* I will add, in deference to W&L theory and the ULM, that the stated presence of boron does provide a more acceptable pathway for the high gain.
This would be due to the very high cross-section of boron for neutrons (thermal neutrons). I do not know that boron retains the high cross-section for cold neutrons, but if you look at the tables, which do not address this AFAIK - there is reason to believe that it would be higher - not lower. Thermal neutrons undergo a strong reaction with the boron-10, with the result being an alpha particle and lithium 7. Those two would be the ash, so the hypothesis is easily falsifiable. The downside of the hypothesis is that the boron is not located in the reactor, so how do cold neutrons migrate? This is a very energetic reaction and bremsstrahlung would not have been missed by V&B, so in summary, this route is just as doubtful as any nuclear route - unless the there is a "new physics" version of some kind to hide high energy photons. Jones
