Minimum size of a power producing polywell?

ladajo · Post by **ladajo** » Sun Nov 25, 2012 8:10 am

Approximate Tenth Value Thicknesses (Gamma)
Material 1/10 Value 1 MeV 1/10 Value 6 MeV
Lead 1.5 inches 2.0 inches
Steel 3.0 inches 4.0 inches
Concrete 12 inches 24 inches
Water 24 inches 48 inches

Note these are theorectical and do not account for Buildup.
This also assumes a Cs-137 source for the 1MeV and N-16 for the 6MeV.

ladajo · Post by **ladajo** » Sun Nov 25, 2012 8:12 am

You can also measure in "half values", as Paperburn1 suggested. But more common in my own experience has been tenth thickness.

paperburn1 · Post by **paperburn1** » Sun Nov 25, 2012 12:31 pm

ladajo wrote:You can also measure in "half values", as Paperburn1 suggested. But more common in my own experience has been tenth thickness.

Like I said before "I just sleep in a holiday inn express last night." Last time I even dabbled in this was as a youth in the military . We also rode dinosaurs and were frightened by fire. So I am just a little out of date

Blankbeard · Post by **Blankbeard** » Sun Dec 02, 2012 1:59 am

Here's a pie in the sky method of dealing with gamma radiation.

Let's start with a fungus - perhaps one that's known for ethanol production

http://news.mongabay.com/bioenergy/2007 ... nvert.html

This one might do, even better if we can find one works with sewage.

Then we induce melanin production. Here's why:

http://www.scienceagogo.com/news/200704 ... _sys.shtml

http://www.ncbi.nlm.nih.gov/pubmed/21966422

http://www.ncbi.nlm.nih.gov/pubmed/18426412

The first is the popular argument, details of why it works in the other two.

Now we have a radiation shield that produces ethanol from sewage. I have no idea how this would compare in weight or size with traditional shields or whether this can be done in a cost effective manner. But I can think of many areas where a "combined arms" approach to producing power, clean water, fuel, and possibly fertilizer while simultaneously lowering both air and water pollution.

I have this concept of a fusion reactor that uses its waste heat to supply a city with fuel, clean water and sewage services. It would be nice if such turned out to be practical.

ladajo · Post by **ladajo** » Wed Dec 05, 2012 1:11 am

Now we have a radiation shield that produces ethanol from sewage.

How do you get a "shield" out of all that? There is no discussion of any shielding effect. Simply that some of the gamma interacts with melanin and produces energy. I did not see where a gamma meter was placed in front and behind the fungus to see how much gamma made it through and thus produce some semblence of a shielding rating.

Funny idea though.

Blankbeard · Post by **Blankbeard** » Wed Dec 05, 2012 3:48 am

ladajo wrote:
Now we have a radiation shield that produces ethanol from sewage.
How do you get a "shield" out of all that? There is no discussion of any shielding effect. Simply that some of the gamma interacts with melanin and produces energy. I did not see where a gamma meter was placed in front and behind the fungus to see how much gamma made it through and thus produce some semblence of a shielding rating.

Funny idea though.

It's interacting with the melanin which means it's being absorbed. A lower energy photon might be emitted but it's probably thermal. An absorbed photon, even a gamma ray, is blocked. That's the definition of shielding. I doubt if anyone has done any testing to see how thick you'd have to make it to say, reduce gamma radiation by half.

But if there are already fungi close to being viable for commercial production and if adding melanin production doesn't lower the rate too much and if ethanol production doubles or triples with the tripling growth rate, you'd have something. Lot of ifs though. Needs more study.

93143 · Post by **93143** » Wed Dec 05, 2012 9:36 am

D Tibbets wrote:The shielding thickness for a 60 MW P-B11 reactor verses a 6 GW reactor would be less. My understanding of radiation shielding is that a certain thickness of a material would be required to stop 90% (or some other selected portion) of the radiation. An additional same thickness of material would stop 90% of the remaining radiation, etc. If a foot of lead is needed to stop the gamma radiation of a 6 GW reactor, then 60MW could be two halving' s less (?). So 3 inches would be needed for a 60 MW reactor to achieve the same final radiation exposure.

Doesn't work like that. Halving thicknesses are the same thing as tenth-value thicknesses, only smaller - they only reduce the radiation by half instead of 90%. The reference in both cases is to how much stuff you need to cut the radiation by a factor of X. At no point do you actually halve the thickness.

Think about it this way - say you have a radiation source and you want to cut the intensity by a factor of 1000. You put one halving thickness of lead in front of it. It's now 500 times too intense. Another. It's now 250 times too intense. You need 3.32 halving thicknesses (1/log(2)) to equal one tenth-value thickness, and make the radiation 100 times too intense instead of 1000. Add two more tenth-value thicknesses, and the shield is complete.

Tenth-value thicknesses (and halving thicknesses) add. For gamma rays in the range 4-16 MeV, the tenth-value thickness is somewhere between 1" and 2" (they replaced the graph on Wikipedia. The old one seems to agree with ladajo's numbers above). Reducing the reactor power by a factor of 100 will therefore reduce the required thickness by 4" at most, leading to a shield thickness between 7" and 10" for a 60 MW reactor if my recollection is correct...

ladajo · Post by **ladajo** » Wed Dec 05, 2012 5:07 pm

Blankbeard wrote:
ladajo wrote:
Now we have a radiation shield that produces ethanol from sewage.
How do you get a "shield" out of all that? There is no discussion of any shielding effect. Simply that some of the gamma interacts with melanin and produces energy. I did not see where a gamma meter was placed in front and behind the fungus to see how much gamma made it through and thus produce some semblence of a shielding rating.

Funny idea though.
It's interacting with the melanin which means it's being absorbed. A lower energy photon might be emitted but it's probably thermal. An absorbed photon, even a gamma ray, is blocked. That's the definition of shielding. I doubt if anyone has done any testing to see how thick you'd have to make it to say, reduce gamma radiation by half.

But if there are already fungi close to being viable for commercial production and if adding melanin production doesn't lower the rate too much and if ethanol production doubles or triples with the tripling growth rate, you'd have something. Lot of ifs though. Needs more study.

I got the part about energy absorption. My question was more on relative effectiveness (density verses absorption, as well as burnout phenomena.) I see you also note that there is no visible testing on these lines. Taking out to an extreme, you can also say that people are gamma shields...just not effective.

In any event, I had heard about the fungus proliferation at Cherenoble, but had not seen studies on it. Thanks for the links.

Blankbeard · Post by **Blankbeard** » Wed Dec 05, 2012 6:00 pm

ladajo wrote:
Blankbeard wrote: I got the part about energy absorption. My question was more on relative effectiveness (density verses absorption, as well as burnout phenomena.) I see you also note that there is no visible testing on these lines. Taking out to an extreme, you can also say that people are gamma shields...just not effective.

In any event, I had heard about the fungus proliferation at Cherenoble, but had not seen studies on it. Thanks for the links.

kk. As far as I know no one has looked into that use (PATENT OFFICE!!!) so effectiveness is unknown. The novelty is a shield that is a money producing asset instead of a costly liability.

Also, if you took all of the politicians in the world and stacked them like cord wood, I would be comfortable testing them as radiation shielding.

ladajo · Post by **ladajo** » Wed Dec 05, 2012 9:10 pm

change all to most, and I am with you on the politcians. We could see if they develop a "Penguin Method" and self rotate themselves from outer to inner to spread the absorption across the group. I am more inclined to think that they will not all for one, but one for all it. Someone is going to stay on the farside of the burn...