i  

Naturally Occurring Radioactive Material (NORM) and Technically Enhanced Radioactive Material (TENORM)

April 12, 2015

by

NORM Workshop Presenters

NORM and TENORM: Occurrence, Analysis, Methods, Monitoring, Handling and Disposal – R&D Needs

5/12/2014

and

The NORM Working Group at The Ohio State University

Authors: See acknowledgments on page 19

Contact: Jeff Daniels, Director, Subsurface Energy Resource Center

http://serc.osu.edu/

The Ohio State University

ii  

INDEX

Executive Summary ................................................................................................. 1

Naturally Occurring Radioactivity ....................................................................... 3

Ionizing Radiation and Radioactivity ....................................................... 3

Background Radioactivity and Radiation ................................................ 5

Radon as Background Radiation ............................................................... 7

Summary of Natural Background Radiation Doses ................................ 8

Rocks and NORM ................................................................................................... 9

The Formation of Sedimentary Rocks Bearing Hydrocarbons and Radioactive Materials – Appalachian Example ....................................... 9

Rocks and Radioactivity .............................................................................11

Radioactivity in Shale .................................................................................12

NORM in Unconventional Oil and Gas Production ............................................13

TENORM in Unconventional Oil and Gas Production .......................................15

Operational Framework for Handling NORM and TENORM .........................16

Conclusions ..............................................................................................................18

Acknowledgments ...................................................................................................19

References ................................................................................................................20

APPENDIX - Basics of Radioactivity ....................................................................21

1  

Executive Summary

Naturally Occurring Radioactive Material (NORM) is any terrestrial material (rock, soil, water) that contains radioelements that emit radiation. Technologically-Enhanced, Naturally-Occurring Radioactive Material (TENORM) is produced when activities such as uranium mining, or sewage sludge treatment, concentrate or expose radioactive materials that occur naturally in ores, soils, water, or other natural materials (US EPA). Radiation from extraterrestrial and terrestrial sources is ubiquitous in our environment. NORM occurs at the surface and in the subsurface in shale and some other sedimentary rock formations throughout the U.S. Most of the rocks in the earth contain some amount of 40K, uranium and thorium, as well as the radioactive daughter products of the uranium and thorium decay series. Geologic strata that frequently contain elevated NORM concentrations include: coal seams, phosphate-rich marine deposits, some granitic rocks, some sandstones, some evaporate minerals (e.g., sylvite and potassium phosphate), and marine black shale. Any radionuclide in crustal rock can occur in shale. They may include: 40K, 232Th, 238U, 226Ra, 228Ra, and 222Rn. NORM bearing shale is prominent in surface rock exposures throughout many regions of the U.S., but the overall mineral composition of shale and the quantity of radioactive material in shale varies with geographic location. Naturally occurring radioactive materials may also occur naturally in ground water located near the surface.

The term NORM has come to be associated with terrestrial materials that emit radiation, but background radiation also reaches the surface of the earth from solar and cosmic sources. Radiation that can produce ionization in the media through which it passes can be hazardous to individuals, and the exposure to radiation is called a dose. Ionizing radiation present in our natural environment can be classified according to its origin and type, and includes sources as disparate as solar particles and cosmic rays, and terrestrial radiation from the radioactive decay of radioelements in the Earth. Determining the hazard potential, or potential dose, requires considering several environmental factors, including: the type of radionuclides and associated radiation emitted; where the radionuclides are located and how they are contained; the environmental pathways (soil, water, air, food, etc.); concentrations and levels or radioactive materials; the distance and shielding between radiation sources and humans; the modes and routes of entry for exposure (inhalation, ingestion, or dermal absorption); duration of exposure; and other factors (e.g., individual or biological factors). Cosmic and terrestrial radiation doses have been well documented for different regions of the U.S.

The concern regarding hydraulic fracturing is that the radiation dose to individuals from primordial terrestrial radiation will be increased as a consequence of bringing to the Earth’s surface radionuclides (NORM) that are contained in shale buried within the earth. NORM from oil and gas operations may occur as gas, solids, or liquids. Radon gas may appear in methane and during production off-gassing. NORM may also occur in rock chips created during the drilling process, or in flowback water.

2  

Oil and gas workers and members of the public may be exposed to the radioactive material derived from unconventional oil and gas development. Exposures of workers are characterized as occupational exposures and exposures to members of the public are characterized as non-occupational exposures. Potential exposure pathways for workers may include direct radiation exposure to contaminated drill cuttings, direct radiation exposure to equipment contaminated with radionuclides, and inhalation of dust containing radionuclides. For members of the public, potential exposure pathways could include radon inhalation, dust inhalation from radioactive material blown offsite, external exposure to radioactive material blown offsite, ingestion of radioactive material blown offsite, and radiation exposure through the spreading of brine on roadways, pit abandonment, and brine discharges to land.

The safe handling and disposal of NORM and TENORM begins on site, with the classification and appropriate handling of drilling waste. The elements of a successful NORM management practices include: advanced establishment of action limits; detection of NORM at the drill site; establishing contamination control procedures at a drill site; control and proper handling of NORM contaminated waste and equipment; and appropriate handling and disposal of NORM contaminated waste and equipment.

