In reply to Eric Walker's message of Thu, 9 May 2013 20:49:04 -0700: Hi, [snip] >On Thu, May 9, 2013 at 2:47 PM, <[email protected]> wrote: > >> In reply to Eric Walker's message of Mon, 6 May 2013 18:21:16 -0700: >> Hi, >> [snip] >> >If that fails, because, for example, Robin shows >> >overwhelming evidence that the experimenter would be harmed by secondary >> >EMF if there were watts of 4He's being generated (setting neutrons aside), >> >I will feel compelled to consider one of these alternatives: >> >> ???????? >> >> Where did I do this? >> > >I was hoping you try to model this scenario -- it was a request! ;) > >If you can show that a flux of alphas produced by several watts of d+d >reactions (dumping the energy to kinetic energy of the alphas) will be sure >to cause EMF that will escape from a reactor housing, that will allay >concerns on my part that this idea has been too hastily adopted as an >assumption. By contrast, if you were to model the situation and determine >that any secondary radiation (apart from neutrons) is unlikely to escape, >or that the question is difficult to determine, that will egg me on in >thinking that a basic assumption in some of the cold fusion reasoning has >been flawed. > >I am thinking of trying to model the system myself, but it looks complex. > >Eric
If you are thinking about Ron's model, then the alphas will have at least 22.9 MeV. The alpha itself can only travel a distance of microns through a solid or liquid, but with an alpha that is that energetic, there are going to be secondary reactions. i.e. a few direct fusion reactions of the alpha with other nuclei, and also production of spallation neutrons, some of which will escape, and some of which will fuse with other nuclei to create excited states that decay via gamma radiation. Suppose that about 1/10000 alphas creates a spallation neutron (there is some experimental evidence to suggest that this figure is in the ballpark). A power output of 1 W would require 2.6E11 reactions / sec, which at a rate of 1 in 10000, implies about 2.6E7 spallation neutrons / sec. That in turn implies a gamma source of about 7E-4 Ci, if all of the neutrons are absorbed, and each reaction only creates a single gamma. However most neutrons will escape, and more than one gamma / reaction is likely, which tend to compensate one another, so 1E-4 Ci of gamma radiation should be (very) roughly in the ballpark. Note that a smoke detector carries a radiation warning, and it's only 1 micro-Curie of alpha radiation at about 5.5 MeV which isn't enough to liberate neutrons from most isotopes. In short a 1 W reactor would produce about a 100 times more dangerous gamma radiation than a smoke detector produces (almost) harmless alpha radiation (as long as the 241Am not ingested or inhaled). My radiation dosage calculator says:- Activity: 1E-4 Ci Distance: 2 m Lead shielding: 2 cm Received dose rate: 0.01 mr/hr Unshielded dose rate: 0.025 mr/hr Where I live, the background rate is about 0.018 mr/hr. In short, very roughly, a 1 W unshielded power source would double the background rate. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
