2    INVENTORY BY SOURCE OF RADIOACTIVITY

 

2.1    Description of Sources Pertinent to the Great Lakes

    The sources of radioactivity include natural background radiation from cosmogenic and terrestrial sources, residual debris from weapons testing in fallout, atmospheric deposition of radionuclides emitted in gaseous discharges from various facilities, liquid emissions from various facilities, and many smaller sources that require identification. Facilities include uranium mining and milling operations, refining, processing, fuel fabrication, nuclear power plants, waste management facilities, and reprocessing and tritium-recovery operations. Smaller sources include research nuclear reactors, radiochemical and radiobiological laboratories, hospital nuclear medicine departments, and industrial sources. The various sources are discussed separately, along with comments on the data acquisition, analysis procedures, and reported emissions. The Task Force made no judgements as to the potential hazards implied by the sources.

  2.2    Natural Sources of Radioactivity in their Undisturbed State

    The Task Force first examined the natural background of radionuclides for the Great Lakes Region. Since the earth's beginning, every component of the environment has been exposed to a natural level of radioactivity. This natural background forms a baseline against which to evaluate the levels and impacts of other sources of radioactivity in the Region, and an inventory of natural radionuclides in this natural background provides clues to the inventories of other radionuclides of the same elements that arise from other processes and sources.

    What is the natural background for radiation? Because what some groups have called "natural," other groups have called "technically or technologically enhanced," the Task Force adopted the following definition:

     The natural background radiation levels in the Great Lakes Basin are those derived from cosmic rays and from natural geochemical materials in undisturbed strata.

    The Task Force further based its analysis on the earliest reliable measurements it could find. Increases in natural radiation since then belong to the category TENR (technologically enhanced natural radioactivity), which refers to the increase in apparent natural or background radiation resulting from some technical activity ( e.g., mining of uranium ore, which leaves radioactive tailings exposed to the atmosphere).

    There are two sources of natural background radiation: the interaction of cosmic radiation with various atoms in the atmosphere and a fixed geochemical quantity of naturally occurring radionuclides in the earth's crust. Atmospheric processes include the bombardment of stable nuclei by cosmic rays, other radioactive particles and atomic particles, as well as collisions between selected stable nuclei. Some terrestrial radionuclides decay to gaseous elements ( e.g ., radon), which reach the earth's surface through diffusion through soil layers and can then enter the atmosphere. The cosmogenic production of radionuclides and release to the atmosphere of radionuclides from crustal processes occur at rates that are balanced by the decay of the radionuclides produced and released. The natural production of atmospheric radionuclides is essentially a steady-state process, provided the cosmic ray flux and the concentration of target atoms remain constant.

    Radionuclides ultimately decay to stable (non-radioactive) radionuclides. Further, the decay of radioactive crustal material continuously decreases the natural radioactive content of terrestrial materials. This assures that, over geological time (millions of years), the total inventory of natural background radionuclides declines globally and systematically.

    Assessing the natural background of a radionuclide is often a difficult task, and some of the estimates include scientific and political controversies. Although the natural background level should either remain constant or decrease, sometimes a situation arises of an apparent increase in natural background levels reported for a radionuclide, usually explained by either various environmental processes that transport or translocate radionuclides from one region to another ( e.g ., climate processes, oceanic movements, geophysical upheaval) or that past monitoring of background levels of a given radionuclide was not sufficient by today's standards to quantify the sources of a radionuclide. Once in the environment, contributions from various natural sources (in disturbed and undisturbed states relative to the natural occurrence) and artificial sources were subject to the various mixing processes that incorporate the radionuclide into the ambient observed radiation. This observed ambient radiation is sometimes equated to natural background, although it actually represents some unknown summation of contributions from natural and artificial sources. With regard to past monitoring of background levels, the Task Force notes the importance of knowing whether measurements began after rather than before the onset of nuclear weapons testing programs, and the sensitivity, accuracy and calibration standard of the instrumentation used.

    A few radionuclides that arise mainly from artificial sources can also arise from natural processes ( e.g. , 3 H and 14 C). For certain minor sources, such as nuclear reactions in extraterrestrial dusts and meteorites, the rates of natural production are virtually zero or so small relative to other processes as to be insignificant. Other naturally occurring radionuclides become environmentally active after some human action. Such radionuclides are "technically enhanced" natural radiation. The United States Environmental Protection Agency (EPA) invented the term in the early 1970's, and it "stuck." Examples include uranium and thorium and their decay products, which enter the environment from mining, milling, ore processing, and the burning of fossil fuels with a high radioactive mineral ash.

  2.2.1    Primordial (Terrestrial) Radionuclides

    If the half-life of a radionuclide found in geological strata approximates the estimated age of the earth, then the radionuclide is primordial ; it was presumably present from the time of the earth's beginning. Inventories of primordial radionuclides are essential parts of the natural background level of radioactivity in the environment.

    Two classes of radionuclides occur naturally in geological strata: those in the decay series of thorium and uranium and those which do not originate from decay series. Uranium and thorium are natural radioactive elements in various minerals and ores as well as trace contaminants in coal and phosphate-bearing rocks. Geologists and geochemists have intensively studied the mineral deposits of uranium and thorium and have compiled extensive and reliable data on mineral inventories. The non-decay series radionuclides include the well-known 40 K (potassium-40) and 87 Rb (rubidium-87); radioactive forms of vanadium, cadmium, platinum, cerium, and other rare earth (lanthanide) elements; and one isotope of bismuth. Tables 1a and 1b present the primordial and decay series radionuclides and the decay chains of the latter. Of the non-decay series radionuclides, those of 40 K, vanadium ( 50 V), and 87 Rb are useful in assessing the inventories of unstudied radionuclides.