3  

Naturally Occurring Radioactivity

Uranium, potassium, and thorium are the most common radioactive materials in rocks and soils, and these radioactive materials are most frequently contained in clay-stone and shale (both sedimentary rocks), and in rocks from deep within the Earth (known as igneous or metamorphic rocks). The most common rocks containing radioactive materials in sedimentary rock formations occur in carboniferous shale and clay. These rocks are exposed on the surface in many areas. For example, the Ohio Shale occurs at the surface in various locations in the Columbus area (e.g., Hoover Reservoir, Alum Creek Reservoir, along the stream in Whetstone Park, in several deep ravines that cut across Columbus, Ohio etc.), and shale will occasionally be penetrated by excavations for buildings throughout the city of Columbus. In Utica New York, the Utica Shale formation is exposed on the surface – hence the reason for the name of this particular formation; likewise, the Marcellus formation is exposed on the surface in Marcellus, New York. Naturally occurring radioactive materials also occur in fresh ground water – fresh water herein is distinguished as water that is potable and located near the surface as contrasted from deep non-potable brine. Radiation from extraterrestrial and terrestrial sources is ubiquitous in our environment.

Ionizing Radiation and Radioactivity

Ionizing radiation is defined as high-energy radiation capable of producing ionization in substances through which it passes. It includes non-particulate radiation, such as x-rays, and radiation produced by energetic, charged alpha and beta particles, and by neutrons, as from a nuclear reaction (American Heritage Dictionary, 2011). Different sources and types of ionizing radiation exist naturally and are often isolated and enriched by human activities. Research and clinical cases have confirmed that human exposure to ionizing radiation may result in related adverse impacts and illnesses. Similar to toxic chemicals, ionizing radiation may result in adverse biochemical and physiological changes manifested as abnormalities, illnesses, or premature deaths among individuals or their offspring exposed to sufficiently elevated doses. Ionizing radiation-related illness can be due to short- or long-term exposures and health impacts can range from dermal redness, acute radiation sickness, somatic and genetic mutations, and cancers. Radiation exposure has never been demonstrated to cause hereditary effects in human populations (UNSCEAR, 2001). Research has also demonstrated that ionizing radiation is ubiquitous in the environment, primarily from natural sources, and long-term low-level exposure poses a low risk of radiation-related illness. Nonetheless, there is justifiable concern for risk of adverse human health effects associated with both natural and anthropogenic sources of ionizing radiation, but several factors must first be considered. A primary guiding principle that underlies studies of radiation related human health impacts is that without human exposure to ionizing radiation there is no exposure hazard. To

4  

determine and/or estimate the hazard potential associated with ionizing radiation several environmental factors must be considered as listed and summarized below.

Types of Radionuclides and Associated Radiation Emitted – Radionuclides vary in many ways, including their respective decay rates and the penetrability and hazard associated

with the radiation emitted. For example, gamma () rays penetrate materials, including

human tissue, more readily than beta () or especially alpha () particles. Radiation that

readily penetrates the skin ( or ), for example, is an “external” hazard, but other types,

such as particles, are attenuated by skin and must be inhaled, ingested or injected to cause systemic effects and are designated as an “internal” hazard.

Sources of Radionuclides and Radiation – Proximity to and containment of NORM influences its hazard potential; there is typically lower hazard potential associated with immobilized or more contained forms of radionuclides since they are less likely to be distributed or spread within the environment.

Environmental Matrices and Pathways of Contact – Soil, water, air, food, products, and wastes represent various matrices that may be contaminated with radioactive materials. Contact with these matrices determines the pathway (e.g., airborne) and associated mode (e.g., inhalation) and route (e.g., respiratory system) involved for potential human exposure.

Concentrations and Levels – The concentration of radionuclides in a matrix and the levels

and types of radiation (, , or ) may increase the hazard potential and likelihood of exposure and risk for initiating radiation-related response or illness.

Distance and Shielding Between Radiation Sources and Humans – Increasing the distance and/or shielding (depending on material e.g., lead vs. wood) decreases the levels of radiation and potential human exposure.

Modes and Routes of Entry for Exposure – Inhalation, ingestion, and dermal absorption represent modes and respiratory, gastrointestinal, and dermal systems, respectively, the corresponding routes of exposure and entry of radiation. For example, inhaled alpha-emitting radionuclides may target and adversely impact the lungs, but dermal contact with alpha-emitting radionuclides may be limited to minor redness or burning of the skin, depending on levels of exposure. The range of alpha particles in skin is less than the thickness of the dead layer of the skin (stratum corneum).

Duration of Exposure – When contact with sources of and exposure to radiation occurs, the risk of initiating an adverse health effect increases with the duration of exposure.

Other Exposure Factors -- When measurable human exposure occurs, other non-environmental factors associated with each individual, or biological factors, such as genetic predisposition to disease, for example, influence the risk or probability of a radiation-related adverse impact or illness occurring.

Further technical information about radiation is provided in the Appendix.

5  

Background Radioactivity and Radiation

Ionizing radiation present in our natural environment can be classified according to its origin or its type. The National Council on Radiation Protection and Measurements (NCRP) has separated natural background radiation into four categories: external exposure from space radiation (solar particles and cosmic rays), external exposure from terrestrial radiation, internal exposure from inhalation of radon and thoron, and internal exposure from radionuclides in the body (NCRP 2009).

