Post by COB on May 27, 2012 19:27:46 GMT -7
Sorry I gave credit to the wrong poster. 
This came from cwi555
________________________________________
I am reposting information I put in another thread since that thread was not intended to cover this subject directly.
My personal background on the subject is as follows:
NDE neutron and gamma gamma radiography, troxler gages, 250kv x-ray tubes to 12 MeV accelerator x-ray. Beginning in 1989, I worked my first commercial nuclear outage, and in the following years DOE sites, and DOD sites.
In all I've logged in excess of 700 hours of radiation safety training both in the states and abroad, and several thousand hours working in radioactive and contaminated environments.
If there is a health physicist or nuclear physicist among you, please feel free to chime in. This will be based on my training, and experience, but I am neither an HP or a NPH. I do carry NDA certifications (non destructive assaying) as well.
Purpose: Ron brought up a point in another thread about disinformation.
On the subject of nuclear safety, between the bunny huggers, and the fear mongers, there are most definitely reams of it spewing forth. Then there is the dated information and or dumbed down information some .gov or .mil organizations like to spew out to make the sheeples warm and fuzzy.
My intent is to do my best to clarify the subject matter until such time as we are graced with an HP or NPH.
If any mods or persons think this thread inappropriate, please feel free to wax it, but based on recent conversations, and some research today on what’s floating around on the net. I feel it is a subject that needs to be addressed in its own thread. On this particular subject, ignorance or following some flight of fancy some teen in his basement hacked together could get some folks in serious trouble should they actually need to know the information.
With that said:
Some basics.
There are multiple forms of radiation. Thermal, electromagnetic, etc.,
the radiation of interest is ionizing radiation.
Ionizing radiation was discovered by William Conrad Retrogen in 1895.
This is an x-ray as produced by an x-ray vacuum tube.
In 1896, French scientist Henri Becquerel discovered the nature of natural ionizing elements. Specifically uranium.
Between the two, it didn't take long for the first radiographs (x-rays as medical types call them) to be taken. This was discovered by darkened photographic plates in the presence of these 'sources'.
Adam and Marie curie followed the work of Becquerel expanding on it, and through refinement, discovered radium. The first industrial radiography source.
(It killed them both in the end)
Between them all, the first four types of ionizing radiation was discovered:
Alpha particles
Beta particles
Gamma EMF
X-ray
Neutron radiation (technically both particle and EMF) was discovered during the Manhattan project.
Alpha particles can be blocked totally by a sheet of paper
Beta particles can be blocked totally by a thicker piece of cardboard.
It gets fuzzy when you get to the EMF types.
The wavelength of X-rays is in the range of one angstrom and that of Gamma rays is 0.0001 angstrom. Therefore, on average, the gamma tends to be more penetrating than the x-ray when compared energy to energy. (as measured in electron volts)
Ionizing radiation is measured by the electrical charge imparted on 1^3 centimeter of dry air in a sealed chamber. (ion chamber). This is further broken down into REM. (retrogen equivalent man) or R.
The REM or R is broken down into millirem. Or 1000 MR (millirem) = 1 R.
This is how the human effect is measured.
For an idea, the United States Nuclear regulatory commission has set an administrative limit of 5R per year for industrial radiation workers. 5 REM is what the NRC considers the maximum industrial exposure that is safe.
Then you get to the three basic types of EMF ionizing effects in order of weaker to stronger.
Photoelectric
Compton Scattering
Pair production
(technically there are two more for production of x-rays, they are Bremsstrahlung radiation, and K-shell emission, but since their effects are much the same as PE, CS, and PP I will not discuss them further for the most part)
Photoelectric effect is the weakest, and consist of the phenomenon of electrons are emitted from matter when they are hit with energy of a very short wavelength. Photoelectric effect can be either ionizing, or non ionizing.
Compton Scattering: This was discovered by Arthur Compton in 1923 for which he won the Nobel in 1927. When a mid level energy Photon impacts an electron, it recoils, absorbing some of the initiating energy and sends a longer wavelength, less energetic photon on a different angle on its way. It also will eject an electron which goes to an even lower energy state (the photoelectric effect).
The effect of this is to weaken the incident radiation.
It is in the Compton Effect that you are incorrect. A sufficient amount of material will in fact totally absorb an incident radiation source if that material is of a sufficiently dense material. (internal/side scatter)
Then there is pair production.
You should only see pair production in 10 MEV linear accelerators (advanced x-ray tubes) or in a nuclear reaction. (bomb or nuclear plant)
The incident photon strikes the nucleus of the atom emitting a negative electron, and a positive positron.
Anything past pair production is in fact the atom being destroyed. (splitting the atom so to speak). Nuclear fission or fusion is the only source of neutron radiation. So unless you have a runaway nuclear plant in your area, or a bomb goes off over your head, you shouldn't see it. However; for a bomb shelter, there is that potential, thus my water defense.
As far as the radiation half value layers, you can in fact reach a point of total absorption. That will get you into the mass attenuation coefficients (non linear scatter/absorption) and attenuation coefficients (linear scatter/absorption)
The eV (electron volts typically in MeV when talking about ionizing radiation)
and the material characteristics all have a hand in this.
Material density, elasticity, number of K shells, all come into play.
to give you a scale, I'll use two man made sources for demonstration.
The half value layer for Iridium 192 (common radiographic source)
Iridium has 5.9 R per hour at 1 foot distance per curie (curie = quantity)
Iridium-192 Concrete(1.75) Steel(0.5) lead(0.19) tungsten(0.13) depleted uranium(0.11) (in inches)
Now lets look at cobalt60 for comparison.
Cobalt has 14.4 R per hour at 1 foot distance per curie. It has a higher energy level (MeV) than IR192
It's half value layers are as follows:
Concrete (2.38) Steel(0.85) lead (0.49) tungsten(0.31) Depleted uranium(0.27) (in inches)
Now that the basics of what ionizing radiation (shortened to radiation from here on out) is has been discussed we get to the following:
• Sources of radiation
• Measures of radiation
The sources of radiation are broken down three sources.
• Cosmic
• Natural
• Manmade
Cosmic is as it states. From outer space/ the sun. This usually doesn't come into play for most folks. However; Control of exposure to radiation is achieved by:
• Time - Amount of time spent in a radiation field
• Distance - Distance from the source of radiation
• Shielding - What you can put between yourself and the source of radiation
When it comes to elevation, the higher your at, the more your going to get from cosmic sources. This gets back to distance and shielding. The higher you are, the closer you are to the source, and the less shielding (atmosphere) you have between you and it.
(This by the way is why I schedule flights for night time whenever I can.)
There are areas in Peru/Brazil where this adds up to 2 R a year dose. (added to the natural background, it can range up to 25 R per year in some remote villages that are sitting on top of uranium deposits and other sources)
That brings us to natural sources. Potassium 40, and others are natural emitters. They are in various foods we eat, and others. We also receive radiation form things like radon gas etc.
Then there is manmade sources. X-Ray tubes when you go to the dentist, or the doctor, medical sources, and others.
The three combine for an over all background radiation level.
That fact becomes important when you look at the sources for biological effect studies.
The majority of what you find is based on radiation levels above the background level. Someones dose (absorbed amount of radiation) is monitored in terms of what is above the background, not the total dose received from all sources. If your natural background in your area is 2R a year, then (in the united states) your industrial background allowance is above and beyond that (5R + 2R = 7R total for a year)
Now we get to measures of radiation.
The first stop is to understand the measure of the radiation sources.
This is in terms of "curies" and for SI (metric) "Becquerel's"
1 curie = 3.7x10^10 decays per second. (in one second, 3.7 billion atoms stabilize or "decay".
