**1. Introduction**

262 Environmental Monitoring

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Environmental radioactive air sampling and monitoring is becoming increasingly important as regulatory agencies promulgate requirements for the measurement and quantification of radioactive contaminants. While researchers add to the growing body of knowledge in this area (Byrnes, 2001; Till & Grogan, 2008), events such as earthquakes and tsunamis demonstrate how nuclear systems can be compromised. The result is the need for adequate environmental monitoring to assure the public of their safety and to assist emergency workers in their response. Two forms of radioactive air monitoring include direct effluent measurements and environmental surveillance.

Direct effluent radioactive air sampling is typically conducted at the exhaust point. The considerations for analysis should include particulates and gases in use; one cannot neglect short-lived radioisotopes or hard-to-detect (HTD) radionuclides. An emission point may be in the form of an actively exhausted stack or vent. Emissions may come from several industries, such as medical isotope production, hospital use, research institutes, and industrial processes.

Environmental surveillance is conducted when emissions emanate from a fugitive pathway such as a waste pile, abandoned building, or contaminated land mass or breather tank. Monitoring stations are often located at near the facility boundary or nearby public areas in the affected directions. Often, a combination of direct effluent (point source) sampling and post release environmental monitoring is employed to assure the public, demonstrate low emissions of radioactive material, and comply with regulations.

This chapter presents basic concepts for direct effluent sampling and environmental surveillance of radioactive air emissions, including information on establishing the basis for sampling and/or monitoring, criteria for sampling media and sample analysis, reporting and compliance, and continual improvement.

### **2. Basis for sampling and/or monitoring**

Releases of airborne radionuclides into the environment are typically managed so that they are minimized, utilizing the As Low As Reasonably Achievable (ALARA) concept. These releases encourage the need to demonstrate that the environment is protected, which is usually accomplished through direct effluent sampling at the point of exhaust and/or through environmental surveillance at locations both on and off the site (Fig. 1). A

Concepts for Environmental Radioactive Air Sampling and Monitoring 265

Over 40 years ago, proscriptive sampling methods were normative, with an emphasis on the isokinetic sampling of airborne radioactive material from exhaust points (ANSI, 1970). Since then, advances in sampling techniques and improved technology have yielded a new approach to representative sampling (ANSI, 2011; ISO, 2010). Because of these advances, the goal of achieving an unbiased, representative sample now results in a standards-based approach with definitive criteria to establish the sampling at a well-

Point sources are discrete, well-defined locations (such as a stack, vent, or other functionally equivalent structure) from which radioactive air emissions originate (Washington Administrative Code [WAC], 2005; U.S. Environmental Protection Agency [EPA], 2002a). Point sources are actively ventilated or exhausted. Emissions from a point source may be captured, treated, monitored, sampled, and/or controlled. At some threshold, direct effluent sampling must be conducted to verify low emissions, and a graded approach based on potential emissions is recommended. Table 1 shows the ANSI N13.1-2011 approach to direct effluent sampling and monitoring requirements based on the U.S. limit of 0.1 mSv/yr

> Continuous sampling for a record of emissions and in-line, real-time monitoring with alarm capability; consideration of separate accident monitoring

<sup>2</sup>Continuous sampling for record of emissions, with

Table 1. Graded approach to sampling and monitoring (ANSI N13.1-2011)

necessity of field tests conducted in the stack or vent (Recknagle et al., 2009).

Annual administrative review of facility uses to confirm absence of radioactive materials in forms and quantities not conforming to prescribed

Using a graded approach to determine direct effluent sampling and monitoring needs (Table 1) and to design a robust sampling system (whereby the sample is extracted at a homogeneous location within the point source) requires an evaluation of the sample environment, transport mechanisms, and collection materials. The criteria for the homogeneous sampling location includes a determination of the angular or cyclonic flow, uniformity of the air velocity profile, gas concentration profile, and particle concentration profile (ISO, 2010; Table 2). Scaled tests may be utilized to demonstrate compliance with these criteria; however, as technology improves, modeling techniques such as computational fluid dynamics may be used to validate a well-mixed location without the

<sup>3</sup>Periodic confirmatory sampling and off-line

specifications and limits

**Monitoring and Sample Analysis Procedures Potential Fraction of** 

retrospective, off-line periodic analysis >0.01 and ≤0.5

analysis >0.0001 and ≤0.01

**Allowable Limit** 

>0.5

≤0.0001

**2.1 Sampling point source releases of radioactive substances** 

mixed location.

**Potential Impact Category** 

1

4

(10 mrem/yr) (EPA, 2002a).

system

combination of both methods may be employed depending on the facility needs and regulatory requirements.

Fig. 1. Example facility showing stacks, fugitive emissions, and on-site monitoring station locations

Exposure to humans from the release of radioactive materials into the atmosphere would generally occur through the inhalation or ingestion pathway; an open wound would be another possible way for internal deposition. Additional exposure comes from immersion, material deposited on the soil and vegetation, and through the resuspension of material when disturbed. Hence, the categories for consideration in establishing radioactive air sampling systems include particulate radionuclides, gases (e.g., tritium and carbon-14), and special categories such as radioiodines and other HTD radionuclides (e.g., those with a short half-life or very weak radiation emission). In-depth implementation methods are available in established standards such as *Sampling Airborne Radioactive Materials From the Stacks and Ducts of Nuclear Facilities* (International Organization for Standardization [ISO], 2010) and *Sampling and Monitoring Releases of Airborne Radioactive Substances From the Stacks and Ducts of Nuclear Facilities* (American National Standards Institute [ANSI], 2011) as well as in *Radioactive Air Sampling Methods* (Maiello & Hoover, 2010). When sampling/monitoring is not conducted, releases may be estimated.

combination of both methods may be employed depending on the facility needs and

Fig. 1. Example facility showing stacks, fugitive emissions, and on-site monitoring station

Exposure to humans from the release of radioactive materials into the atmosphere would generally occur through the inhalation or ingestion pathway; an open wound would be another possible way for internal deposition. Additional exposure comes from immersion, material deposited on the soil and vegetation, and through the resuspension of material when disturbed. Hence, the categories for consideration in establishing radioactive air sampling systems include particulate radionuclides, gases (e.g., tritium and carbon-14), and special categories such as radioiodines and other HTD radionuclides (e.g., those with a short half-life or very weak radiation emission). In-depth implementation methods are available in established standards such as *Sampling Airborne Radioactive Materials From the Stacks and Ducts of Nuclear Facilities* (International Organization for Standardization [ISO], 2010) and *Sampling and Monitoring Releases of Airborne Radioactive Substances From the Stacks and Ducts of Nuclear Facilities* (American National Standards Institute [ANSI], 2011) as well as in *Radioactive Air Sampling Methods* (Maiello & Hoover, 2010). When sampling/monitoring is

regulatory requirements.

locations

not conducted, releases may be estimated.
