Radiation
Basics:
Manufactures
or resellers of radiation detectors often have some
information about radiation. Another good place to read up on
the
subject is on Wikipedia (Link Below).
However, I will provide a
quick background here.
Ionizing radiation
is what we
are talking about when we say that something is
"Radioactive".
Ionizing radiation gets its name from the fact that it can knock
sub-atomic particles out of an atom, thus altering or
destroying that atom. This is what makes ionizing
radiation so dangerous.
RF radiation,
such as from
mobile phones, commercial antennas, microwave ovens, and wireless data
links does not destroy atoms. (although it can raise
their
energy levels temporarily). Your mobile phone,
wireless
PDA, or microwave oven
is not radioactive, nor can it make you, or
anything else radioactive.
The detectors and meters that are the topic of this guide detect the
more dangerous ionizing
radiation only.
OK, so now that we have RF radiation and ionizing radiation separate in
our minds, lets talk about 3 important types (sources) of ionizing
radiation.
- Alpha Particles -
Alpha
particles are the cores (nucleus)
of helium atoms (helium
balloons contain complete helium atoms, and are not
radioactive). Alpha particles are
easily stopped as soon as they hit anything (molecules of air, or a
sheet of paper). Even though they are easily stopped, they
can
damage
the atoms of what ever they strike. If you swallow a source
of
Alpha particles, they will be stopped by your insides, and damage will
occur. We really do not want to eat anything that is emitting
Alpha particles.
- Beta Particles -
Beta
particles are also pieces of atoms flying
along without the rest of the atom. In this case, it is an
electron and it is traveling free (not down a wire, for
example).
It takes a little more to
stop a beta particle, but thin metal - even tinfoil will stop most of
them. Again, if you swallow a Beta source - what stops them
(and
what is damaged) is going to be your insides.
- Gamma Radiation -
Gamma
rays are made of the same
particles as non-ionizing radiation, but at much, much higher
energies. Gamma Rays, Cosmic Rays, and X-Rays are all
basically
the same thing. The only difference in the terminology stems
from
how the particles are made:
- Cosmic
Rays are natural, and come from space. Stars (including
our own Sun), Black Holes, etc. all make Cosmic
Rays. We
live in a constant drizzle of natural Cosmic Rays.
- Gamma
Rays come from the decay of radioactive elements here on
Earth. This can be natural, or from
man-made nuclear reactions.
- X-Rays
are created by man-made devices, such as medical
equipment, or basically anything in which electrons strike
metal.
(Such as picture tubes).
Gamma Rays are very hard
to stop, and a Gamma source even quite distant from the body can be
very
dangerous.
There are other particles not listed above, but Alpha, Beta, and Gamma
are the 3 most common forms of ionizing radiation.
Detecting
Radiation:
If any of the ionizing particles mentioned above pass through a tube of
a
certain
(harmless) gas that has an electrical charge, a detectable electrical
pulse will be generated. This is
called a Gieger-Muller tube, after its inventors. In the rest
of
this article, I will refer to it as a GM tube.
The
electrical pulses generated by the GM tube are counted by either
analog or digital circuitry. If the counts are fed into a
simple computer chip, they can be averaged
over time and converted into different measurement
units. The device can also trigger alarms to warn of
dangerous
levels. The
combination of a Gieger-Muller tube and counting circuitry is where
we get the term Gieger
Counter.
The term Geiger Counter has become
somewhat outdated, but all of the devices that are the subject of
this article contain GM tubes. This article does not cover
scintillation devices or any kind of dosimeter without a GM
tube.
For more details on the difference between GM counters and other
types of dosimeters, see the Link Below.
Do
Radiation
Meters give off
Radiation? Am I Going to Get Cancer from Having one of These
Devices Around?
No.
These devices detect radiation, they do not cause it. Thinking
you are going to get radiation from something that detects radiation is
like thinking you are going to get fat from standing on a scale.
Even surplus radiation meters were likely
never
used in a radioactive
environment, and even if they were, the odds that they "picked up" any
significant amount of radiation is extremely unlikely. If
they
did, they would not be available for sale. Some very old
civil
defense or survey meters do have a very
weak
radioactive test sample attached to
them. I
definitely would not recommend
eating this sample, or placing it under your pillow, but short of
literally
doing something like that, the test source is harmless. Most
meters do not have any such test source and emit no ionizing
radiation. GM tubes do operate at
high voltage, and thus these devices may create a very small electrical
field around them. This field is
much weaker than emissions from many other common devices such
as TV's, computers, microwave ovens, mobile
phones, etc. In this sense, using a radiation meter is
comparable
to using a pocket calculator, or using a PDA that does not have
wireless
capability.