    Several uranium and thorium isotopes can also undergo a spontaneous fission process. This mode of decay is very rare compared with the normal decay mode of alpha disintegration, making it relatively unimportant for purposes of calculating an inventory.

  2.2.2    Mobility and Transport of Terrestrial Radionuclides

    The atmospheric release of radionuclides from geological strata is a multistage process: formation of a radionuclide of a gaseous element, diffusion of the radionuclide through soils to the soil surface (soil-atmosphere interface), and release to the atmosphere. The most important gaseous radionuclide is the noble gas radon, 222 Rn, and its long-lived progeny 210 Pb and 210 Po. Radon gas has a half-life of 3.8 days. Once radon reaches the atmosphere, it dissipates quickly while continuing its radioactive decay. Its decay products are solids and aerosol-forming radionuclides, which can deposit on soil or water, but inventories of radon per se are not important for contamination of the water in the Great Lakes, although radon as an air pollutant within the Great Lakes region may be important in health assessments of residents.

TABLE 1A
PRIMORDIAL RADIONUCLIDES OF TERRESTRIAL ORIGINS

TABLE 1B
THE DECAY CHAINS OF URANIUM AND THORIUM

    Soil radioactivity includes 40 K, the thorium and uranium decay series, and the other natural radionuclides in trace amounts. In particular, radionuclides occur in coal, phosphate-bearing rocks, and extractable minerals. The radioactivity can be released in burning of fossil fuel, building materials, or use of phosphate fertilizers. The GLWQB reports present the data for these source of radioactivity in the Basin (IJC 1977, 1983, 1987 b ). Only the uranium mine and mill tailings have been included as important point sources of radioactivity in the inventory of radionuclides in the Basin. Radionuclides in fertilizers should be considered under non-point-source pollutants. Building materials may pose local problems but do not appear to be an important source of radioactivity to the Basin. The Task Force considers that the radioactivity in fossil fuel emissions remain an unquantified source of radioactivity.

  2.2.3 Cosmogenically Formed Radionuclides

    The interaction of cosmic radiation with the earth's atmosphere produces many radionuclides. At high altitudes, hydrogen atom nuclei (protons) are 95% of the available targets subject to cosmic ray bombardment. Other atmospheric targets include ions and nuclei of helium, argon, krypton, oxygen, and nitrogen and the carbon atoms in carbon dioxide and carbon monoxide. Many cosmogenically produced radionuclides have short half-lives and do not affect the inventory of natural radionuclides. Some can serve as tracers for small-scale atmospheric processes (Reiter 1975). Table 2 lists the major cosmogenically produced radionuclides.

TABLE 2
COSMOGENICALLY PRODUCED RADIONUCLIDES

Tritium ( 3 H )

    Although tritium is produced in the atmosphere, it is more difficult to determine its natural background, because environmental measurements of tritium began after the onset of nuclear weapons testing. UNSCEAR (1982) reviewed data that suggested that the natural concentration of tritium in lakes, rivers, and potable waters was 0.2-1.0 Bq/L (5-25 pCi/L) prior to the advent of weapons testing.

     Most cosmogenically formed tritium deposits in oceans. The small fraction that goes to the Great Lakes can be estimated by comparing the size of the Great Lakes with that of the oceans. Table 3 summarizes data on the inventory of tritium of cosmogenic origin.

Beryllium-7,10

    Two radioactive beryllium radionuclides, 7 Be (half-life: 53.6 days) and 10 Be (half-life: 2.6 million years), are produced cosmogenically, mainly in the stratosphere. Exchanges between atmospheric compartments produce a slow build-up of these isotopes in the troposphere. Production of 7 Be occurs mainly at higher latitudes and shows a seasonal variation in rainfall with maximum values in spring of about 4 mBq/m 3 and minimum values of about 1.5 mBq/m 3 (Kolb 1970).

    Beryllium deposited in wet and dry fallout goes mainly to sediments and terrestrial soils. Land surfaces accumulate 71% of 7 Be, and aquatic surfaces receive 28%. Deep ocean sediments receive 71% of the 10 Be, and terrestrial areas receive 28%. The differences in the inventories for the two isotopes reflects the differences in their half-lives: the longer lasting 10 Be reaches terrestrial and aquatic repositories before it has decayed significantly. According to the National Council on Radiation Protection and Measurements (1975), the depositional rates of the two beryllium isotopes are relatively constant. Table 4 presents the beryllium data.

Carbon-14

    Probably more is known about the natural background of 14 C than any other cosmogenically produced radionuclide. 14 C is produced by neutron bombardment of 14 N in the atmosphere. The variations in the atmospheric content of 14 C are caused by changes in the cosmic ray flux. The neutron bombardment of 14 N also follows airborne detonation of nuclear weapons. Libby (1958) estimated that each equivalent ton of TNT explosive produced an average of 3.2 × 10 26 atoms of 14 C. [A gram-atom (14 grams) of 14 C contains 6.023 × 10 23 atoms, and each ton of equivalent TNT explosive in a nuclear weapon produces approximately 7,500 grams of 14 C.] 14 C rapidly oxidizes to carbon dioxide (CO 2 ), and moves environmentally in this form. Because oceans receive most of the carbon dioxide, understanding the behavior of 14 C requires a model of global transport with atmosphere-ocean coupling processes.

    In discussing 14 C relative to 12 C, researchers sometimes use the terms "normal ratios" and "excess ratios." The normal ratio refers to the ratio of 14 C/ 12 C that results from the natural production of these two isotopes. When the ratio of radioactive to stable carbon found in some sample exceeds the normal ratio, that portion of the ratio unaccounted for by natural processes is called excess . Occasionally a researcher reports a reference value of the geochemical ratio, 14 C/ 12 C, calls it " normal," and then designates any observed increase in the ratio over his/her value as an excess ratio for certain analysis. Such reference values used in technical papers need to be checked against normal ratios.

