First of all the center of single story wood frame house gives you a 50% reduction in exposure. (I believe this assumes your windows and doors are closed and radioactive particles are not blowing inside.) This report makes an observation that I never seen before. There is more exposure from the ground outside the house than from the roof. (p. 17) Those of us with a significant slope behind the house should probably bias Shelter Cramer towards the slope side of the house. My suggestion awhile back about building a box of ammunition in which to take refuge may need some modification. (I am sure most of my readers have 10,000 rounds of lead shielding combined with brass in little boxes.)
It would appear that building a wall around you might be a more effective shield than a ceiling of lead. Two inches of lead gives a reduction of about 1/8th. Let's see: two boxes of .223 stacked with ammo facing outward should give us something approaching 2" (and the brass helps also, as does the metal of the ammo cans.). Put all this under your kitchen table near the center of the house. Combined with the 50% reduction of your house this means about 1/16th reduction. Now stack all your bottles of water and canned food inside the lead wall, or on top of the table where you can reach it with minimal exposure. Water is not a great shield (low density) but at least irradiated water produces very little secondary radiation, unlike heavy metals. Maybe all combined you get a 1/20th reduction. You also want food and water where you can easily access it. You are probably going to make hopefully short visits to whatever bathroom is most interior to the house. Water may not continue pumping unless you have 1000 gallon gravity fed water tank like my last house, but even failing to flush will be less stinky and unpleasant than using a 5 gallon drum as a toilet. A proper fallout shelter is a reduction to 1/40th, so for a improvised shelter, this is not too bad. This is not ideal, but if you are over 50, the postwar chaos, starvation, and cannibalism (aren't I cheery today) are more likely to kill you than cancer.
UPDATE: As I was thinking about this, it struck me that having your ammunition wall bunker near the kitchen or laundry room can be advantageous: a refrigerator, stove, or oven all have a fair amount of steel which will certainly contribute to attenuation. If you have marble countertops or the artificial kind (Silestone) these are not much inferior if at all inferior to concrete for shielding. Put your under table shelter in the shadow of these so that fallout on neighboring roofs and trees had to go through these as well.
Of course the best improvised shelter if you have enough warning is dig a six foot deep (that deep so you have room to move around, and if it does not work, you simplify the work of whoever buries you) and long trench, put doors on it and pile dirt three feet deep. (Earth arching effect will distribute the load to the surrounding ground, preventing collapse.) Next park your cars on top to add another layer of metal shielding. Remember you need an entrance after the cars are parked. The simple solution is to drive them across the trench to get shielding from the ends of the car, but I would worry the weight of the car might be too much load for earth-arching. Drive them on top longitudinally and stay near the engine block ends of the trench.
You still want those mountains of ammunition between you and the entrance.
Not enough ammo? AmmoToGo has an ad on the right side.
Because Putin has been making sort of under his breath reminders that cutting them financially does not preclude them from a nuclear Gotterdamerung, I have thinking through bolt out of the blue scenarios (yes, I am having trouble sleeping). There are only two nearby targets: Boise (state capital) and Mountain Home Air Force Base. These are 28 and 68 miles away, respectively. A detonation at either location would generate a flash that should wake even the heaviest of sleepers. That is instantaneous for practical purposes. At that distance prompt radiation is completely absorbed. The blast wave is 2.8 or 6.8 minutes later. With a little care you can open all the windows in your house so the shock wave does not break the windows. (As near as I can compute even a one megaton bomb will not break windows that far way) This not only reduces risk of glass cuts as you madly build your fallout shelter, but also lets you close the windows before fallout blows in from Portland, Seattle, Bremerton, and Hanford. It is probably wise to calculate blast wave arrival time from your nearest targets. Blast waves move at roughly the speed of sound (300 m/s).
The amount of shielding provided by different materials depends on the energy of the radiation. UP to about 80 KeV, lead is pretty effective. However, above that, what matters is the amount of mass between the radiation source and whatever you're trying to shield. As a result, people designing shielding are more likely to use concrete than lead.
ReplyDeleteHere's a nice chart:
This happens to be for iron, but here's one for concrete:
You'll notice that at 200 KeV, the mass attenuation coefficients are about the same. So for nuclear fallout, what matters is how much mass you can put between yourself and the outside.
Thank you for the clarification. Those charts did not come through. Links?
DeleteLet's see if these will work. Putting them in brackets seems to have made them invisible.
ReplyDeletehttps://physics.nist.gov/PhysRefData/XrayMassCoef/ComTab/concrete.html
Mass attenuation coefficient for concrete by photon energy
https://en.wikipedia.org/wiki/Mass_attenuation_coefficient#/media/File:Attenuation_Coefficient_Iron.svg
You'll notice this is broken down into several photon/matter reactions, including scattering, photoelectric absorption, and conversion of photon energy into matter. When the photon energy is high enough that it exceeds the energy needed to bounce the innermost electron completely out of an atom, the photoelectric effect ceases to contribute to photon absorption, and only scattering matters.
The strength of the photoelectric effect depends on the Z of the atomic nucleus, and goes roughly as Z cubed. So for medical x-rays, where the energy is on a par with the energies needed to knock electrons out of atoms, lead aprons are worth using. Higher energy photons, such as those used in radiation therapy, are above this range, and lead aprons are of much less utility. The best way to avoid radiation of this energy is to put as much mass between yourself and the radiation emitter, or as much distance, or both. (Radiation decreases according to an inverse-square effect, so doubling the distance decreases exposure by a factor of four.)
Since my copy of the Radiological Physics Handbook is at work and I'm telecommuting on account of a compromised immune system, I'm looking elsewhere for this information.
Here's another link you may find useful:
https://www.nist.gov/pml/x-ray-mass-attenuation-coefficients
Look particularly at tables 3 and 4.
In any event, in the case of a nuclear explosion, your best approach to shielding is to put as much mass between yourself and the radiation source. This can include concrete, wood, soil, books, water (swimming pool or tanks of emergency stores), or just about anything else. Just keep track of the density of the material, and aim for roughly six feet of equivalent to water.
Notice also this deals with photons only. Alpha particles are stopped by a sheet of paper, and beta particles are stopped by a few inches of matter. In the case of beta particles, it's best to use low atomic number material such as water or plastic. If you run high-energy beta particles into lead, you will find you've created a powerful x-ray source, as the lead decelerates the beta particles very quickly and causes them to emit that energy in the form of high-energy photons.
Not advisable.
Otherwise, alpha and beta emitters are forms of internal contamination. This is why fallout is a problem. If radioactive dust, especially alpha emitters find their way into food and are eaten, they become internal sources of radiation and the limited range of travel through matter ceases to be a factor.
The third major form of radiation is neutrons. These are emitted at the moment a bomb goes off and can impart a massive dose of radiation. Neutrons are best stopped by materials that are high in hydrogen. If you can arrange to have your emergency water supply or your swimming pool between yourself and the explosion at the moment it goes off, you've got good shielding. Again six feet is a good thickness of shielding. Plastic is also a good shielding material against neutrons, as is oil, wax, or similar substances.
This is all off the top of my head and based on what I could find without cracking open reference books and notes. I hope this is all perfectly useless information for the near future.