Features
to Look for:
As
I
mentioned, radiation detectors simply generate an electrical pulse
when an ionizing particle passes through the detector tube. Some simply
flash a light and make a click for each pulse. Others pass the pulse
to rather sophisticated computing circuits and digital displays.
Extra features are always nice,
but a
simple flash is fully
sufficient to indicate the presence of radioactivity. My
DRSB-88
has
only a light and clicker, but if I place it near something, and it
starts to flash frequently, I know that object is dangerous.
In
this
case, displaying a radiation level on a meter or digital display is
meaningless in a way, since I would get a totally different number by
moving the detector a few inches closer or farther way. Once you get
used
to how often your detector clicks when detecting normal background
radiation, you will notice any significant change. For
example, if you are if you are considering buying a house, take your
detector with you. Even without a display, you will be able to
notice if the detector flashes more or less often than it does at
your present home. With the help
of a watch, events per
minute can be counted even on units with no display or meter. By
factoring in some other known quantities, counts
per minute (CPM) can then be converted to other units.
Basically, this
is what the units with digital readouts do, and having them do it
automatically is a very nice feature, but you pay for it.
In addition to the flash and click, some of the
low end units have another light and possibly a buzzer that warns of
levels above a preset warning level. While this alarm feature may
make you feel more comfortable, the limits are often not
adjustable.
A
very important
feature is
some sort of window or removable cover over the actual detector.
As I
mentioned, alpha particles are stopped by almost anything. If
the detector is inside a metal or plastic device, it is not going to
detect alpha particles. To solve this problem, better units have a
removable cover or window that when opened, exposes the GM detector.
When
transporting the device, or specifically to filter alpha particles,
the cover is closed or replaced. Obviously, a window is better than a
simple cover,
since covers are likely to be lost. If the cover is lost, the
detector becomes very susceptible to damage. Some detectors
claim
to be
able to indicate the
direction to the source of radiation. It would take thick concrete or
lead shields to block
gamma rays coming from different directions, so unless you need a
crane to lift the device, it cannot provide any meaningful
directional information about a gamma source. Other sources are usually
not detected unless you are fairly close to them anyway, so by taking a
few steps in different directions, any detector or meter will help you
locate the radioactive object.
Claims
of some special ability to indicate direction would make me suspicious
of all
claims made by that manufacture or vendor.
Almost all
personal radiation meters are powered by batteries.
I prefer radiation meters that use common types of batteries. In an
emergency, it may be difficult to get specialized
batteries. I would avoid rechargeable batteries.
Rechargeable batteries loose their charge over time,
and it is possible that the power will be out, or that you will not
have time to charge them in an emergency. Modern, name-brand
alkaline batteries have a very good shelf life, and are better than
they used to be about leaking. If stored in, (or better yet
-- in
a bag next to) your radiation meter, you can count on them working even
after a number of years.
Sensitivity and
Accuracy:
Accuracy, per sey, is not an issue for devices that have only a light
and a
clicker. Units that
count dose, (i.e. ones that have a digital display), must contain a
timer. With modern crystal controlled
timing, even very inexpensive units are sufficiently
accurate.
On
the other hand, the size of the GM tube
its self is an important factor for some applications.
The
GM tube in pocket or keychain detectors is usually very
small. Because of
this, fewer ionizing particles are going to pass through it than would
pass
though a larger tube. Think of the particles as drops of rain
--
a bigger bucket is going to catch more rain than a small one.
This does not mean that small units (that have a display) are not going
to give the correct reading. When converting counts to RADs
or
Sieverts, the counter should factor in the detector size.
Again,
with modern
electronics, even the inexpensive ones can do this calculation
correctly. Consider the following example: If I
were to go
someplace where the ambient radiation level is 10 times what it was
elsewhere, both a unit with a large detector, and a unit with a small
detector should indicate 10 times higher counts per unit time than they
did before. Also, if I am testing a particular
object for radioactivity, I will likely be placing the detector very
close to, or directly on the object in question. Even the cheapest
detectors make it very obvious when they are in close proximity to
something even mildly radio active. The difference in
detector
size becomes important when scanning a room for a suspected
radioactive object.