    UNSCEAR (1977) noted that "the fossil records of 14 C in tree rings and lake and ocean sediments suggest that the natural 14 C levels have remained relatively unchanged for many thousands of years. ... the long-term fluctuation over a period of 10,000 years is attributed to a cyclical change of the dipole strength of the earth's magnetic field, which results in a cyclical change of the cosmic ray flux, which in turn changes the 14 C production rate." UNSCEAR thus implied that the normal geochemical ratio value of 14 C/ 12 C has been constant since primordial times despite different estimates for the natural production rate of radiocarbon, ranging from a low of 1.8 atoms·cm -2 ·s -1 to a high of 2.5 atoms·cm -2 ·s -1 . UNSCEAR cited as a "currently most accepted" value, 2.28 atoms·cm -2 ·s -1 , although some geochemists have long used the upper value of 2.5 atoms·cm -2 ·s -1 in calculations of a radiocarbon inventory.

TABLE 3
INVENTORIES OF COSMOGENICALLY PRODUCED TRITIUM ( 3 H)

TABLE 4
INVENTORIES OF COSMOGENICALLY PRODUCED BERYLLIUM ( 7 Be and 10 Be)

    Table 5a presents the inventory data for 14 C based on information available before 1970. In 1972, a revised estimate of the average rate of production of the radionuclide in the atmosphere over the 11-year solar cycle suggested a slightly lower value than given in Table 5a. Also, UNSCEAR (1977) presented a method of estimating a natural inventory based on "units of atmospheric content of 12 C" (referred to herein as "carbon units"), the main stable isotope of carbon. Those additional inventories appear in Table 5b.

    The "carbon units of 12 C" are multiples of 6.17 × 10 17 , which Broecker et al. (1960) used as an estimate of the stable carbon atom content of the atmosphere in 1963. This estimate would suggest that the biosphere (atmosphere and oceans) contains 67 units of carbon. However, Broecker reported that the concentrations of 14 C in carbon units in the surface ocean and deep ocean were lower than concentrations of the isotope in the atmosphere by 4 and 17%,  respectively. This would result in inventories of 14 C in the combined surface ocean and deep ocean compartments of 56 units of the activity of 14 C (about 3.8 MCi), and revise the atmospheric production to 2.28 atoms·cm -2 ·s -1 . Broecker then estimated that about 8% of the inventory of 14 C was in oceanic sediments, which corresponds to a total inventory for natural production of 14 C of about 230 Mci.

Krypton-81 and Argon-37, 39, 41

    Cosmogenic processes produce several radionuclides of noble gases: 81 Kr and 37, 39, 41 Ar. The inventories for these radionuclides are mainly limited to the atmosphere. Only 81 Kr decays to stable krypton. Argon radionuclides decay to isotopes of potassium and chlorine, which combine rapidly with oxygen and water vapor to form oxides and hydroxides. These attach to particulate matter and deposit on terrestrial and aquatic media. Table 6a presents selected data for two of these noble gas radionuclides.

Radionuclides Formed by Neutron Bombardment of Argon Nuclei

    Several important radionuclides of atomic weights 20-50 form cosmogenically by spallation reactions of neutron and other particle bombardment of stable argon nuclei. These include such long-lived radionuclides as chlorine-36 ( 36 Cl , half-life: 3.08 × 10 5 years), aluminum-28 ( 28 Al, half-life: 7,400 years), and silicon-32 ( 32 Si, half-life: 280 years) as well as shorter lived radionuclides such as phosphorus-32 and -33 . Table 6b presents selected data for several of these radionuclides.

TABLE 5A
BACKGROUND INVENTORY OF COSMOGENICALLY PRODUCED CARBON ( 14 C)

TABLE 5B
COSMOGENICALLY PRODUCED CARBON ( 14 C)
AS SUGGESTED BY BROECKER (1963) AND UNSCEAR (1977

TABLE 6A
INVENTORIES OF COSMOGENICALLY PRODUCED 81 Kr AND 41 Ar

TABLE 6B
RADIONUCLIDES PRODUCED COSMOGENICALLY BY NEUTRON BOMBARDMENT OF ARGON -- PART I:
CHLORINE ( 36 Cl), SULFUR ( 35 S), AND ALUMINUM ( 26 Al)

  2.3    Anthropogenic Sources of Radiation

    Anthropogenic sources refer to those that are mainly human in origin: military, industrial, educational, recreational, medical, or somehow reflecting a human use, intervention, or process. The two main anthropogenic sources are the fallout of military weapons testing and the generation of electrical power at nuclear power plants. Medical, commercial, and other sources are many in number, but their emissions are individually very small, raising the possibility that the sources may, in the aggregate, be a major contributor to the anthropogenic inputs of radioactivity to the Basin.

  2.3.1 Fallout from Atmospheric Testing of Nuclear Weapons

    Nuclear technologies over the past 50 years have introduced significant quantities of artificial radionuclides into the global environment. Historically, the greatest part of this radioactivity has come from atmospheric nuclear weapons tests conducted prior to the 1963 Limited Test Ban Treaty, although tests were carried out since then by non-signatory nations. Fallout from the tests has been distributed globally, with the maximum occurring in the North Temperate Zone, which encompasses the Great Lakes Basin. From 1963 to 1996, many weapons tests were carried out underground. Radioactive material occasionally vented to the atmosphere from these tests, but the impact on global fallout was minimal (UNSCEAR 1993). With the signing of the Comprehensive Test Ban Treaty in 1996, even this source of radioactivity has hopefully been eliminated.

