In reply to Jones Beene's message of Mon, 24 Jan 2011 14:20:27 -0800: Hi, [snip] >Robin, > >"There could however be the occasional neutron from collisions of the S >with other nuclei" > > >Occasional? I don't think so. My recollection it that the rule of thumb for >spallation neutrons is 1 neutron per MeV of the accelerated particle >(proton)... wouldn't more neutrons that be likely with the heavier >accelerated ion, no?
Your recollection is incorrect. 1) It takes about 5-10 MeV just to free the neutron from the other nucleus (the exact amount depending on which target nucleus we are talking about). 2) A smoke detector has about 1 micro Curie of Am241 which emits a 5.4 MeV alpha particle. If the "rule" you mention were correct then that should result in about 5 neutrons / alpha particle, or over 200000 neutrons / sec. Somehow, I doubt this would be acceptable in the average home. ;) 3) The S32 has a charge of 16 as opposed to only 2 for an alpha particle and is moving at only half the speed, so it will be much harder for it to hit another nucleus than it would be for the alpha particles. 4) The Spallation Neutron Source (http://neutrons.ornl.gov/facilities/SNS/media/technical-parameters.pdf) uses 1000 MeV protons to produce neutrons efficiently, and I doubt they would use such energetic protons if they could get away with far less. 5) I urge you to provide some evidence that neutron spallation due to fission fragments is even significant in a normal fission reactor. (There will be some due to the occasional fast neutron, but that doesn't count). Frankly, I would be surprised if you can even find mention of it. > >Even if not, I would think that there would be substantial spallation >neutrons. That reaction seems most unlikely to me. But it raises the larger >issue. > >Why the hell does everyone keep trying to shoehorn these reactions into >KNOWN reactions? ..because if it can be explained with a known reaction, then that is likely to be the explanation. (Occum's razor). > >I'll give you big odds that eventually we will find that the culprit >reaction is presently UUNKNOWN to us. > >Jones > ...and I get the distinct impression you would prefer it so. :) Of course, you could be correct, but if we are ever to understand what is going on then we need to explore the possibilities (if for no other reason than to eliminate those that don't work). Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/Project.html