External exposure from space radiation is a consequence of bombardment of the earth by solar particles and cosmic rays coming to the earth from space. In general, this radiation increases with increasing altitude and latitude and contributes about the same fraction of the average natural background radiation dose to an individual in Ohio as does terrestrial radiation.

Terrestrial radiation is a consequence of the radioactive decay of atoms (known as radionuclides) that are present in the earth. Terrestrial radiation can be generally classified as being either alpha

(), beta () or gamma-ray () radiation. Alpha, beta and gamma-ray radiation are emitted in the decay of radioactive nuclei. Alpha particles are energetic helium nuclei that are emitted in radioactive decay. Beta particles are energetic electrons that are emitted in radioactive decay, and gamma-rays are energetic photons that are emitted in radioactive decay. The classification above of radiation as either alpha, beta, or gamma-ray radiation is not entirely precise, since electrons can be emitted in radioactive decay processes that are not strictly classified as beta particles (for example, conversion electrons); also energetic photons can be emitted in radiation decay processes that are not strictly classified as gamma-rays (for example, x-rays).

Terrestrial radiation can be classified as primordial or cosmogenic. Primordial terrestrial radiation is a consequence of the radioactive decay of radionuclides that were present when the earth was formed. Cosmogenic terrestrial radiation is a consequence of the radioactive decay of radionuclides that are produced by cosmic rays interacting with and transforming nuclei in the earth’s atmosphere. These radionuclides are then incorporated into the matter of the earth. Examples of primordial terrestrial radionuclides are uranium-238 (238U), uranium-235 (235U), thorium-232 (232Th), and potassium-40 (40K). An example of a cosmogenic terrestrial radionuclide is carbon-14 (14C). In general, cosmogenic terrestrial radionuclides contribute a small fraction of the average terrestrial radiation dose to an individual in comparison to primordial terrestrial radionuclides.

The distribution of space and terrestrial radiation doses for North America are shown in Figures 1 and 2, respectively.

6  

 

 

 

 

7  

Radon as Background Radiation

The 238U, 235U, and 232Th primordial radionuclides decay through radon-222 (222Rn), radon-219 (219Rn), and radon-220 (220Rn); respectively.1 These gaseous radionuclides can migrate from soil into structures such as homes and lead to internal exposures, primarily from inhalation of their short-lived radioactive progeny. The average radiation dose to a member of the U.S. population from these gaseous radionuclides and their short-lived radioactive progeny is estimated to be 2.28 mSv/yr, with about 93 percent coming from 222Rn and its short-lived progeny and 7 percent coming from 220Rn and its short-lived progeny (NCRP 2009). Because of its very short half-life (3.96 s), the radiation dose from 219Rn and its progeny is very small.

According to the U.S. Environmental Protection Agency, the average indoor radon level is estimated to be about 1.3 pCi/L while the average outdoor radon concentration is 0.4 pCi/L. Figure 3 illustrates the distribution of indoor radon concentrations in the United States. This map was developed using five factors to determine radon potentials: indoor radon measurements, geology, aerial radioactivity, soil permeability, and foundation type. In Figure 3, indoor radon concentrations are divided into three zones. Zone 1 contains counties with a predicted average indoor screening level greater than 4 pCi/L, Zone 2 contains counties with a predicted average indoor radon screening level between 2 and 4 pCi/L, and Zone 3 contains counties with a predicted average indoor radon screening level less than 2 pCi/L. For example, central Ohio and parts of western Pennsylvania are predominantly in Zone 1 (see Figure 3). Since radon (i.e., 222Rn) is a progeny of uranium, high concentrations of radon at the surface tend to be associated with some rocks that have intruded into the Earth’s near-surface (some, but not all, igneous intrusive and volcanic rock), shale rock, and soil containing glacial or shale debris. Most of Zone 1 occurs in the northern states and along regions where igneous rocks have recently intruded into the Earth’s surface in the past hundreds of millions of years (e.g., Hawaii, and along the Appalachian Mountains). In Ohio, counties with average radon concentrations greater than 4 pCi/L seem to be associated with the north-south trending Ohio Shale outcrop band, in limestone glacial soils, and in some residual limestone soils (USGS 1993).

                                                            1 222Rn is referred to as “radon,” 220Rn is referred to as “thoron,” and 219Rn is referred to as “actinon.” 

8  

Summary of Natural Background Radiation Doses

Figure 4 illustrates the contributions of the four categories of natural background radiation to the total natural background radiation dose of 3.11 mSv/yr (NCRP 2009). Internal exposures from radon and thoron account for about 73 percent of the total radiation dose from natural background radiation, while external exposures from space radiation, internal exposures from radionuclides in the body, and external exposures from terrestrial radiation account for 11 percent, 9 percent, and 7 percent of the total radiation dose, respectively.