    Previous Commission reports (IJC 1977, 1983, 1987) have extensively covered the inputs of radionuclides from this source . Since 1987, atmospheric inputs have not been significant. The Task Force briefly reviews this topic to complete the inventory of radionuclides currently stored in the water column and sediments of the Great Lakes. It is recognized, however, that radioactive fallout deposited on land will also eventually make its way into waters through weathering, surface runoff, ground water movement, and various mechanisms of biological incorporation and biological decay.

    Of the many radionuclides produced by nuclear detonations, 3 H, 14 C, 90 Sr, and 137 Cs have received the greatest attention in environmental monitoring programs. They have been measured in air, water, soil, and food products. Other important radionuclides include 95 Zr, 95 Nb, 106 Ru, 131 I, 144 Ce, 239,240 Pu, 241 Pu, and 241 Am. Most of radionuclides listed, except the plutonium and americium isotopes, emit beta radiation. Plutonium and americium emit alpha radiation. Although many of the individual radionuclides mentioned are not monitored, agencies of both countries typically report measurements of gross beta radiation. After the brief rise in 1986 due to the Chernobyl accident, the radioactive fallout in the Basin is approaching a level that is entirely due to naturally occurring radionuclides, especially 210 Pb. The decreasing trends for the Great Lakes Basin are similar to values across Canada and the United States. The total inventories of the most important fallout radionuclides are reported in the section on Radionuclide Inventory of the Great Lakes.

    The lifetime or cumulative radiation dose that will be received by individuals in the North Temperate Zone from all atmospheric detonations conducted between 1945 and 1980 is estimated to be about 1.9 mSv (UNSCEAR 1993). In addition to this dose, there will be a small contribution from weapons-generated 14 C extending far into the future. Only about 5% of this dose will have been delivered by 2045.

  2.3.2    The Nuclear Fuel Cycle Support Industries

    The nuclear fuel cycle is currently the main source of anthropogenic radioactivity emitted to the Great Lakes. The cycle consists of mining and milling of uranium; converting the mined uranium to fuel material (typically an oxide of uranium with possible enrichment in 235 U); fabricating fuel elements (uranium pellets encapsulated into metallic fuel rods); incorporating fuel elements into a nuclear reactor; bringing the reactor to criticality and "burning" of the fuel; reprocessing spent fuel to extract radionuclides for further use; transporting material between fuel-cycle installations; and management of radioactive wastes from each step. All components of the nuclear fuel cycle have been operative in the Great Lakes Basin for some interval of time over the past 35 years.

Uranium Mining and Milling

     All uranium mining and milling operations in the Great Lakes Basin are located in the Elliot Lake and Bancroft areas in Ontario.

    Elliot Lake once had as many as 15 uranium mining and milling operations. The radioactive tailings of these operations were disposed of in various holding ponds, which empty into the Serpent River and, from it, into Lake Huron. In 1983, the Commission reported that eight mining and milling facilities were operational, and two had closed. By 1987, the Commission had reported that four mines were operational, and one was "under care and maintenance." Further, the Commission noted that there "were several idle and unlicenced tailings areas in the region," which were sources of radionuclides to the environment from leachates. The last operating mine was closed in 1996. The AECB has developed plans for the major waste management areas. These plans feature "the wet cover option" because of acid generation on the mine tailings.

    Uranium rock contains, as previously noted, all of the radioactive elements of the uranium and thorium decay chains. The uranium ore from the Elliot Lake area is considered low grade, containing 0.2% natural uranium and 0.4% thorium. Thus, one metric tonne of this ore contains about 2 kg of uranium oxide and has an activity of about 21 MBq from each of the 14 principal members of the 238 U chain, or a total of about 0.29 GBq. In contrast, the ore in the more recent uranium mining operations in Saskatchewan are high grade and typically contain 2-4% natural uranium. According to UNSCEAR (1982), releases from the mine are primarily radon gas, but the milling operations results in the accumulation of large quantities of tailings containing significant quantities of the uranium decay series isotopes. About 14% of the total radioactivity in the ore feed appears in the uranium concentrate, which achieves better than 90% extraction. According to Ahier and Tracy (1995), Elliot Lake mills extract 95% of the uranium and 10-15% of the other radioactivity. This implies that about 86% of the radioactivity from the uranium decay chain, 0.25 GBq per tonne of ore, and 5% of the uranium, will be retained in the waste as a long-term source of environmental pollution. The principle radionuclides in the waste are radium, thorium, and radon.

    Only a very small portion of the radium in uranium ore is water soluble. Mill liquid effluents will vary in activity but will contain all of the uranium decay series radionuclides. The addition of barium chloride (BaCl 2 ) to the holding ponds usually precipitates 226 Ra. Table 7 has information on the radionuclides in milling effluents typical of Elliot Lake Mines.

TABLE 7
EFFLUENTS FROM URANIUM MINING AND MILLING

    Radon gas originates from the in situ decay of 226 Ra. Most radon released to the atmosphere from tailings piles originates in the top surface layers of tailings. Radon from deeper soil layers, the concentrated cake or the decay of radionuclides in rock mass, must diffuse through dense materials, a long process. The readily observed radon production probably occurs mainly in the top 1-2 m of the tailings, although increasing the depth a few more metres does not necessarily change release rates. By covering a tailings pile with clean earth fill and revegetating a tailings area, one reduces the radon release rate by a factor of about 2 for each metre of cover (UNSCEAR 1977). The control of radon emissions is an obvious requirement. Soil or water covers over decommissioned mill tailings are necessary for the control of radon.

