radon Ölçüm teknikleri

8/6/2019 Radon lm Teknikleri

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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

radon Ölçüm teknikleri

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