9  

  

 

Rocks and NORM

The Formation of Sedimentary Rocks Bearing Hydrocarbons and Radioactive Materials – Appalachian Example

In the depths beneath the Appalachian surface, the upper part of Earth’s subsurface is divided into two major rock layers called the sedimentary section and basement rocks. Basement rocks are ancient (mostly greater than 1 billion years old) metamorphic and igneous rocks, while the overlying sedimentary rocks are younger, formed when our region was periodically covered by oceans and shallow seas. The depth of the ocean water and the climate at any given time determined the type of sedimentary rock deposited. If the ocean water was warm and shallow, coral reefs formed, while other times, the ocean water would recede slightly and sandy beaches would form, creating layers of sandstone. At the mouth of rivers emptying sediments into the ocean, deltas and swamps would form, while out in the deep water, fine grained clays and organic material would be deposited. Each of the sediment layers (coral, sand, swamp muck, and clays) eventually were buried and compacted as the overlying ocean depth and the regional climate changed, forming a different rock layer (younger rock layers stacked on top of older

10  

rocks). Under the pressure of burial, the coral was compacted into limestone, the organic rich muck of the swamps became coal, the sand became sandstone, and the clays became shale.

These layers of different rock types form what geologists call the sedimentary section (see Figure 5). Organic compounds in the shale were converted, after millions of years of burial, to hydrocarbons (oil and gas). A portion of the oil and gas moved (migrated) into overlying porous sandstone and limestone where it was geologically “trapped” in certain geographic locations. Until very recently, exploring and developing (drilling, extraction, and sometimes hydraulic fracturing) geologic traps in sandstone and limestone with vertical drilling has been the mainstay of the petroleum industry, and is often referred to as conventional petroleum development. During the first century and a half of the petroleum industry, most of the natural gas, and some oil, remained untapped in the shale where the hydrocarbons originated. Beginning in the 21st century, horizontal drilling and hydraulic fracturing have enabled the petroleum industry to tap into the hydrocarbons trapped in the shale. The term “gas shale” has become the common term for unconventional sources of hydrocarbons extracted from the shale rock. The shale layers that are the primary targets of exploration in the Midwest are the Marcellus Shale, formed approximately 385 million years ago, and the deeper Utica Shale, formed approximately 475 million years ago.  

 

11  

Rocks and Radioactivity

With the exception of non- potassium bearing chemical precipitates (e.g., calcium carbonate, anhydrite, halite, and kieserite) and some pure mineral forms of igneous rocks and minerals (e.g., quartz) and metamorphic rocks (e.g., quartzite), most of the rocks in the earth contain some amount of 40K, the uranium decay series (begins with 238U) , actinium decay series (begins with 235U, and/or the thorium decay series (begins with 232Th). The original source of radioactive material in rocks (igneous, metamorphic, and sedimentary) is igneous and metamorphic rocks (plutonic and volcanic) that existed at the time the Earth was formed. These igneous rocks were weathered (by wind and water), disaggregated, transported by streams and rivers, and deposited in the form of inorganic sediments on the surface of the earth and in the ocean. Sediments deposited in the ocean are called marine sediments, while those deposited on land and in fresh water are called terrestrial or fluvial sediments, respectively. Sediments deposited close to the ocean-land margins are called marginal marine deposits. Geologic strata that frequently contain elevated NORM concentrations include: coal seams, phosphate-rich marine deposits, some granitic rocks, some sandstones, some evaporate minerals (e.g., sylvite and potassium phosphate), and marine black shale. The concentration of uranium in common rocks is shown in Figure 6. 

According to Schubert (2014), the average NORM concentrations in the Earth’s crust (basement rocks below the surface of the Earth) are as shown in Figure 7.

12  

Radioactivity in Shale

Geologically, shale is a laminated, indurated, fissile, sedimentary rock composed mostly of silt- and clay-sized grains. A photograph of a Marcellus Shale outcrop is shown in Figure 8.

Hydrocarbon bearing shale’s were predominantly formed by the deposition of wind and water eroded materials from exposed continental crustal rock. The deep ocean conditions that formed the Marcellus Shale in the Appalachian oceanic basin occurred approximately 375 million years ago (Devonian), and for the Utica Shale the deep ocean deposits formed approximately 475 million years ago (Ordovician). The fine-grained material accumulated

on the sea floor. Radioactive materials (40K, uranium decay series, and thorium decay series minerals) were likely introduced into the sediments from terrestrial, and possibly oceanic source on the sea floor, while the fine-grained materials were still in an unconsolidated form lying on the ocean floor. Changes in sea level, caused by movement of the continents, and/or tectonic movement of the basement rocks (plutonic and volcanic) beneath the ocean caused calcium carbonate inter-beds and other lithological layers between the fine-grained shale layers. Eventually, long-cycle sea level changes caused the ocean deep to evolve into another non-shale geologic environment (carbonate reef, beach, marginal marine, etc.), terminating the formation of the shale layer. The geologic regime for the formation of shale is shown in Figure 9.

13  

Shale is generally classified as gray shale or black shale, referring to the color of the shale. Gray shale and black shale have the following characteristics (Babcock 2014):

Gray shale and black shale often occur together (see Figure 10)

Gray shale has a higher calcium carbonate content

Black shale tends to have higher organic carbon and iron sulfide content

Gray shale tends to contain 40K and members of the thorium decay series

Black shale contains 40K, and members of the thorium and uranium decay series

Black shale is the primary source rock for hydrocarbon accumulation

Any radionuclide in crustal rocks can be expected to be present in shale, including the primordial radioisotopes (238U, 235U, 232Th, and 40K) and decay products (progeny). The radionuclides possibly present include: 40K, 232Th, 238U, 226Ra, 228Ra, and 222Rn. In summary, according to Babcock (2014) shale can have high NORM values for the following reasons:

The radionuclides originally present in crustal source rocks, usually as impurities in their mineral components, are present in shale.

