As suggested, steam would reduce the flux of thermalized neutrons in the reactor and shut it down. To maintain criticality, reactivity would need to be added, probably by the movement of control rods to increase the flux of fast neutrons upon which criticality depended. Control systems, including the mechanical portion of the system for insertion of negative reactivity—the control rods, need to be very fast to avoid super critical conditions. The design of fast control systems with high reliability is a problem IMHO given the complex analysis associated with knowing the local variety of materials at any given place.
The “nice” thing (RELATIVELY SPEAKING) about normal fission reactors is the reliable knowledge of the location of the various isotopes in a dynamic reactor with pressure, temperature and dimensional change occurring rapidly. Bob Cook ________________________________ From: mix...@bigpond.com <mix...@bigpond.com> Sent: Tuesday, April 30, 2019 12:34:22 PM To: vortex-l@eskimo.com Subject: Re: [Vo]:Thorium breeding now? In reply to JonesBeene's message of Tue, 30 Apr 2019 06:42:54 -0700: Hi Jones, [snip] >Robin, > >On first glance, one obvious thermodynamic problem is steam – in that every >fission fragment capable of knocking off a neutron is also able to boil off >several hundred million molecules of heavy water in the process of >thermalizing. As you can see, from the second message I posted in this thread, this type of reactor was in fact among the first reactors ever built. They do work. Furthermore, I think steam production would probably be a negative feedback mechanism which helps control the reactor. I.e. steam bubbles are less dense, which reduces the amount of moderation available between nuclei, resulting in faster neutrons with a lower fission cross-section. That means that steam formation reduces the power generated and results in a self stabilizing reactor. In fact they (google AHR), were known to be very easy to control, see the second message I posted. See also http://large.stanford.edu/courses/2012/ph241/tilghman2/ There were corrosion problems when uranyl sulphate was used, but these were largely overcome when they switched to uranyl nitrate in a stainless-steal vessel. I suspect that corrosion could be further reduced by lining the metal parts with teflon. However what I was really wondering is whether or not fission fragments can contribute significantly to the neutron efficiency by splitting D nuclei, in a heavy water base? I'm guessing they do, because the AHR is known for a high neutron flux, which would appear to make it a reasonable choice for a thorium based breeder. > > Consequently maintaining a liquid state with uniformly dissolved salt > becomes impossible even under high pressure.. A molten salt would be feasible > but not a dissolved salt in the liquid state. > > > > >? Please see http://rvanspaa.freehostia.com/Thorium_breeder_in_solution.html > >Regards, Robin van Spaandonk > > Regards, Robin van Spaandonk local asymmetry = temporary success