    Radium in liquid effluents from mining and milling activities is a reported chemical parameter in the monitoring activities under existing permits, but radon is not. Most material reviewed by the Task Force on radon inventories reported estimates based on the authors choosing "typical values" for the airborne release rates for radon and parameters of atmospheric dispersion. The Task Force did not attempt an inventory for radon because of questions about what is a "typical airborne release" and no indications of consistent monitoring of radon.

    All of the Elliot Lake mine tailings areas are located within the Serpent River watershed. The Ontario Ministry of the Environment and Energy monitors surface water quality in the Serpent River. One of the monitoring locations (Highway 17) is located downstream of all the mines and provides a good indicator of trends in discharges entering Lake Huron Average annual concentrations of 226 Ra at this location are presented in Figure 1.

FIGURE 1. ANNUAL AVERAGE CONCENTRATION OF 226 Ra

IN THE SERPENT RIVER SURFACE WATER

Uranium Refining, Conversion, and Fuel Fabrication

     All uranium fuel fabrication and conversion facilities in the Great Lakes Basin are located in Canada

    Most fuel fabrication and conversion facilities in the Great Lakes Basin are in Canada. CAMECO operates facilities at Port Hope and Blind River. Up until 1983 the Port Hope facility consisted of a uranium oxide refinery and a uranium hexafluoride production facility. Then CAMECO moved the refinery operation to Blind River but retained and expanded its conversion facility in Port Hope. The closing of the Port Hope refinery ended the release of 226 Ra to Port Hope Harbour. Joshi (1991) noted, however, that the sediments still contain heavy loadings of radionuclides from earlier radium processing (1933-1953) and uranium recovery (1942-1983). Figures 2 and 3 present liquid and airborne emissions respectively for the Port Hope facility, while Figures 4 and 5 show emissions for the Blind River facility.

    CAMECO also maintains two low-level radioactive waste management facilities in the vicinity of the Port Hope conversion facility. The Welcome waste management area received waste from the Port Hope uranium processing facility between 1948 and 1955. Although inactive, the site is licensed by the AECB. Groundwater and surface water is collected and treated prior to its release to Lake Ontario. Liquid effluent releases from this site are shown in Table 8.

    Similarly the Port Granby waste management area operated from 1955 to 1988. Treated liquid effluent from this facility is shown in Table 9.

    The releases from these facilities appear to be important sources of radionuclides to Lake Ontario. Information concerning these sources should be evaluated further to assess the significance of the releases.

    Other facilities include a fuel fabrication facility at Port Hope operated by Zircatec and fabrication facilities in Toronto and Peterborough operated by Canadian General Electric.

    The uranium ore concentrates undergo further processing before use in nuclear power plant reactors, including enrichment with 235 U before producing the uranium dioxide or metal for fuel elements. Heavy water reactors can use an unenriched uranium concentration; light-water reactors need an enriched uranium (about 2-4%) fuel.

     Port Hope is an "Area of Concern" of the RAPs Programs of the Great Lakes Water Quality Agreement. Data from the Port Hope area show that most radionuclide pollutants from fuel fabrication and processing sorb to sediments.

    Port Hope is an Area of Concern under the Remedial Action Plan (RAPs) programs of the Agreement. It is the only Area of Concern in which radioactivity is a documented problem causing impaired uses of the resources, and the RAPs documentation contains information on radionuclide levels in various environmental compartments. The Task Force has used the RAP documents as source materials for the Inventory (Krauel et al. 1990).

FIGURE 2. CAMECO PORT HOPE FACILITY

ANNUAL AVERAGE URANIUM CONCENTRATIONS --

RELEASES OF COOLING WATER FROM NORTH UO 2 AND WEST UF 6 PLANTS

FIGURE 3. CAMECO PORT HOPE FACILITY

ANNUAL AVERAGE AIRBORNE URANIUM EMISSIONS

FIGURE 4. CAMECO BLIND RIVER REFINERY

ANNUAL AVERAGE URANIUM CONCENTRATIONS -- LIQUID RELEASES

FIGURE 5. CAMECO BLIND RIVER REFINERY

ANNUAL AVERAGE AIRBORNE URANIUM EMISSIONS

TABLE 8
CAMECO WELCOME LOW-LEVEL WASTE MANAGEMENT FACILITY LIQUID RELEASES

TABLE 9
CAMECO PORT GRANBY LOW-LEVEL WASTE MANAGEMENT FACILITY
LIQUID RELEASES

    The seminal work of Wahlgren et al. (1980) on the transuranics showed that these elements in Lake Michigan strongly bind to sediments. A similar process appears to occur for these elements in Port Hope harbour sediments. Originally the concerns about these sediments focused on elevated levels of heavy metals in the turning basin and west slip. In 1984, Environment Canada and the AECB undertook a joint study, "Benthological, Chemical, Radiological and Chronological Evaluation of Sediments in Port Hope Harbour, Ontario" (McKee et al. 1985). Surficial sediments and sediment cores were studied from various locations for both their heavy metal and actinide contents.

Fuel Reprocessing

    Once a reactor has come on line, nuclear fission reactions in the fuel generate power. As the fuel becomes depleted, waste products of fission and activation radionuclides build up in the fuel elements. Some waste products poison the nuclear fission process, requiring eventual removal of a fuel element from service. Because a spent fuel element contains high-level radioactive wastes, it must "cool down" (high-activity radionuclides must decay) on site for periods varying from 6 months to several years before any further processing of the fuel element, such as extraction of unused uranium and plutonium to produce new fuel elements (fuel reprocessing) on-site or off-site, or on-site storage for future disposal or shipment to a high-level waste repository. As of the time of publication of this report, fuel reprocessing is currently not being carried out at facilities in North America.