When you say decay, a radioactive isotope is radioactive because the atom (electron, neutron, proton) is unbalanced. It will continue to eject electrons etc until it becomes balanced for the given element it originated from. This is the root source of radiation
1 Bq = 2.70×10^11 Ci (curie) or 1 decay.
For this purpose, I will use the curie only.
A curie can be broken down into several smaller units. Micro ( divide by 100), milli (divide by 1000) etc.
Now for how it works on you.
In the United States it's measured in terms of REM or R. Roentgens Equivalent Man for absorbed 'dose'
In other countries they are measured in terms of Grays or sieverts (metric based countries)
In all cases, it's based on the biological effects
The rad is a unit of absorbed radiation dose in terms of the energy deposited in tissue. The rad is an absorbed dose of 0.01 joules of energy per kilogram of tissue. The more recent SI unit is the gray, which is defined as 1joule of deposited energy per kilogram of tissue. To assess the risk of radiation, the absorbed dose is multiplied by the relative biological effectiveness of the radiation to get the biological dose equivalent in rems or sieverts.
From this point forward, It will be in terms of REM or R only.
Ok, now that we know all that, what does it mean?
What it means has been a subject for debate for a long time.
It should be mentioned that various parts of the body are more sensitive to radiation than others as are children and fetus's.
The reproductive organs are the most sensitive to radiation, followed by the nervous system, and followed by the whole body (neck to stomach) then to the eyes and finally the extremities (legs and arms) in order of descending sensitivity.
Dose (rem absorbed) is further broken down into acute vs. chronic dose and is generally in terms of a whole body dose.
Acute is a large dose received in a short period of time
Chronic is a small does received over a long period of time
The following chart is for an acute dose only (less than 72 hours):
0-25 R no noticable effect
>25 to 75 R. Blood changes are possible, some minor sickness.
76 R to 150 R Those with weak immune systems are at risk of death, general sickness is likely (stomach lesions, possible skin sores)
Going up to 250 R it gets into the medium lethal dose. Without treatment serious health effects are likely, and some will die.
Up to 500 R you get into a 50% chance of death no matter how healthy you are, with a large number of people requiring bone marrow transplants etc to survive.
At 1,000 R your pretty well screwed. Not many will survive if any.
Now that we have spoken of Dose Rem etc.
A mention of the effects of contamination is in order.
Contamination is by definition, radioactive (particles/materials) where they should not be, or are not designed to be.
This can include various gases as well.
Contamination can put off alpha, beta, and gamma.
When this is inhaled/ingested or in contact with the skin, this will add to your dose received.
For the survivalist, it is my opinion that contamination is much more of a risk, than a gamma burst. You could survive a 100R gamma burst, but in turn be killed over a period of a few months by being crapped up (contaminated) without taking care of it.
Half lives are the time it takes an radioactive isotope to decay to half it's original intensity. (10 curies to 5 curies).
Half lives depend on the nature of the material. Some material have half lives as little as minutes, while others can have half lives up to 10,000 years.
Some things like iodine 131 will go straight for your thyroid gland, others will go for different parts of your body.
All of them that are in excess of the normal background as previously defined.
This is why this segment will be short and sweet.
Keeping yourself uncontaminated is critical.
When you get these contaminates in your body, only your natural biological functions and the materials half life will get them out.
The effect of the radiation does not go away, it simply accumulates while it's trapped in your body.
Showers and cleansing facilities become paramount in the event of a dirty bomb or other contaminating event.
These facilities should be isolated from your normal water/shower facilities.
In no way shape or form should they share water source, it's simply to much of a risk.
Now how is the measurement of contamination defined?
For this I have to address briefly some information on equipment.
There will be a section on it, but to understand how it's measured, a brief description is necessary.
The proverbial Geiger Mueller counter (GM tube) is not the catch all device that many supply stores etc. would have you believe. Not only is it not a magic bullet, it will get you killed if your not careful and use the right tool for the right job.
The proper detector is a Scintillation counter. While there are many of them, the basic design puts a phosphor material in front of a light sensor that when ionizing radiation strikes it, it glows slightly, that is in turn picked up and amplified electronically.
The counter/scanner typically measures contamination in terms of DPM. Disintigrations per minute. DPM is the number of atoms that have decayed, not Counts per minute CPM in which the disintrigrations are measured against a given quantity of radioactive material.
Now some places still use a GM tube, but due to it only reacting to specific frequency ranges, you can find yourself stepping into something you really don't won't to.
Now that we have established the unit of measure and what should be used.
The DPM is the standard. What is considered radiologically contaminated is 1000 dpm per 100 centimeters squared, above background above the normal background. Remember that radiation is all around us 24 hours a day, "In safe levels".
1000 dpm above that natural background is what's considered a "contaminated area". (the current U.S. federal guidline, it is different in other countries.)
A high contamination area would be 10 times that amount.
It is the high contamination area's that are of particular concern to the survivalist.
As a side note, there are also three different forms of contamination.
those are
• Fixed
• loose
• airborne
Walking around in it would be a mistake if your not dressed right.
The fixed will stay fixed unless you disturb it.
The loose and the airborne are the ones in particular that are a problem.
When you get into high contamination areas, you run a much bigger risk of a hot particle. Particularly in a fallout situation.
A hot particle will be discrete in size but giving off a high level of radiation.
That should give a better understanding of what "contamination" is.
So how do you prevent becoming contaminated?
Stay out of contaminated areas unless it's life for death.
If you absolutely must, or find yourself in an area where it is unavoidable:
You will need some basic gear.
Duct tape, neck to ankle to wrist overalls (tightly woven cotton), cloth covers for your shoes and ankles, and rubber overboots. Cotton hand liners (can be found at medical supply stores), rubber gloves, cotton hood that covers your head past the neck and the front of your neck, and a surgeons cap.
If this is for your BOL or bunker, you will need to establish a clean zone / step off pad (area for discarding contaminated clothing), and immediately past it, isolated shower and cleaning facilities.
To dress:
1 Put on coveralls,
2 Put on cloth shoe covers, tucking them in under your coveralls.
3 Tape the ends of the coveralls to the cloth covers. Be sure to leave a tab so you can remove it later.
4 Put on rubber overshoes.
5 Put on surgeons cap, then cotton hood. Be sure to capture your hair underneath it, and tape it down so it stays.
Put on cotton liner gloves under overall sleeves, then put on the rubber gloves over the sleeves and all. Tape them down to the cover all sleeves.
Your now ready to work in a C zone. (contaminated zone).
If it's an HCA (high contaminated zone) You will need a respirator. Depending on the level of contamination, you may need to repeat the dress out process over the first one. (if it's that hot there better be a D*** good reason to risk that kind of exposure, otherwise do not do it)
When it comes time to get out of all that garb, there is a procedure for that to.
1, remove rubber boots.
2. remove rubber gloves.
3. remove head cover up and away from your head.
4. remove surgeons cap.
5. remove coveralls
at this point you have only your cloth shoe covers and cotton glove liners remaining.
6 remove shoe covers one at a time. As you remove them, be sure to remove them in the direction of the dirty side. As you remove them, place your foot onto the stepoff pad/clean zone. Then the other foot, and finally remove the cotton lines into the dirty zone.
This is the general procedure for working within a contaminated environment.
Effects of radiation:
There have been a myriad of studies performed over the years on the biological effects of radiation. There are just as many variations of the potential effects.
However; in saying that there has been a general consensus around these numbers:
(scale is for an acute dose only)
0 - 25 rem.............No observable effects
25 - 100 rem.........Slight blood changes, no other observable effects
100 - 200 rem.......Vomiting may occur within 3 hours of exposure. Moderate blood changes are possible. Except for the blood-forming system, recovery will occur in essentially all cases within a few weeks.
200 - 600 rem.......Vomiting for most people occurs within 3 hours. Loss of hair after 2 weeks, severe blood changes, hemorrhaging, and infection. Death may occur. The recovery period is one month to one year.
