Radionuclides associated with hydraulic fracturing

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Radionuclides associated with hydraulic fracturing are man-made radionuclides which are used in the hydraulic fracturing process as radioactive tracers or naturally occurring radionuclides released by this process. Injection of man-made radioactive tracers, along with the other substances in hydraulic-fracturing fluid, is often used to determine the injection profile and location of fractures created by hydraulic fracturing.[1] In addition, hydraulic fracturing releases naturally occurring radioactive materials (NORM) from shale deposits, and these substances return to the surface with wastewater.[2] Concerns have been expressed over the potential health and environmental impact of these materials.

Naturally occurring radionuclides[edit]

There are naturally occurring radioactive materials (NORM), for example radium, radon,[3][4] uranium, and thorium,[5][6][7] in shale deposits.[8] Brine co-produced and brought to the surface along with the oil and gas sometimes contains naturally occurring radioactive materials; brine from many shale gas wells, contains these radioactive materials.[8][9][10] When NORM is concentrated or exposed by human activities, such as hydraulic fracturing, it is classified as TENORM (technologically enhanced naturally occurring radioactive material).[11][12] Naturally occurring radionuclides are of more concern than man-made radionuclides used in fracture monitoring because the former have longer half lives and so remain in the environment longer.

Injected radionuclides[edit]

Use of radioactive tracers is strictly controlled. It is recommended that the radiotracer is chosen to have readily detectable radiation, appropriate chemical properties, and a half life and toxicity level that will minimize initial and residual contamination.[13] Operators are to ensure that licensed material will be used, transported, stored, and disposed of in such a way that members of the public will not receive more than 1 mSv (100 mrem) in one year, and the dose in any unrestricted area will not exceed 0.02 mSv (2 mrem) in any one hour. They are required to secure stored licensed material from access, removal, or use by unauthorized personnel and control and maintain constant surveillance of licensed material when in use and not in storage.[14] Federal and state nuclear regulatory agencies keep records of the radionuclides used.[14]

As of 2003 the isotopes Antimony-124, argon-41, cobalt-60, iodine-131, iridium-192, lanthanum-140, manganese-56, scandium-46, sodium-24, silver-110m, technetium-99m, and xenon-133 were most commonly used by the oil and gas industry because they are easily identified and measured.[13][15] Bromine-82, Carbon-14, hydrogen-3, iodine-125 are also used.[14][13]

Some radioactivity may by brought to the surface at the well head during testing to determine the injection profile and location of fractures. Typically this uses very small (50 kBq) Cobalt-60 sources and dilution factors are such that the activity concentrations will be very low in the topside plant and equipment.[13]

Examples of amounts used are:[14]

Nuclide Form Activity
Iodine-131 Gas 100 millicuries (3.7 GBq) total, not to exceed 20 mCi (0.74 GBq) per injection
Iodine-131 Liquid 50 millicuries (1.9 GBq) total, not to exceed 10 mCi (0.37 GBq) per injection
Iridium-192 "Labeled" frac sand 200 millicuries (7.4 GBq) total, not to exceed 15 mCi (0.56 GBq) per injection
Silver-110m Liquid 200 millicuries (7.4 GBq) total, not to exceed 10 mCi (0.37 GBq) per injection

Concerns about environmental impact[edit]

In 2010 the Pennsylvania Department of Environmental Protection (DEP) limited surface water discharges from new treatment plants to 250 mg/l chloride; the chloride limitation was designed to preclude most of the potential for radium contamination. Existing water treatment plants were "grandfathered," and still allow higher discharge concentrations.[16] In 2011, the level of dissolved radium in hydraulic fracturing wastewater released upstream from drinking water intakes had been measured to be up to 18,035 pCi/L (667.3 Bq/l),[10] and the gross alpha level measured to be up to 40,880 pCi/L (1,513 Bq/l).[8][10] The New York Times reported that studies by the United States Environmental Protection Agency and a confidential study by the drilling industry concluded that radioactivity in drilling waste cannot be fully diluted in rivers and other waterways.[17] Recycling the wastewater has been proposed as a solution but has its limitations.[18] A recent Duke University study sampled water downstream from a Pennsylvania wastewater treatment facility from 2010 through Fall 2012 and found the creek sediment contained levels of radium 200 times background levels.[19] The surface water had the same chemical signature as rocks in the Marcellus Shale formation. The facility denied processing Marcellus waste since 2011. In May 2013 the facility signed another agreement to not accept or discharge wastewater Marcellus Shale formations until it has installed technology to remove the radiation compounds, metals and salts.[20][21] According to the Duke researches the ‘waste treatment solids/sludge’ have exceeded U.S. regulations for radium disposal to soil.[22] The study by Duke University also found that radium has been ‘absorbed and accumulated on the sediments locally at the discharge’.[22]

Potential health impact[edit]

The U.S. Environmental Protection Agency and regulators in North Dakota considers radioactive material in flowback a potential hazard to workers at hydraulic fracturing drilling and waste disposal sites and those living or working nearby if the correct procedures are not followed.[23][23][24][24]

