A little very basic radiation information for those who care and don't already know.
DOSIMETERS are one of the most usefull of radiation instruments. Radiation is undetectable by humans as it has no smell, feel or other indicator of it's presence. It causes cumulative damage to the body over time. The amount you receive in a period of time is known as DOSE. If you are exposed to a RATE of 10 rads for 2 hours you then receive a DOSE of 20 rads. To measure RATE one needs a RATE meter, such as a Geiger Counter or Survey Meter. More on those in another thread.
To measure your personal DOSE requires a DOSIMETER (dose meter). There are several types but the one of interest to us here is a "pen" or electrostatic type. They have been made since the forties and remain essentially the same today, still being manufactured. They can be purchased new for about $100 each or surplus for just a few dollars. They are very rugged and rarely fail. Most exhibit a little leakage but it is easily compensated for. Leakage is a manufacturing defect from what I have read. Those few with problems are easily identified and can either beused with the known fault or trashed. I leak test all of mine and mark the leak rate on the instrument for future reference and compensation. Those with high leak rate get tossed while th low leaakage ones are good to use.
The principle of these is simple. An electrostatic charge is impressed on the instrument until the indicator rests at zero. If radiation penetrates the unit, a small amount of that charge is lost in proportion to the amount of radiation. As charge is lost, the indicator moves up scale. Leakage, the most common fault, is when the indicator moves slowly up scale when no radiation is present (other than background). To test for leakage, charge each instrument to a zero reading and place them in a location where they will not be disturbed. Read them every 12 hours and record where the indicator is. After several 12 hour periods (or other convienent tiem) dust off the calcutator and figure the rate of change per 12 hours. Use felt tip marker and put the leak rate on each instrument. Just that simple!!! Example: After 36 hours, a reading of 12 rads is shown. Leak rate, therefore is 36/12=3 periods. 12/3=4 rads per period Mark as 4/12. In use, the leak rate is subtracted from the reading during exposure. Leak and exposure both need to be for same time period. A few refuse to charge, have "sticky" indicator, cloudy or internally dirty viewing window; these get tossed.
Dosimeters are available in several ranges. I have Civil Defense ones that are 0-200 RADS (Gold Clip, CD V-742), 0-20 RADS (Green Clip CD V-730 ) and 0-200 MILLIRADS (Black Clip CD V-138 ). The instruments are most accurate at 1/2 scale. If you accumulating a DOSE of 100 RADS in a day or two, the Shit has truly splattered all over the fan!! These 0-200 R are the range most commonly sold and the cheapest. By all means, get a few, test and mark them for leakage and put in your stash. The lower range ones are likely to be more useful in anything short of terrorist attack close by so try to get a few of those as well. Always carry the higher range AND lower range when exposure is possible so that if you exceed your low range one you can have some idea of by how much! There are nifty electronic dosimeters out there. They are more expensive, require batteries and are more complex, therefore, maybe, less reliable. The CD type should be your first purchase and ALWAYS kept around as a reliable back-up.
Chargers: Many variations exist. CD V-750 is the yellow box you often see for sale. They use 1 "D" cell and also provide illumination. They are a simple and reliable electronic circuit that dates to the early sixties. Light is provided by a one cell flash lite bulb. Most common problem is leaking batteries. DO NOT store with battery installed!! If you buy one that has a lot of corrosion, set aside for parts and buy another.
Lamp failure: Merely requires a new bulb.
"Noisy" pot. The adjusting pot can (and often does) get scratchy, just like old volume controls did. A small squirt of electronic control cleaner will often cure it.
Circuit failure: Set aside for parts. The transistor used hasn't been made for 30 years! Substitutions are possible if you are into electronic repair and have the time. This sort of failutre is actually very rare.
Self powered type PP1578A/PD as used by the Army. I recently obtained a number of these and all check good. Last Army "calibration" was 1984. No battery required, simple and rugged. Disadvantage is they do not provide illumination. A window or flashlight is required. Due to not needing a battery they are great for SHTF!! We all know how difficult it could get to obtain batteries if the balloon ever goes up!!
Use of the above goodies:
An excellent reference book is the FEMA Radiation Safety In Shelters circa 1983. They can also be purchased for around $15. which I STRONGLY suggest!! (Any idea how long the internet will operate after a SHTF event?)