Shale is the final repository of crustal weathering products, and can concentrate those mineral components that cannot be readily broken down further

Shales have higher NORM values than most lithologies because 40K and 232Th preferentially bond to clay minerals

In addition, organic-rich shale (“black shale”) has even higher NORM values because 238U and 235U preferentially bond to organic matter.

NORM in Unconventional Oil and Gas Production

Shale can contain radionuclides in concentrations that are considerably greater than their concentrations in other rock types, such as limestone, and can be classified as NORM. During

14  

unconventional oil and gas production, NORM may appear from several different sources (Lombardo 2014):

Gas – NORM (radon) may appear in methane and during off-gassing.

Solids – NORM may appear in horizontal drill cuttings – rock chips created during the drilling process. Figure 11 shows drill cuttings on a vibrating mud screen.

Liquids – NORM may appear in process and flowback water. In addition, when NORM-containing water is treated, the resulting sludge, filter cakes, etc. almost always concentrate the NORM as a solid.

The concern regarding hydraulic fracturing is that the radiation dose to individuals from primordial terrestrial radiation will be increased as a consequence of bringing radionuclides that are deep within the earth to the earth’s surface. However, the cuttings (from vertical and horizontal drilling) do not have much greater concentrations of NORM than the same surface rock and soil from the same geologic formations. Potential pathways for NORM to the surface are shown in Figure 12.

There are two groups of people who may be exposed to the radioactive material derived from unconventional oil and gas development; workers and members of the public. Exposures of workers are characterized as occupational exposures and exposures of members of the public are characterized as non-occupational exposures. Typical exposure pathways for workers may include direct radiation exposure to contaminated drill cuttings, direct radiation exposure to equipment

15  

contaminated with radionuclides, and inhalation of dust containing radionuclides. Dust inhalation could also occur when contaminated scale or sludge is cleaned from the inside surfaces of equipment during well work-over operations Smith (1992). Direct contact with contaminated scale and sludge could result in beta particle exposures to the skin. Potential external exposures could occur when the concentration of radioactivity inside equipment is high enough that gamma rays penetrate the equipment walls, and contaminated scale and sludge are removed from the equipment, thereby eliminating the shielding factor provided by the equipment walls (Smith 1992). Smith (1992) considered external exposure to be the pathway of greatest concern for workers. Wastes from the treatment of production waters may also contain concentrated radioactive material and, if so, controls would be required to limit radiation exposure to workers handling this material as well as to ensure that this material is disposed of in accordance with applicable regulatory requirements (DEC 2011).

For members of the public, potential exposure pathways could include radon inhalation, dust inhalation from radioactive material blown offsite, external exposure to radioactive material blown offsite, ingestion of radioactive material blown offsite, and radiation exposure through the road spreading of brine, pit abandonment, and brine discharges to land. If flowback or produced waters were discharged to surface or ground waters, exposures through these pathways could also occur. However, EPA regulations strictly regulate the construction of hydraulic fracturing wells and the handling of these waters, so these pathways are not likely to be significant.

TENORM in Unconventional Oil and Gas Production

Technically enhanced NORM, or TENORM is naturally occurring radioactive materials where the concentration of NORM has been increased by human activity, or relocation, or processing of NORM has increased potential radiation exposure to humans (Schubert 2014). TENORM accumulates along with other drilling by-product material as scale on pipes (see Figure 13) and drilling equipment, and tends to accumulate in the sludge that is concentrated from the drilling process. Sludge is a concentration of particulate matter that is a byproduct of water treatment and filtration processes. For example, barium extraction inadvertently concentrates radium in filter cake sludge (drilling mud and very fine particles ground up by the drilling process), as do filter socks (fine mesh) that separate the water from the particulate matter. Scale is enhanced by acidity, temperature and pressure in the well environment. Typically, when present in

16  

NORM, TENORM contained in pipe and tank scale is included in the Group IIA elements (barium, strontium, calcium, and radium).

Argonne National Laboratory recently evaluated the potential radiation doses from waste streams containing TENORM in North Dakota (Harto et al. 2014). The waste streams included the scale accumulated within pipe and other oilfield equipment, sludge accumulated in produced water storage tanks and vessels, filter cake from filtration of water, disposable filter socks, and some synthetic fracturing proppants that have been found to contain low levels of TENORM. For workers, the exposure scenarios evaluated included mixing of hydraulic fracturing fluid, produced water filtration, pipe cleaning, storage tank cleaning, equipment cleaning at a gas processing plant, and sludge treatment. The results in Harto et al. (2014) suggest that it may be important to monitor and limit the duration of exposure for workers involved in pipe and storage tank cleaning activities and that the use of proper Personal Protective Equipment (PPE) is important to protect workers with regular exposure to TENORM.

