Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Neutron flux and safety
Date: May 26, 09:10 am
Poster: Richad Hull

On May 26, 09:10 am, Richad Hull wrote:

This is good info and I knew it, but never posted the specific figures. Thanks Jim for the precise values.

I realized this early on after "turning the handle" on the math, as Jim has done, I have repeatedly posted that fast neuts were of no concern whatsoever to the experimenter in amateur fusors.

In spite of this, fast neutrons are the most dangerous form of radiation known, (highest RBE - Relative Biological Effectiveness), and the levels Jim mention have been changed to about 10 fast neutrons/cm2/sec for protracted activity. Even the most rabid fusor fan with a superlative system and auto operational controls will rarely run a system for more than 1 hour. To date, I have run my fusor over 20 times for neutron production and have never run more than 18minutes in the longest run and 5 minutes in the shortest. An average might be 10 minutes. This is not a protracted expossure time and I am over 1 meter away. This means that a trip to california on a 747 will give one about 50 times the radiation damage than during all the operational time I have on my system!

In short, once again, not to worry. Use common sense and distance to protect you. These should be totally sufficient to about 10e5n/sec. No one I know has hit this yet.

above this light shielding of borated parafin or borated water (borax-sodium borate) will thermalize those neuts to a much less hazardous form of radiation. (lower RBE)

One must also watch for X-radiation, especially in glass bell jars above 18kv. In totally enclosed stainless steel systems, 50kv would be the watchout point. View ports are very dangerous above 25kv. Bell Jars just can't be used above this.

Richard Hull