Radiation leak test instruments

In summary: If the leak test detects any amount of radioactivity greater than 10μCi, the source is considered to be leaking and must be repaired or replaced.In summary, you are looking for a device which can measure the amount of radiation leaked from a very old smoke detector. There are many instruments, but none of them are suitable for this task. A mass spectrometer may be the best option, but it will cost you a lot of money.
  • #1
Happy Days2021
17
0
I would like to find out please what is the preferred instrument to leak test very low levels of leaks of Americium, say in school sources. I mean an instrument which could measure leaks of 0.0005 microcuries. There are so many instruments. Some people say to measure the gamma emissions, others say measure the alpha emissions? Would an HpGe be more efficient to lower levels than say a handheld gamma Geiger Counter or is an alpha/beta smear counter best? Thanks
 
Last edited by a moderator:
Science news on Phys.org
  • #2
This likely does not exist. You are looking for 18 Hz of decays, spread out over some area that you don't tell us. Most of these are alphas, which are stopped in a few inches of air. You won't see them. There's also a 50 keV x-ray, which will travel through air, but will likely be absorbed by the counter's outer material.

Can you tell us more about your application?
 
  • #3
I am looking for an instrument which would be suitable for leak testing a very old smoke detector and want a detector to read down to the lowest levels possible of Americium. Which of the instruments from my post above are mot suitable?
 
  • #4
None of them.
 
  • #5
Can you tell me what instrument would be suitable then please, even to measure to 0.05 microcuries of leakage or lower?
 
  • #6
This is so close to zero as to be close to impossible. I can think of ways to do this, but they would be very expensive: basically the first step would be to clean every exposed surface and then to survey what's left when the water/alcohol has evaporated.

You are essentially trying to find a slice of a banana based on its radioactivity. Doing this requires a major research lab, not a survey meter.
 
  • #7
Happy Days2021 said:
I am looking for an instrument which would be suitable for leak testing a very old smoke detector and want a detector to read down to the lowest levels possible of Americium.
This wording is very odd, so just to be clear; what you are describing is leaking radiation, not leaking Americium. Is that what you really want? And where did you get the precision you specified? What is the purpose of this investigation?
 
  • #8
Yes what I am wanting to wipe test is to check for any leaking Americium. I have a very old smoke detector with Americium and what to check if any radiation has leaked from the source. I want to find out should I use an alpha or gamma reader? HpGe/alpha beta counter/handheld gamma geiger counter. Thanks all.
 
  • #9
The cost to measure this will be many orders of magnitude more expensive than throwing this one away and buying another smoke detector.
 
  • Like
Likes russ_watters
  • #10
Happy Days2021 said:
Yes what I am wanting to wipe test is to check for any leaking Americium. I have a very old smoke detector with Americium and what to check if any radiation has leaked from the source.
Again: these are not the same thing.

I think the device you are looking for may be a mass spectrometer. Or it my be that you don't understand/know what you are looking for.
 
  • #11
I have a very old smoke detector and I want to check that due to its age that none of the Americium has leaked from the source and hence I want to perform a wipe test and measure any emissions from it. I want to know the best instrument to use for measuring such low levels and do I measure the alpha or gamma emissions?
 
  • #12
As said before, this isn't going to work.

A "good" smoke detector has a very weak source (think banana) and the radiation needs to pass through its enclosure, the intervening material and air, the sensor enclosure in order to be detected. If you have a "leaky" but still working smoke detector the path is almost unchanged. The only difference is that maybe a tiny amount of material is outside the enclosure - but so what if there is? It means the rate will increase a tiny bit. 5%? 1%? Not only is it hard to measure to this level of accuracy, you have nothing to compare to.

Russ is right - you don't want to do this with radiation. The best way I can see is not to look for Americium radiation but to look for Americium atoms. This is analytical chemistry. I'm guessing a good lab would charge you $20,000.

But suppose they told you that it was "leaky" - something that I would find unlikely if it was not also "damaged". What are you going to do? Throw away the old detector and buy a new one. That costs $20 or so.

Why pay $20,000 to determine you don't need to spend $20?
 
  • Like
Likes davenn, russ_watters and Motore
  • #13
The NRC only requires a leak test for alpha sources greater than 10μCi. A leak test is performed by wiping the source with a suitable material (damp filter paper swab ) and determining the activity removed. If greater than 0.005μCi, the source must be removed from service.

Probably the best detector is a windowless gas flow proportional counter in which you place the wipe sample inside the detector's sensitive volume. This will give about a 50% counting efficiency and will have a low sensitivity to background radiation. You might be able to build one yourself.
 
  • Like
Likes Happy Days2021
  • #14
Happy Days2021 said:
I am looking for an instrument which would be suitable for leak testing a very old smoke detector and want a detector to read down to the lowest levels possible of Americium. Which of the instruments from my post above are mot suitable?
A new mode detector would be a lot cheaper than a Scientific Instrument.
 