For members of the public, the exposure scenarios evaluated were based on improper waste disposal, and included a child playing with a used filter sock, a load of filter socks being disposed of in an urban dumpster, and a child playing in a pile of spilled synthetic proppants. While the results in Harto et al. (2014) suggest that the risks to the public are likely relatively low from short-term exposure to waste that is improperly disposed of, they are not representative of all possible exposures, and Harto et al. (2014) states that extra care should be taken to ensure that such exposures do not occur.

Operational Framework for Handling NORM and TENORM

The safe handling and disposal of NORM and TENORM begins on site, with the classification and appropriate handling of drilling waste. As discussed in Gannon and Lopez (2014), NORM management programs should be implemented that include basic radiation safety practices, reduction of occupational and public exposures, reduction of environmental liability, and reduction of costs. As illustrated in Figure 14 the elements of a successful NORM management could include:

Detection of NORM

Establishing Action Limits

Contamination control procedures

Control of NORM-contaminated waste

Control of NORM-contaminated equipment

Development of standard operating procedures to cover potential contingencies.

17  

Figure 14. NORM management framework (modified from Gannon and Lopez 2014).

Especially important is the protection of on-site workers, which can be achieved through worker training and awareness, a hazard identification program, appropriate radiological controls, and through the use of personal protective equipment.

A more general view of the disposal process from a regulatory perspective is shown in Figure 15 for the overarching operational lifecycle framework for NORM and TENORM handling and disposal.

18  

 

Figure 15. The overarching decision process for handling NORM and TENORM on and off the drilling site (personal communication, Paul Ziemkiewicz, West Virginia University). (TCLP is the toxicity characteristic leaching procedure (USEPA Publication SW 846). RCRA is the Resource Conservation and Recovery Act of 1976. Subtitle B specifies the authorities of the administrator of the Office of Solid Waste. Subtitle C specifies the “cradle to grave requirements” for solid waste disposal under RCRA. Subtitle D specifies procedures for handling non-hazardous solid waste. NPDES is the National Pollutant Discharge Elimination System (water permitting) as authorized by Section 402 of the Clean Water Act.)

Conclusions

Naturally occurring radioactive material is ubiquitous in subsurface rocks that are also sometimes exposed as outcrops at the Earth’s surface. Like background solar and cosmic radiation, they are a normal component of the radiation exposure on the Earth’s surface. Radioactive minerals tend to concentrate in shale. Prior to hydraulic fracturing for oil and gas production in shale, there was little concern about the relatively small quantities of shale rock waste brought to the surface by conventional, vertical, oil and gas production in porous sandstone and limestone producing zones. However, oil and gas production in a typical horizontal well can yield several hundred cubic yards of solid waste from a single hole, and some of this waste contains radioactive material that must be disposed of in RCRA Subtitle C landfills.

In order to separate waste containing radioactive material from uncontaminated material, special procedures have been developed to handle solid (drilling chips) and liquid waste (sludge, and flowback water) on drill sites. These procedures involve the identification of the waste according to accepted standards and following the appropriate handling options (treatment, stabilization, dilution, and transportation).

Although practices and procedures are in place at most drilling sites to ensure safe handling and disposal of NORM and TENORM, the development of automated methods for on-site classification and packaging of NORM contaminated waste could save time and money, and help to ensure safe handling procedures. Research that better identifies the mineral constituents of

19  

shale that are most likely to be associated with radioactive elements could provide an improvement in predicting zones within a lateral drill hole that are likely to yield NORM materials. In addition, the development of a process to separate and concentrate radioelements from shale drilling waste would help to decrease the total amount of waste that requires Subtitle C disposal.

Acknowledgments

NORM workshop presenters: Loren Babcock, The Ohio State University, Columbus, OH; Tarunjit Butalia, The Ohio State University, Columbus, OH; Prabir Dutta, The Ohio State University, Columbus, OH; John Frazier, consultant, Knoxville, TN; Mark Gannon, AMEC Environment & Infrastructure, (Carnegie, PA); Mike Hall, Clean Harbors Environmental Services, (Ogden, UT); Dennis Leeke, Pace Analytical, (Greensburg, PA); Andy Lombardo, Perma-Fix Environmental Services, Beaver, PA; Alex Lopez, AMEC Environment & Infrastructure, (Carnegie, PA); Mark Moody, Battelle, Columbus, OH; Holly Pearen, Environmental Defense Fund, Boulder, CO; Jeff Schubert, Paul C. Rizzo Associates, Pittsburgh, PA; Bill Thomas, Integrated Environmental Management, Findlay, OH; Elisabeth Widom, Miami University, Oxford, OH; Paul Ziemkiewicz, West Virginia University, Morgantown, WV

NORM Working Group: Nick Basta, The Ohio State University, Columbus, OH; Mike Bisesi, The Ohio State University, Columbus, OH; Thomas Blue, The Ohio State University, Columbus, OH; Tarunjit Butalia, The Ohio State University, Columbus, OH; Raymond Cao, The Ohio State University, Columbus, OH; Bob Chase, Marietta College, Marietta, OH; Roman Lanno, The Ohio State University, Columbus, OH; John Lenhart, The Ohio State University, Columbus, OH; Steve Maheras, Pacific Northwest National Laboratory, Columbus, OH; Dan Mueller, Environmental Defense Fund, Austin, TX; Doug Patchen, West Virginia University, Morgantown, WV; Doug Southgate, The Ohio State University, Columbus, OH; Tom Williams, Environmentally Friendly Drilling, The Woodlands, TX; Bill Wolfe, The Ohio State University, Columbus, OH

Special Thanks to Steve Maheras (PNNL), Thomas Blue (Ohio State), and Mike Bisesi (Ohio State) for their extra efforts on early drafts of this paper.

