There are plenty of things you can buy quite
legally that will get your Geiger counters ticking. Perhaps the most common
radioactive item, found in most homes, is the humble smoke alarm. Most models
use a device called an ionisation chamber to detect smoke particles. Inside
the chamber there is a small amount of an artificially produced radioactive
isotope called Americium 241 (Am-241). The tiny radioactive pellet emits
alpha and low energy gamma rays, which are mostly absorbed by the detector module's metal
casing. However, very small amounts of radioactivity can escape and may be detected using instruments with highly sensitive ‘Pancake’ and scintillation type probes. Unfortunately these tend to be quite expensive and the probes are often delicate and easily damaged.
Another household product, available from most supermarkets, which emits very low-level
radioactivity is ‘Lo Salt’, the low sodium alternative to common table salt.
Again, there are measurable emissions from the Potassium
Chloride it contains, that can be picked up by some of our more advanced instruments. Brazil nuts and cat litter are other well-known low-level sources, and step outside your home into the street and there’s a fair
chance that the kerbstones and road surface are gently radiating. This is due to the presence of granite, which can be
surprisingly 'hot' due to it containing trace amounts of naturally ocurring unranium minerals.
In some parts of the UK (notably Cornwall, Devon and
parts of Scotland), where the bedrock contains substantial quantities of granite you can find quite 'lively' radioactive rocks
lying around on the ground, on beaches and around the
spoil tips of abandoned tin and uranium mines. If you don’t fancy prospecting
yourself – and it’s really not a good idea to mess about in old mines -- radioactive
minerals are readily available from dealers and good old ebay. Small
chunks of Uranium ore and samples of Autunite, Betafite Uranitite, to name just a few, sell for a few pounds. Provided the pieces are not too large and
the radioactive emissions are below a set threshold they are legal to sell, buy
and own. However, they can crumble and produce dust so it is wise to store them
inside metal containers, well away from children and food preparation areas.
If you have any old clocks, watches compasses or aircraft instruments
with glow in the dark luminous hands or dials, and they were made prior to the mid 1950s, then
there is a very fair chance they will contain radium paint. This can
produce a quite dramatic response, even from our most basic detectors.
Radium emits beta and some gamma particles and these can make excellent check sources. However, great care should be taken in the handling of these items, and never attempt to dismantle anything. Clocks and watches with boken or cracked glasses should also be given a very wide berth. That's because old radium paint can peel off or become flaky and liable to produce
a fine dust. This can become airborne or get on to your hands or clothes and could represent a health hazard
if inhaled or ingested. Indeed some of the workers involved in the manufacture of these articles suffered terrible ilnesses and death due to prolonged exposure and the practice of licking their brushes to obtain the fine point needed to paint small, intricate items. Old aircraft instruments can be very radioactive, and a fair amount of vintage military equipment contained radioactive materials and components. Quite often they were not clearly labelled (or the labels fell off), so it is wise to keep a geiger counter handy if you tinker with old militaty surplus equipment.
Gas mantles, doped with radioactive Thorium (to increase
luminosity) are no longer made in the UK but they are still being manufactured
in other parts of the world, such as China and South America and they can be purchased from hardware shops and
camping stores. The amount of radioactivity varies but some of the mantles we’ve tested
have been highly reactive and capable of producing a quite dramatic response on all
of our instruments. Again they should be handled with care – preferably left in
their protective wrapping and stored in metal containers -- as they are made of cotton and liable to shed fine
fibres or dust.
Radioactive gas mantles are now effectively illegal so you wont find them in your local DIY megastore or camping shop anymore. They sometimes turn up in long established local hardware stores that have have some old stock in
their storerooms, Sadly these venerable establishments are rapidly disappearing from out high streets but vintage gas mantles, usually still in their
original boxes, occasionally turn up in antique shops and at car boot sales. When installed and burnt the mantles produce a very fine dusty residue and if touched they crumble into tiny particles.In old victorian house there are often radioactive patches on walls and ceilings in areas where gas the lights used to be.
One of the most interesting sources of radioactive materials
is old glass and porcelain, usually made prior to 1950, which can contain
measurable amounts of uranium. The most famous examples are green-coloured
‘Vaseline’ glass. Well known makers include the British company Bagley, which
produced vast amounts of Vaseline glass items, which frequently turn up in
antique fairs and car boot sales. The uranium content is typically well below
2% and it is safe to handle, though like any glass article it breaks easily and
the real danger is from the sharp edges, rather than the radioactive content.
The amount of radioactivity, and hence the degree of response varies
enormously, from quite scary, to hardly anything.
Uranium is also a key ingredient in vividly coloured ‘Fiesta
ware’ pottery. This was popular in the 1930s and 40s and the really radioactive
stuff was mostly only sold in the US prior to WW II when the uranium content was reduced. Fiesta ware was produced in this country
but it tends to be mostly non-radioactive, though pieces do turn up from time