Over 600 rem.........Vomiting occurs within one hour. Other effects include severe blood changes, hemorrhage, infection, and hair loss. Probability of death is at least 80% within two months. Survivors convalesce over a long period of time
Those numbers are fairly close as measured by the effects of cobalt60 cancer treatments. However, the Co60 for medical procedures are generally concentrated, and strictly controlled. However; that is why many who undergo the treatment lose their hair etc. No matter how tightly controlled, some collateral damage is going to be done to the body.
Time; distance; shielding:
I had an individual in Punto Fijo cordovan refinery, Venezuela that grabbed a source by his hand. He lost his hand. He forgot the distance part works both ways.
Time: The least time you spend in a field of ionizing radiation, the less dose you will accumulate.
If you spend 10 hours in a 100mr/hr field, you will have received 1R or 1000mr.
If you spend 1/2 hour in the same field, you will only receive 50mr.
Distance: Distance is a bit more complicated, but there are some rules of thumb that make it easier to calculate. Gamma radiation follows the inverse square law. If your the math wizard type, you'll know what that means.
However; there is an easy way to get usable values without breaking out the calculator.
Half the distance a quarter the intensity.
If you have a radiation intensity of 80mr/hr at 1ft distance from the source of that radiation, and you move to 2ft away, you are now standing in a 20mr/hr (millirem per hour) field. If you move to 4ft then you are in a 5mr/hr field.
In another example, if you have 100mr/hr at 20 feet, and move closer to 10 feet away from the source, then you do the numbers in reverse.
Your half the distance, so the original intensity (100mr) is multiplied by 4.
So by moving in 10 feet from 20 feet you increase the dose rate to 400mr/hr.
Just remember; half the distance quarter the intensity works both ways.
10 to 5' or 5' to 10', etc.
shielding;
The more you have between you and it, the less dose your going to receive.
The nature of the source also plays a roll as to the effectiveness of that shielding.
paper for alpha particles, cardboard for beta particles, lead/tungsten/ fir gamma, and concrete and water for neutron.
Each material will have a "half value layer".
If you started with 10mr/hr, a half value layer of shielding will reduce that to 5mr. I've previously posted this part already, but any mention of time, distance, shielding requires the whole spiel, not just part of it.
TDS is your primary means of protection against receiving dose. If you forget everything else, remember time, distance, shielding.
After the last statement, I'll bump up one of the equipment criteria.
It was stated that the standard geiger cannot detect alpha and most beta.
A general understanding of equipment is needed after that.
There are a myriad of detectors. Someone can spend 50 grand and still not have all the specialized detectors that are needed.
Not to many people can afford that option. Most will be doing good to get one good one, much less the full battery.
I can list a number of the detectors, but for the survivalist, it's a waste of money and resources to set up like your operating a nuclear plant. At the same time you need a good idea of what your environment has in store for you.
So whats a person on a budget to do?
General Purpose Ratemeter
Radiation Detector
Gamma Detector
The first one is a general purpose meter. It's a 0-2Rem range gamma/x-ray
Followed by a list of remote options. (an external detector that connects to the main unit via a cable.)
The second is the minimum accessory.
If you can swing it, get the third.
Between the three they will cover 95 percent of possibilities. To get a higher percentage is going to put you into the multiple meters/devices and 50k plus.
With prudence and education, the first two can get you by, and with the third, your in excellent shape.
One thing ludlum and the other manufactures don't want to tell you is the frequency these items show up in flea markets, army navy stores, and other such places.
Problem is, most people blow right by them without recognizing either the value or what they are.
Then you get people who try to make their own. There are hundreds of designs on the internet, but in my opinion it is a mistake to go that route.
While the don't look like much with the lid off, they do in fact require specific values of materials/fit/etc to have any worth at all.
A poorly built meter/detector is about like a pistol with a hole drilled into the chamber. You may get away with firing it a few times, but it can just as easily get you killed.
When you find a surplus meter/detector, you need to jump on it if it's functional.
I purchased all three of those items at a gunshow a few years back for 100 bucks.
The battery check function on the device will charge all the circuits and give you a fault if it's screwed.
Further it is legal to have a 1mr source check device for the public, or in lieu of that, you can check old cesium emergency exit lights, your glow in the dark night sites, and other sources of low level radiation. If it works at all, the most it could need is calibration.
Calibration can be done cheaper than most realize, and for a static item, doesn't need the same frequency as these devices that are used every day.
As a semi-final note on this particular subject, I understand the military has recently upgraded most of these devices. I made a few calls, but can't check until this weekend, but I believe the market will be flush with them.
If you can afford to buy new, that is your best option. The only problem is it's a captive market. There are not many manufactures of this item out there.
Put simply, internal dose and external dose come together to mean total effective dose. (industry calls it total effective dose equivalent or TEDE)
You cannot forget to count any internal dose that you receive.
Having said that, you need to know where to begin.
American nuclear society
ANS : Public Information : Resources : Radiation Dose Chart
If you run through the checklist, it will tell you how much you likely receive per year from all sources. You need this information as a baseline for setting up any program for dose absorbed monitoring.
Internal dose is considerably more difficult to measure than absorbed dose from external sources.
To make it short, for the none HP without access to reams of cash, the best way is through bio-essay. That means exactly what it implies. If you've ever taken a drug test, it's no different. Your bodies effluence will be the best measurement of internal dose for you to base dose received on.
That is the primary purpose of the gamma detector from the previous post.
It has other purposes, but the energy range of that particular model will cover the majority of potential internal contaminates.
Basically you urinate in a cup, and scan it with the detector.
The scale on the base unit should be in Rem, not DPM or CPM. Your not looking specifically for dpm, your looking for how much dose is received.
It should also be noted again that this is a rough estimate. If the test is positive after an excursion into a suspected contaminated area the exact level of it, and exact dpm should be counted. This should be done again in 24 hours, then 72 hours, then 2 weeks. This should be compared against the half lifes of known material to get an idea of what it is you have taken in.
It's not exact, it's not the best option, but again, unless you've got reams of cash, it's the only option I am aware of.
These two in particular should be watched for:
iodine concentrates in the thyroid
radium and strontium are bone seekers
The iodine part can be mitigated by iodine pills just prior to, or during the event. The radium and strontium are another animal. They are going to affect your marrow and bone.
Between them is the secondary purpose of the same monitor. Direct readings over the area of interest. Thyroid, spinal cord, etc. It's not going to be accurate, but it will give you an idea of what is being affected, and once you know that, most natural medicine has reams of data on what it takes to clear that particular body part/organ.
Document, document, document, you must keep accurate and concise records for this to do you any good.
Now as far as external dose, a simple film badge will do the job.
That does not mean a TLD or thermo-luminescent dosimeter.
The tld basically uses the interaction of ionizing radiation (gamma x-ray and sometimes beta) with a crystal to record absorbed dose.
Problem is it requires heating/burning that crystal at a specific temperature and in a specific condition to get the reading out of it.
This machine is an example of what is used to do that:
Harshaw 3500 Manual TLD Reader
For gamma only, a film badge will work. A film badge is simple. It contains a small strip of x ray film. The level of through transmission of light determines the does received. The higher the dose received, the darker the film gets when developed. It must be remembered that special care has to be taken for development of it. Exact temperatures of the developer and fix chemicals as well as exact timing and processing is required for this to be of any value.
You also have to have a baseline to judge it against.
Every x ray film has a specific R factor (or amount of radiation required to achieve a specific darkening of the film)
It's late and I have to be up in 5 hours, so I'll leave it at that until the morning. I'll pick up on how to get the standard and how to process it tomorrow. This is very important. Knowing or at least having an idea of how much dose you've received is key to what you can and cannot do in a survival situation. The results of these readings will determine your course of action in a radiological event.