Regulation in the US[edit]

The NRC and approved state agencies regulate the use of injected radionuclides in hydraulic fracturing in the United States.[14]

The US EPA sets radioactivity standards for drinking water.[25] Federal and state regulators do not require sewage treatment plants that accept gas well wastewater to test for radioactivity. In Pennsylvania, where the hydraulic fracturing drilling boom began in 2008, most drinking-water intake plants downstream from those sewage treatment plants have not tested for radioactivity since before 2006.[26] The EPA has asked the Pennsylvania Department of Environmental Protection to require community water systems in certain locations, and centralized wastewater treatment facilities to conduct testing for radionuclides.[8][27][28] and although water suppliers are required to inform citizens of radon and other radionuclides levels in their water, this doesn't always happen.[29][30][31]


  1. ^ Reis, John C. (1976). Environmental Control in Petroleum Engineering. Gulf Professional Publishers.
  2. ^ "Iodine 131 Found in Philadelphia's Drinking Water" (Press release). Bucks County Water & Sewer Authority. 12 April 2011. Retrieved 11 May 2012. "In response to these results, PWD is working with the EPA and DEP and taking the following actions: Developing a Joint PADEP, EPA, PWD Action Plan for all Radionuclides; Initiating a focused sampling program for Iodine; Developing an aggressive track down program with EPA and DEP to identify the potential sources of Iodine 131 in our source waters." 
  3. ^ Staff. "Radon in Drinking Water: Questions and Answers". US Environmental Protection Agency. Retrieved 7 August 2012. 
  4. ^ "Public Health Fact Sheet on Radon - Health and Human Services". Mass.Gov. Retrieved 2011-12-04. 
  5. ^ Weinhold, Bob (19 September 2012). "Unknown Quantity: Regulating Radionuclides in Tap Water". Environmental Health Perspectives. NIEHS, NIH. Retrieved 11 February 2012. "Examples of human activities that may lead to radionuclide exposure include mining, milling, and processing of radio­active substances; wastewater releases from the hydraulic fracturing of oil and natural gas wells... Mining and hydraulic fracturing, or "fracking", can concentrate levels of uranium (as well as radium, radon, and thorium) in wastewater..." 
  6. ^ Heather Smith (7 March 2013). "County's potential for fracking is undetermined". Environment / Pollution. Discover Magazine. Retrieved 11 August 2013. 
  7. ^ Helman, Christopher (23 January 2013). "Energy's Latest Battleground: Fracking For Uranium". Forbes. Retrieved 11 August 2013. "Fracking for uranium isn’t vastly different from fracking for natural gas. UEC bores under ranchland into layers of highly porous rock that not only contain uranium ore but also hold precious groundwater. Then it injects oxygenated water down into the sand to dissolve out the uranium. The resulting solution is slurped out with pumps, then processed and dried at the company’s Hobson plant." 
  8. ^ a b c d Urbina, Ian (26 February 2011). "Regulation Lax as Gas Wells' Tainted Water Hits Rivers". The New York Times. Retrieved 22 February 2012. "The level of radioactivity in the wastewater has sometimes been hundreds or even thousands of times the maximum allowed by the federal standard for drinking water." 
  9. ^ Linda Marsa (1 August 2011). "Fracking Nation. Environmental concerns over a controversial mining method could put America's largest reservoirs of clean-burning natural gas beyond reach. Is there a better way to drill?". Environment / Pollution. Discover Magazine. Retrieved 5 August 2011. 
  10. ^ a b c White, Jeremy; Park, Haeyoun; Urbina, Ian; Palmer, Griff (26 February 2011). "Toxic Contamination From Natural Gas Wells". The New York Times. 
  11. ^ "TENORM Sources". United States Environmental Protection Agency. Retrieved 2012-09-12. 
  12. ^ "Oil and Gas Production Wastes". United States Environmental Protection Agency. Retrieved 2012-09-12. 
  13. ^ a b c d (PDF) Radiation Protection and the Management of Radioactive Waste in the Oil and Gas Industry (Report). International Atomic Energy Agency. 2003. pp. 38-40. Retrieved 20 May 2012. "Beta emitters, including 3H and 14C, may be used when it is feasible to use sampling techniques to detect the presence of the radiotracer, or when changes in activity concentration can be used as indicators of the properties of interest in the system. Gamma emitters, such as 46Sc, 140La, 56Mn, 24Na, 124Sb, 192Ir, 99Tcm, 131I, 110Agm, 41Ar and 133Xe are used extensively because of the ease with which they can be identified and measured. ... In order to aid the detection of any spillage of solutions of the 'soft' beta emitters, they are sometimes spiked with a short half-life gamma emitter such as 82Br..."
