Radiation detection

[x-ray]

Eric,

Drop me a PM if you need something precisely measured for radiation. I have access to some advanced radiation detection equipment.

The question you want to ask yourself is that are concerned with dose or contamination or both. Radiation exposure/dose is sort of like the heat and light from a camp fire whereas the contamination would be hot smoke, embers, etc that can get on your hands. A good meter for contamination (e.g. to check and see if you get speedometer radium dial dust on your hands) isn't the best tool to also measure how much radiation dose you get from the intact gauge at a few inches away from it.

An ion chamber is great for dose rate exposures and a thin-window Geiger is best for contamination.

If you want a simple yes/no meter to detrmine whether something is radioactive or not, the CDV-700 civil defence geiger counters are actually adequate for most circumstances. I think I have a few sitting around - I picked up Thousands from Albany, New York Civil defense in August 2001, After September The federal government contacted me and wanted them to give out to federal agencies - and I gave them to the feds for no charge 9/11 got us all scared of a nuke attack. will check and see if I kept one you can have. Will PM you if I find one.

 

[Carl_in_NH]

Chuck – I guess we just disagree about the relative rarity of the G-M type CDV-700 meters – I’ve seen many of them, and none of them all that costly. Cheaply made? Perhaps – but certainly functional pieces of equipment. You’re correct in that there are many more survey meters that were made relative to the decontamination meters – and you do need to know what you’re looking for so you can sort the wheat from chafe – but that’s the same whether you’re buying an MV or a radiation meter, you’ve got to do your homework before purchasing or you’ll end up with something that’s not as useful – or even useless - for your application. You just pointed out the same type of issue with obsolete batteries used in particular military meters – again, knowing what you’re looking for is critical. Finding a CDV-700 6B today is much easier than it was years ago sorting through all those you find at auctions and various other sales.

I didn’t intend to tick you off, but it appears I have. Sorry about that. I still contend, however, there’s nothing wrong with CDV-700 6B for this type of low-level detection.

As to the PDR27’s being plentiful and cheap, I’d really like to know where you’re purchasing them, because I didn’t run across them when I was looking for a G-M meter.

 

[stumps]

Eric,
Radiation exposure/dose is sort of like the heat and light from a camp fire whereas the contamination would be hot smoke, embers, etc that can get on your hands.

Sort of, but not really...

Gamma radiation is gamma radiation. It's the quantity that kills you, not the source.

The difference between a G-M tube survey meter, and a hand held ionization chamber survey meter is one of magnitude. I don't really want to get into the physics of the devices, but a good visualization aid would be to think of the difference between a one inch micrometer, and a yardstick.

The micrometer does a bang-up job of measuring the sizes of the drills in your number drill index, all the way down to the very smallest, but it has trouble measuring the auger that the phone guys use to bore holes in the ground for telephone poles.

The yardstick, on the other hand, is marked in 1/8 inch increments, and has no where near the fineness needed to catalog your number drills, but wow can it measure really big auger bits.

When the big one hits, both G-M and ionization chamber survey meters will each have their place: The G-M meters will help you keep the safe living quarters as clean and radiation free as possible... your long term health requires you to keep your 24/7 exposures to radiation to the minimum..., and the ionization chamber survey meters will allow you to venture out into the deadly highly contaminated areas for reasonably safe (short) amounts of time.

If your question is about military equipment, and radiation, you want a G-M tube counter. Exposure from your unsmashed instruments isn't worth worrying about. The G-M tube counter will help you clean up the contamination that was spread about when you smashed your speedometer, though.

The Ionization Chamber survey meters will never be of any use to you, unless the big one hits.... The big one will leave radiation that will be much as if you smashed billions of speedometers, and spread the remains over every square inch of the terrain. Not a good thing.

-Chuck

 

[stumps]

Chuck – I guess we just disagree about the relative rarity of the G-M type CDV-700 meters ...

I didn’t intend to tick you off, but it appears I have. Sorry about that. I still contend, however, there’s nothing wrong with CDV-700 6B for this type of low-level detection.

As to the PDR27’s being plentiful and cheap, I’d really like to know where you’re purchasing them, because I didn’t run across them when I was looking for a G-M meter.

Hi Carl,

In the course of the time I have been here on SS, only two people have really ticked me off. You are definitely not one of them. If my posts are being perceived as angry, I will have to continue to work on my tone, as I am very very rarely angry about anything.