  • #15
gleem said:
The NRC only requires a leak test for alpha sources greater than 10μCi. A leak test is performed by wiping the source with a suitable material (damp filter paper swab ) and determining the activity removed. If greater than 0.005μCi, the source must be removed from service.

Probably the best detector is a windowless gas flow proportional counter in which you place the wipe sample inside the detector's sensitive volume. This will give about a 50% counting efficiency and will have a low sensitivity to background radiation. You might be able to build one yourself.
Thank you. I don't have a gas flow counter but I have access to a HpGe detector-would this be suitable for leak testing to 0.005 microcuries? Or would a handheld Gamma counter (geiger counter) be better. I don't understand why some people say measure the alpha emissions, but others say measure the gamma emissions.
 
  • #16
Vanadium 50 said:
he only difference is that maybe a tiny amount of material is outside the enclosure
Where would the accumulate outside the enclosure-do you mean on the outside of the actual source, or the outside of the ionisation chamber?
 
  • #17
Happy Days2021 said:
Thank you. I don't have a gas flow counter but I have access to a HpGe detector-would this be suitable for leak testing to 0.005 microcuries? Or would a handheld Gamma counter (geiger counter) be better. I don't understand why some people say measure the alpha emissions, but others say measure the gamma emissions.

GM? Maybe if you can get a thin Mylar window GM tube with a thickness of less than 4 mg/cm2. You still would have significant absorption by the window. You could use a HpGe to detect the gammas but being only 5% of the α-decays your count rate would at best be 20X lower ( ~ 4 cps) not correcting for absorption by the housing.

Since the sources are around 1 uCi, if the HpGe is available why not just put your source next to it and see what the count rate is. and report back.

In any event, you will need to calibrate the detector to get a dpm/cpm estimate.
 
  • #18
gleem said:
GM? Maybe if you can get a thin Mylar window GM tube with a thickness of less than 4 mg/cm2. You still would have significant absorption by the window. You could use a HpGe to detect the gammas but being only 5% of the α-decays your count rate would at best be 20X lower ( ~ 4 cps) not correcting for absorption by the housing.

Since the sources are around 1 uCi, if the HpGe is available why not just put your source next to it and see what the count rate is. and report back.

In any event, you will need to calibrate the detector to get a dpm/cpm estimate.

What would be the point of doing this? Would this be better than taking a wipe of the surface and then checking for emissions?
gleem said:
Since the sources are around 1 uCi, if the HpGe is available why not just put your source next to it and see what the count rate is. and report back.
 
  • #19
You know the source is emitting radiation. if the source is not leaking the wipe will have no activity.
 
  • #20
gleem said:
You know the source is emitting radiation. if the source is not leaking the wipe will have no activity.
Thanks but would the count rate of the actual smoke alarm tell me if it was leaking or not?
 
  • #21
No. How could you tell if the radiation was coming from the inside of the source or the outside.
 
  • #22
If the wipe test was clear from around the outside of the ionisation chamber, then would that not prove all activity was from the source-would cpm actually tell you anything about a leaking source?
 
  • #23
I do not know the actual construction of the fire detector sources but they must have a very thin covering to allow the alphas to penetrate. This covering might be fragile and touching it might disturb this covering. Any leaking would most likely plate out on the inside. Since it would not be advisable to touch or disturb this source a wipe of the inside of the chamber might tell you if it was leaking but would not provide information on how much. On the other hand, a negative wipe does not necessarily tell you if the source has leaked. I do not understand your need to determine if this source is leaking as it is not handled, produces no gaseous radioactive products, and is enclosed in a container if left intact provides adequate shielding.
 
  • Like
Likes Happy Days2021 and Vanadium 50
  • #24
gleem said:
I do not know the actual construction of the fire detector sources but they must have a very thin covering to allow the alphas to penetrate.

The source itself (not the ionization chamber) is a thin piece of foil. Americium is extracted from reactors and the oxide is produced. This is insoluable in water, which is good. It's plated with gold and the whole thing is rolled again and again until you get very thin foil. Gold leaf, really. Then the leaf is bonded to something more macroscopic so it can be handled.

The amount of americium is really small. I'd guess about 200 ng for modern smoke detectors. That's an n as in nano and not some other letter.

As far as "leaking", does gold leaf leak?

As far as finding a "leak", it's surely easier to look for micrograms or maybe even milligrams of gold than nanograms of Americium. But, as I mentioned upthread, it's easier still to run over to Home Depot and get another one.
 
  • Like
Likes gleem
  • #25
Thanks all
gleem said:
I do not know the actual construction of the fire detector sources but they must have a very thin covering to allow the alphas to penetrate. This covering might be fragile and touching it might disturb this covering. Any leaking would most likely plate out on the inside. Since it would not be advisable to touch or disturb this source a wipe of the inside of the chamber might tell you if it was leaking but would not provide information on how much. On the other hand, a negative wipe does not necessarily tell you if the source has leaked. I do not understand your need to determine if this source is leaking as it is not handled, produces no gaseous radioactive products, and is enclosed in a container if left intact provides adequate shielding.
Why would a negative wipe not tell you if it had leaked, surely negative wipe=no leak? Also would an HpGe not tell you the amount which had leaked on a wipe?
 
