Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!caip!meccts!mvs From: mvs@meccts.UUCP (Michael V. Stein) Newsgroups: net.sci Subject: Re: About the life of nuclear wastes Message-ID: <479@meccts.UUCP> Date: Thu, 7-Aug-86 20:22:29 EDT Article-I.D.: meccts.479 Posted: Thu Aug 7 20:22:29 1986 Date-Received: Sat, 9-Aug-86 07:17:40 EDT References: <1970@brl-smoke.ARPA> <320@rtech.UUCP> Reply-To: mvs@meccts.UUCP (Michael V. Stein) Organization: MECC Technical Services Lines: 65 In article <859@tekigm2.UUCP> timothym@tekigm2.UUCP (Timothy D Margeson) writes: >There has been some discussion about nuclear waste and the side effects: >...I put to you the fact there are documented cases of arsenic disposal sites >created in the 1930's used for drinking water wells in the 1980's. A mere >50 years and we lost the dangers lurking beneath the ground. >...I don't have the answers, nor do I have the right questions to ask, but I do >intuitively know that creating large amounts of 'stuff' that we don't know >what we are going to do with after we make it, scares me. You bring up the major problems with waste disposal, whether it be chemical, biological or nuclear. But, lets look a little more closely at nuclear waste disposal. The annual high level wastes from a 1000 MW nuclear power plant would occupy approximately 90 cubic feet. (A cube 4.5 feet on each side.) This cube would contain around 20 million curies of radioactivity making it an obvious health hazard. The radiation intensity will decrease by a factor of 10 after a hundred years, and by a factor of 10,000 after four hundred years. After 6 hundred years, the only hazard is if it is ingested. Therefore the "hundreds or thousands of years" reference is a bit overstated. The long term safety of geologic disposal depends on ensuring that the wastes aren't released into the outside environment. There are three ways that a waste release could occur: Exhumation from the repository by some natural event; Exhumation as a result of human intrusion; Slow transport of waste materials via ground water into water supplys. To prevent radionuclides from getting into the groundwater, all disposal plans call for the wastes to be stored in glass or ceramics so it not neither chemically active or water soluble. Then the repository is located away from all ground water. (This is why you often hear about the use of salt mines.) The most commonly mentioned type of human intrusion is drilling and intercepting a canister. This is why the disposal site would be located in an area unlikely to have the natural resources that would attract such drilling. So, for human exposure to occur, the following unlikely chain of events would have to occur. First, the presence of the repository would have to be forgotten. Secondly, there would have to be some reason to choose the repository as an exploration site. Thirdly, the radioactivity of the material would have to go unnoticed during drilling. Fourth, for noticeable health effects, the drilling would have to hit a canister nearly head on. Fifth, the radioactive material would have to be brought to the surface and left exposed. If any of these did not occur, significant release of radiation would not occur. While all of the above is theoretically possible, it is much less risky then almost any other hazardous material that we dispose of in the environment. Geologic disposal has emerged as the preferred waste disposal system in each of the major nuclear countries. The West German program emphasizes disposal in salt, as does the Netherlands. Sweden, the United Kingdom, France and Canada are concentrating on crystalline rocks, such as granite and basalt. Italy and Belgium are investigating clays, mudstone and shales. -- Michael V. Stein Minnesota Educational Computing Corporation - Technical Services UUCP ihnp4!dicome!meccts!mvs