Speaker
Giuseppe Mazzone
(Unità Tecnica Fusione)
Description
Among the design activities of the DEMO divertor cassette carried out in the frame of EUROfusion an important parameter is the operating temperature of the divertor cassette. As for the DEMO breeding blanket Eurofer has been chosen as structural material of the divertor cassette due to its low long-term activation, low creep and swelling behavior under neutron fluence. The choice of the operating temperature, i.e. the coolant condition, is driven by different and often conflicting requirements and must consider a range of aspects, e.g. type and pressure of coolant, loss of coolant accident consequences, the application of design code, or the compatibility for power conversion in the balance of plant. Different options are therefore discussed in this article and the rationale for the selection is outlined.
The first option aims at operating within the temperature window of 350-550°C that is recommended in order to reduce the degradation of the material properties due to the irradiation with high energy neutrons in DEMO. This aims in particular at avoiding a shift of the ductile-to-brittle-transition temperature to temperatures higher than room temperature that is known to occur at irradiation temperatures below ~350°C. This temperature level however practically excludes the use of liquid water as a coolant, leaving helium or steam as alternatives.
Other options foresee operation at temperatures below 350°C using liquid water as coolant. The feasibility of such options is discussed focusing particularly on the impact of material degradation on the design assuming moderate neutron fluence as defined for the DEMO divertor cassette. In DEMO design it is currently foreseen that the divertor shall be replaced after two full power years. Neutronics analysis indicates that the maximum neutron damage in the Eurofer-based divertor cassette will reach only 6 dpa for the specified lifetime.
Co-authors
Christian Bachmann
(PPPT, EUROfusion, Boltzmann Str. 2, 85748, Garching, Germany)
Domenico De Meis
(Unità Tecnica Fusione, ENEA-Frascati, Frascati, Italy)
Domenico Marzullo
(Department of Industrial Engineering (DII), CREATE Consortium/University of Naples Federico II, Piazzale Tecchio 80 – 80125 Napoli, Italy)
Giovanni Mariano
(Department of Astronautics, Electrical and Energetics Engineering, Sapienza University of Rome, Corso Vittorio Emanuele II, 244 - 00186 Rome, Italy, Italy)
Giuseppe Di Gironimo
(Department of Industrial Engineering (DII), CREATE Consortium/University of Naples Federico II, Piazzale Tecchio 80 – 80125 Napoli, Italy)
Giuseppe Mazzone
(Unità Tecnica Fusione, ENEA-Frascati, Frascati, Italy)
Jarir Aktaa
(Institute for Applied Materials, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany)
Jeong-Ha You
(Max Planck Institute for Plasma Physics, Boltzmann Str. 2, 85748 Garching, Germany)
Maria Teresa Porfiri
(Unità Tecnica Fusione, ENEA-Frascati, Frascati, Italy)
Michael Rieth
(IAM-AWP, Karlsruhe Institute of Technology, , POB 3640, 76021 Karlsruhe, Germany)
Paolo Frosi
(Unità Tecnica Fusione, ENEA-Frascati, Frascati, Italy)
Rosaria Villari
(Unità Tecnica Fusione, ENEA-Frascati, Frascati, Italy)
