In reply to Axil Axil's message of Mon, 6 Jan 2014 19:34:06 -0500: Hi, >The neutron budget in the thorium fuel cycle is very weak. At best with >proliferation sensitive fuel reprocessing, the breeding ratio is 1.06 to >1.14, but in reality it gets no greater than 1.06 to make the thorium fuel >cycle proliferation safe. > > > >To make thorium a breeder we need to add U235 and/or Pu239 to get the >breeding ratio high enough to burn Np237. That is why Np237 is removed, to >save neutrons.
It seems I was wrong about 237Np anyway. Upon checking I find that the radiative capture cross section for thermal neutrons is 164 barns, while the fission cross section is only millibarns. It is (strangely?) 238Np that is fissile. > > >If we burn Np237, we must add more U235 on Pu239 to get the neutron budget >over one. Understandable given the high capture cross section. > >Thorium is usually tied to an ADS or Fusion neutron generator because of >its weak breeding ratio. [snip] ...surely this is only initially necessary? I was under the impression that 233U actually produced fractionally more neutrons that 235U, implying that once enough had been produced, you could enrich with 233U rather than 235U or Pu. Or is this a long term losing proposition, i.e. you can never breed enough to keep the process going? BTW, what does the "we" imply? ;) Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
