Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/26/83; site ihuxm.UUCP Path: utzoo!linus!philabs!cmcl2!floyd!clyde!ihnp4!ihuxm!gjphw From: gjphw@ihuxm.UUCP (Not really but: Patrick H. Wyant) Newsgroups: net.physics Subject: Re: Nuclear Fusion Message-ID: <573@ihuxm.UUCP> Date: Mon, 26-Sep-83 16:20:42 EDT Article-I.D.: ihuxm.573 Posted: Mon Sep 26 16:20:42 1983 Date-Received: Wed, 28-Sep-83 05:03:50 EDT Organization: BTL Naperville, Il. Lines: 66 While it has been awhile since I have seriously discussed and performed homework problems in nuclear physics, I would still like to enter the upcoming fray on nuclear fusion. Too often, fusion is presented as the savior to our large-scale, long-term energy needs. It is supposed to be tasteless, odorless, colorless, harmless, and nonfattening. Not being an expert in plasma fusion, I am unable to dwell in great detail on the mechanisms, but I can tell you what I have heard that makes sense. Hydrogen fusion is the mechanism assumed to be in operation in the Sun, despite the observation that the neutrino flux is not as predicted. The fusion of four hydrogen atoms into a helium yields lots of energy, which we see as neutrinos, gamma rays, and heat. The conditions that allow such fusion to occur are difficult to realize without the high forces that can exist in a star (e.g., for gravitation or densities). These conditions are sufficiently difficult to achieve on Earth that the fusion of hydrogen is probably not the best route to take for controlled power generation. Either deuterium or lithium would be fuel more suitable for terrestrial fusion. Both are fairly plentiful on Earth. However, the use of either of these two fuels, or perhaps a combination of the two, gives results that are not exactly the same as the hydrogen fusion cycle of the Sun. The use of either deuterium or lithium does not have as high a yield as hydrogen. Also, the use of these fuels generates a sizable number of neutrons (high neutron flux) as an additional byproduct of the fusion. This neutron flux contributes to the heat given off by the fusion reaction, and will act to make the containment vessel for the fusion radioactive. One of the oft overlooked aspects of fusion research is how to make the containment vessel resist the corrosive effects of neutron irradiation, and how to dispose of the material (or how often will it have to be replaced). As stated by J. Halle (houxz!halle1), the radioactive wastes produced by nuclear fusion are more easily contained that those from fission. If some problem occurs, the fusion process is quickly quenched and the only lingering radioactive material is the containment vessel. The fission process makes lots of radioactive solids and liquids, while fusion is expected to affect only solids (mostly metals). Unfortunately, I have no information as to how the quantity of radioactive materials from the two processes compare. What I have heard is that the radioactivity from nuclear fission covers a wide spectrum of half-lives, while the fusion-induced radioactivity is almost all long-lived. Fusion will produce radioactive metals that cannot be further refined and must be safely stored for many centuries. The Scientific American article, mentioned by S. Bechtolsheim (pur-ee!svb), fails to discuss much about the radioactive wastes from the fusion process because they are considered to be more manageable than those from the fission process, and because not much attention has been given to it. From what I have read, there is little effective protection that can be given to the containment vessel to protect it against neutron corrosion. And, that is the primary source of radioactivity in the fusion process. Further comments? Patrick Wyant AT&T Bell Laboratories (Naperville, IL) *!ihuxm!gjphw P.S. I must also agree with J. Halle in his complaint about how nuclear wastes are treated. Often, they are used as pawns in a political power struggle between different interest groups. At the same time, wastes from more conventional power sources (e.g., coal) are overlooked and sometimes ignored (e.g., acid rain) because they may be too familiar.