Letter Re: Too Good to Be True? Nationally Advertised Radiation Detector for $60?

Hi James,
Just wondering if you have a recommendation for or warning against this surplus (but “brand new condition”) CDV-720 portable radiation detector from the Sportsman’s Guide Catalog: http://www.sportsmansguide.com/cb/cb.asp?a=256259
It looks snazzy, but I thought (with the exception of the Kearny Fallout Meter) that viable radiation detectors ran in the hundreds of dollars…? – David in Pleasanton, California (One of your $100 contributors)

JWR Replies:  A CDV 720 is a Civil Defense surplus survey meter. If it is truly working, then at $60 it is a bargain. I recommend that you go ahead and order one. When it arrives, immediately inspect it inside and out. (Corrosion caused by battery acid is one of the worst culprits.) Then test it. Some of the better detectors come with their own small built-in radioactive test source. If you don’t have a test source, then you might get a reading from a tritium firearm sight, or a beta light. If the unit doesn’t work, then return it immediately for a refund or replacement. You may have to sequentially order two or three in before you get one that works well. If the company guarantees the meter to work, then take full advantage of their return policy until you have a one that works. Your only extra expense will be the cost of return shipping. Who knows? You might get one that works the first time.

First, to explain some basics:

Geiger counters measure point sources of radiation, such as grains or flakes of radioactive fallout.

Dosimeters measure your cumulative radiation dose.

Rate meters (also known as survey meters) measure the rate at which you are receiving radiation at any given time.

To have a fully equipped shelter, you would need all three.  (But if you have plenty of supplies, you can probably get by with just a dosimeter and ratemeter.) 

To explain the $60 price: Civil Defense organizations bought rate meters in huge numbers back in the late 1950s and early 1960s. Uncle Sugar’s original cost was probably around $120 each (in 1960 dollars!) Most of them just sat around in warehouses for decades. Those are now hitting the surplus market. For a good general background on dosimeters and and rate meters, see this FAQ: http://www.radmeters4u.com/ as well as Bruce Beach’s excellent article:  http://www.ki4u.com/nuclearsurvival/survival/detectors/index.htm  True Geiger counters are a much more sophisticated device, designed for finding point sources of radiation. Because they were much more expensive initially, and made in much smaller number, these do cost hundreds or even thousands of dollars, unless you get lucky. In general, if a meter has a separate hand-held probe (typically a nickel-plated rod), then it is classified as a Geiger counter.  (Although their quality/sensitivity varies a bit.) Unlike dosimeters and and rate meters, Geiger counters are what is needed for decontamination of someone that is entering a fallout shelter that is possibly contaminated. (So you can identify and brush/hose off bits of radiating fallout.) However, for those with a well-stocked home fallout shelter, where you plan to “button up” for the duration of a radiological event, rate meters (also known as survey meters) will be your most important radiation monitoring tools. You will also need a pen-type dosimeter to measure your accumulated dose while sheltered. Together, they will be how you determine when it is safe to exit your shelter. (Initially for just short periods of work, and then when the radiation level has fallen considerably for all but sleeping hours, and eventually when the radiation has dropped to near background level, you can quit shetlering altogether.)

In closing, I strongly recommend that you get a copy of Cresson Kearny’s book, Nuclear War Survival Skills. It is available from the Oregon Institute of Science and Medicine.