More tomorrow. For now, some standard terms and definitions
CDC Radiation Emergencies | Glossary of Radiological Terms
Film badge:
Every x-ray/radiography film, medical or industrial has what is known as a sensometric curve AKA H&D curves/Hurter Driffield curve etc.
Those of you who have performed radiography or higher end photography already know what that is.
Put simply, it's a measure of the quanity of light that passes through to the other side as judged against a known standard.
If side A of the film reads 50 foot candles, and side B of the film reads 23 foot candles then you have a loss of 17 foot candles as compared a known standard. (every film will have a base loss. On a densitometer, it's typically .03) simplified further, it's a measure of loss of light. The darker the tint is on your sunglasses, the less light gets through.
The math is: Density = Log (Io/It)
Io = the amount of light on one side of the film
It = the amount of light transmitted through the film from the Io side.
So if only one percent of the initial light made it through to the other side, it would be a density value of 2.
Thats a brief look into something you really don't need to know unless your a photographer or a radiographer etc.
What you do need to know is this:
The more energy received by that peice of film, either in ionizing radiation, or visible light, the darker that film is going to be.
If you receive nothing, then it will be clear when developed.
Now a bit more about the film badge how you can do it at home.
Most of you have seen photographic film at the store. You still can if you haven't noticed though it is getting rarer.
They come in various speeds, with the lower number = the slower speed film. I.E. Kodak 200. This is in contrast with a faster speed film I.E. Kodak 400 or 600.
The slower speed film for film badges and x ray film have a silver halide emulsion on them. When exposed to a source of energy (radiation) they undergo a chemical change. This is done when two sources of energy (photons/electrons) hit the silver halide crystal, but when they do, it turns that into a stable silver metal crystal. The varying degrees of this exposure determine the relative darkness of the image.
The unexposed silver halide crystals are reduced and effectively taken out, while other areas contain a mix of reduced and exposed areas.
This is how black and white and x-ray film creates the images that they do. However; this is why it can also be used to measure the amount of radiation you absorb.
By having fast speed of emulsion on one side of the film, and a slow speed of emulsion on the other, it can measure low and high quanitys of absorbed dose.
If it receives little dose, the slow side silver halides will nearly all wash away, while the fast side will darken.
If it receives a high does, both sides will darken.
The end result is, x amount of radiation will darken that film to a specific density.
Now if you have reams of cash to throw around, you can just buy a TLD burner, or in the case of a film badge, a reader to do it for you, but if your on a budget (and most are) you can simply buy or make a comparator strip.
I'll first describe the comparator strip and how to make one to clarify it.
Simply put, two pieces of the film your going to use as a film badge is exposed to a known source and strength of radiation. Most NDE / NDT labs will do this for roughly 75 to 100 bucks for you. You need to have a slow speed film and a fast speed film back to back.
To do this, you must have two chunks of steel, (if making your own film badge) one that is 1/2" thick, and the other that is 1" thick. Very often the NDE lab will have that laying around, especially if it's a well established one that has been around a while. The film to be exposed is layed out in thirds. one area free of steel, one area with the 1/2" steel over it, and the third with the 1" steel over it. (in contact)
It is exposed by the radiographer for a predetermined time based on delivering 2500 millirem to the uncovered area.
For the iridium 192 source (What I suggest is used) the 1/2" of steel will be a single half value layer. The 1" peice will provide 2 half value layers.
When the film is exposed, That means for the single HVL the dose under that steel will be 1250millirem and the area under the 2hvl will be 625mr. You can do it in more steps to be more accurate, but if you know the R factor (amount of dose required for a specific density) then between the slow and the fast speed films you just had exposed, you have a base line of a range of doses. This is because you can back calculate the differences between the slow and the fast speed film.
If you have an HD on the fast film of 4, then the slow speed will be around 2. By the time your calculations are done (which I will provide tomorrow for AGFA D3 vs D7 film) you have a close approximation of how much dose will be received at varying energy levels. (D3 takes approximately 5.6Rem for a 2.0HD and D7 takes 1.2Rem for a 2.0HD)
That difference between 2R and 5.6R can be used to back calc higher and lower doses without spending a ream of money on 20 plus exposures at the NDE lab to get a full set the hard way. They can be loaded in one film cassette and shot as one shot. Your going to need two shots of the same thing if you intend to do it at home after the fact.
Once you have your baseline shot developed you need to store it in a low humidity 68F environment sealed.
After that your only going to get it out (via cotton glove liners) for comparison against any film your home badge uses.
This is where the second piece comes in. Whatever your developing techniques are (there are reams of how to's on the net for film development, I'll leave it up to you unless you ask for specific instructions), your going to need to be able to reproduce that method. Once you have developed your second set of film, then it must be compared against the control set. At this time, the second set has become the standard for your specific film developing technique as judged against the professionally ran film.
If you have a good digital camera, you can play with it and get an image of the film that you can print and post on the wall of your BOL with a chart displaying what each image density equals for absorbed dose.
The chemicals, the film, the shots, all should be doable for less than 400 bucks and some elbow grease.
It won't be scientifically accurate, but will be close enough for you to have a pretty good approximation of your does received without spending 35 grand, and still getting you in the ballpark of the living.
If you are unclear on any of this, please post a question, this is the first method of measuring your external gamma received, it's also the most important to get down right in my opinion.
Pocket ion chambers or pocket dosimeters:
These are your simplest forms of recording dose.
They come in several ranges, but put simply, they consist of a pocket ion chamber. They are typically a tube about 1/2" diameter, and about 4" long.
They are only good for gamma, and have a finite limit to the amount they can record.
If you go this route rather than the film badge, here is what you will need.
You will need a charger;
Pocket ion chamber.
When you charge it, your not really charging it, it's more like your discharging it. The ion chamber picks up the gamma dose and through excitation of individual atoms within the chamber, a weak electrical current is produced.
build up of this current causes a needle to move across a calibrated scale which in turn denotes your dose received.
If you go this route, ideally you need more than one. If the device receives an unexpected impact, it can go off scale or otherwise stop working properly.
You can forgo the film badge if you record your dose from this device frequently, as well as charge it frequently.
It can also give you an estimate of R/hr. If for instance you receive 10millirem in 1 hour thats a 10mr/hr field. If you receive that same 10 in 1 minute, mulitiply it by 60 which tells you that you are in a 600mr/hr field.
It's not the most accurate method, but it's the cheapest method to at least have an idea. It will not pick up alpha or beta either.
Over all, and armed with the previous information, a plan can be put together for any radiological event.
Time, Distance, Shielding must be remembered.
If you don't have any life threatening reason to be there, don't.
If you must, keep as much distance and sheilding inbetween you and the source of radiation as possible.
Internal contamination is a distinct issue for any terrorist related threat.
It's unlikely they will have access to super power weapons of mass destruction. However; it is very likely they will have low level items like Co60 to seed a normal chemical explosive with for a dirty bomb.
Personally, I don't plan for a direct nuclear bomb hit. Thats about like planning for getting shot in the head, it really doesn't matter, your screwed regardless. As for anything other than a direct bomb hit, If I can't get out with at least 60 minutes advanced warning, I am not going to bother trying.
At that time you need to have already had your plan in place.
Panic will get you killed far faster than a nuclear threat.
With proper planning and preparation, anything short of an outright 1 megaton bomb direct hit can be survived.
With the information provided, a plan specific to your needs can be put together.
Sohrabi M. World high level natural radiation and/or radon prone areas with special regards to dwellings. In: Proceeding of the 4th International Conference on High Levels of Natural Radiation (ICHLNR), Beijing, China, 1996 (Wei L, Suahara T and Tao Z Ed), pp. 3-7, 1997
Natural Radiation: High Background Radiation Areas (HBRAs) of Ramsar, Iran
This came from cwi555________________________________________
I am reposting information I put in another thread since that thread was not intended to cover this subject directly.