    Fuel reprocessing has several steps, each of which generates high-level and low-level radioactive waste effluents. The steps first separate uranium and plutonium from other radionuclides, and then from each other, and produce gaseous and liquid effluents, which also require further processing before release to the environment. Gaseous effluents contain tritium and radioactive isotopes of iodine, krypton, xenon, ruthenium, and tellurium. Liquid effluents usually contain isotopes of rare earth elements, cesium, and a few actinides. Special processes aim to recover and remove the iodine radionuclides, especially 129 I (half-life of 16 million years). The liquid wastes are usually concentrated through evaporation, and stored in underground tanks for eventual disposal as high-level waste.

    Although the radionuclides expected in reprocessing effluents are known, the Task Force lacked sufficient quantitative data for an inventory of the radionuclides. However, fuel reprocessing is not considered a major source of radioactivity relative to the nuclear power plants. As the Task Force receives additional data on reprocessing effluents, it will consider supplements to the inventory report.

     A facility once used for fuel reprocessing plant at West Valley, New York, now serves as a low-level waste repository.

    The Western New York Nuclear Service Center (West Valley) once operated as a fuel reprocessing plant. It was the only reprocessing plant in the Basin. The facility ceased the reprocessing in 1972, but continued as a storage site for its own locally produced high-level and low-level wastes, and to receive low-level wastes from other facilities. In 1982, the United States Department of Energy (DOE) proposed a long-term management strategy for the nuclear wastes on the site. DOE proposed to concentrate, chemically treat, and convert the liquid high-level wastes to a solid form suitable for transportation off site and permanent placement in a federal geological repository. In 1988, DOE proposed a project with "alternatives" to complete closure or long-term management of the facilities and, in 1995, proposed an implementation plan for the various alternatives. In 1996, DOE announced availability of a Draft Environmental Impact Statement (61 Federal Register 11620) for "Completion of the West Valley Demonstration Project and Closure or Long-Term Management of Facilities at the Western New York Nuclear Service Center."

    The New York State Energy Research and Development Agency (NYSERDA) owns the West Valley site on behalf of the "taxpayers of New York." The site receives low-level radioactive wastes and has some wastes from industrial activities, and generates other wastes. The proposed decommissioning alternatives affect the estimation of radionuclide inventories and may signal current and future thinking by government agencies on decommissioning strategies, especially in a period of very tight and highly constrained budgets. The proposed decommissioning alternatives for West Valley appear in Table 10. As of the time of this report, the decision from DOE was pending. The Environmental Impact Statement does not indicate a DOE or NYSERDA preferred alternative.

TABLE 10
PROPOSED ALTERNATIVES FOR THE DECOMMISSIONING OF
WESTERN NEW YORK NUCLEAR SERVICE AT WEST VALLEY, NEW YORK
(adapted from 61 Federal Register 11620 - March 21, 1996)

  2.3.3    Emissions from Nuclear Power Plants in the Great Lakes Basin

    Nuclear power in the Great Lakes Basin dates from 1962 and the commissioning of the Big Rock Point Plant. In 1997, there are 15 facilities. Decommissioning of reactors may begin as early as 2000 with the expiration of the license for Big Rock Point. Table 11 presents data on the licensed nuclear power plants in the Basin. As of the time of this report, Ontario Hydro has taken seven of its reactors off-stream and may consider decommissioning them. This unexpected action occurred in late August 1997.

    There are three kinds of nuclear power plants in the Basin: two kinds of light-water reactors (LWR) and heavy-water reactors (HWR). The LWR systems are the "pressurized water reactor" (PWR) and "boiling water reactor" (BWR). The United States facilities are all LWR systems and the Canada facilities are all HWR systems. The systems' names describe the reactor cooling and moderating systems used. A fourth type of reactor found in North America at university and hospital research laboratories is the gas-cooled reactors (GCR) but is not used for electric power production. Under development is a fast-breeder reactor (FBR). The nuclear power plant, Fermi 1, had a FBR system, but the reactor was decommissioned following an accident and replaced by Fermi 2, a reactor of the BWR type.

TABLE 11
NUCLEAR POWER PLANT REACTORS IN THE GREAT LAKES BASIN

    The relative quantities radionuclides produced depend on the reactor type, including the technology and materials of construction, the amount of electricity generated, and the processes used to handle effluents and waste products. UNSCEAR documents present nuclear power plant data in a format based on reactor type and power production. UNSCEAR also applies a special averaging technique, normalization, which puts radionuclide production in a reactor on a unit energy basis, averaged over all reactors worldwide of the given type. The Task Force calculated normalization of the data but did not find it useful.

    Data on atmospheric emissions from the nuclear power plants in the Great Lakes show varying degrees of completeness, specificity, and descriptive information. All power plants report particulate matter, tritium, total -emissions excluding tritium, and 131 I. Some plants report "total noble gases," and radiation; other plants also list specific noble gas radionuclides ( e.g. , 41 Ar, 85 Kr, 133 Xe, 135 Xe); and other plants report other radionuclides of iodine ( e.g., 133 I, 134 I, and 135 I). The measurement of xenon radionuclides depends on their energy spectrum: those emitting radiation below 1 MeV might not be reported. Canadian (thus HWR) plants generally report fewer radionuclides, but Canadian regulations consider the effect of all radionuclides migrating to humans through all pathways. The Task Force learned that while many radionuclides do not require reporting, sometimes the power plant authorities collect this information, but without any consistency or regularity.

    The following radionuclides receive consistent reporting in the atmospheric and aquatic emissions from most United States and Canadian facilities: tritium ( 3 H), strontium ( 90 Sr), iodine ( 131 I), cesium ( 134 Cs, 137 Cs), and noble gases (a mixture of radioactive isotopes of krypton and xenon). Table 12 summarizes the cumulative amount of each radionuclide released from the three reactor types by the air and water pathways. The results have been summed over all lakes. Tritium and noble gases dominate the radioactivity of atmospheric releases; tritium also dominates the radionuclides in aquatic releases. The emission of the six major radionuclide types are discussed below.