  • #26
Happy Days2021 said:
Why would a negative wipe not tell you if it had leaked, surely negative wipe=no leak? Also would an HpGe not tell you the amount which had leaked on a wipe?

Assuming you did not wipe the actual source a negative wipe just tells you that there is no activity on the surfaces that you wiped. The detector will only tell you the counts per second but not the activity of the wipe sample. The counts have to be corrected for the efficiency of the system. The source in the smoke detector
was not meant to be handled (wiped?). Assuming you only wiped areas accessible without dismantling the chamber i.e. the outside, you need to find a certified Am241 source to calibrate the detector to determine if any removed activity is significant.
 
  • #27
gleem said:
Assuming you did not wipe the actual source a negative wipe just tells you that there is no activity on the surfaces that you wiped. The detector will only tell you the counts per second but not the activity of the wipe sample. The counts have to be corrected for the efficiency of the system. The source in the smoke detector
was not meant to be handled (wiped?). Assuming you only wiped areas accessible without dismantling the chamber i.e. the outside, you need to find a certified Am241 source to calibrate the detector to determine if any removed activity is significant.
Ok thanks...so will an HpGe always need a source to calibrate it, or can it not be calibrated and still show up activity?
 
  • #28
It will show activity but you will not know if it is significant. And by the way, have you ever performed any radiation counting experiments before? Do you know how to evaluate the significance of your reading?
 
  • #29
sophiecentaur said:
A new mode detector would be a lot cheaper than a Scientific Instrument.

Also if this detector is 10 or more years old it should be considered EOL and replaced anyway. Using it after any amount of testing should be considered a hazard to your life.

BoB
 
  • #30
rbelli1 said:
Also if this detector is 10 or more years old it should be considered EOL and replaced anyway. Using it after any amount of testing should be considered a hazard to your life.

BoB
Especially for a member of teaching staff in a UK school. Radioactivity is one of those things that kids really don't need hands - on experience of. There are so many other parts of the GCSE and A level course that are hassle free and can involve student participation at a concrete level.
Also, because radioactivity scares the pants of parents and senior (non-Scientist) members of staff, you can find yourself in hot water if all the i's are not dotted and t's crossed.
I remember watching a head of Science giving a demo of ' bromine behaviour' which involved dressing up (teacher only, of course) and warning the kids that it was extremely dangerous. What a needless risk to a class of thirty kids (also him and me) and to what end? I think it could have been a testosterone thing for him.
 
  • #31
sophiecentaur said:
Radioactivity is one of those things that kids really don't need hands - on experience of.

Getting trapped in a burning building due to a defective smoke alarm is also pretty bad.

@Happy Days2021 What is your goal here?

BoB
 
  • #32
rbelli1 said:
Getting trapped in a burning building due to a defective smoke alarm is also pretty bad.

@Happy Days2021 What is your goal here?

BoB
Replacing detectors at appropriate intervals is what will ensure against that - not teaching kids about faulty old devices. There are two entirely different issues here.
 

FAQ: Radiation leak test instruments

What are radiation leak test instruments?

Radiation leak test instruments are devices used to detect and measure the presence of radiation in a given area or object. They are commonly used in nuclear power plants, medical facilities, and other industries where radiation exposure is a concern.

How do radiation leak test instruments work?

Radiation leak test instruments work by using detectors, such as Geiger counters or scintillation detectors, to measure the amount of radiation present. These detectors can detect different types of radiation, such as alpha, beta, and gamma particles, and convert them into an electrical signal that can be measured and displayed.

What types of radiation leak test instruments are available?

There are several types of radiation leak test instruments, including handheld meters, area monitors, and personal dosimeters. Handheld meters are used to measure radiation levels in a specific location, while area monitors are used to continuously monitor a larger area. Personal dosimeters are worn by individuals to measure their personal exposure to radiation.

What are the safety precautions for using radiation leak test instruments?

When using radiation leak test instruments, it is important to follow safety precautions to minimize exposure to radiation. This includes wearing appropriate protective gear, keeping a safe distance from the radiation source, and following proper handling and storage procedures for the instruments.

How accurate are radiation leak test instruments?

The accuracy of radiation leak test instruments depends on the type of instrument and the calibration process. Most instruments have a margin of error of around 10%, but regular calibration can improve their accuracy. It is important to regularly calibrate and maintain these instruments to ensure accurate readings.

Similar threads

Replies
6
Views
2K
Replies
20
Views
5K
Replies
1
Views
1K
Replies
8
Views
7K
Replies
24
Views
2K
Replies
4
Views
2K
Back
Top