My personal background on the subject is as follows:
NDE neutron and gamma gamma radiography, troxler gages, 250kv x-ray tubes to 12 MeV accelerator x-ray. Beginning in 1989, I worked my first commercial nuclear outage, and in the following years DOE sites, and DOD sites.
In all I've logged in excess of 700 hours of radiation safety training both in the states and abroad, and several thousand hours working in radioactive and contaminated environments.
If there is a health physicist or nuclear physicist among you, please feel free to chime in. This will be based on my training, and experience, but I am neither an HP or a NPH. I do carry NDA certifications (non destructive assaying) as well.
Purpose: Ron brought up a point in another thread about disinformation.
On the subject of nuclear safety, between the bunny huggers, and the fear mongers, there are most definitely reams of it spewing forth. Then there is the dated information and or dumbed down information some .gov or .mil organizations like to spew out to make the sheeples warm and fuzzy.
My intent is to do my best to clarify the subject matter until such time as we are graced with an HP or NPH.
If any mods or persons think this thread inappropriate, please feel free to wax it, but based on recent conversations, and some research today on what’s floating around on the net. I feel it is a subject that needs to be addressed in its own thread. On this particular subject, ignorance or following some flight of fancy some teen in his basement hacked together could get some folks in serious trouble should they actually need to know the information.
With that said:
Some basics.
There are multiple forms of radiation. Thermal, electromagnetic, etc.,
the radiation of interest is ionizing radiation.
Ionizing radiation was discovered by William Conrad Retrogen in 1895.
This is an x-ray as produced by an x-ray vacuum tube.
In 1896, French scientist Henri Becquerel discovered the nature of natural ionizing elements. Specifically uranium.
Between the two, it didn't take long for the first radiographs (x-rays as medical types call them) to be taken. This was discovered by darkened photographic plates in the presence of these 'sources'.
Adam and Marie curie followed the work of Becquerel expanding on it, and through refinement, discovered radium. The first industrial radiography source.
(It killed them both in the end)
Between them all, the first four types of ionizing radiation was discovered:
Alpha particles
Beta particles
Gamma EMF
X-ray
Neutron radiation (technically both particle and EMF) was discovered during the Manhattan project.
Alpha particles can be blocked totally by a sheet of paper
Beta particles can be blocked totally by a thicker piece of cardboard.
It gets fuzzy when you get to the EMF types.
The wavelength of X-rays is in the range of one angstrom and that of Gamma rays is 0.0001 angstrom. Therefore, on average, the gamma tends to be more penetrating than the x-ray when compared energy to energy. (as measured in electron volts)
Ionizing radiation is measured by the electrical charge imparted on 1^3 centimeter of dry air in a sealed chamber. (ion chamber). This is further broken down into REM. (retrogen equivalent man) or R.
The REM or R is broken down into millirem. Or 1000 MR (millirem) = 1 R.
This is how the human effect is measured.
For an idea, the United States Nuclear regulatory commission has set an administrative limit of 5R per year for industrial radiation workers. 5 REM is what the NRC considers the maximum industrial exposure that is safe.
Then you get to the three basic types of EMF ionizing effects in order of weaker to stronger.
Photoelectric
Compton Scattering
Pair production
(technically there are two more for production of x-rays, they are Bremsstrahlung radiation, and K-shell emission, but since their effects are much the same as PE, CS, and PP I will not discuss them further for the most part)
Photoelectric effect is the weakest, and consist of the phenomenon of electrons are emitted from matter when they are hit with energy of a very short wavelength. Photoelectric effect can be either ionizing, or non ionizing.
Compton Scattering: This was discovered by Arthur Compton in 1923 for which he won the Nobel in 1927. When a mid level energy Photon impacts an electron, it recoils, absorbing some of the initiating energy and sends a longer wavelength, less energetic photon on a different angle on its way. It also will eject an electron which goes to an even lower energy state (the photoelectric effect).
The effect of this is to weaken the incident radiation.
It is in the Compton Effect that you are incorrect. A sufficient amount of material will in fact totally absorb an incident radiation source if that material is of a sufficiently dense material. (internal/side scatter)
Then there is pair production.
You should only see pair production in 10 MEV linear accelerators (advanced x-ray tubes) or in a nuclear reaction. (bomb or nuclear plant)
The incident photon strikes the nucleus of the atom emitting a negative electron, and a positive positron.
Anything past pair production is in fact the atom being destroyed. (splitting the atom so to speak). Nuclear fission or fusion is the only source of neutron radiation. So unless you have a runaway nuclear plant in your area, or a bomb goes off over your head, you shouldn't see it. However; for a bomb shelter, there is that potential, thus my water defense.
As far as the radiation half value layers, you can in fact reach a point of total absorption. That will get you into the mass attenuation coefficients (non linear scatter/absorption) and attenuation coefficients (linear scatter/absorption)
The eV (electron volts typically in MeV when talking about ionizing radiation)
and the material characteristics all have a hand in this.
Material density, elasticity, number of K shells, all come into play.
to give you a scale, I'll use two man made sources for demonstration.
The half value layer for Iridium 192 (common radiographic source)
Iridium has 5.9 R per hour at 1 foot distance per curie (curie = quantity)
Iridium-192 Concrete(1.75) Steel(0.5) lead(0.19) tungsten(0.13) depleted uranium(0.11) (in inches)
Now lets look at cobalt60 for comparison.
Cobalt has 14.4 R per hour at 1 foot distance per curie. It has a higher energy level (MeV) than IR192
It's half value layers are as follows:
Concrete (2.38) Steel(0.85) lead (0.49) tungsten(0.31) Depleted uranium(0.27) (in inches)
Now that the basics of what ionizing radiation (shortened to radiation from here on out) is has been discussed we get to the following:
• Sources of radiation
• Measures of radiation
The sources of radiation are broken down three sources.
• Cosmic
• Natural
• Manmade
Cosmic is as it states. From outer space/ the sun. This usually doesn't come into play for most folks. However; Control of exposure to radiation is achieved by:
• Time - Amount of time spent in a radiation field
• Distance - Distance from the source of radiation
• Shielding - What you can put between yourself and the source of radiation
When it comes to elevation, the higher your at, the more your going to get from cosmic sources. This gets back to distance and shielding. The higher you are, the closer you are to the source, and the less shielding (atmosphere) you have between you and it.
(This by the way is why I schedule flights for night time whenever I can.)
There are areas in Peru/Brazil where this adds up to 2 R a year dose. (added to the natural background, it can range up to 25 R per year in some remote villages that are sitting on top of uranium deposits and other sources)
That brings us to natural sources. Potassium 40, and others are natural emitters. They are in various foods we eat, and others. We also receive radiation form things like radon gas etc.
Then there is manmade sources. X-Ray tubes when you go to the dentist, or the doctor, medical sources, and others.
The three combine for an over all background radiation level.
That fact becomes important when you look at the sources for biological effect studies.
The majority of what you find is based on radiation levels above the background level. Someones dose (absorbed amount of radiation) is monitored in terms of what is above the background, not the total dose received from all sources. If your natural background in your area is 2R a year, then (in the united states) your industrial background allowance is above and beyond that (5R + 2R = 7R total for a year)
Now we get to measures of radiation.
The first stop is to understand the measure of the radiation sources.
This is in terms of "curies" and for SI (metric) "Becquerel's"
1 curie = 3.7x10^10 decays per second. (in one second, 3.7 billion atoms stabilize or "decay".
When you say decay, a radioactive isotope is radioactive because the atom (electron, neutron, proton) is unbalanced. It will continue to eject electrons etc until it becomes balanced for the given element it originated from. This is the root source of radiation
1 Bq = 2.70×10^11 Ci (curie) or 1 decay.
For this purpose, I will use the curie only.
