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Author Topic: How good is one of those suits? Can it stop gamma radiation?  (Read 42766 times)

Offline yor_on

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X-ray Proofing.
He gives away suits to Japan, for use in their Fukushima plant trying to stop the fuel rods melting. I really hopes it works as they states. He seems a very bright, and good, guy.

==Quote

Gamma radiation is the most penetrating and energetic form of nuclear radiation. To absorb half the incoming Gamma you need two and a half inches of concrete or almost half an inch of lead. So my eyebrows went up when I saw a press release for an organization called Radiation Shielding Technologies, or RST, selling protective clothing with this startling claim:

"DemronTM 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."

This sounds like it merits either a Nobel Prize or an Ig Nobel, the award for bad science. Check their site and you’ll find details of an independent test claiming that their anti-radiation blanket really does stop a significant fraction of gamma (about 28 percent at a 90 degree angle).

What’s the secret? Well, the ‘blanket’ involved is 30 inches by 36 and weighs 60 pounds… So it’s basically equal to one-seventh of an inch of lead, and it works because it’s so dense. I checked with RST, and research scientist James Bradshaw agrees:

"You are correct in stating that in attenuation of gamma and x-ray radiation, cross-sectional density is the key parameter. A number of other much more minor effects are also at play, such as the role a supporting matrix has in excepting ejected electrons, etc. We do integrate heavy atomic absorbers into our material, though completely none toxic, that act as the primary attenuation component.

Our material meets or exceeds the absorption capabilities of lead by weight equivalent… Certainly, when it comes to high energy radiation, you can’t beat fundamental physics, but luckily you can get away from using lead."

==end of quote==

And it seems to have to do with ionized salt? Is that what he calls the 'heavy atomic absorbers'. And, by the way, it also allows heat to escape? It's almost star trek that one..

So, how does it work?
« Last Edit: 18/03/2011 06:07:05 by yor_on »


 

Offline CliffordK

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It would be easy enough to test...
You put one of a number of types of radiation counters, either real time, or cumulative, inside the suit, and put it near the gamma source.

This is supposed to be equivalent to what X-Ray technicians wear, so it might get a person closer to the plant, but certainly wouldn't be sufficient for entering a reactor core.

That is certainly an old article.
Do they now have an SCBA version?

$600 each...
Is it a One-Time-Use & Throw Away?
 

Offline Geezer

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These things won't be much better than a raincoat at blocking high energy gamma radiation. Notice the reference to shielding "low energy gamma radiation", in other words, X-rays.
 

Offline yor_on

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How good is one of those suits? Can it stop gamma radiation?
« Reply #3 on: 18/03/2011 06:08:46 »
But it's definitely better than what they had before
Cotton suits :)

Well on telly it seemed like that, at least?
 

Offline yor_on

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How good is one of those suits? Can it stop gamma radiation?
« Reply #4 on: 18/03/2011 06:11:41 »
It's the best I could find at short notice. Can add this quote though.

"The effectiveness of x-ray (photon) shielding can be divided into three regions; below ~200 KeV, 0.5 to ~2 MeV, and above ~2 MeV.

Below ~200 KeV (all-x-ray machines)
The shielding mechanism below ~200 KeV is the deep-core photoejection (photoelectron) total absorption of incident x-rays, very dependent on the binding energy of inner atomic electrons in the shielding material. The K-edge, L-edge, and M-edge peaks in the lead attenuation coefficient (shown in the post #3 thumbnail above) represent the binding energies of K, L, and M-shell electrons. Very roughly, the K-shell binding energy is ~13.6(Z-1)2 eV, where Z is the atomic number of the material, and 13.6 eV is the binding energy of the electron in the hydrogen atom. For lead, Z=82, and the K edge is ~ 88 KeV, while for aluminum (Z=13), the K edge is only ~1.7 KeV. Compare the plots for aluminum and lead in thumbnail above. Bismuth (Z=83), used in the Demron radiation protection clothing (see previous post), is slightly better (K edge ~ 90.5 KeV) than lead.

