Determination of removal factor of an indirect contamination measurement using the exhaustion method
Tirronen, Mikko (2024)
2024
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2024081924215
https://urn.fi/URN:NBN:fi:amk-2024081924215
Tiivistelmä
The removal factor is a parameter of measuring radioactive contamination from surfaces with an indirect measurement. It is the most difficult parameter to evaluate since it is affected by several variables from human differences and error to the material being investigated. The conservative value traditionally used for the calculations in instrumentation is 10%.
The goal of the thesis is to determine the removal factor using the quantitative method on several different surfaces, with contamination bound on different kinds of conventional dirt, with the aim to test the conservative value of 10%. A number of smear samples shall be taken by several individuals from contaminated surfaces. The surface shall be wiped until all the contamination is exhausted. The activity captured by the first sample shall be compared to the cumulative activity in all the samples; this ratio is referred as the removal factor.
If a higher value can be shown to be valid, the result will be more accurate contamination measurements. This would lead to decreased time and other resources being used to decontaminate, measure out and free release material from controlled areas.
If values below 10% are recorded, it may indicate that it is possible that the instrumentation reading the samples is providing values that are too low. This would mean that contamination with values over the limits might end up being handled with insufficient radiation protection measures.
Due to practical limitations of other work by our staff, sufficient data could not be produced to execute a significant research. The results indicate to support the use of the conservative value of 10% for the removal factor, but further research is needed to challenge the use of this value.
The goal of the thesis is to determine the removal factor using the quantitative method on several different surfaces, with contamination bound on different kinds of conventional dirt, with the aim to test the conservative value of 10%. A number of smear samples shall be taken by several individuals from contaminated surfaces. The surface shall be wiped until all the contamination is exhausted. The activity captured by the first sample shall be compared to the cumulative activity in all the samples; this ratio is referred as the removal factor.
If a higher value can be shown to be valid, the result will be more accurate contamination measurements. This would lead to decreased time and other resources being used to decontaminate, measure out and free release material from controlled areas.
If values below 10% are recorded, it may indicate that it is possible that the instrumentation reading the samples is providing values that are too low. This would mean that contamination with values over the limits might end up being handled with insufficient radiation protection measures.
Due to practical limitations of other work by our staff, sufficient data could not be produced to execute a significant research. The results indicate to support the use of the conservative value of 10% for the removal factor, but further research is needed to challenge the use of this value.