I started my collection with Victoreen CD meters, and I looked for years for any that had G-M tubes in vain. I found a few, but the guys that owned them were way too proud of them, wanting several hundred dollars each. Eventually, I ditched all of the CD meters I had, keeping only some of the pocket dosimeter sets. There was a period of time 10 years, or so ago when all of the CD shelters were scrapped. I wasn't paying much attention to CD meters back then, so I could easily have missed the glut.

I have found PDR27's just about everywhere. Many from hamfests, several on auction... though not so much anymore, and even ebay. Even Fair Radio has them in their catalog from time-to-time.

I have never said, nor implied that there was anything wrong with any counter that has a G-M tube for measuring low level radiation. The V700 is a fine light weight meter for that purpose.... indeed that is exactly what it was made for. Every CD shelter, no matter how small had at least one, of them, and dozens of the survey meters.... they also had bunches and bunches of the pocket dosimeter pens... though I am not sure why. They are so insensitive that about all they tell you is when someone is among the walking dead...

-Chuck

 

[Carl_in_NH]

Fair enough, Chuck. No harm, no foul. You didn’t sound upset; animated - perhaps

I don’t see any of the military units in the normal places I’d look for one at the moment. I’ve not run across them at hamfests – but I’ve got to admit I really wasn’t looking for them, either. The 700 / 6B units do seem to be available for a reasonable price from a number of Internet sources – and that’s the reason I was defending that particular model as a good candidate for someone that wants to do some low level detection. The prices do vary all over the map – from almost free for unknown units, to ones that are calibrated and certified and command a price of a few hundred dollars. My working unit was $60 shipped – and I consider that reasonable to be able to insure that I don’t accidently open an instrument with a radium dial.

My interest in these units developed over months and not years – when I became curious about the various meters and instruments I had kicking around, and which ones had radium dials – so I only have the background of days of detailed research into what’s available for this application, and not the long exposure you’ve had. For my application, I couldn’t justify the purchase of a scintillation counter - but I will keep an eye open for one of them at the right price, along with a PDR27. One can never have too much instrumentation.

 

[stumps]

Hi Carl,

Animated is one of my goals I like to keep things interesting.

$60 is a great price for a Victoreen 700 counter. If I could have found one for that price there would be some in my collection. But as it is, I have been concentrating on mostly OD and battleship gray counters. The most I ever paid was $80 for a PDR63 (I think?). It is a belt loop mounted counter system that was made in the 1980's.

If you are playing around with this old stuff, you really owe it to yourself to have a working counter. I met a guy at a flea market that had several display trays full of radium dialed Army watches... we're talking hundreds. I wished I had had a counter with me to show him what he was doing to himself, but instead, I left him with the gentle advice that he probably shouldn't keep storing them under his bed, but rather in a garage, or shed.... I am really surprised that the radiation counters on the large interstate highways hadn't caught up with him yet.

-Chuck

 

[x-ray]

" The difference between a G-M tube survey meter, and a hand held ionization chamber survey meter is one of magnitude. I don't really want to get into the physics of the devices, but a good visualization aid would be to think of the difference between a one inch micrometer, and a yardstick."

Perhaps - if you were only talking about common civil defense versions. However Ion chambers and pressurized ion chambers are quite capable of precise detection of radiation exposure (gamma and X-ray), even in very low levels. Additionally an ion chamber is more precise and an ion chamber is quite linear over a wide energy range, whereas a Geiger can overrespond at low energies. I've used both and many others in nuclear plants, hospitals and research applications, and design radiation detection systems and radiation shielding for medical and government applications.

There are different ways to recieve radiological harm: exposure (like radiant photon energy from gamma or X-rays as one example) or inhalation and ingestion of radioactive materials that will give an intimate dose to tissues inside the body. One cannot simply measure an inhalation dose with any handheld instrument like a geiger or an ion chamber. Geiger (especially thin window ones) will more easily detect contamination presence on surfaces and objects - so you can avoid surface contaminated objects (and presumably ingestion) and they are probably the most handy for detecting radioactive trinkets like instruments, watches and the like, but are not the best gauge of defining safe versus unsafe levels, but perhaps adequate in many applications if its energy compensated.

Gamma radiation is gamma radiation. It's the quantity that kills you, not the source.