A curie can be broken down into several smaller units. Micro ( divide by 100), milli (divide by 1000) etc.
Now for how it works on you.
In the United States it's measured in terms of REM or R. Roentgens Equivalent Man for absorbed 'dose'
In other countries they are measured in terms of Grays or sieverts (metric based countries)
In all cases, it's based on the biological effects
The rad is a unit of absorbed radiation dose in terms of the energy deposited in tissue. The rad is an absorbed dose of 0.01 joules of energy per kilogram of tissue. The more recent SI unit is the gray, which is defined as 1joule of deposited energy per kilogram of tissue. To assess the risk of radiation, the absorbed dose is multiplied by the relative biological effectiveness of the radiation to get the biological dose equivalent in rems or sieverts.
From this point forward, It will be in terms of REM or R only.
Ok, now that we know all that, what does it mean?
What it means has been a subject for debate for a long time.
It should be mentioned that various parts of the body are more sensitive to radiation than others as are children and fetus's.
The reproductive organs are the most sensitive to radiation, followed by the nervous system, and followed by the whole body (neck to stomach) then to the eyes and finally the extremities (legs and arms) in order of descending sensitivity.
Dose (rem absorbed) is further broken down into acute vs. chronic dose and is generally in terms of a whole body dose.
Acute is a large dose received in a short period of time
Chronic is a small does received over a long period of time
The following chart is for an acute dose only (less than 72 hours):
0-25 R no noticable effect
>25 to 75 R. Blood changes are possible, some minor sickness.
76 R to 150 R Those with weak immune systems are at risk of death, general sickness is likely (stomach lesions, possible skin sores)
Going up to 250 R it gets into the medium lethal dose. Without treatment serious health effects are likely, and some will die.
Up to 500 R you get into a 50% chance of death no matter how healthy you are, with a large number of people requiring bone marrow transplants etc to survive.
At 1,000 R your pretty well screwed. Not many will survive if any.
Now that we have spoken of Dose Rem etc.
A mention of the effects of contamination is in order.
Contamination is by definition, radioactive (particles/materials) where they should not be, or are not designed to be.
This can include various gases as well.
Contamination can put off alpha, beta, and gamma.
When this is inhaled/ingested or in contact with the skin, this will add to your dose received.
For the survivalist, it is my opinion that contamination is much more of a risk, than a gamma burst. You could survive a 100R gamma burst, but in turn be killed over a period of a few months by being crapped up (contaminated) without taking care of it.
Half lives are the time it takes an radioactive isotope to decay to half it's original intensity. (10 curies to 5 curies).
Half lives depend on the nature of the material. Some material have half lives as little as minutes, while others can have half lives up to 10,000 years.
Some things like iodine 131 will go straight for your thyroid gland, others will go for different parts of your body.
All of them that are in excess of the normal background as previously defined.
This is why this segment will be short and sweet.
Keeping yourself uncontaminated is critical.
When you get these contaminates in your body, only your natural biological functions and the materials half life will get them out.
The effect of the radiation does not go away, it simply accumulates while it's trapped in your body.
Showers and cleansing facilities become paramount in the event of a dirty bomb or other contaminating event.
These facilities should be isolated from your normal water/shower facilities.
In no way shape or form should they share water source, it's simply to much of a risk.
Now how is the measurement of contamination defined?
For this I have to address briefly some information on equipment.
There will be a section on it, but to understand how it's measured, a brief description is necessary.
The proverbial Geiger Mueller counter (GM tube) is not the catch all device that many supply stores etc. would have you believe. Not only is it not a magic bullet, it will get you killed if your not careful and use the right tool for the right job.
The proper detector is a Scintillation counter. While there are many of them, the basic design puts a phosphor material in front of a light sensor that when ionizing radiation strikes it, it glows slightly, that is in turn picked up and amplified electronically.
The counter/scanner typically measures contamination in terms of DPM. Disintigrations per minute. DPM is the number of atoms that have decayed, not Counts per minute CPM in which the disintrigrations are measured against a given quantity of radioactive material.
Now some places still use a GM tube, but due to it only reacting to specific frequency ranges, you can find yourself stepping into something you really don't won't to.
Now that we have established the unit of measure and what should be used.
The DPM is the standard. What is considered radiologically contaminated is 1000 dpm per 100 centimeters squared, above background above the normal background. Remember that radiation is all around us 24 hours a day, "In safe levels".
1000 dpm above that natural background is what's considered a "contaminated area". (the current U.S. federal guidline, it is different in other countries.)
A high contamination area would be 10 times that amount.
It is the high contamination area's that are of particular concern to the survivalist.
As a side note, there are also three different forms of contamination.
those are
• Fixed
• loose
• airborne
Walking around in it would be a mistake if your not dressed right.
The fixed will stay fixed unless you disturb it.
The loose and the airborne are the ones in particular that are a problem.
When you get into high contamination areas, you run a much bigger risk of a hot particle. Particularly in a fallout situation.
A hot particle will be discrete in size but giving off a high level of radiation.
That should give a better understanding of what "contamination" is.
So how do you prevent becoming contaminated?
Stay out of contaminated areas unless it's life for death.
If you absolutely must, or find yourself in an area where it is unavoidable:
You will need some basic gear.
Duct tape, neck to ankle to wrist overalls (tightly woven cotton), cloth covers for your shoes and ankles, and rubber overboots. Cotton hand liners (can be found at medical supply stores), rubber gloves, cotton hood that covers your head past the neck and the front of your neck, and a surgeons cap.
If this is for your BOL or bunker, you will need to establish a clean zone / step off pad (area for discarding contaminated clothing), and immediately past it, isolated shower and cleaning facilities.
To dress:
1 Put on coveralls,
2 Put on cloth shoe covers, tucking them in under your coveralls.
3 Tape the ends of the coveralls to the cloth covers. Be sure to leave a tab so you can remove it later.
4 Put on rubber overshoes.
5 Put on surgeons cap, then cotton hood. Be sure to capture your hair underneath it, and tape it down so it stays.
Put on cotton liner gloves under overall sleeves, then put on the rubber gloves over the sleeves and all. Tape them down to the cover all sleeves.
Your now ready to work in a C zone. (contaminated zone).
If it's an HCA (high contaminated zone) You will need a respirator. Depending on the level of contamination, you may need to repeat the dress out process over the first one. (if it's that hot there better be a D*** good reason to risk that kind of exposure, otherwise do not do it)
When it comes time to get out of all that garb, there is a procedure for that to.
1, remove rubber boots.
2. remove rubber gloves.
3. remove head cover up and away from your head.
4. remove surgeons cap.
5. remove coveralls
at this point you have only your cloth shoe covers and cotton glove liners remaining.
6 remove shoe covers one at a time. As you remove them, be sure to remove them in the direction of the dirty side. As you remove them, place your foot onto the stepoff pad/clean zone. Then the other foot, and finally remove the cotton lines into the dirty zone.
This is the general procedure for working within a contaminated environment.
Effects of radiation:
There have been a myriad of studies performed over the years on the biological effects of radiation. There are just as many variations of the potential effects.
However; in saying that there has been a general consensus around these numbers:
(scale is for an acute dose only)
0 - 25 rem.............No observable effects
25 - 100 rem.........Slight blood changes, no other observable effects
100 - 200 rem.......Vomiting may occur within 3 hours of exposure. Moderate blood changes are possible. Except for the blood-forming system, recovery will occur in essentially all cases within a few weeks.
200 - 600 rem.......Vomiting for most people occurs within 3 hours. Loss of hair after 2 weeks, severe blood changes, hemorrhaging, and infection. Death may occur. The recovery period is one month to one year.
