SpudFiles

http://tinyurl.com/4btf737

3 Mile Island inspired the invention.

Teledyne was our overseas sales rep.

No one else besides NIH were interested.

Were we 30 years ahead of the need?

I have a feeling you are going to get nuked for this post... lol

If I understand what you're meaning, it's just a geiger counter with an integrated alarm.

Such a thing already exists. I saw it in a small video fragment yesterday evening.

(would be pretty cool if it was your design )

boyntonstu wrote:Were we 30 years ahead of the need?

Did the unit ever go into production? My friend holds a patent for a nuclear reactor granted about 30 years ago. It never made it to manufacturing but, it looks great framed and hanging on the wall .....along with all the canceled checks to the Patent office and Lawyers.

We made a bunch and sold them for $79.95.

It is NOT a Geiger counter.

It is a smoke alarm chip used upside down.

(I am always inventing upside down thingys.)

The Original name was Nuke-Alert.

Renamed to Radiation-Sentry

It runs on a 9V battery.

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So, it is a not-geiger counter with an integrated alarm?

If it gives an alarm signal, it still has to count the radiation

Labtecpower wrote:So, it is a not-geiger counter with an integrated alarm?

If it gives an alarm signal, it still has to count the radiation

It alarms at 2 MR/Hr.

Press the red button, time the seconds to alarm, view the graph on the back, radiation is measured.

Teledyne Isotopes tested and verified it.

There is no Geiger tube in it.

Without even looking at the patent I would guess it is an ion chamber, except the chamber isn't necessarily actual a closed volume. Just like radiation based home smoke detectors. In this case you don't need the Americium radiation source since you are trying to detect external radiation.

Ionizing radiation creates ions in air. With a sensitive amplifier (a couple of FETs will do) you can measure the radiation induced conductivity of air with using a digital voltmeter.

Geiger counters work a bit different. Ionization inside the GM tube gives a cascade of electrons since the tube has a ~800 V potential across it. A GM tube with associated electronics will detect a single photon of gamma, or a single particle of beta radiation (usually). In other words, GMs are much more sensitive than are ion chambers but ion chambers are simple to make.

2mRem/hr is a pretty significant dose rate. Not "too late now you are already dead" rate but a lot higher than most radiation health monitors would be set to trigger at.

jimmy101 wrote:Without even looking at the patent I would guess it is an ion chamber, except the chamber isn't necessarily actual a closed volume. Just like radiation based home smoke detectors. In this case you don't need the Americium radiation source since you are trying to detect external radiation.

Ionizing radiation creates ions in air. With a sensitive amplifier (a couple of FETs will do) you can measure the radiation induced conductivity of air with using a digital voltmeter.

Geiger counters work a bit different. Ionization inside the GM tube gives a cascade of electrons since the tube has a ~800 V potential across it. A GM tube with associated electronics will detect a single photon of gamma, or a single particle of beta radiation (usually). In other words, GMs are much more sensitive than are ion chambers but ion chambers are simple to make.

2mRem/hr is a pretty significant dose rate. Not "too late now you are already dead" rate but a lot higher than most radiation health monitors would be set to trigger at.

You understanding is correct.

We used a cake tin as the ionization chamber.

As the air becomes ionized a tiny current travels to an insulated center plate centered in the can.

A smoke detector uses a radioactive material to create a constant minuscule current. Smoke particles stop the current and the detector senses the loss of current and it sounds the beeper.

We took advantage of the well designed, inexpensive chip.

We had to hand screen transistors to find low leakage (Picoamps).


It is good to speak with knowledgeable people.

Have you ever sold any units?

In any case, I highly doubt this would have done much good for Japan. A tiny device that alarms at or above a certain radiation level won't stop an earthquake and tsunami from damaging reactors.

I don't think it'd be suitable for such a slow leaking reactor such as the situation in Japan, authorities had ample time to issue warnings and any necessary evacuations.

It'd probably be better for a catastrophic reactor failure in which all safety systems and alarms in the plant are rendered useless and you're located a fair distance away where failure of the plant wouldn't be immediately noticeable but there are winds that could carry radiation to your location in a short period of time. Nuclear war would be the only other situation I could think of where it may be handy.

I've got a GM counter (CDV-700) and a "pancake" ion chamber survey meter (CDV-715), and several dosimeters (CDV-750) with their charger, all are cold war surplus. The manuals are interesting.

The GM counter measures background radiation without any problem, so any radiation (most sensitive to gamma, OK sensitivity for beta, useless for alpha) above background is easy to detect.

The ion chamber detector is more along the lines of "too late now you are already dead" level of sensitivity.

Couple sources that are fairly easy to find (the GM counter has a built in test source of unknown, at least to me, composition):
1. Coleman Lantern mantles (surprisingly hot due to the use of thorium)
2. Pottery and marbles tinted with Uranium Oxide ("Depression glass" and "vaseline glass")
3. The Americium-241 source (~1uCurrie) from an ionization smoke detector (extremely illegal to disassemble that kind of smoke detector )
4. Salt Substitute (KCl, from the grocery store) is just barely active above background.

Looking at Ebay postings, the price of this setup has gone up as much as 10X since I bought it a couple years ago. I suspect most of that run-up has been in the last couple weeks.