20  

References

American Heritage, 2011, Dictionary of the English Language, Fifth Edition, Houghton Mifflin Harcourt Publishing Company.

Babcock LE. 2014. “The Geologic Nature of Shale.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

DEC (New York State Department of Environmental Conservation). 2011. Revised Draft Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution Mining Regulatory Program, Well Permit Issuance for Horizontal Drilling and High-Volume Hydraulic Fracturing to Develop the Marcellus Shale and Other Low-Permeability Gas Reservoirs. New York State Department of Environmental Conservation, Albany, New York.

Frazier JR. 2014. “Ionizing Radiation and Hazard Potential.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

Gannon M and A Lopez. 2014. “Approaches with Recycle, Treatment, and Disposal of Flowback and Produced Water and the ABCs of Managing NORM in the Marcellus Shale Region.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

Harto CB, KP Smith, S Kamboj, and JJ Quinn. 2014. Radiological Dose and Risk Assessment of Landfill Disposal of Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) In North Dakota. Report No. ANL/EVS-14/13.

Lombardo A. 2014. “NORM and Unconventional Oil and Gas Production.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

Moody M. 2014. “Basics of Drilling, Coring, and On-Site Disposal of Solids and Fluids.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

NCRP (National Council on Radiation Protection and Measurements). 2009. Ionizing Radiation Exposure of the Population of the United States. NCRP Report No. 160. National Council on Radiation Protection and Measurements, Washington, D.C.

OEPA (Ohio Environmental Protection Agency). 2015. Marcellus and Utica Shale Regions in Ohio. Available at http://epa.ohio.gov/MarcellusandUticaShale.aspx.

Schubert J. 2014. “NORM and TENORM Related to Geological Deposits and the Oil & Gas Industry.” Presented at NORM and TENORM: Occurrence, Characterizing, Handling, and Disposal Workshop, May 12, 2014, Columbus, Ohio. Available at http://serc.osu.edu/node/432.

Smith KP. 1992. An Overview of Naturally Occurring Radioactive Materials (NORM) in the Petroleum Industry. Report No. ANL/EAIS-7. Argonne National Laboratory, Argonne, Illinois.

UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation). 2001. Report of the United Nations Scientific Committee on the Effects of Atomic Radiation to the General Assembly. New York, New York.

USGS (U.S. Geological Survey). 1993. Geologic Radon Potential of EPA Region 5. Open File Report 93-292-E.

USGS (U.S. Geological Survey). 1997. Radioactive Elements in Coal and Fly Ash: Abundance, Forms, and Environmental Significance. U.S. Geological Survey Fact Sheet FS-163-97.

21  

APPENDIX

Basics of Radioactivity

Steven Maheras, PNNL, steven.maheras@pnnl.gov

Jeff Daniels, OSU, daniels.9@osu.edu

I. Radiation

Radiation is energy in transit, either as particles or electromagnetic waves, and radioactivity is the characteristic of some materials that emit radiation. Radioactive materials emit radiation, and are often called radionuclides.

In the most fundamental definition, radiation is the term that describes the transmission of energy through time and space, without the necessity of a physical medium to support the wave. The different types of radiation are shown in Figure A1. A wave can propagate (move) through a vacuum (e.g., outer space). Radiation may be in the form of waves (e.g., electromagnetic), subatomic particles (e.g., neutrons, electrons), or subatomic energy packets that have wave and particle characteristics (e.g., light, gamma rays, x-rays). Each type of radiation spreads out (radiates) from a source, and the intensity of the radiation diminishes away from the source.

 

Figure A1. The electromagnetic spectrum and ionization (http://www.arpansa.gov.au/radiationprotection/basics/ion_nonion.cfm).

22  

Ionizing radiation is radiation that has enough energy to ionize atoms and change the structure and nature of atoms. We usually think of gamma-rays, neutrons, and x-raysas ionizing radiation. Radiation interacts with matter by imparting some, or all, of its energy in the matter that it hits. Charged particles (e.g., alpha and beta particles) ionize or excite the atoms in matter, while gamma rays and x-rays interact primarily with electrons. Ionization is the process wherein the radiation interacts with matter and deposits some, or all, of its energy in atoms (or molecules) by dislodging one or more electrons from the atom or molecule. After ionization, the atom is ionized, and the atom is deficient by one or more electrons. If the atom is part of a molecule, then ionization may lead to molecular dissociation (breaking) and subsequent recombination.

Radionuclides lose energy when they emit radiation, and they are said to decay with each emission of radiation. At some point, the energy loss of the atom of a radionuclide reaches a point whereby the original atom loses an alpha particle (a helium nucleus), gamma photon, or beta particle (an energetic electron) and becomes a new atom with a lower energy level: The original atom is called the parent atom, and the new atom is called the progeny atom. Figure 2(a) illustrates the basics principle of radioactive decay.