~0.5 to 2 MeV (some nuclear gammas)
The shielding mechanism is Compton scattering of x-rays (photons), which is proportional to the number of electrons per gram (aluminum is better than lead; see thumbnail). So aluminum per gram is slightly better than lead for the primary 1.1 and 1.3 MeV gammas from Cobalt-60.

Above ~2 MeV (mainly bremsstrahlung from electron accelerators)
Here, the shielding (photon absorption) mechanism is pair production by high-energy photons in the vicinity of high-Z nuclei (like lead and bismuth). The pair production cross-section is proportional to ~Z2. Personnel protection clothing is no substitute for area perimeter protection (microswitches on access points to radiation areas).

Bob S"
 

Offline Bored chemist

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How good is one of those suits? Can it stop gamma radiation?
« Reply #5 on: 18/03/2011 06:58:17 »
The major benefit from something like this is not the reduction in gamma dose or even the blocking of alphas and betas. The biggest merit is that it's pretty much waterproof so any contamination stays on the outside of the suit.
At the end of he shift the worker can take it off.
However that can be done much more cheaply.
 

Offline yor_on

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How good is one of those suits? Can it stop gamma radiation?
« Reply #6 on: 18/03/2011 07:12:48 »
I think it may make a difference if you are there a longer time, I'm sure I would want one if so at least. But I'm wondering the same as Clifford. Can you reuse it? Or is it only one time use?
 

Offline imatfaal

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How good is one of those suits? Can it stop gamma radiation?
« Reply #7 on: 18/03/2011 10:41:46 »
Per BC - the danger is not so much radiation per se - but contamination by radioactive particles. Gamma radiation will go through most suits and alpha and beta can be easily blocked (sheet of newspaper would do a fair job) - but the inhalation or injestion of an alpha or beta source is the beginning of a nasty chain of events. 

If there is a significant gamma source - then there is pretty much nothing you can do apart from send in remote vehicles.  Otherwise what needs to be done is protect the workers from internalising any radioactive particulate matter; radiation falls off with distance rapidly - but dust can spread for miles on even the gentlest breeze.  For a worker to be in danger 1000m from a source due to radiation, that source would have to being emitting a huge amount of radiation such that the immediate environs would be glowing white hot. There is a huge amount of nonsense being written in the popular press
 

Offline Madidus_Scientia

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How good is one of those suits? Can it stop gamma radiation?
« Reply #8 on: 18/03/2011 12:58:56 »
These things won't be much better than a raincoat at blocking high energy gamma radiation. Notice the reference to shielding "low energy gamma radiation", in other words, X-rays.

The higher energy gamma radiation is less dangerous, because along with the suit, your body is more transparent to them.
 

Offline Geezer

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How good is one of those suits? Can it stop gamma radiation?
« Reply #9 on: 18/03/2011 18:25:32 »
This is why I think some basic science education should be mandatory in the US.

There was a piece on the TV this morning about this that was, frankly, awful reporting. The "Doctor" who is flogging this "stuff" did a demo where he shielded a Geiger counter from a radiation source with his amazing "wonder cloth".

Wow! The Geiger counter almost stopped counting. Did the reporter ask any questions at all - nope! If he had at least a basic understanding of science, he might have suggested substituting a sheet of paper, or a chunk of drywall. Alas, no.

So the good "Doctor" was able to get a huge free plug for his product. No doubt a bunch of scientifically challenged Americans will now rush out and buy these things. Probably the same ones that have bought up all the available supplies of potassium iodide.
 

Offline Phractality

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How good is one of those suits? Can it stop gamma radiation?
« Reply #10 on: 18/03/2011 18:31:44 »
For protection while in the presence of a gamma source, you need a heavy lead suit, like the vest your dentist might put over you while x-raying your teeth. Depending on the power of the source and duration of exposure, you might need a 50kg, 100kg or 1000kg suit. Obviously, there's not much you can do in a lead suit, so they really need suicide volunteers for the most dangerous jobs.