A
unit with
a small GM tube may have to be very close to the object before you
notice it react.
Construction
and Circuit Design:
Consumers in western countries have basically 3 choices.
The first is buying expensive laboratory grade devices. The second is
buying surplus civil defense meters. The third option is
purchasing devices made for retail sale
in Eastern Europe via an on-line retailer or auction house.
If
you are in a position to afford lab
equipment, and you can find one that is compact, battery powered, and
easy to use, then that is your best option.
Antique civil defense units are
best
purchased for their nostalgic value primarily, and utility second.
Even if a surplus meter has been recently calibrated,
the components may be so old that the calibration may be invalid a weak
after it is done. If you walk into your local
grocery
store with a big yellow civil defense meter, it is very likely that you
will get more attention than you really want. The last option
is
best
for most people who want a reasonably sized, and consumer-friendly
device. For most of us, this means purchasing them from eBay,
or
some on-line reseller. It is very unlikely that it will be
possible for the consumer to see or try the devices prior to
purchase. This guide does not cover the intricacies
or
potential dangers of buying on eBay or buying from unknown on-line
retailers. I
will caution, however, that expensive electronic devices are favorites
for those committing fraud on on-line auction sites. Learn to
be
a savvy eBay'er or on-line shopper.
That said, there are a wide variety of personal radiation detectors
available from Russian and Eastern European
companies. It
is important to understand that these companies are not big,
established consumer electronics manufactures line Apple or
Sony.
Do not expect the
industrial design or
construction to be like that of an iPod or Playstation Portable
.
In many cases the build quality is more like hobby projects I made
in highschool. The simple units with black or white cases and
nearly
square corners are the worst in this respect. They are made
of a
brittle substance that either is Bakelite, or some plastic that is very
similar to it. Expect battery doors, catches, clips
and
covers to break easily, or simply fall off after some use.
Units
that look like a more modern design are usually more up to expectations
for consumer
electronics.
The
story is similar for the insides of these devices too.
The
circuitry in some of the sub- $20 units is reminiscent of a 1970's
transistor radio. This isn't necessarily a problem,
however.
Many
1970's transistor radios still work. Also, some Russian circuits
designs may
appear strange by western standards, but they function well.
Even
the
cheapest units that I have personally reviewed seem to get very good
battery life. Although these units do not use the latest
construction techniques, they also seem to be at least relatively
durable. In my review of the DRSB-88, I mention that I accidentally
dropped it onto a tile floor twice, and it is still working. It is
very important that these units never be disassembled. Due to the afore
mentioned construction techniques it is very likely that if you take
one apart, you will never get it back together and working.
Additionally, the GM tubes run
at a very high voltage. Even a keychain device that runs on a couple
watch batteries has hundreds or thousands of volts inside. If opened,
they can cause a serious electric shock even if they are switched off
and/or the batteries are removed. The more
elaborate devices with LCD displays contain logic and microprocessor
chips made by the established chip companies. The use of digital
technology
insures that these meters will not "drift" or need
recalibration. Speaking of calibration, some units come with
a
certification from one or more countries. These certificates
have
no legal backing outside the country of issue, and there is no
guarantee that a certain vendor is even providing an authentic
certificate. However, If you can find the
manufacturer's
website (not
just the retailer's), and they mention the certificate, then at least
you know that the particular unit has been approved as genuine and
accurate by the respective governments.
Cost:
Let the buyer beware: Some Radiation Detectors are being sold
for
outrageous prices on eBay and specialty sites. On the street
in
places
like Russia and Ukraine simple detectors are sold for a few
dollars. From my research, the prices on eBay or websites
reselling to the US and Western Europe are about twice what
the
devices sell for on the street in Russia, Ukraine, etc. Given
the
effort these resellers go through to market the devices in English,
translate specifications and instructions, and deal with international
funds transfers,
I feel
that this
markup is completely fair.
Beware however, of prices much higher than this. I have seen
keychain detectors selling for $149.99 on
eBay! An educated guess (backed by a review below
that
mentions them
selling
in the
US for $8) is that they sell for $5 to $15 dollars
in retail stores in Moscow or Kiev. Thus, an auction starting
price of $29.99 is in my opinion fair (I could not find anyplace to buy
them for $8), but I would attempt to avoid higher
"Buy It Now" prices, and the $129 to $149 prices are, in my opinion,
not good deals.