While it does take a significant quantity of gamma radiation to cause health effects, its generally assumed less is better, depending on what dose-effect model is being used. Also not all gamma rays are truly reciprocal in health effects - although you would have to dig deep into the physics - remember photoelectric effect, compton scatter and pair production in ionization are energy dependent, a 67 keV gamma ray from Americium 241 is indeed different than gammas from Cobalt-60 in the MeV range. Generally gammas are considered equal, but if you convert skin entry dose into energy per mass of tissue, there is truly a difference.

In regards to quantity and safe levels - low levels of contamination from"ingested" alpha particles (which are emitted from radium dials and gauges) can be a more serious risk than that of the gamma rays from the same source like a radium speedo. While alpha energy can be easily shielded, and isn't an external hazard, alphas directly ionize and have high linear energy transfer - why the quality factor converter for alpha dose equivalence is 20 versus 1 for gamma rays. So if you ingest radium, the contaminants (Radium) behalves like calcium in the body and has a long biological burden. The American Health Physics Society is about to take the position that there should be the avoidance of all alpha contamination even in trace levels - since there can be a correlation between cancer and low levels of alpha contamination.


For the big one - One should concern yourself with contamination and exposure. But generally most folks don't encounter radiation exposure levels in high enough quantity to warrent a precise measurement tool. Most want a detector that can give a reasonable "yes" or "No" response or give relative levels of radiation and either avoid the area, or avoid ingestion or handling of radioactive objects that could contribute to contamination. If you handle radium gauges, alpha ingestion should be avoided. Best to always wash hands and keep areas cleaned when handling gauges.

My .

 

[AN/ARC186]

Anyone have a PDR-27/S they want to sell?

 

[stumps]

" The difference between a G-M tube survey meter, and a hand held ionization chamber survey meter is one of magnitude. I don't really want to get into the physics of the devices, but a good visualization aid would be to think of the difference between a one inch micrometer, and a yardstick."

Perhaps - if you were only talking about common civil defense versions. .

CD meters is where this thread began, so did you really have any doubt that I was talking about CD meters?

DH was looking for a device to measure the radiation from gages and other devices that he might encounter on MV's. He had located a bunch of CD meters, and was wondering if they would do the job.

Use that as your criterion, and then revisit whether or not the CD ionization chamber meters will do what DH wanted. Clue: they won't.

As I said in the above quote, I really don't think this discussion will be improved by me getting into the physics and design of counters... be they ionization chamber's, GM tubes, scintillation meters, or what have you.

Suffice it to say a GM counter is what DH will likely be able to find and afford that will work for what he wants to do.

About 20 years ago, I designed a counter that used an EG&G PIN photodiode as a gamma detector. It was very sensitive, and would count such sources, but I haven't seen too many of them on the market. The large area PIN photodiode was kind of expensive.

-Chuck

 

[m376x6]

I dug this unit up to show folks who may not know what is being discussed. This is an unusual unit in that is has an external speaker attached. That was an option. This is a series 6 so it requires 5 D cell batteries. The speaker uses 2 D cells. There is a check source on the side but they are half lifing and are not as strong as they were when they were manufactured a number of decades ago. While I ran the program here in this state I located a number of end window GM tubes located in a government warhouse and modified these CD V700 units. My techs and I found they were comparable to the Ludlum units at the time as far as sensitivity but not quite as accurate, which when you're looking for contamination the few mr/hr difference doesn't matter. I have one of those meters I kept for myself along with this one somewhere around here. I'll have to dig it up.

There is a window on the wand that can be rotated to expose the tube and allow some Beta radiation to be detected. Normally these uits were used with a single earpiece attached to your head, not built for comfort lets say. Of all the various units produced for the OCD (and all its later names including FEMA) this is the oinly one that stands a chance of detecting the radium in dials and gauges.

I closed the program over 10 years ago and have no idea whatever happened to the many thousands of units that were in inventory. Whether they are stacked somewhere or surplused is anyones guess.

 

[rat4spd]

Sort of, but not really...

Gamma radiation is gamma radiation. It's the quantity that kills you, not the source.

His analogy is accurate. When dealing with low or high level radiation sources, although the dose rate is of fairly significant concern, the source is equally, or more important.