 

Figure A2. Fundamental elements of radioactive decay: a) generalized decay and particle emission, b) radioactive decay of 238U to 234Th.

The type of radioactive decay depends upon the original radionuclide, and decay mode may result in emitting a gamma ray, a neutron, a beta particle, or an alpha particle. The radioactive decay of 238U to 234Th is illustrated in Figure 2(b). The amount of time it takes for a parent radionuclide to decay to a progeny radionuclide is called the half-life of the radionuclide. The range of half-lives for radionuclides varies from very short (e.g., 160 sec for 214Po) to very long (e.g., 4.5 billion years for 238U).

Primordial terrestrial radiation is mainly a consequence of the radioactive decay of radionuclides in three naturally occurring decay series. These decay series are known as the uranium series, the actinium series, and the thorium series. These series begin with 238U, 235U, and 232Th respectively. A schematic for the uranium and thorium decay series and associated half-lives is shown in Figure A3.

23  

   

Figure A3. Uranium and Thorium Decay Series (Gannon, Lopez, 2014).

Here, the symbol U or Th represents the element Uranium or Thorium and the number following the element symbol is the number of nucleons (protons and neutrons) in the nucleus of the atom. The nuclei that begin the three naturally occurring decay series are the longest lived radionuclides in their respective series. They have half-lives (the time that it takes for the concentration of a specific radionuclide to decrease by a factor of ½, assuming there is no migration of the radionuclides) on the order of the age of the earth. The three series end in stable isotopes of lead, 206Pb, 207Pb, and 208Pb for the Uranium, Actinium and Thorium series respectively. The radionuclides in the series decay by alpha, beta, and gamma-ray emission. The rate of decay (number of decays per unit time) of each of the nuclei in the decay series would be equal to the rate of decay (activity) of the radionuclide beginning the series (a phenomenon known as secular equilibrium), if there were not migration of the radionuclides in the earth.

24  

II. Measures of Radioactivity

Radioactivity is measured in terms of the number of radioactive particles or photons emitted by a material and the energy of the particles or photons. The quantity, or number, of radioactive particles or photons emitted by a radioactive material is called its activity, and the non-SI unit of measure for activity is often expressed in terms of the curie (Ci), where 1 Ci = 3.7 1010 decays/s, which is approximately the activity of 1 gram of 226Ra. The SI unit is the becquerel (Bq), which is 1 decay per second (1 Ci = 3.7 1010 Bq). For radiation to be ionizing, it must have an energy greater than about 34 electron volts (eV).

The curie is also commonly used as a measure of the amount, by mass, of a radioactive material. For example, the mass of 1 curie of radium is 1.01 grams of radium. The lower the emission rate, and higher atomic mass, radioactive elements require a much higher mass per curie of material. For example, it takes about 9.1 × 106 grams of 232Th or about 2.9 × 106 grams of 238U to comprise 1 curie of material. Hence, the activity per unit mass (specific activity) is much lower for 232Th and 238U than for 226Ra.

A radiation dose is caused by exposure to radiation or radioactive material. An internal dose is caused by radioactive materials that may enter the body by inhalation, ingestion, injection, or dermal absorption. An external dose is caused by exposure to radiation emitted by radioactive materials that are outside of the body. The total radiation dose is the sum of the internal and external doses to a specific organ or tissue.

For internal doses, the radiation doses is calculated based on the intake of a radionuclide, which may be calculated from an intake rate and duration of intake or calculated from a bioassay, and a dose coefficient, which is provided by published data2 and is based on the radionuclide, chemical and physical form, and the route of intake:

Dose = Intake Dose coefficient

External doses are calculated from the external radiation dose rate from a radionuclide and the duration of exposure:

Dose = Dose Rate Exposure Duration

External dose rates can vary with time and location, and may also be reduced by shielding.

The unit of measure for radiation dose in non-SI units is called the rem, where the rem is defined in terms of the energy deposited per unit mass of tissue (1 rem = 100 erg/g). The SI unit of radiation dose is the Sievert (Sv), where 1 Sv = 1 joule/kg and 1 Sv = 100 rem. Both the rem and

                                                            2 Two commonly used compilations of dose coefficients are contained in: 1) ICRP (International Commission on Radiological Protection). 2001. The ICRP Database of Dose Coefficients: Workers and Members of the Public. Version 2.0.1. New York, New York: Elsevier, and 2) EPA (U.S. Environmental Protection Agency). 2002. Federal Guidance Report 13, CD Supplement, Cancer Risk Coefficients for Environmental Exposure to Radionuclides, EPA. EPA‐402‐C‐99001, Rev. 1. Washington, D.C.: U.S. Environmental Protection Agency. 

25  

the Sv take into account the biological damage caused to an organ or tissue by the specific type of radiation (e.g., , , or ) and the risk of developing cancer or a severe genetic effect in the organ or tissue.

The average annual radiation dose from natural background radiation sources and medical sources are shown in Figures 4 and 5, respectively.

         

Figure A4. Annual Radiation Dose from Natural Sources

 

Figure A5. Annual Radiation Dose from Medical Sources (NCRP, 2009).