The suits that are light enough to work in can only assure that your exposure ends when are away from the source and out of the decontaminated suit. They can be reused if they pass some tests after each use.
 

Offline yor_on

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How good is one of those suits? Can it stop gamma radiation?
« Reply #11 on: 18/03/2011 18:53:26 »
Interesting Maddidus, didn't now that, Gamma rays over 10 MeV seem too pass right, but looking I found this too.

"All ionizing radiation causes similar damage at a cellular level, but because rays of alpha particles and beta particles are relatively non-penetrating, external exposure to them causes only localized damage, e.g. radiation burns to the skin. Gamma rays and neutrons are more penetrating, causing diffuse damage throughout the body (e.g. radiation sickness), increasing incidence of cancer rather than burns.

External radiation exposure should also be distinguished from internal exposure, due to ingested or inhaled radioactive substances, which, depending on the substance's chemical nature, can produce both diffuse and localized internal damage. The most biological damaging forms of gamma radiation occur in the gamma ray window, between 3 and 10 MeV, with higher energy gamma rays being less harmful because the body is relatively transparent to them." So how about those between 3-10 MeV? Yes, if ingested (inhaled or begotten through edible substances) the gamma rays definitely seems the least dangerous as they have a greater possibility off passing right through the body.

But I was thinking of the irradiation primarily, the radiation you would get from the core/rods once you're working close to it? I would expect them to use some sort of gas masks, but they won't have any protection for the rays between 3-10 MeV as a guess? Tried to find what that 'window' could do but it's hard reading.

"Estimations for DNA based on results with the constituents indicate that 25% of OH· radicals react with deoxyribose units and 75% react approximately equally with the nucleic acid bases. Irradiation of DNA also leads to rupture of sugar-phosphate bonds between two nucleoside residues or single strand breaks. A significant fraction of the apparent strand breaks are induced by the assay technique of alkaline sucrose gradient centrifugation. These "alkali-labile" bonds are not scored as strand breaks in vivo...

The oxygen enhancement ratio (OER) is defined as the of the radiation sensitivity of a biological system in the absence of oxygen relative to that with oxygen. A typical OER is about 3 for mammalian cells exposed to gamma-rays. High LET radiation has a lower OER and higher RBE than low LET radiation. The reason for this is that the "heavier" primary damage from high LET radiation is less repairable and therefore less likely to be affected by oxygen. This result has led to the use of high LET radiation in cancer therapy. The cancer cells in the core of a solid tumor have a lower oxygen concentration than well-oxygenated normal tissues which limits the radiation dose. This "trade-off" is quantified by the therapeutic ratio (TR) defined as the ratio of the normal tissue tolerance dose to the tumor lethal dose.

The potential advantage of high LET radiation for cancer therapy is that the damage to cancer cells is comparable to well-oxygenated normal tissues which increases the TR. Exogenous chemical agents referred to as anoxic sensitizers such as the drug metronidizole are intended to that mimic the effects of oxygen and sensitize the more poorly oxygenated tumor regions. The technique is not widely used, however." From Radiation.

This is kind of weird?

I would have expected us to have clear studies on this, after all, we've had atomic bombs since 1945, as well as nuclear plants? It should be in everyones interest to study the effects? When looking I did notice two aspects though. Those that have been exposed to a atomic device, and those that hasn't. Those that hasn't still classify it, it seems? 70 years after our first atomic experiments?

"X rays and gamma rays can travel appreciable distances through matter without producing ionizations; however, they interact with atoms to produce energetic secondary electrons, which behave identically to incident electrons of the same energy.

In aqueous media, over the incident photon energy range 0.1-10 MeV, the predominant photon interaction is Compton scattering, a process in which an incident photon transfers part of its energy to an atomic electron, creating a free electron and a lower energy photon.

The energy of a Compton electron is positively correlated with the incident photon energy. Consequently, as the incident photon energy is reduced within this energy range, a higher fraction of the energy is dissipated in the form of lower energy (higher LET) electrons, resulting in more complex DNA damage and, therefore, perhaps an increased RBE.

