Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!news.cs.indiana.edu!att!cbnews!cbnews!military From: hagerp@iuvax.cs.indiana.edu (Paul Hager) Newsgroups: sci.military Subject: Re: Thermonuclear Trigger Message-ID: <1990Dec17.045714.27246@cbnews.att.com> Date: 17 Dec 90 04:57:14 GMT References: <1990Dec4.002646.10188@cbnews.att.com> <1990Dec7.012233.2025@cbnews.att.com> <1990Dec8.223807.29796@cbnews.att.com> <1990Dec11.020358.27627@cbnews.att.com> Sender: military@cbnews.att.com (William B. Thacker) Organization: Indiana University, Bloomington Lines: 55 Approved: military@att.att.com From: hagerp@iuvax.cs.indiana.edu (Paul Hager) Just a short followup to Charles Seeger's comments. Regarding Th-232/U-233 fuel cycles: During the INFCE (International Nuclear Fuel Cycle Evaluation) which was instituted at the behest of the Carter Administration to look into "proliferation resistant" fuel cycles, a number of different approaches were investigated. For U/Pu fuel cycles, "spiking" and/or "denaturing" of the Pu (adding a highly radioactive nuclide or using high burnup Pu + leaving highly radioactive nuclides in during reprocessing), among other approaches, were suggested. The idea was to make the Pu self-protecting from theft or diversion because of the intense radiation field. The Th/U fuel cycles were predicated on the idea of advanced thermal reactor designs that had breeding ratios of 1.0. The idea was that the initial fissile load would never be augmented. Of course, for this to work, it would be necessary for radwaste to be removed continuously (some of it is a neutron poison) and to sequester the Pa-233 which, if memory serves, has a half-life of 40 days or so (don't have a nuclide table handy, sorry) until it decays to U-233. Two candidate systems were the Molten Salt Reactor and the Gas Core Reactor. The various components of the MSR system were tested at Oak Ridge in the late '60s through the mid-70s in the Molten Salt Reactor Program. These tests included laboratory demonstration of on-line reprocessing (all of this is covered in the quarterly progress reports). The Gas Core Reactor was more exotic and would have operated using U-333 hexafloride gas as the fuel. Again, this is from memory, I seem to recall that the fissile loading for a Gas Core system would have been about 100 kg of U-233. The sequestration of the Pa-233 in the breeding process was to prevent neutron capture and beta decay to U-234, which is a diluent and not fissile. The U-234 is significant only because if it is present, it means that U-233 is not -- in other words, the system would be designed to maximise conversion of Pa-233 produced by neutron capture into U-233 to get the 1.0 breeding ratio. Finally, although I'm a real champion of the Th-232/U-233 fuel cycle, I think the "proliferation resistance" argument is not a strong one. Ultimately, there are ways around design safeguards and even high-burnup Pu could be used to make nuclear devices. Pre-initiation from the neutrons present due to spontaneous fission decay in Pu-240 is, so far as I know, a "solved-problem" for sophisticated nuclear weapons technologies. -- paul hager hagerp@iuvax.cs.indiana.edu "I would give the Devil benefit of the law for my own safety's sake." --from _A_Man_for_All_Seasons_ by Robert Bolt