 

[98taco3]

I dug this unit up to show folks who may not know what is being discussed. This is an unusual unit in that is has an external speaker attached. That was an option. This is a series 6 so it requires 5 D cell batteries. The speaker uses 2 D cells. There is a check source on the side but they are half lifing and are not as strong as they were when they were manufactured a number of decades ago. While I ran the program here in this state I located a number of end window GM tubes located in a government warhouse and modified these CD V700 units. My techs and I found they were comparable to the Ludlum units at the time as far as sensitivity but not quite as accurate, which when you're looking for contamination the few mr/hr difference doesn't matter. I have one of those meters I kept for myself along with this one somewhere around here. I'll have to dig it up.

There is a window on the wand that can be rotated to expose the tube and allow some Beta radiation to be detected. Normally these uits were used with a single earpiece attached to your head, not built for comfort lets say. Of all the various units produced for the OCD (and all its later names including FEMA) this is the oinly one that stands a chance of detecting the radium in dials and gauges.

I closed the program over 10 years ago and have no idea whatever happened to the many thousands of units that were in inventory. Whether they are stacked somewhere or surplused is anyones guess.

From what i hear, the civil defense stuff here in CO is now stacked in the basement of the federal center. I guess there are TONS of gear in good shape.

 

[papabear]

As usual you fellers have taken a simple task and turned it into a major mission requiring all kinds of special equipment.

If ya wanna check your gages...just take them apart and lick the dials. If your teeth start to fall out in about a month or you experience bleeding gums...either you have radiated gages...or you are in Europe...England specifically....what's so hard about that...Wreckerman does it all the time!!

As far as "The Big One".....look for a mushroom cloud...if ya see it kiss yer ass goodbye. If you see the brilliant flash...it's too late.
If the heat or blast don't get you...the radiation will...why do ya wanna know when??

Life gets so simple as ya get er......more experienced?

 

[Cleveland Iron]

Hey, Iz gotz one of them Victoreen CD meters with the Ionified chamber. Came in real handy looking for zombies last Uhm... I thinks it wus late October. Came out one eveing and there wuz bunches of strange things creeping around. Here is a picture of one of them that approached me. Wouldn't go away until I gave it some - of all things - chocolate.

( Actually it was the most creative costume of the night and the CD meter made a great prop. )

 

[stumps]

His analogy is accurate. When dealing with low or high level radiation sources, although the dose rate is of fairly significant concern, the source is equally, or more important.

If his ashes/fire analogy is correct, it is lost on me.

Gamma is just light... photons. Photon energy is proportional to the frequency (color, if you will) of that light (E = hn). In the photon spectrum, radio waves are about the lowest energy, microwaves, next. IR is higher, then comes visible, UV higher still, and finally we get into soft Gamma. After soft Gamma comes hard gamma, and we march right along into cosmic rays as the probable top of the known list.

All of them just photons, with varying energy levels depending on "color".

After a given nuclear event, the source of the gamma is essentially all the same. It is the quantity of photons that strike you that puts you at greater, or lesser risk.

The CD ionization chamber meters are designed to measure greater quantities of photons than are the GM tube meters. In either case, the photons have to have enough energy to penetrate the steel case that surrounds the GM tube, or the ionization chamber. Beyond that each meter type is relatively indifferent about what energy level photon it can detect.

Your skin, being much less dense than steel lets all of the photons from IR through cosmic rays pass through to varying degrees. The damage the photon does depends on the energy level (frequency), and the quantity.

-Chuck

 

[doghead]

So far this thread has confused me more than it has informed me!

I think I want to get a CDV-700, from what I read here. I am gonna continue reading up and also wait to see if X-ray has one available.

I did find(but can't find the site now), a place online that does sell and test/certify the meters. They said they should be tested/certified about every three years. I think it was about $80 to certify and close to $300 for a tested and certified CDV-700 unit, there.

I am not worried about the apocalyptic circumstances, I want one for fun and preliminary testing of Military items I purchase.

PB, when my teef look like Mike Myers', I will now wonder if it was radiation, poor hygiene or my English genetics.

 

[rat4spd]

If his ashes/fire analogy is correct, it is lost on me.

Gamma is just light... photons. Photon energy is proportional to the frequency (color, if you will) of that light (E = hn). In the photon spectrum, radio waves are about the lowest energy, microwaves, next. IR is higher, then comes visible, UV higher still, and finally we get into soft Gamma. After soft Gamma comes hard gamma, and we march right along into cosmic rays as the probable top of the known list.