As the incident photon energy is reduced further, below 0.1 MeV, photoelectric absorption becomes increasingly important compared to Compton scattering, and the variation of LET with the photon energy is no longer monotonic."

I did find a lot of material on Japan though, but as I'm not sure how to use that for comparing it with radiation from a nuclear plant, I'll let it be for the moment. But when looking at Chernobyl, there was a lot of gamma radiation.


The 60% mentioned in the image under, gamma.gif, conclude that it is from " external gamma radiation. (not ingested) One percent from inhalation (atmospheric particles) and thirty eight percent from internal radiation."  And remember that this is a average, meaning that there will be spikes upwards as well as downwards in this estimate, as well as USSR was/'is' rather big. We had some in Sweden too due to Chernobyl, for some decade, or more?

« Last Edit: 18/03/2011 20:25:18 by yor_on »
 

Offline Geezer

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How good is one of those suits? Can it stop gamma radiation?
« Reply #12 on: 18/03/2011 19:08:17 »
For protection while in the presence of a gamma source, you need a heavy lead suit, like the vest your dentist might put over you while x-raying your teeth. Depending on the power of the source and duration of exposure, you might need a 50kg, 100kg or 1000kg suit. Obviously, there's not much you can do in a lead suit, so they really need suicide volunteers for the most dangerous jobs.

The suits that are light enough to work in can only assure that your exposure ends when are away from the source and out of the decontaminated suit. They can be reused if they pass some tests after each use.

There is nothing special about lead. It's mass that shields gamma radiation. The main reason they use lead in aprons etc. is because it reduces bulk. Equal masses of lead and concrete will provide the same amount of shielding.

That's why I'm so upset with the "magic suit" idea. Despite a lot of highly suspect marketing hype, AFAIK there is no exotic material that can get around the mass rule.
 

Offline SeanB

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« Reply #13 on: 18/03/2011 19:12:39 »
Most of those vests that dentists use are made from a denser material than lead, most use depleted Uranium as the blocking material. Good for short exposure to low energy Xrays, but the worst thing to wear when exposed to high energy neutrons. Best thing is distance and a lot of iron shielding between you and it, not exactly a wearable item.
 

Offline Geezer

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How good is one of those suits? Can it stop gamma radiation?
« Reply #14 on: 18/03/2011 19:27:33 »
Most of those vests that dentists use are made from a denser material than lead, most use depleted Uranium as the blocking material. Good for short exposure to low energy Xrays, but the worst thing to wear when exposed to high energy neutrons. Best thing is distance and a lot of iron shielding between you and it, not exactly a wearable item.

Sean, why is iron better than anything else? As I understand it, it's simply a question of mass.
 

Offline burning

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How good is one of those suits? Can it stop gamma radiation?
« Reply #15 on: 18/03/2011 20:10:20 »
Most of those vests that dentists use are made from a denser material than lead, most use depleted Uranium as the blocking material. Good for short exposure to low energy Xrays, but the worst thing to wear when exposed to high energy neutrons. Best thing is distance and a lot of iron shielding between you and it, not exactly a wearable item.

Sean, why is iron better than anything else? As I understand it, it's simply a question of mass.

Neutron shielding works by capturing neutrons into nuclei.  This changes the isotope mix of the material, and you don't want to make your shielding material dangerously radioactive by creating a bunch of nuclei of a short half-life unstable isotope.

Iron is about 92% 56Fe, 6% 54Fe, and 2% 57Fe, which are all stable.  So if you capture a neutron, you have a 92% chance of creating a 57Fe nucleus, which is stable, a 6% chance of creating a 55Fe nucleus, which has a half-life of 2.7 years, and a 2% chance of creating a 58Fe nucleus, which is also stable.

Comparing to lead, the composition is 52% 208Pb.  209Pb has a half life of about 3 hours, so using lead for neutron shielding will convert the neutron radiation to another sort of radiation with fairly high efficiency.
 

