Answer to Question #10722 Submitted to "Ask the Experts"

I am working on the analysis of environmental samples using gamma spectrometry. I have a question related to the baseline data. My question is: What is the role of gamma spectrometry in the establishment of baseline data? If you have any reference reports, articles, or presentations, I will be thankful to you.

Baseline radiological environmental data are important because they are typically used to characterize the radiological nature of a site where a nuclear facility is to be located. Such measurements can then be used after operation of the facility is underway to make comparisons with postoperational environmental measurements. Thus, it is common, depending on the type of facility involved, to take preoperational baseline measurements of radioactivity in air, water, soil, vegetation, and any other environmental media of note on the site and/or nearby (e.g., fish, meat from animals raised in the area, milk, etc.) so that the quantities of specific radionuclides in the specific media may be defined. After operation has begun, the same types of media are sampled from time to time in a routine program of environmental monitoring to determine whether the operation is impacting the radiological characteristics of the site. The baseline data are also important in the event that an accidental release of radioactivity occurs during operation so that the effects of the release on the environmental media may be evaluated.

Gamma spectrometry is a convenient method of assessing radionuclides that emit significant gamma radiation. It is a very popular and powerful tool for radionuclide identification and quantification. In addition to laboratory measurements of samples taken from the environment, in-situ gamma spectrometry is sometimes used to survey the radioactivity in the soil over relatively large areas. Such measurements provide a broad view of the radionuclide composition of the soil, but do not preclude the need for doing sampling of individual media. Naturally, for radionuclides that do not emit significant gamma radiation, other measurement techniques would be employed.

You can find numerous references to baseline measurements by searching the internet. The nature and extent of such survey work depends significantly on the type of facility that is intended for the site. You can find typical examples and recommendations in documents online. Regulatory Guide 4.14 from the US Nuclear Regulatory Commission, Radiological Effluent and Environmental Monitoring at Uranium Mills, discusses baseline and operational monitoring for such facilities. Another example of environmental baseline measurements using gamma spectrometry is in this article by A.M. Umar and colleagues, Baseline Measurement of Natural Radioactivity in Soil, Vegetation and Water in the Industrial District of the Federal Capital Territory (FCT) Abuja, Nigeria.

Good luck.

George Chabot, PhD, CHP