We live in Japan and wondering if you can use these devices to screen foods from farms or supermarkets in Japan?
In principle, yes. RIDs are designed to perform gamma spectroscopy to discern which nuclides are present in the nearby environment. These are the type of devices that can tell the difference between natural radioactivity and fission product isotopes from Fukushima (as opposed to Geiger counters). These devices tend to be quite expensive, however. One also needs to learn how to properly operate them in order to get out useful information.
You may know this, but just for completeness: Non-spectroscopic detectors (such as Geiger counters) are good at telling whether something is very radioactive or not. If you live in a highly affected area of Japan, such a counter could help you avoid any high contamination. However, if there is not high contamination, these detectors will be of limited usefulness.
Mark [BRAWM Team Member]
Thank you very much for your kind reply. We live in Tokyo which is less affected externally but we are in danger of internal exposure via foods. This is because foods from affected areas and surroundings are being sold across supermarkets. Milks from affected areas are diluted with clean milks so the levels pass the legal limit set by the government. Many people seek foods from alternative regions but there is a possibility that contaminated foods are trafficked and mixed in non-affected areas. Recently there are some companies screening their foods before shipping and selling to customers. We wish to utilise such companies, though we are not certain of the types of equipments they use and how accurate they can deliver (not detected results are meaningless if the equipments used are not sensitive enough or as you put above for GM counter). We wish to seek more knowledge about different types of equipments.
I have been searching the posts on this web and seems someone posted the use of GM counters to screen veggies. This is very informative. I would like to further inquire if basic scintillators (say with NaI detectors) would be sufficient to qualify the amount of radiation present in food?
When you said that RIDs can in principle use to detect radioisotopes in foods but training is required, do you mean in terms of sample preparation techniques or interpretation of the gamma spectra (or both)? Additionally could these equipments report the findings of each radioisotopes (mainly Cs here now) in bq/kg or it really depends on the models and manufacturers? We have looked into some models and it seems the scanning process is made for dummies (i.e. anyone can do it, just wave it over the samples) though I am personally very skeptical if it is the marketing tactic.
Overall, I would like to ask if you could spare sometime for a review regarding types of equipments which are available for screening of or quantitative identification of radioactive or radioisotopes contaminations in foods (or please feel free to cite references or publications to my email). We are talking about a large degree of contamination in affected areas and a perhaps a small degree in other parts. Foods sold in supermarkets here in Tokyo are mainly from the Fukushima surrounding areas (a few prefectures down south, north and west) and some are from Fukushima itself!
I'm sure Mark and the other team members know more about this than me, but you may wish to read this paper. When spending this much money you will want to make sure what you buy meets your needs.
I think the thing we need here is primarily to be able to see the cesium isotopes, although it would be nice to look for the alpha emitters too.
Thank you very much for your reply and the link.
We are not actually planning to get one of these for personal use (yes, too expensive for us and now added the problem of operation). I am just wondering if some private sectors in Japan are using one of these though and how reliable their results can be. With some information I (or Japanese speaking friends) can have a little bit of knowledge when taking to them.
So I see,
"It is a difficult problem to automate an identification algorithm that can analyze a broad range of radionuclides. Many factors such as acquisition time, calibration drift, temperature changes, changes in background radiation levels, etc., complicate the challenge. False positive and false negative identifications are common, particularly for
spectra collected under realistic field conditions. Furthermore, an instrument can only identify isotopes that it has been programmed to recognize. For practical reasons the developers of instruments are forced to limit the number of isotopes in the libraries used for identification. No effort has yet been made to quantify the number of failed
identifications reported herein that are the result of the radioisotope simply not being included in the library of a particular instrument."
From what I gather from the charts, it looks like these instruments are accurate when taking background radiation (others have almost more or less equal chance of false -ve, false +ve and correct). Is this correct?
Now coming back, simple scintillator with NaI probes would be a good tool for roughly indicate contamination in food, say better than GM counters?
In fact, I recently came across an ad for these products by Berkeley Nucleonics Corp. (BNC, no relation to UC Berkeley). These are marketed as a set of equipment to be used for fission isotope identification in food:
Scintillators, because of their worse energy resolution, are not as sensitive as germanium detectors and their spectra are harder to interpret. That is why BNC has specialized software to interpret the spectra of their devices.
As BC posted above, ORTEC markets RIDs using germanium detectors, which have many advantages over scintillators.
However, no matter how good your system and software are, there is always the possibility that a gamma-ray line can be misidentified. It is always important that the operators know what they are doing. In fact, such a misidentification happened early on in the Fukushima crisis, when the very short-lived isotope Chlorine-38 and the inexplicable Arsenic-74 were reported to be detected. This caused a fright, because the presence of Chlorine-38 could only have been explained as induced radioactivity through recriticality of the reactors, and Ar-74 has no obvious explanation. These detections were later retracted by TEPCO.
Moral of the story: it's important that the operators know what they are looking at, since the software can be wrong.
Great stuff fella, you sure know how to write a gripping article, tell you what if you are ever down under and want to catch up, my number is (04)88932137
the name's Darrie, Brandon Darrie
UC Berkeley • College of Engineering • Contact
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