Robert F. Bourque

Helium cooling of fusion reactors

Abstract On the basis of worldwide design experience and in coordination with the evolution of the International Thermonuclear Experimental Reactor (ITER) program, the application of helium as a coolant for fusion appears to be at the verge of a transition from conceptual design to engineering development. This paper presents a review of the use of helium as the coolant for fusion reactor blanket and divertor designs. The concept of a high-pressure helium cooling radial plate design was studied for both ITER and PULSAR. These designs can resolve many engineering issues, and can help with reaching the goals of low activation and high performance designs. The combination of helium cooling, advanced low-activation materials, and gas turbine technology may permit high thermal efficiency and reduced costs, resulting in the environmental advantages and competitive economics required to make fusion a 21st century power source.

Divertor and first wall armor design for the TIBER-II engineering test reactor

TIBER-II is a compact, high-power-density, steady-state current-drive engineering test reactor that uses a double-null divertor configuration, operating in the high recycle mode with low particle temperature. The nominal peak heat flux is 3.3 MW/m2, with off-normal condition peaks of up to 6.6 MW/m2. Plasma disruptions may cause peak energy deposition of up to 13 MJ/m2. The design uses water-cooled copper alloy tubes with brazed-on protective tiles. During early operating phases when disruptions may be frequent, these tiles will be made of carbon. During the nuclear testing phase, disruptions must be limited so that more erosion-resistant tungsten tiles may be used. The first walls of TIBER-II experience a heat flux of 0.23 MW/m2 with disruption energy density of 2.4 MJ/m2. They are protected by carbon-carbon composite armor tiles. The TIBER-II design requirements are challenging, and although the divertor and first wall armor designs successfully meet these requirements, significant issues must be resolved to verify their performance. These critical issues and the R&D required to resolve them are described.

Pulsed plasmoid electric thruster

A method of electric propulsion is presented where low temperature ionized gases containing internal electric currents (called plasmoids) are formed and expanded down a diverging electrically conducting nozzle. The toroidal electric current provides a confining magnetic field which holds the plasma in a torus shape. Image currents in the nozzle wall keep the plamoids from contacting the wall. The mutual repulsion between the wall current and the current in the plasmoid generates the thrust. During the expansion of the plasma both the inductive and thermal energies are converted to directed kinetic energies, producing thrust. Since most of the energy is inductive, losses due to dissociation and ionization are small. Specific impulses can be in the 5000 to 20000 s range with thrusts from 1.0 to 5000 N, depending on available power. A wide variety of propellants appear possible including hydrogen, lithium, nitrogen, sodium, and possibly aluminum, silicon, and sulfur. The high specific impulse is possible eve...

Innovative low activation designs for the LMF target chamber system

Because neutron activation can serious impede access to the proposed laboratory microfusion facility (LMF), the authors examined several low-activation design concepts for the target chamber, shielding, and final optics protection. The reference baseline is an aluminum chamber using low-density frost protection. It uses helium-gas cooling, a vacuum for thermal insulation, and a room-temperature water shield. A composite version of the chamber (also with frost protection) was studied. Two options considered were a thin-walled, laminated composite and a thick-walled cast silica-filled epoxy chamber. The latter was used in a study of the entire experimental facility, using rubber-mounted concrete optics supports.<<ETX>>