Offline yor_on

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How good is one of those suits? Can it stop gamma radiation?
« Reply #16 on: 18/03/2011 20:31:37 »
Very interesting Burning. So how about it. Anyone that can point me to a study over gamma radiations effect on humans working near or in the core of a nuclear plant? There should be some studies made, like from Chernobyl, Three mile island etc? And not one that dig itself down in tissue samples and chemical compounds, those I already found :) I mean actual surveys over the radiation, without 'assumptions' on either nature, positive or negative.

Statistics perhaps?
 

Offline Phractality

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« Reply #17 on: 18/03/2011 20:39:54 »
Though a decent respirator will prevent inhaling radioactive dust, you need a self-contained breathing aparatus (SCBA; the U in SCUBA is for underwater) to keep out radon and other radioactive gasses. The rest of the suit is for a false sense of security. If all you had was the SCBA, and you take a good shower immediately after exposure, that's nearly as good as having the whole suit; plus you can work faster and spend less time in the danger zone.
 

Offline Geezer

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How good is one of those suits? Can it stop gamma radiation?
« Reply #18 on: 18/03/2011 21:28:23 »
Most of those vests that dentists use are made from a denser material than lead, most use depleted Uranium as the blocking material. Good for short exposure to low energy Xrays, but the worst thing to wear when exposed to high energy neutrons. Best thing is distance and a lot of iron shielding between you and it, not exactly a wearable item.

Sean, why is iron better than anything else? As I understand it, it's simply a question of mass.

Neutron shielding works by capturing neutrons into nuclei.  This changes the isotope mix of the material, and you don't want to make your shielding material dangerously radioactive by creating a bunch of nuclei of a short half-life unstable isotope.

Iron is about 92% 56Fe, 6% 54Fe, and 2% 57Fe, which are all stable.  So if you capture a neutron, you have a 92% chance of creating a 57Fe nucleus, which is stable, a 6% chance of creating a 55Fe nucleus, which has a half-life of 2.7 years, and a 2% chance of creating a 58Fe nucleus, which is also stable.

Comparing to lead, the composition is 52% 208Pb.  209Pb has a half life of about 3 hours, so using lead for neutron shielding will convert the neutron radiation to another sort of radiation with fairly high efficiency.

Now I'm really confused! I thought Gamma radiation was high energy photonic radiation. What do neutrons have to do with it?
 

Offline burning

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« Reply #19 on: 18/03/2011 21:57:58 »
SeanB brought up the high energy neutrons, and that was the context he used for saying iron was the best shielding.  So when you asked why, I answered in the context of neutron shielding.  I don't know why he specifically brought up neutrons, but they certainly will be a risk to someone getting very close to a reactor.
 

Offline Geezer

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« Reply #20 on: 18/03/2011 22:11:40 »
SeanB brought up the high energy neutrons, and that was the context he used for saying iron was the best shielding.  So when you asked why, I answered in the context of neutron shielding.  I don't know why he specifically brought up neutrons, but they certainly will be a risk to someone getting very close to a reactor.

Ah, right! Thanks!
 

Offline yor_on

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« Reply #21 on: 18/03/2011 23:29:52 »
"Ionizing radiation comes in several further flavors. The ones of concern in the context of this post are alpha, beta, gamma, and neutron radiation. Alpha and beta radiation are similar in that they are a byproduct of radioactive decay in which high energy, short-ranged (milimeters or less) particles are emitted. Alpha decay releases alpha particles, which are identical to helium nuclei. Beta decay releases electrons and certain antimatter particles. Alpha radiation is less dangerous than beta radiation, as an external source does not penetrate the skin. An external source of beta radiation can cause burns if it makes contact with skin. Both can be harmful or fatal if the sources of radiation are in some way ingested, as the radioactive material can become concentrated in the tissues of vital organs.