Over 600 rem.........Vomiting occurs within one hour. Other effects include severe blood changes, hemorrhage, infection, and hair loss. Probability of death is at least 80% within two months. Survivors convalesce over a long period of time
Those numbers are fairly close as measured by the effects of cobalt60 cancer treatments. However, the Co60 for medical procedures are generally concentrated, and strictly controlled. However; that is why many who undergo the treatment lose their hair etc. No matter how tightly controlled, some collateral damage is going to be done to the body.
Time; distance; shielding:
I had an individual in Punto Fijo cordovan refinery, Venezuela that grabbed a source by his hand. He lost his hand. He forgot the distance part works both ways.
Time: The least time you spend in a field of ionizing radiation, the less dose you will accumulate.
If you spend 10 hours in a 100mr/hr field, you will have received 1R or 1000mr.
If you spend 1/2 hour in the same field, you will only receive 50mr.
Distance: Distance is a bit more complicated, but there are some rules of thumb that make it easier to calculate. Gamma radiation follows the inverse square law. If your the math wizard type, you'll know what that means.
However; there is an easy way to get usable values without breaking out the calculator.
Half the distance a quarter the intensity.
If you have a radiation intensity of 80mr/hr at 1ft distance from the source of that radiation, and you move to 2ft away, you are now standing in a 20mr/hr (millirem per hour) field. If you move to 4ft then you are in a 5mr/hr field.
In another example, if you have 100mr/hr at 20 feet, and move closer to 10 feet away from the source, then you do the numbers in reverse.
Your half the distance, so the original intensity (100mr) is multiplied by 4.
So by moving in 10 feet from 20 feet you increase the dose rate to 400mr/hr.
Just remember; half the distance quarter the intensity works both ways.
10 to 5' or 5' to 10', etc.
shielding;
The more you have between you and it, the less dose your going to receive.
The nature of the source also plays a roll as to the effectiveness of that shielding.
paper for alpha particles, cardboard for beta particles, lead/tungsten/ fir gamma, and concrete and water for neutron.
Each material will have a "half value layer".
If you started with 10mr/hr, a half value layer of shielding will reduce that to 5mr. I've previously posted this part already, but any mention of time, distance, shielding requires the whole spiel, not just part of it.
TDS is your primary means of protection against receiving dose. If you forget everything else, remember time, distance, shielding.
After the last statement, I'll bump up one of the equipment criteria.
It was stated that the standard geiger cannot detect alpha and most beta.
A general understanding of equipment is needed after that.
There are a myriad of detectors. Someone can spend 50 grand and still not have all the specialized detectors that are needed.
Not to many people can afford that option. Most will be doing good to get one good one, much less the full battery.
I can list a number of the detectors, but for the survivalist, it's a waste of money and resources to set up like your operating a nuclear plant. At the same time you need a good idea of what your environment has in store for you.
So whats a person on a budget to do?
General Purpose Ratemeter
Radiation Detector
Gamma Detector
The first one is a general purpose meter. It's a 0-2Rem range gamma/x-ray
Followed by a list of remote options. (an external detector that connects to the main unit via a cable.)
The second is the minimum accessory.
If you can swing it, get the third.
Between the three they will cover 95 percent of possibilities. To get a higher percentage is going to put you into the multiple meters/devices and 50k plus.
With prudence and education, the first two can get you by, and with the third, your in excellent shape.
One thing ludlum and the other manufactures don't want to tell you is the frequency these items show up in flea markets, army navy stores, and other such places.
Problem is, most people blow right by them without recognizing either the value or what they are.
Then you get people who try to make their own. There are hundreds of designs on the internet, but in my opinion it is a mistake to go that route.
While the don't look like much with the lid off, they do in fact require specific values of materials/fit/etc to have any worth at all.
A poorly built meter/detector is about like a pistol with a hole drilled into the chamber. You may get away with firing it a few times, but it can just as easily get you killed.
When you find a surplus meter/detector, you need to jump on it if it's functional.
I purchased all three of those items at a gunshow a few years back for 100 bucks.
The battery check function on the device will charge all the circuits and give you a fault if it's screwed.
Further it is legal to have a 1mr source check device for the public, or in lieu of that, you can check old cesium emergency exit lights, your glow in the dark night sites, and other sources of low level radiation. If it works at all, the most it could need is calibration.
Calibration can be done cheaper than most realize, and for a static item, doesn't need the same frequency as these devices that are used every day.
As a semi-final note on this particular subject, I understand the military has recently upgraded most of these devices. I made a few calls, but can't check until this weekend, but I believe the market will be flush with them.
If you can afford to buy new, that is your best option. The only problem is it's a captive market. There are not many manufactures of this item out there.
Put simply, internal dose and external dose come together to mean total effective dose. (industry calls it total effective dose equivalent or TEDE)
You cannot forget to count any internal dose that you receive.
Having said that, you need to know where to begin.
American nuclear society
ANS : Public Information : Resources : Radiation Dose Chart
If you run through the checklist, it will tell you how much you likely receive per year from all sources. You need this information as a baseline for setting up any program for dose absorbed monitoring.
Internal dose is considerably more difficult to measure than absorbed dose from external sources.
To make it short, for the none HP without access to reams of cash, the best way is through bio-essay. That means exactly what it implies. If you've ever taken a drug test, it's no different. Your bodies effluence will be the best measurement of internal dose for you to base dose received on.
That is the primary purpose of the gamma detector from the previous post.
It has other purposes, but the energy range of that particular model will cover the majority of potential internal contaminates.
Basically you urinate in a cup, and scan it with the detector.
The scale on the base unit should be in Rem, not DPM or CPM. Your not looking specifically for dpm, your looking for how much dose is received.
It should also be noted again that this is a rough estimate. If the test is positive after an excursion into a suspected contaminated area the exact level of it, and exact dpm should be counted. This should be done again in 24 hours, then 72 hours, then 2 weeks. This should be compared against the half lifes of known material to get an idea of what it is you have taken in.
It's not exact, it's not the best option, but again, unless you've got reams of cash, it's the only option I am aware of.
These two in particular should be watched for:
iodine concentrates in the thyroid
radium and strontium are bone seekers
The iodine part can be mitigated by iodine pills just prior to, or during the event. The radium and strontium are another animal. They are going to affect your marrow and bone.
Between them is the secondary purpose of the same monitor. Direct readings over the area of interest. Thyroid, spinal cord, etc. It's not going to be accurate, but it will give you an idea of what is being affected, and once you know that, most natural medicine has reams of data on what it takes to clear that particular body part/organ.
Document, document, document, you must keep accurate and concise records for this to do you any good.
Now as far as external dose, a simple film badge will do the job.
That does not mean a TLD or thermo-luminescent dosimeter.
The tld basically uses the interaction of ionizing radiation (gamma x-ray and sometimes beta) with a crystal to record absorbed dose.
Problem is it requires heating/burning that crystal at a specific temperature and in a specific condition to get the reading out of it.
This machine is an example of what is used to do that:
Harshaw 3500 Manual TLD Reader
For gamma only, a film badge will work. A film badge is simple. It contains a small strip of x ray film. The level of through transmission of light determines the does received. The higher the dose received, the darker the film gets when developed. It must be remembered that special care has to be taken for development of it. Exact temperatures of the developer and fix chemicals as well as exact timing and processing is required for this to be of any value.
You also have to have a baseline to judge it against.
Every x ray film has a specific R factor (or amount of radiation required to achieve a specific darkening of the film)
It's late and I have to be up in 5 hours, so I'll leave it at that until the morning. I'll pick up on how to get the standard and how to process it tomorrow. This is very important. Knowing or at least having an idea of how much dose you've received is key to what you can and cannot do in a survival situation. The results of these readings will determine your course of action in a radiological event.
