)
Bibliographic Reference: Article: Fusion Engineering and Design, Vol. II (1990) pp. 455-466
Record Number: 199011145 / Last updated on: 1994-12-01
Original language: en
Available languages: en