radon Ölçüm teknikleri
TRANSCRIPT
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Radon Measurement Devices
Long-Term Measurements
Short-Term Measurements
Sampling Methods
Passive Devices
Active Devices
Radon Measurement
Radon Measurement Techniques
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Passive Devices
Passive radon testing devices do not need power to function. These
include charcoal canisters, alpha-track detectors, charcoal liquid
scintillation devices, and electret ion chamber detectors which are
available in hardware, drug, and other stores; they can also be ordered by
mail or phone. These devices are exposed to the air in the home for a
specified period of time and then sent to a laboratory for analysis. Bothshort-term and long-term passive devices are generally inexpensive.
Some of these devices may have features that offer more resistance to
test interference or disturbance than other passive devices. Qualified
radon testers may use any of these devices to measure the home's radon
level.
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Active Devices
Active radon testing devices require power to function. These include
continuous radon monitors and continuous working level
monitors. They continuously measure and record the amount of radon
or its decay products in the air. Many of these devices provide a report of
this information which can reveal any unusual or abnormal swings in theradon level during the test period. A qualified tester can explain this
report to you. In addition, some of these devices are specifically
designed to deter and detect test interference. Some technically
advanced active devices offer anti-interference features. Although these
tests may cost more, they may ensure a more reliable result.
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Radon Measurement Techniques
There are several radon measurement devices that may be used to
test a home or building for radon.
These devices fall into two broad categories: those used forlong-term
measurements (testing period of 3 to 12 months in duration) or those
designed forshort-term measurements (testing period of less than 3months and more typically 2 to 7 days).
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Long-Term
Measurements
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Alpha Track Detector
These detectors use a small piece of special plastic or film inside acontainer with a filter-covered opening. Air being tested diffuses
(passive detector) or is pumped (active detector) through a filter
covering a hole in the container. When alpha particles from radon and
its decay products strike the detector, they cause damage tracks. At the
end of the test period the container is sealed and returned to alaboratory for reading. The radon exposure duration of an alpha track
detector is usually 1 to 12 months.
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Electret Ion Chamber
This device consists of a special plastic canister (ion chamber)containing an electrostatically charged disk detector (electret). The
detector is exposed during the measurement period, allowing radon to
diffuse through a filter-covered opening into the chamber. Ionization
resulting from the decay of radon produces a reduction in the charge
on the electret. The drop in voltage on the electret is related to theradon concentration. The detectors may be read in the home using a
special analysis device to measure the voltage or mailed to a
laboratory for analysis. This type of detector may be deployed for 1 to
12 months.
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Digital Detector
This detector plugs into a standard wall outlet much like a consumer
carbon monoxide detector, and continuously monitors for radon. It is
a passive device based on an ion chamber. It allows the
homeowner to make radon measurements in different areas of the
home. After being plugged in for an initial period of 48 hours, thedevice displays the average radon concentration continuously.
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Short-TermMeasurements
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Activated Charcoal Adsorption
These devices utilize an airtight container filled with activated
charcoal and covered with a screen and filter. The detector is
opened in the area to be sampled and exposed to the air for a
specified period of time. Radon present in the air adsorbs onto the
charcoal. At the end of the sampling period, the container is sealed
and then sent to a laboratory for analysis using a scintillation
detector. Charcoal detectors may be subject to effects from drafts
and high humidity. These detectors are normally deployed for
measurement periods of 2 to 7 days.
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activated charcoal filter element
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Charcoal Liquid Scintillation
This method is very similar to the activated charcoal detector in that itemploys a small vial of activated charcoal for sampling the radon.
Following exposure, the vial is sealed and returned to a laboratory for
analysis by treating the charcoal with a scintillation fluid, then analyzing
the fluid using a scintillation counter. These detectors are also deployed
for normal periods of 2 to 7 days.
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Electret Ion Chamber
This is the same device described for long-term tests. However,variations in the design of the electret allows for a short-term
measurement as well. The short-term electret ion chamber is deployed
for 2 to 7 days.
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Continuous Radon Monitoring
This detection category includes devices that record real-time
continuous measurements of radon gas over a series of minutes and
report the results in hourly increments. Air is either pumped or diffuses
into a counting chamber, typically a scintillation cell or ionization
chamber. The result using this type of detector is normally available at
the completion of the test in the home or building without additionalprocessing or analysis. These detectors are normally deployed for a
minimum of 48 hours.
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Continuous Working Level Monitoring
These devices record real-time continuous measurement of theradioactive decay products of radon in the air. Radon decay
products are sampled by continuously pumping air through a filter.
Alpha particles from the decay of products trapped on the filter are
counted to determine the concentration of radon decay products in
the air sampled. Continuous working level monitors should bedeployed for a minimum of 48 hours.
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Sampling Methods
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Grab sampling
Grab samples consist of essentially instaneous measurements of the radon or
radon progeny concentration in air over time intervals that are short (on the
order of minutes) compared to the time scale of fluctuations in concentration.
The air is collected in a container and brought back to the laboratory for
analysis. Typical containers include plastic bags, metal cans and glass
containers. The volumes of the containers are usually between 5 liters and 20
liters.
Continuous sampling
Continuous sampling involves the automatic taking of measurements at closelyspaced time intervals over a long period of time. The result is a series of
measurements which can give information on the pattern with which the
concentration varied throughout the measurement interval.
Integrating Sampling
Integrating devices collect information on the total number of radition eventswhich occur throughout some fairly long period of time, usually on the order of
several days to months. The result from integrating devices is an estimate of
the approximate average concentration through the environment interval.
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Ev-ii radon konsantrasyonlarnn lmleri pasif yntemle, CR-39
plastik detektrlerin kullanm ile yaplmtr. Pasif nkleer iz detektr
olarak doal fon alfa n izlerinin dk olmas nedeniyle, ticari ad CR-
39 olan alil diglikol karbonat plastik detektrler tercih edilmitir.
Detektrler zerlerindeki barkot numaralar deftere kaydedilmitir.Radon
ve bozunma rnlerinin yaynladklar alfa tanecikleri difzyon kaplarnn
iine girerek detektrle etkilemekte ve detektr yzeyinde gzle
grlemeyecek byklklerde izler oluturmaktadr.
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Ev ile ilgili daha ayrntl bilgiye ulamak iin on sorudan oluan bir anket
uygulanmtr. Detektrler, 60 gn srelerle evlerde bekletilmitir. 60 gnlkgzlem sresi sonunda toplanan detektrler zerindeki alfa izlerinin
grlebilir hale getirilebilmesi iin kimyasal iz kazma ilemi uygulanmtr.
Bu ilem iin detektrler otomatik kimyasal iz kazma cihaznda 4 saatlik bir
kimyasal ileme tabi tutulmaktadr. Daha sonra bilgiyara bal gelimi bir
mikroskop sistemi ve softwareden oluan otomotik radon iz okuma
cihaznda 2 er kez okumalar yaplarak aritmetik ortalamalar alnm vekonsantrasyonlar tayin edilmektedir.
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Otomatik iz okuma sistemi
Kimyasal iz kazma banyosu