More tomorrow. For now, some standard terms and definitions
CDC Radiation Emergencies | Glossary of Radiological Terms
Film badge:
Every x-ray/radiography film, medical or industrial has what is known as a sensometric curve AKA H&D curves/Hurter Driffield curve etc.
Those of you who have performed radiography or higher end photography already know what that is.
Put simply, it's a measure of the quanity of light that passes through to the other side as judged against a known standard.
If side A of the film reads 50 foot candles, and side B of the film reads 23 foot candles then you have a loss of 17 foot candles as compared a known standard. (every film will have a base loss. On a densitometer, it's typically .03) simplified further, it's a measure of loss of light. The darker the tint is on your sunglasses, the less light gets through.
The math is: Density = Log (Io/It)
Io = the amount of light on one side of the film
It = the amount of light transmitted through the film from the Io side.
So if only one percent of the initial light made it through to the other side, it would be a density value of 2.
Thats a brief look into something you really don't need to know unless your a photographer or a radiographer etc.
What you do need to know is this:
The more energy received by that peice of film, either in ionizing radiation, or visible light, the darker that film is going to be.
If you receive nothing, then it will be clear when developed.
Now a bit more about the film badge how you can do it at home.
Most of you have seen photographic film at the store. You still can if you haven't noticed though it is getting rarer.
They come in various speeds, with the lower number = the slower speed film. I.E. Kodak 200. This is in contrast with a faster speed film I.E. Kodak 400 or 600.
The slower speed film for film badges and x ray film have a silver halide emulsion on them. When exposed to a source of energy (radiation) they undergo a chemical change. This is done when two sources of energy (photons/electrons) hit the silver halide crystal, but when they do, it turns that into a stable silver metal crystal. The varying degrees of this exposure determine the relative darkness of the image.
The unexposed silver halide crystals are reduced and effectively taken out, while other areas contain a mix of reduced and exposed areas.
This is how black and white and x-ray film creates the images that they do. However; this is why it can also be used to measure the amount of radiation you absorb.
By having fast speed of emulsion on one side of the film, and a slow speed of emulsion on the other, it can measure low and high quanitys of absorbed dose.
If it receives little dose, the slow side silver halides will nearly all wash away, while the fast side will darken.
If it receives a high does, both sides will darken.
The end result is, x amount of radiation will darken that film to a specific density.
Now if you have reams of cash to throw around, you can just buy a TLD burner, or in the case of a film badge, a reader to do it for you, but if your on a budget (and most are) you can simply buy or make a comparator strip.
I'll first describe the comparator strip and how to make one to clarify it.
Simply put, two pieces of the film your going to use as a film badge is exposed to a known source and strength of radiation. Most NDE / NDT labs will do this for roughly 75 to 100 bucks for you. You need to have a slow speed film and a fast speed film back to back.
To do this, you must have two chunks of steel, (if making your own film badge) one that is 1/2" thick, and the other that is 1" thick. Very often the NDE lab will have that laying around, especially if it's a well established one that has been around a while. The film to be exposed is layed out in thirds. one area free of steel, one area with the 1/2" steel over it, and the third with the 1" steel over it. (in contact)
It is exposed by the radiographer for a predetermined time based on delivering 2500 millirem to the uncovered area.
For the iridium 192 source (What I suggest is used) the 1/2" of steel will be a single half value layer. The 1" peice will provide 2 half value layers.
When the film is exposed, That means for the single HVL the dose under that steel will be 1250millirem and the area under the 2hvl will be 625mr. You can do it in more steps to be more accurate, but if you know the R factor (amount of dose required for a specific density) then between the slow and the fast speed films you just had exposed, you have a base line of a range of doses. This is because you can back calculate the differences between the slow and the fast speed film.
If you have an HD on the fast film of 4, then the slow speed will be around 2. By the time your calculations are done (which I will provide tomorrow for AGFA D3 vs D7 film) you have a close approximation of how much dose will be received at varying energy levels. (D3 takes approximately 5.6Rem for a 2.0HD and D7 takes 1.2Rem for a 2.0HD)
That difference between 2R and 5.6R can be used to back calc higher and lower doses without spending a ream of money on 20 plus exposures at the NDE lab to get a full set the hard way. They can be loaded in one film cassette and shot as one shot. Your going to need two shots of the same thing if you intend to do it at home after the fact.
Once you have your baseline shot developed you need to store it in a low humidity 68F environment sealed.
After that your only going to get it out (via cotton glove liners) for comparison against any film your home badge uses.
This is where the second piece comes in. Whatever your developing techniques are (there are reams of how to's on the net for film development, I'll leave it up to you unless you ask for specific instructions), your going to need to be able to reproduce that method. Once you have developed your second set of film, then it must be compared against the control set. At this time, the second set has become the standard for your specific film developing technique as judged against the professionally ran film.
If you have a good digital camera, you can play with it and get an image of the film that you can print and post on the wall of your BOL with a chart displaying what each image density equals for absorbed dose.
The chemicals, the film, the shots, all should be doable for less than 400 bucks and some elbow grease.
It won't be scientifically accurate, but will be close enough for you to have a pretty good approximation of your does received without spending 35 grand, and still getting you in the ballpark of the living.
If you are unclear on any of this, please post a question, this is the first method of measuring your external gamma received, it's also the most important to get down right in my opinion.
Pocket ion chambers or pocket dosimeters:
These are your simplest forms of recording dose.
They come in several ranges, but put simply, they consist of a pocket ion chamber. They are typically a tube about 1/2" diameter, and about 4" long.
They are only good for gamma, and have a finite limit to the amount they can record.
If you go this route rather than the film badge, here is what you will need.
You will need a charger;
Pocket ion chamber.
When you charge it, your not really charging it, it's more like your discharging it. The ion chamber picks up the gamma dose and through excitation of individual atoms within the chamber, a weak electrical current is produced.
build up of this current causes a needle to move across a calibrated scale which in turn denotes your dose received.
If you go this route, ideally you need more than one. If the device receives an unexpected impact, it can go off scale or otherwise stop working properly.
You can forgo the film badge if you record your dose from this device frequently, as well as charge it frequently.
It can also give you an estimate of R/hr. If for instance you receive 10millirem in 1 hour thats a 10mr/hr field. If you receive that same 10 in 1 minute, mulitiply it by 60 which tells you that you are in a 600mr/hr field.
It's not the most accurate method, but it's the cheapest method to at least have an idea. It will not pick up alpha or beta either.
Over all, and armed with the previous information, a plan can be put together for any radiological event.
Time, Distance, Shielding must be remembered.
If you don't have any life threatening reason to be there, don't.
If you must, keep as much distance and sheilding inbetween you and the source of radiation as possible.
Internal contamination is a distinct issue for any terrorist related threat.
It's unlikely they will have access to super power weapons of mass destruction. However; it is very likely they will have low level items like Co60 to seed a normal chemical explosive with for a dirty bomb.
Personally, I don't plan for a direct nuclear bomb hit. Thats about like planning for getting shot in the head, it really doesn't matter, your screwed regardless. As for anything other than a direct bomb hit, If I can't get out with at least 60 minutes advanced warning, I am not going to bother trying.
At that time you need to have already had your plan in place.
Panic will get you killed far faster than a nuclear threat.
With proper planning and preparation, anything short of an outright 1 megaton bomb direct hit can be survived.
With the information provided, a plan specific to your needs can be put together.
Sohrabi M. World high level natural radiation and/or radon prone areas with special regards to dwellings. In: Proceeding of the 4th International Conference on High Levels of Natural Radiation (ICHLNR), Beijing, China, 1996 (Wei L, Suahara T and Tao Z Ed), pp. 3-7, 1997
Natural Radiation: High Background Radiation Areas (HBRAs) of Ramsar, Iran