A
good rule of
thumb is that no radiation
detector without a digital display is worth more than $50.
Obviously, there are exceptions to this rule. A rare classic
Civil
Defense or lab meter in premium condition could have significant value
as a collectors
item. Also, make allowances for other things included with
the
meter,
such as batteries, chargers, additional books or videos, etc.
Good
quality, modern, digital counters with programmable alarms and other
features are available in Eastern European countries and Russia for
under $80. Again, you will pay for the service of
someone
distributing them, so allow for that, but if you pay over $200 for one,
it had better be a calibrated piece of lab equipment.
Lastly, note that many sellers in Russia or Eastern Europe use third
party "money handlers" to handle auction payments. The seller
will instruct you to send payment (PayPal, Credit Card, Money Order,
etc.) to a third party in the US. The third party will
acknowledge
payment to the seller, and the seller will then ship the
product.
The third party will then transfer payment to the seller (less a
profit, of course). This should set off every warning bell in
your head about buying on-line or on eBay. I do not recommend
these types of transactions for first time eBayer's. Check
out
these sellers and their payment partners before bidding. If
you
do not know how to check out the seller and the payment method
carefully, then get some help from someone who does, or simply avoid
the auction. It is beyond the scope of this document to teach
you
how to do these checks, or what to look for. I can say
however,
that while there is a lot of on-line fraud, and some of it is based in
Russia, there are also legitimate sellers and payment agents that do
transactions like this on a daily basis. Another thing that I
think is kinda cool about these gadgets is simply looking at the
postmarks on the package when it finally arrives. Most of us
do
not receive mail from Russia or Ukraine on a regular basis.
In Closing, I want to make something clear. I am
NOT
against nuclear power. In my opinion, spent nuclear fuel in a
fuel rod is easier to control (or recycle)
than the products of burned coal or tar in the atmosphere. Obviously,
neither coal, oil
or nuclear fission power is the ideal solution. I have been following
the efforts over at the National Ignition Facility (
Link
Below).
Anybody from there want to to see a copy of my resume?
Please post on the forums if you can provide a review or a
link to a review of
any such device. I particularly need reviews of the
"DRSB-90",
and the "MASTER-1". Please Post comments, questions,
reviews, or stories of radioactive
things you have found to the
Linuxslate
Forums
Links:
General Info about Radiation
US
Radon Gas Map
Wikipedia
Entry on Natural Nuclear Reactors
Wikipedia
Entry on Ionizing Radiation
What's the Difference
Between
Survey Meters, Geiger Counters and Dosimeters?
Radioactive
Products and Other Sources Of Radiation
National Ignition
Facility
(Lawrence Livermore National Labs)
Reviews of
Specific Personal Radiation
Detection Devices:
New:
Linuxslate.com
review of the
IdealRatio Rodnik 3 Portable Radiation Detector
Linuxslate.com
review of the
DRSB-88
Linuxslate.com review of the
Ecotest
МКS-05 "Terra-P"
Review
of a keychain detector at rockhounds.com
Dr.
Covington's WeBLOG (Review of the DRSB-01)
Steven
Young's Review of the DRSB-01 (Another excellent
review of
the DRSB-01 - With a cool video.)
Disclaimer:
THIS DOCUMENT IS
PROVIDED BY THE AUTHOR "AS IS". IN
NO EVENT
SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES, INJURY, OR ILLNESS
ARISING IN ANY WAY OUT OF THE USE
OF THIS DOCUMENT, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE,
INJURY, OR ILLNESS.
IF YOU HAVE SOMETHING THAT YOU THINK IS RADIOACTIVE, OR OTHERWISE
HAZARDOUS, OR IF YOU SUSPECT OTHERS OF HAVING SUCH, CONTACT YOUR LOCAL
POLICE. THIS GUIDE IS A TECHNICAL DESCRIPTION OF CONSUMER
ELECTRONIC
DEVICES ONLY, IT DOES NOT, NOR DOES IT PURPORT TO GIVE MEDICAL OR ANY
FORM OF HEALTH ADVICE. IF YOU SUSPECT THAT YOU HAVE BEEN
EXPOSED
TO A
HAZARDOUS SUBSTANCE, OR ARE HAVING HEALTH PROBLEMS, CONTACT A PHYSICIAN
OR YOUR LOCAL EMERGENCY SERVICES. |
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the property of the companies
that own them.