Tritium

    The six graphs that compose Figure 6 show the emissions over time for tritium from the three reactors types and for the air and water pathways. Summations have been carried out over all lakes. All results are expressed in terabecquerels (1 TBq = 10 12 Bq or 27 Ci). When comparing graphs, note that the scales vary.

    The information shows that, throughout the entire time period, tritium emissions from HWRs consistently exceed by two orders of magnitude those from PWRs and exceed by three orders of magnitude those from BWRs. Further, the HWRs show a clearly increasing trend with time in both the airborne and waterborne emissions. This comports with expectations for HWRs. Deuterium in the heavy water readily captures neutrons from the fission process to become tritium. As the heavy water "ages," tritium levels increase in the water. If operating conditions do not change, the emissions of tritium will gradually increase in proportion to their concentration in the water. However, the high emissions for these reactors, such as for airborne tritium in 1981, 1983, and 1989 and for waterborne tritium in 1987, 1988, 1989, 1991, and 1992, do not reflect a gradual increase or an increase in the number of reactors operating but rather anomalous releases. The Task Force has learned that tritium is currently removed from all Ontario HWRs at the Darlington facility. This facility also releases tritium to the Great Lakes airshed. Also, HWR generating capacity increased considerably over the time period: 140% compared with an increase of only 30% for PWRs and BWRs. Time trends are much less apparent in the emissions from the PWRs and BWRs. Occasional elevated values from these reactor types occur in the earlier years. Explanations for these anomalies require review of the detailed reactor records.

    The two graphs that compose Figure 7 show the cumulative emissions of tritium for both the airborne and waterborne pathways. The units are petabecquerels (1 PBq = 10 15 Bq or 27,000 Ci). These results were obtained by integration of the year-by-year data from the previous graphs, then summing over the three reactor types, and correcting each radionuclide for subsequent disappearance through radioactive decay. While this simplistic approach ignores the disappearance of tritium from the Great Lakes ecosystem through dispersion, drainage, or incorporation into sediments, the graphs do show the total burden of tritium placed upon the global biosphere attributable to reactor emissions in the Basin. Quite simply, the tritium must go somewhere until its final transformation into stable helium-3 by radioactive decay. Table 13 shows tritium production and emission for different types of nuclear power plant technologies.

Strontium-90

    The four graphs that compose Figure 8 show the 90 Sr emissions. The Task Force obtained data only for the United States reactors (PWRs and BWRs). The units here are megabecquerels (1 MBq = 10 6 Bq or 27 microcuries (µCi)). No clear time trends appear in the emission data. Some early data on BWRs in the 1970s showed a few anomalously high values. The PWRs showed an elevated value in 1984 for the airborne emissions, and in 1990 for the waterborne emissions.

    The two graphs that compose Figure 9 show cumulative emissions of 90 Sr analogously to Figure 7. With a half-life of about 30 years, the 90 Sr will slowly decay from the global biosphere, provided the absence of new 90 Sr releases.

TABLE 12
CUMULATIVE AIRBORNE AND WATERBORNE EMISSIONS OF THE MAJOR
RADIONUCLIDES FROM THE THREE REACTOR TYPES (1980-1993)

TABLE 13
TRITIUM PRODUCTION AND EMISSIONS FOR DIFFERENT TYPES OF NUCLEAR
POWER PLANT TECHNOLOGIES

Iodine-131

    The five graphs that compose Figure 10 show the reported emissions for 131 I. The data show no clear trends, but rather some anomalous emissions in the earlier years. Airborne emissions of 131 I are highest for the BWRs, although all three reactor types show some releases. In the BWR, the primary coolant boils to produce steam for the turbines. A volatile radionuclide, such as 131 I, is readily released from the coolant to the atmosphere. Waterborne releases of 131 I are much less. The Task Force did not generate a cumulative graph for this radionuclide, since its half-life of only 8 days assures that it does not accumulate in the biosphere.

Cesium-134 and Cesium-137

    Cesium emission data are not available from the HWRs. Figures 11 and 12, which are each composed of four graphs, show the emissions of both isotopes of cesium for the BWRs and PWRs, respectively. The display of the results reflects the fact that often the emissions of both isotopes occur in parallel. The units are in gigabecquerels (1 GBq = 10 9 Bq, or 27 millicuries (mCi)). Cesium is somewhat more volatile than strontium; thus, its emissions are higher than strontium. Except for a few anomalies in the early years, the data do not show any time trends in the cesium emissions.

     134 Cs (half-life: 2.05 years) is removed fairly rapidly from the biosphere. The two graphs that compose Figure 13 show the cumulative emissions for the longer lived 137 Cs (half-life: 30 years). The slow decrease in the 137 Cs burden with time means that the emissions have been fairly steady, and that the isotope disappears rather slowly from the biosphere.

Noble Gases

    Figure 14 shows the noble gas emissions to air for the combined BWRs and PWRs. Generally, emissions were higher before 1984 than after that time, with one anomalously high value in 1975. Since noble gases are not water soluble, their emissions to water are not considered significant. Most radionuclides of noble gases decay by -particle emission to elements that form oxides and hydroxides, either in particulate or aerosol form. Other non-gaseous fission and activation radionuclides can form aerosols, which accompany airborne effluents. The aerosols and particulates become part of atmospheric fallout. Monitoring data are available both for "total noble gases" and total particulates in gaseous emissions. Air pollution control systems at nuclear power plants prevent the emissions of all but the very finest particulates.