Gamma radiation is different from Alpha and beta radiation in that it is not a particle per se, but a wave frequency in the electromagnetic spectrum, similar to x-rays. In nuclear bombings and accidents, gamma radiation is released after radioactive materials have undergone alpha or beta decay. High energy gamma radiation is more penetrating than alpha and beta radiation, which means that the whole body and its tissues can be irradiated by an external source. High energy neutrons can make other matter into sources of radiation via a process called neutron activation, which can turn otherwise well-intentioned matter into unstable, radioactive matter. They also have the ability to ionize atoms. Neutron radiation is more penetrating than alpha and beta radiation. It is sometimes more penetrating than gamma radiation as well. " From
Radiation: How it Works and What it Does.

"The earthquake, followed by the tsunami, absolutely wiped out their infrastructure, causing the cooling pumps to lose power. They have also experienced fires in the pumps providing cooling water to the spent fuel pools. Without a flow of cooling water, the water in the core or spent fuel pool eventually boils. With no water to remove the decay heat, the temperature of the fuel rises, causing the pressure to increase. In the limit, it can increase to the point that the fuel cell ruptures, which would release radioactive fission products. Chernobyl is the only example where this has happened."

And "When a uranium atom fissions, or splits, it releases energy as it splits into two other midweight atoms. ... These unstable radioactive atoms decay as they seek a stable state, emitting radiation in the process. Fissions still occur when the reactors are shut down -- just not at the rate when the reactor is "critical" or producing power. The shutdown fission rate is 8-10 or more orders of magnitude lower than during reactor operation.

Two types of radiation -- gamma rays (think of X-rays) and neutrons -- emitted from these decay products generate heat by mechanical interaction. Some of the neutrons are absorbed in the uranium fuel, causing more fission and more heat. So while the shutdown reactor doesn't require anywhere near the cooling needed when it is operating, it still requires cooling. Even the spent fuel removed from the reactors still generates heat. Water is the most prevalent coolant.

You may have heard that boric acid or borated water is being pumped into the cores. (Editor's note: South Korea has agreed to send some of its boron reserve to Japan.) Boron has a tremendous affinity for neutrons. It prefers to absorb them rather than the fuel, reducing the heat generated." from
foolish FAQ: The Fukushima Nuclear Crisis.
 

Offline Bored chemist

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« Reply #22 on: 19/03/2011 14:29:14 »
OK,
here are a few facts.
Lead is, on a weight for weight basis a much better attenuator of gammas than, for example, iron
The scattering is proportional to the square of the atomic number.
OK, lead bismuth and, ironically, uranium are very good gamma blockers.
However, you need inches of lead to screen against high energy gammas and so there's just no way of making that portable, never mind wearable.
Gamma-blocking clothing is a non starter.

Iron isn't a particularly good neutron absorber. It has a capture cross section ( for thermal neutrons) of just 2.5 barns.
One of the metals used as a neutron shield is cadmium which as a capture cross section roughly a thousand times greater than iron. If you want to try something more exotic gadolinium tops the league with 49000 barns. With isotopically enriched Gd you can do even better but that's not practical
On a practical note the sea water being used to cool the reactors in Japan has a lot of salt in it; chlorine has a high cross section too (35.5 barns) so the sea water cannot act as a neutron moderator and produce an accidental criticality in the way that fresh water (possibly) might.

The other material used as a neutron sink is boron.

Since they scrammed the reactors before the tsunami hit and they are dumping salt water and borate onto the reactors there is very little chance of any significant neutron production anyway.
 

Offline Geezer

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« Reply #23 on: 19/03/2011 17:03:44 »
Thanks BC. So if you square the atomic number and divide by the atomic weight of an element, you get a rough idea of its relative effectiveness as a gamma shield, weight for weight, against other elements.

On that basis, lead is way up there at around 32. Uranium is even better at around 35 and silicon, for example, is around 7.
 

Offline burning

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« Reply #24 on: 19/03/2011 18:05:04 »
My thanks also, BC.  I allowed myself to get drawn into "reverse engineering" another's post, but I wasn't careful enough to think of the broader picture.  I appreciate you setting the facts straight.
 

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