Backgrounder - radioactive wastes at Chalk River Laboratories
The Chalk River Laboratories (CRL) of Atomic Energy of Canada, Ltd. (AECL) are located on the Ontario bank of the Ottawa River about 150 km northwest of Ottawa (Fig 1). AECL has been at the Chalk River site since 1944. The site includes five nuclear reactors (two currently operating) and numerous other facilities related to the development of nuclear power for domestic and export markets. AECL operates a commercial nuclear waste disposal facility at Chalk River, and has numerous areas for disposal of radioactive wastes from its own experimental activities.
The CRL reactors and other research facilities are mostly located in the "Active Area (labelled "Laboratories) (gif:24K)", a fenced-in compound along the Ottawa River. The CRL property also includes an "Outer Area" comprising about 3700 ha of forest land, lakes, rivers, and bogs. AECL uses this property for disposal of solid and liquid radioactive wastes. It also uses the atmosphere above the property for disposal and dilution of radioactive waste gases (Ar-41, H-3, etc.). Tall stacks (50-m and 61-m high) are used to disperse these radioactive wastes in order to limit worker exposure. Permissible releases of Ar-41 and H-3 from the 50-m NRU reactor stack are about 500 quadrillion Bq per year, but actual releases of these two gases in 1993 were only 13 quadrillion Bq and 46 trillion Bq, respectively (AECB 1994a; Palmer 1981).
The seven reactors at CRL are:
AECL began construction of a new reactor, the MAPLE-X10, in 1990. It was to be a 10 MW open-tank reactor using ordinary water as coolant and moderator, fueled with 20% enriched uranium. It was intended to replace the NRU reactor for isotope production and to serve as a demonstration model for export markets. After construction was in progress, a major design defect in the MAPLE concept was discovered that could lead to a loss of coolant accident. A decision was made in November 1993 not to proceed with further development of the MAPLE-X10. The design of the new MAPLE1 and MAPLE2 reactors (that have experienced major problems during commissioning) is based in part on the design of the MAPLE-X-10.
The CRL property has Canada's largest inventory of radioactive wastes (12K) in terms of activity. Even when only low-level wastes are considered, the estimated 20,000 TBq of radioactivity at CRL exceeds the 16,000 TBq in all the uranium tailings at Elliot Lake, and dwarfs the 570 TBq of historic refinery wastes in the Port Hope area (AECL 1987). There are at least 11 areas at CRL where low-, medium- and high-level wastes have been placed in the ground, and additional sites where high-level liquid wastes and irradiated solid nuclear fuels are stored above ground (AECB 1991). Most of this waste is generated on site, but additional wastes are received from other nuclear facilities, other radioactive waste dumps, industries, hospitals, universities, etc.
High-level (reactor fuel) wastes on the CRL property were mainly generated by operations of the NRX and NRU reactors, and the now-decomissioned NPD reactor at Rolphton. The fuel bay for the NRX reactor was never properly sealed and leaked thousands of liters of water per day, causing a large plume of tritium and strontium-90 that directly contacts the Ottawa River for several hundred meters. There are also two plumes emanating from the NRU reactor. After being removed from the fuel bays, the waste fuel rods were moved to in-ground concrete "tile holes". Water has entered some of these tile holes and the high-level wastes in them are now the subject of a major remediation project.
Owing to a history of serious accidents, high-level fission and activation products have been dumped in a number of places into the shallow, sandy soils of the CRL property. A large plume emanates from "Area A"(16K), containing 52 TBq of Sr-90 and unknown amounts of other isotopes. It is spreading at a rate of about 2 metres per year. This plume contains wastes from the 1952 NRX meltdown and additional acidic high-level liquid wastes that were dumped in the 1950's. An experimental Ammonium Nitrate Facility was built and operated briefly in the early 1950's. It malfunctioned repeatedly and was dismantled and buried on site. Liquid wastes from accidents at this facility were dumped in a lime-filled pit along with additional wastes from fuel experiments. A plume (20K) containing 55 TBq of mixed fission products has migrated 400 metres from the pit, and will emerge in a swamp in about seven years. A nearby Thorium Nitrate Pit, also used to dump contaminated (Sr-90, Cs-137, Ce-144) liquid wastes from nuclear fuel experiments, has produced a similar plume. Waste dumping ceased at "Area A", the Ammonium Nitrate Facility, and the Thorium Nitrate Pit in the 1950's; but AECL has never prepared decommissioning plans or made any efforts to decontaminate these sites.
The position of the Atomic Energy Control Board (AECB), which exercises regulatory oversight over AECL, is that these problems are "the legacy of waste management practices which were followed in the past", and that "current practices... are much improved and more in keeping with present standards" (AECB 1991).
The current procedure for disposing of liquid wastes from reactors and laboratories in the Active Area is to pump them via two, 1.2-km underground pipelines to a "Liquid Dispersal Area"(24K) near "Area A". Tremendous amounts of tritium (about 840 TBq) and lesser amounts of other radioisotopes are dumped annually into the four pits in this area (two "reactor pits", a "chemical pit", and a "laundry pit". The reactor pits receive water from various reactor systems and from storage bays for irradiated fuel rods. The chemical pit receives water from laboratory drains and other contaminated sources.
Plumes from the "Liquid Dispersal Area" are contaminating surface water streams with 25 TBq of tritium and 30 GBq of Sr-90 each year (AECB 1991). Tritium concentrations in the plume from reactor pit #2 are 3-10 million Bq/L within about 100 m of the dispersal point, decrease to 30-100 thousand Bq/L where the plume enters Perch Lake. