Why is it important to take a background count?

Why is it important to take a background count?

Introduction: It is important to measure background radiation, because human beings are always exposed to environmental radiation. The level of gamma dose rate in buildings deponds on the climate / weather , ventilation of living environment , local geology , drainage patterns and other factors.

What is the purpose of counting background radiation?

The evidence or effect on a detector of radiation caused by background radiation. In connection with health protection, the background count includes but is not limited to radiations produced by naturally occurring radioactivity and cosmic rays.

How is background count determined?

The background count rate is measured over a period of 20 minutes because of the random nature of radioactive decay. Dividing by 20 enables the average count rate per minute to be determined. Background count rate is typically 18 counts per minute which does not present a serious health risk to humans.

Why is background radiation subtracted from the sample count?

To obtain a true measure of the contaminant level in a sample, the background radiation level must be subtracted from the total amount of radioactivity measured. When the larger background measurement is subtracted from the smaller contaminant measurement, a negative result is generated.

Why is the measured count rate lower than the activity?

This is because normal detectors do not usually surround the source and so you only detect particles (or photons) emitted into a small angle (see diagram). This means that the observed count rate is always much less than the activity of the source.

Why is it important to quantify radiation in different ways?

Measuring Radiation. When scientists measure radiation, they use different terms depending on whether they are discussing radiation coming from a radioactive source, the radiation dose absorbed by a person, or the risk that a person will suffer health effects (biological risk) from exposure to radiation.

What is meant by background count rate?

The number of counts recorded by a radiation detector from background radiation. The term background radiation refers to the natural ionizing radiation on the Earth.

What is background count in GM counter?

Depending on the elevation and the type of Geiger counter, a typical natural background radiation level is anywhere from five to 60 counts per minute or more. It is important to understand that the Geiger counter indicates when an ion pair is created, but nothing about the type of radiation or its energy.

What are the effects of background radiation?

Exposure to very high levels of radiation, such as being close to an atomic blast, can cause acute health effects such as skin burns and acute radiation syndrome (“radiation sickness”). It can also result in long-term health effects such as cancer and cardiovascular disease.

Why is the count rate different to the activity?

This is because normal detectors do not usually surround the source and so you only detect particles (or photons) emitted into a small angle (see diagram). This means that the observed count rate is always much less than the activity of the source. Count rate is also measured in Bequerel.

What is the instrument used to measure radiation?

Perhaps the most common instrument for measuring radiation levels is the Geiger-Müller counter (the same Geiger who worked with Rutherford to discover the atomic nucleus).

How is the average background count rate determined?

Dividing by 20 enables the average count rate per minute to be determined. Background count rate is typically 18 counts per minute which does not present a serious health risk to humans. The background count rate must be subtracted from any other count rate when measuring the activity of a radioactive source. 1

Why is the background count subtracted from the reading?

The background count is subtracted because otherwise the value would represent the radioactive source plus the background count . This is particularly important if the source is a weak emitter of radioactivity, where the background count is a significant amount of the total reading.

How can you get an accurate background count?

To get an accurate readingfor the background count (or other radioactivesource) you need to calculate the average valueof a large number of readings which have been taken over a longperiodof time. The background countis differentin differentpartsof the country. It is affected by the release of radioactiveradonfrom rocks(granite).

How is the optimal sample and background counting time determined?

The choice of optimal sample and background counting time is determined from: = (6) Since the sample count should be approximately equal to zero (hopefully), then sample and background count rates should be nearly identical, so equal counting times should be spent on both the background and sample count times.