With such a reactor, I would hope a scale-up in size with several prototype reactors is in the card to demonstrate validation of the design concept. Controlling the concentration of dissolved fuel—U-235 in the thorium breeder reactor concept would be difficult to assure a reasonably steady power with good reactivity control IMHO.
Bob Cook ________________________________ From: mix...@bigpond.com <mix...@bigpond.com> Sent: Wednesday, May 1, 2019 2:08:49 PM To: vortex-l@eskimo.com Subject: Re: [Vo]:Thorium breeding now? In reply to bobcook39...@hotmail.com's message of Wed, 1 May 2019 02:47:34 +0000: Hi Bob, Some points. 1) The fuel is dissolved in the water, so initially there is no fuel in the reactor until water is added, then criticality is achieved at startup by pulling control rods somewhat once the water (and fuel) has been added. At this point, the negative temperature coefficient is already in effect. 2) If all the water were to rapidly evaporate, and leave a solid salt (impossible by the way), the reactor would long have shut down because only fast neutrons with a too small fission cross section would remain (i.e. no moderator). If the water were all to leak out, then the fuel would go with it leaving an empty reactor. Leakage should probably be caught in a flat tray with an area large enough to ensure that only a thin layer could exist even with all the water from the reactor in it. The large area thin layer would ensure that too many neutrons would be lost to sustain a chain reaction in the pan. This is a passive safety measure. Furthermore anything leaking into the pan under normal use could be pumped back into the reactor ensuring that it could keep running normally even with a leak. 3) Because fission products are constantly being removed during operation (liquid fuel cycle), there would be few left to produce decay heat, so a melt-down could not happen. 4) If all external systems fail at once, and there is no leak, then the water boils off (pressure release valve) and the reactor shuts down (no moderator). 5) Another advantage of a liquid fuel reactor is that the total fuel load in the reactor at any one time can be kept small, and fuel constantly added as required. I.e. it doesn't need to have years worth of fuel in the reactor at all times. This is another safety feature. >Without water—lost in the steam production—the negative temperature coeff. Is >diminished or lost completely. ...but while this is happening the reaction stops (loss of moderator). > > > >The rate at which reactivity is added to the reactor is important in startup >to avoid super criticality and an uncontrolled –run-away—reaction. Any >positive temperature coeff. resulting in an increase in fast neutron flux is >unacceptable and needs to be avoided. Loss of liquid water would be a >problem if it happened fast and added reactivity and loss of the negative >temperature coeff. > > > >Bob Cook [snip] Regards, Robin van Spaandonk local asymmetry = temporary success
