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[Phys-l] Demron



I'm getting frustrated with all the bad "experts" talking about the nuclear problems in Japan. My particular difficulty last night wa with CNN's Sanjay Gupta and his flimsy, white radiation suit which he made an effort to specifically mention protects against gamma radiation. Sigh.

I decided to look around on the internet, and found this company (Radiation Shield Technologies) that has a big website (don't know whether they are actually as big as they look) that makes suits from a material called Demron (part of the inventors name). Here's the claim: "Demron(tm) not only protects against particle ionizing/nuclear radiation (such as Beta and Alpha), but does what NO OTHER full body radiation protection can do: shield against X-ray and low-energy Gamma emissions. Demron(tm) is non-toxic and completely Lead-free."

The alpha and beta I can buy. The x-ray and gamma I can't, unless it's using some other high-Z (but everything about lead is radioactive) substance. They claim to be using "nanotechnology" but except for a resonance effect, Carbon AIN'T GONNA STOP GAMMAS. I took a look at high-Z, close to Pb. Thallium, mercury, gold, platinum, iridium, osmium,...nope, not going to make a suit out of those. Maybe spun tungsten. But then, the suits weigh 10 lbs. How the heck is 10 lbs of tungsten spread all over your body going to reduce gamma ray flux by any reasonable factor?

The halfthickness of Al for a 100 keV photon is between 1-2 cm (I'm eyeballing a small chart in Krane). For Pb it's a workable 0.2 millimeter or 8 mils. But that's 1 half-thickness. I want at least 4 if I'm in a radiation zone, so now 32 mils of lead. The area of the human skin is about 2 square meters. 1640 cm^3 x 11.3 g/cm^3 of Pb, that's 18 kg of Pb. To protect from 100 keV photons. That does nothing if my radiation zone is a Cobalt-60 area. Even for Cs-137 with a 662 keV gamma, the half-thickness jumps to almost .5 cm. That's a lead skin suit of 113 kg.

The lower Z but higher density of tungsten result in photon transmission above 100 kev to be about 95% that of lead for the same thickness. But the actual density of tungsten is 1.7 times lead. So, all in all, the tungsten suit for the same effect would weigh about 50% more than lead. 10 lb of tungsten has a volume of 236 cm^3. Over the human body, that's a thickness of 0.012 centimeters or 5 mils. But that's not a half-thickness!

Anybody know anything real about Damron?