Leak Test

LEAK TEST

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Leak test

Leak test of radioactive sealed sources is merely a physical test conducted on the capsule by collecting any radioactivity resulting from the leakage.

Procedure in Working with Sealed SourcesProcedure in Working with Sealed Sources

WHY LEAK TEST

ENSURE INTEGRITY OF SOURCE CAPSULE AS PER DESIGNED BEFORE USE DURING USE (PERIODICALLY) BEFORE DISPOSAL

Radionuclides may be categorized into:

Sealed radionuclideso Sealed radionuclide or sealed source is radiation source

consisting of any radioactive material, nuclear material or prescribed substance firmly incorporated in solid and effectively inactive material, or sealed in an inactive container of sufficient strength to prevent, under normal conditions of use, any dispersion of its contents.

o Sealed sources when intact posed an external radiation hazards.

Unsealed radionuclides o These are exposed radionuclides usually in solid, liquid

and gaseous forms. o Unsealed radionuclides posed internal and external

radiation hazards.

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Types and Characteristics of Radiation SourcesTypes and Characteristics of Radiation Sources

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Leak test

Leak test of radioactive sealed sources is merely a physical test conducted on the capsule by collecting any radioactivity resulting from the leakage.


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When to perform Leak test

1. Before initial use ( manufacturer cert).2. periodically ( at least once a year ).3. whenever damage of capsule4. contamination is detected.


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Leak test

A radiation leak is divided into two:

oDesign leak or allowed leakage by the manufacturer on a particular apparatus; and

oDefect of sealed sources, apparatus or machine.

Leak test is a physical test conducted on sealed sources to ensure the integrity of the source capsule. Leak test is also done on irradiation machine (e.g. X-ray machine).


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Cause of Leakage

The sealed radioactive sources may be damaged due to mechanical , physical or chemical factor.

Alpha and beta sources are very fragile and likely to leak due to mishandling by user.


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Leak test

Level of radiation leakage is determined based on the deviation of measured dose from the dose of design leak.

Purpose of leak test is to confirm the classification of sealed sources and performance of irradiation machine is maintained at all times during its use.

Leaks due to defect of sealed sources, apparatus or machine must be assessed periodically (interval is prescribed by the authority) or whenever damage of the source (if radiation source, it is the capsule or seal) is suspected, or when there is a presence of contamination (allowable leaked activity = 185 Bq).


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Methods used in leak test

Test methods used in detecting and measuring leaks from sealed sources may be divided into two:

Radioactive methodso Example of radioactive methods include:

Wipe (smear) test Cellulose tape test Scrub test Soaked-I test Soaked-II test


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Test methods used in detecting and measuring leaks from sealed sources may be divided into two:

Non-radioactive methods o Examples of non-radioactive methods include:

Vacuum bubble test Hot liquid bubble Gas pressurization bubble test Helium test Helium pressurization test Water pressurization test


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1. Dry wipe test. The entire radioactive surface of the

source shall be wiped with filter paper with the application of moderate finger pressure. Removal of radioactive material from the source shall be determined by measuring the radioactivity on the filter paper or by direct measurement of the radioactivity on the source . If the activity is less than 5 nCi (185 Bq), the source is considered to be leak free.

Leak Test MethodsLeak Test Methods

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2. Wet wipe test. The entire radioactive surface of the

source shall be wiped with filter paper, moistened with water, with the application of moderate finger pressure. Removal of radioactive material from the source shall be determined by measuring the radioactivity on the filter paper after it has dried or by direct measurement of the radioactivity on the source following the wet wipe. If the activity is less than 5 nCi (185 Bq), the source is considered to be leak free.


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3. Water soak test. The radioactive source shall be immersed in

water at room temperature for a period of 24 consecutive hours.

The source shall then be removed from the water. Removal of radioactive material from the source

shall be determined by measuring the radioactivity in the residue obtained by evaporation of the water in which the source was immersed.

If the activity is less than 5 nCi (185 Bq), the source is considered to be leak free.


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4. Immersion with Boiling Test. Immerse the sealed source in a solvent which

will not attack the material of which the outer surfaces of the source are made .

Boil for 10 minutes, remove the source (retaining the solvent) and allow to cool, then rinse the source using fresh solvent. Repeat these operations twice, for a total of three tests, using the original solvent for the boiling.

Measure the total activity in the solvent. If the activity is less than 5 nCi (185 Bq) the source is considered leak free.


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Counting equipment is used in leak tests.

Counting equipment used in leak tests are similar to that used to detect the types of radionuclide, radiation as well as to measure the activity of the leak source.

Liquid scintillation counters may be used for beta emitters while gamma counters may be used to measure gamma emitters.


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TESTS OF CONTAMINATION (wipe test)

The most effective method for measuring radioactive surface contamination is the wipe test technique. This procedure will indicate only the levels of removable contamination. No removable contamination should be tolerated. Begin the wipe test with a sketch of the laboratory that includes marked and numbered locations to be examined. Usually, 10 to 20 locations are adequate for most laboratories.

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TESTS OF CONTAMINATION (wipe test)

The wipe test method includes the following steps: Moisten a filter paper (2 cm) with alcohol or water, and wipe

over an area approximately 100 cm2 (10 cm x 10cm). Please note dry wipes can also be used.

Place the filter paper in a vial and count in a gamma well counter (for gamma ray contamination) or in a vial containing scintillation fluid, shake and count in a liquid scintillation counter for alpha and/or beta contamination.

Contamination is present if wipes exceed 0.5 Becquerels per cm squared (Bq/cm2). The contaminated area must be cleaned with

water and detergent or with a commercial decontamination solution such as Decon75, Radwash . Begin with the perimeter of the spill area and work towards the centre, being careful not to spread the contamination during cleaning.

Repeat the wipe testing until the measurements are at or below 0.5 Bq/cm2.

Leak Test

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