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We introduce a new IFE fusion-chamber concept called Hydro*Star that uses DT-ignited DD targets and a water blanket. The driver can be either a 13 to 16-MJ diode-pumped solid-state laser (DPSSL) with fast ignition, or a 4-MJ heavy-ion accelerator operating at a reprate 10 times faster than the fusion chamber to accumulate sufficient energy in storage rings to direct 40 MJ at the target. The driver employs a prepulse system to burn an ionized path through the ambient fusion-chamber vapors, whose operating pressure is about 20 atm. We assume that the targets, which have a yield of about 2800 MJ, can be indirectly driven with two-sided illumination. The blanket, which is 1 to 2-m thick and placed immediately inside the structural wall, is operated just over 100 C either in a liquid or frothed-liquid state, the latter being preferred to reduce stresses in the structural wall. The structural wall, at a radius of 4 to 5 m, is composed of low-carbon steels to avoid the stress-corrosion cracking problems that have plagued certain light-water-reactor (LWR) systems. The functions of the blanket are (1) to shield the structural wall and exterior components from neutron and gamma-ray target emissions, and (2) to supplymore » water for the direct generation of steam. Each fusion pulse vaporizes nearly one-half centimeter of the inside surface of the water blanket, thereby creating hot steam which is vented directly from the fusion chamber into ordinary steam turbines. Thus, Hydro*Star operates just like a simple steam engine, with a basic reprate of only 0.8 Hz per GWe of net output. Because the steam temperature is 900 to 1200 K, the plant thermal efficiency is nearly 50%. This efficiency is much better than the typical 35-40% now being achieved in commercial reactors, and much better than the efficiencies estimated for previous fusion-chamber concepts except CASCADE (55%). Other advantages for the new concept include reduced plant radioactivity (reduced radionuclides inventory), longer component lifetimes, nearly self-cleaning operation, reduced risk for catastrophic accidents, and potentially lower cost of electricity. Although Hydro*Star has many advantages, we identify many serious design issues that require future investigation. These include the problems associated with (1) how to interface the evacuated driver beam lines to the high-pressure fusion chamber, (2) how to propagate the driver beams through the high-pressure steam, and (3) how to obtain the necessary tritium supplies without breeding tritium in the water blanket.« less |