All of them just photons, with varying energy levels depending on "color".

After a given nuclear event, the source of the gamma is essentially all the same. It is the quantity of photons that strike you that puts you at greater, or lesser risk.

The CD ionization chamber meters are designed to measure greater quantities of photons than are the GM tube meters. In either case, the photons have to have enough energy to penetrate the steel case that surrounds the GM tube, or the ionization chamber. Beyond that each meter type is relatively indifferent about what energy level photon it can detect.

Your skin, being much less dense than steel lets all of the photons from IR through cosmic rays pass through to varying degrees. The damage the photon does depends on the energy level (frequency), and the quantity.

-Chuck

Chuck, I appreciate the breakdown on gamma rays, but really, I've been there, done that. As a person that has handled thousands of tagged pieces of radioactive material, packed high level waste while wearing fully body suits and forced air hoods, sluiced resin, deconned nuclear work sites, overseen radioactive repairs, written work packages, cleaned radioactive waste tanks, and done countless thousands of surveys with your AN/PDR 27's, 70's, e140N's, PRM5N, and what ever else we may have had, I can say that where the radiation came from was at least as important as the dose.

As for the analogy, it is what we were taught way back in the day in Naval nuclear power school. The heat from the fire is the energy emitted, the particulate smoke/ash, and fire is the contamination, ie, "The Source."

And after doing many a railroad track with popsicle sticks playing "Clean up the plutonium after a fire in a high explosive device...hint...hint", that ash and smoke and particulate analogy is permanently logged in my brain....oh yeah, while wearing forced air......

As PB said, after a nuclear event, why worry?

 

[m376x6]

Doghead, I'm curious as to what "Certified" means when applied to CD V700. Find out whether or not the check source is still attached to the side of the 700. Generally the criteria for a 700 was that it detect the minimum level of radiation and not accuracy. The combination of transistor and tube technology used in their construction never lent them to having any great deal of accuracy. There are three types of radiation that are generally present with decay. Alpha, beta, and gamma. Each has its own unique impact on the human body, and folks are often surprised as to how damaging they are in relationship to each other. A forum on a military surplus site isn't the place to begin a course on all the aspects of radiation. A lot of interesting theories on the subject have been presented here, none to cause any serious danger to anyone so attempting to enlighten anyone isn't worth the effort. If you have any questions you're certainly welcome to PM me and I'll try to help in any way I can.

 

[stumps]

Chuck, I appreciate the breakdown on gamma rays, but really, I've been there, done that. As a person that has handled thousands of tagged pieces of radioactive material...

You're welcome, but I didn't necessarily put the description there for you. It was more to give the idea of gamma energy in as simple a way as I could.

As for the analogy, it is what we were taught way back in the day in Naval nuclear power school. The heat from the fire is the energy emitted, the particulate smoke/ash, and fire is the contamination, ie, "The Source."

Ok, now I understand what you are getting at: The fire analogy is showing the parallel between an atomic bomb blast and a fire.

There is a pretty close relationship between the two. The heat and fire are the initial blast, and the smoke and ash are the fallout that is left over and lingers...

Neither of the types of CD survey meter were intended to indicate the initial blast (heat and flame). Both were made for registering the fallout... the ionization chamber meter was intended to give you a measurement that allows relatively safe travel in a contaminated area, and the GM tube meter was intended to help in keeping the shelter clear of fallout residue that might be tracked in, or ride in on clothes.

However, the fire analogy has nothing to do with the measuring capabilities of a survey meter using an ionization chamber vs a survey meter using a GM tube. The difference is purely one of quantity. They each treat the energies of all gamma photons as being the same, but shows a measurement of the flux, or number of photons per second.

-Chuck

 

[stumps]

So far this thread has confused me more than it has informed me!

Sorry about that!

The executive summary is: any survey meter with a Geiger-Mueller tube, and a most sensitive scale reading 0.5mr/hour will do just fine.

The Victoreen CD V700 is a good example, as is the PDR27/R/S/T meter.

Visually, the type of meter you want will have a hand held probe that is connected to the meter by way of a flexible cable. You shouldn't have to pay more than $100 for a good meter.

Calibration is not necessary for your purposes. A check source is desirable as a way of confirming operation. If your counter has a speaker, or a set of headphones, cosmic rays will help confirm operation by giving you a tick every 3 or 4 seconds.

-Chuck