  14. ^ a b c d e Jack E. Whitten, Steven R. Courtemanche, Andrea R. Jones, Richard E. Penrod, and David B. Fogl (Division of Industrial and Medical Nuclear Safety, Office of Nuclear Material Safety and Safeguards) (June 2000). "Consolidated Guidance About Materials Licenses: Program-Specific Guidance About Well Logging, Tracer, and Field Flood Study Licenses (NUREG-1556, Volume 14)". US Nuclear Regulatory Commission. Retrieved 19 April 2012. "labeled Frac Sand...Sc-46, Br-82, Ag-110m, Sb-124, Ir-192" 
  15. ^ Dina Murphy and Larry Huskins (8 Sep 2006). letter filed with Department of Environment, New Brunswick, CA (PDF). Penobsquis, CA government. p. 3. Retrieved 29 July 2012. "engineer who works with this radioactive material for a living is exposed to less radiation than an individual who smokes 1.5 packs of cigarettes a day."" 
  16. ^ University of Pittsburgh, Shales Gas Roundtable, p.56, Aug, 2013.
  17. ^ Documents: Natural Gas's Toxic Waste. New York Times. February 26, 2011. 
  18. ^ Ian Urbina (1 March 2011). "Drilling Down: Wastewater Recycling No Cure-All in Gas Process". The New York Times. Retrieved 22 February 2012. 
  19. ^ Carus, Felicity (2 October 2013). "Dangerous levels of radioactivity found at fracking waste site in Pennsylvania. Co-author of study says UK must impose better environmental regulation than US if it pursues shale gas extraction". The Guardian. Retrieved 10 October 2013. 
  20. ^ Warner, Nathaniel R.; Christie, Cidney A.; Jackson, Robert B.; Vengosh, Avner (2 October 2013). "Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania". Environ. Sci. Technol. (ACS Publications). 
  21. ^ Jacobs, Harrison (9 October 2013). "Duke Study: Fracking Is Leaving Radioactive Pollution In Pennsylvania Rivers Business Insider". Business Insider. Retrieved 10 October 2013. 
  22. ^ a b Warner, Nathaniel R.; Cidney A. Christie; Robert B. Jackson; Avner Vengosh (October 2, 2013). "Impacts of Shale Gas Wastewater Disposal on Water Quality in Western Pennsylvania". American Chemical Society: 11849–11857. doi:10.1021/es402165b. 
  23. ^ a b "Radioactive Waste from Oil and Gas Drilling". United States Environmental Protection Agency. April 2006. Retrieved 2013-08-11. 
  24. ^ a b McMahon, Jeff (24 July 2013). "Strange Byproduct Of Fracking Boom: Radioactive Socks". Forbes. Retrieved 28 July 2013. "The U.S. Environmental Protection Agency considers NORM a hazard mostly to workers at the site: “They may inhale radon gas which is released during drilling and produced by the decay of radium, raising their risk of lung cancer. In addition, they are exposed to alpha and gamma radiation released during the decay of radium-226 and the low-energy gamma radiation and beta particles released by the decay of radium-228, according to EPA. “Gamma radiation can also penetrate the skin and raise the risk of cancer.” But North Dakota considers NORM a hazard to the public as well. The state distributes a flyer to oilfield waste haulers that recommends appropriate locations for the disposal of oilfield wastes. The only ones listed that accept radioactive waste are in Colorado, Texas, and South Dakota." 
  25. ^ US EPA, are EPA’s drinking water regulations for radionuclides? What are EPA's drinking water regulations for radionuclides?, accessed 15 Sept. 2013.
  26. ^ Regulation Lax as Gas Wells' Tainted Water Hits Rivers. New York Times. February 26, 2011. 
  27. ^ Shawn M. Garvin (7 March 2011). Letter to PADEP re:Marcellus Shale 030711 (PDF). EPA. Retrieved 11 May 2012. "...several sources of data, including reports required by PADEP, indicate that the wastewater resulting from gas drilling operations (including flowback from hydraulic fracturing and other fluids produced from gas production wells) contains variable and sometimes high concentrations of materials that may present a threat to human health and aquatic environment, including radionuclides....Many of these substances are not completely removed by wastewater treatment facilities, and their discharge may cause or contribute to impaired drinking water quality for downstream users, or harm aquatic life...At the same time, it is equally critical to examine the persistence of these substances, including radionuclides, in wastewater effluents and their potential presence in receiving waters." 
  28. ^ Ian Urbina (7 March 2011). "E.P.A. Steps Up Scrutiny of Pollution in Pennsylvania Rivers". The New York Times. Retrieved 23 February 2012. 
  29. ^ David Caruso (2011-01-03). "44,000 Barrels of Tainted Water Dumped Into Neshaminy Creek. We're the only state allowing tainted water into our rivers". NBC Philadelphia. Associated Press. Retrieved 2012-04-28. 
  30. ^ Susan Phillips (2 November 2012). "DEP Employee Says Agency Withholds Water Contamination Information from Residents". StateImpact Pennsylvania. NPR. Retrieved 10 November 2012. 
  31. ^ Sandy Bauers (21 July 2011). "Cancer patients’ urine suspected in Wissahickon iodine-131 levels". Philadelphia inquirer, Carbon County Groundwater Guardians. Retrieved 25 February 2012.