16
Regulation of Technically
Enhanced Naturally Occurring
Radioactivity in Pennsylvania
John P. Englert
16-1
INTRODUCTION
Naturally occurring radioactive materials (NORM) are present in varying amounts in gas- and
oil-bearing geologic formations, and are routinely encountered in oil and gas exploration, production, and transportation activities. Historically, NORM has not been a significant issue with
Pennsylvania natural gas activities because of relatively low concentrations of NORM in the
geologic formations being developed and the relatively low volume of materials generated from
conventional natural gas operations. Developments in horizontal drilling and hydraulic fracturing technologies have made accessible the natural gas reserves in the Marcellus and Utica shale
formations that underlie substantial portions of Pennsylvania and nearby states, which has resulted in a resurgence of gas exploration and production in and around the Commonwealth.
These shale formations contain higher concentrations of NORM than the gas-bearing formations previously tapped, and the unconventional drilling and development methods used to access the shale gas are bringing more NORM to the surface. Management of the drilling and well
development byproducts has the potential to concentrate the NORM and create a radiological
exposure hazard. NORM under these conditions is referred to as Technologically Enhanced Natural Radioactive Material (TENORM). As a result of increased potential for TENORM, the radiological aspects of shale gas production are being more closely scrutinized and controlled by
both the industry and the Pennsylvania Department of Environmental Protection (the DEP or
the department).
Existing DEP regulations concerning radiation and radioactive materials were not developed
specifically for NORM and TENORM, and are not well suited to address the radiological issues
associated with natural gas operations. Before the shale gas boom, these regulatory issues were
manageable, but are increasingly becoming a problem. The DEP has supplemented its regulations with guidance to address these issues, and has added monitoring requirements for gas
Regulation of Technically Enhanced Naturally Occurring Radioactivity in Pennsylvania
well operators and waste management facilities processing and disposing of shale gas wastes.
The DEP also commissioned a comprehensive radiological survey of natural gas operations in
Pennsylvania, 1 which will help the department identify areas where regulatory changes or additional guidance is needed.
This chapter describes NORM and TENORM in the shale gas industry and reviews the current
regulations and guidance applicable to these materials.
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A PRIMER ON RADIATION
Before discussing the regulation of NORM and TENORM it is helpful to understand the basics of
radiation to understand why it is important to regulate exposure to these radioactive materials.
Radionuclides are chemical elements that are unstable at the atomic level. These unstable atoms undergo transformation through a process called radioactive decay, whereby the atom releases energy (radiation) to become more stable. The radiation can be released as a solid particle
from the nucleus (protons—referred to as alpha particles, or electrons—referred to as beta particles), or as electromagnetic energy (referred to as either gamma rays or x-rays). These processes
are illustrated in Figure 1. The different forms of radiation have different properties. As shown
in Figure 2, the heavy alpha particles can be stopped by a thin piece of paper, whereas the
smaller beta particles can penetrate some materials, and the gamma ray, which is pure energy,
can only be stopped by dense material, such as steel or lead. Radionuclides vary from one another in the type and frequency of decay, as well as the energy associated with each decay, but
each radionuclide decays in the same manner. This allows the radionuclide to be identified by
its unique type, frequency, and energy of decay.
Figure 1
1.
292
Types of Radioactivity.
Technologically Enhanced Naturally Occurring Radioactive Materials Study Report (Perma-Fix Environmental Services, Inc., January 2015) (the Perma-Fix Report), available at http://www.elibrary.dep.state.pa.us/dsweb/Get/Document-112658/Pennsylvania
%20Department%20of%20Environmental%20Protection%20TENORM%20Study%20Report%20Rev%201.pdf.
16-2 A Primer on Radiation
Figure 2
Penetrating Power of the Different Types of Radiation. Source: “Radiation Protection and the Management of Radioactive Waste in the Oil and Gas Industry,” Training Course Series No. 40, International Atomic Energy Agency 2010.
The radiation emitted from an unstable atom can interact with other stable atoms, causing
those atoms to change in a process called ionization. Ionization in air is referred to as exposure,
and if the energy is absorbed in a material such as biological tissue, it is referred to as a dose. If
ionization occurs in a living biological cell, the cell can be damaged, causing it to die or to change
(mutate). These cellular changes can cause health effects to the organism. Because radiation
can cause health effects, it is important to control exposure. As shown in Figure 3, radiation exposure can be external or internal, and depending on the radioactive material, the type of the
exposure can be important. For example, external exposure to alpha particles poses a relatively
low risk because the alpha particles cannot penetrate the skin, whereas internal exposure may
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Regulation of Technically Enhanced Naturally Occurring Radioactivity in Pennsylvania
allow the radionuclide to be incorporated into living tissue, or at least put it in close proximity to
tissue such that its energy can interact with the tissue. By contrast, gamma rays can readily
penetrate most solids, so there is little difference between internal and external exposure.
Figure 3
Internal and External Exposure. Source: International Association of Oil and Gas Producers Report
No. 412 (2008).
Human exposure to radiation occurs from a wide range of sources, including natural background and man-made sources, and involves both internal and external exposures. See Figure 4.
The regulations controlling radiation exposure are designed to recognize these differences, and
establish concentration or activity limits for individual radionuclides in various media, as well
as setting limits based on internal, external, and total exposures and doses.
Figure 4
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Routes of Radiation Exposure to Humans.
16-3 NORM and TENORM
16-3
NORM AND TENORM
Naturally occurring radioactive materials include primordial and cosmogenic radionuclides. Primordial radionuclides are present in rocks and minerals in the earth’s crust and have been
there since Earth was formed (for example, uranium-238, thorium-232, potassium-40). Cosmogenic radionuclides are formed continuously from interactions of cosmic rays with air (for example, carbon-14, tritium). The principal NORM radionuclides associated with natural gas development are uranium-238 and thorium-232. As shown in Figure 5, each of these radionuclides
undergoes a series of nuclear decay reactions, forming other radionuclides in a decay chain that
ultimately ends with stable (nonradioactive) isotopes of lead. In an undisturbed natural state
each radionuclide in the decay series is present in approximately the same radioactive concentration as the other radionuclides in the series—a state referred to as secular equilibrium—but
physical and chemical processes, either in nature or performed by humans, can significantly disturb this state of equilibrium.
Figure 5
Uranium-238 and Thorium-232 Decay Series.
From a radiation exposure perspective, the principal radionuclides of concern are radium-226 in
the uranium-238 decay series and radium-228 in the thorium-232 series. As shown in Figure 5,
each radium radionuclide undergoes additional radioactive decay, shedding energetic particles
or photons to form different radionuclides. Chemically, radium is in the same periodic group as
calcium, and behaves similarly. Consequently, if radium is ingested it can be incorporated into
bone tissue, where it can reside for a long time and contribute to radiological dose as it undergoes further radioactive decay. Other radionuclides of concern in these decay series are radon222 in the uranium-238 series and radon-220 in the thorium-232 series. These radionuclides are
inert gases that can migrate from the parent materials, disrupting equilibrium and presenting a
different potential exposure pathway. These radon nuclides also undergo further nuclear transformations, forming different solid radionuclides as they decay.
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