    Short-lived xenon isotopes account for most of the emissions , assuring essentially no build-up. The one exception is 85 Kr (half-life: 10 years) which remains in the atmosphere and becomes globally dispersed.

Other Radionuclides, Including 14 C and 129 I

     14 C (half-life: 5730 years) and 129 I (half-life: 16 million years) are also important because of their long half-lives, but are not routinely reported by most facilities. 129 I is difficult to measure; however, a new technique involving accelerator mass spectometry may make this possible in the future. This technology is now available at the University of Toronto. Tables 14 and 15 give information on carbon-14 production and emissions.

TABLE 14
CARBON-14 PRODUCTION AND EMISSIONS FOR
DIFFERENT TYPES OF NUCLEAR POWER PLANT TECHNOLOGIES

TABLE 15
PRODUCTION OF 14 C IN NUCLEAR REACTORS
(adapted from Tait et al. 1980)

Figure 6

Reported Airborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: BWR

Reported Waterborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: BWR

Reported Airborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: PWR

Reported Waterborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: PWR

Reported Airborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: HWR

Reported Waterborne Tritium Emissions for All Lakes (in TBq)
Reactor Type: HWR

Figure 7

Reported Airborne Tritium Emissions for All Lakes (in PBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Reported Waterborne Tritium Emissions for All Lakes (in PBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Figure 8

Reported Airborne Sr-90 Emissions for All Lakes (in MBq)
Reactor Type: BWR

Reported Waterborne Sr-90 Emissions for All Lakes (in MBq)
Reactor Type: BWR

Reported Airborne Sr-90 Emissions for All Lakes (in MBq)
Reactor Type: PWR

Reported Waterborne Sr-90 Emissions for All Lakes (in MBq)
Reactor Type: PWR

Figure 9

Reported Airborne Sr-90 Emissions for All Lakes (in MBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Reported Waterborne Sr-90 Emissions for All Lakes (in MBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Figure 10

Reported Airborne I-131 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Reported Waterborne I-131 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Reported Airborne I-131 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Reported Waterborne I-131 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Reported Airborne I-131 Emissions for All Lakes (in GBq)
Reactor Type: HWR

Figure 11

Reported Airborne Cs-134 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Reported Waterborne Cs-134 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Reported Airborne Cs-137 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Reported Waterborne Cs-137 Emissions for All Lakes (in GBq)
Reactor Type: BWR

Figure 12

Reported Airborne Cs-134 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Reported Waterborne Cs-134 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Reported Airborne Cs-137 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Reported Waterborne Cs-137 Emissions for All Lakes (in GBq)
Reactor Type: PWR

Figure 13

Reported Airborne Cs-137 Emissions for All Lakes (in GBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Reported Waterborne Cs-137 Emissions for All Lakes (in GBq)
Cumulative Emissions corrected for DecayiReactor Type: All

Figure 14

Noble Gases (in PBq)
All Lakes

  2.3.4    Emissions from Secondary Sources in the Great Lakes Basin

    The sources not associated with releases from nuclear fuel cycle activities of radioactivity have been designated as "secondary sources." The terminology does not imply that the sources or their emissions are somehow secondary in importance. These non-nuclear fuel cycle sources of radioactivity to Great Lakes Basin are either military or civilian sources such as hospitals, industrial and commercial users, universities, or activities which release a "naturally occurring" radioactive material from an otherwise trapped matrix (technological enhancement), provided that the technological enhancement did not result from an activity associated with the nuclear fuel cycle. Although the emissions from a single source may be negligible, the large number of such sources in the Basin may make their combined effect significant. This discussion addresses open sources of radionuclides, which may eventually be released to the atmosphere or to the sewer systems draining into the lakes. We exclude an even larger category of sealed-source users, which would not be expected to release radionuclides to the air or water. The sealed sources could become a problem only if disposed of indiscriminately in municipal landfill sites.

    All users of radioisotopes must obtain a license from the national regulator (the AECB in Canada or the Nuclear Regulatory Commission in the United States). Regular reporting of measured or estimated emissions is a condition of maintaining the licence. This information is available from the regulators; however, it is not usually in a format that is either convenient or machine readable. At the time of preparation of this report, the Task Force had obtained information from most of the Canadian users, but not on the larger number of United States users. Although these data are incomplete, we present them to give an indication of the magnitude of the emissions. One could obtain a crude estimate of total secondary emissions to the Basin by considering the ratio of the total population in the Basin to that on the Canadian side.

Hospitals and Universities

    The Task Force inquiry on secondary sources emphasized research reactors at universities and industrial sites and the use of radioisotopes in hospitals, research facilities, and medical facilities other than hospitals. The Canadian data, obtained with the cooperation of the AECB, came through questionnaires sent to all its licensees asking them to estimate their emissions. Responses were obtained from 45% of the licensees, which was assumed to include virtually all the licensees with significant emissions. The users of the greatest quantities of radionuclides are nuclear medicine departments of hospitals, which administer radioisotopes to patients for diagnostic purposes. Lesser amounts of radionuclides are used for research or industrial purposes. Generally, about 75% of the radioisotopes administered to patients are assumed to be excreted to sewers.

    Table 16 summarizes the results for the secondary Canadian users of radioisotopes for the years 1993, 1994, and 1995. For most radionuclides the emissions are a few megabecquerels per year, but a few can reach the gigabecquerel per year levels. These levels are insignificant compared with the terabecquerel and petabecquerel levels released from nuclear reactors. Also, the radionuclides from secondary sources all have half-lives much less than one year and therefore do not accumulate from year to year.

TABLE 16
EMISSIONS FROM SECONDARY SOURCES IN CANADA
TO THE GREAT LAKES BASIN BY RADIONUCLIDE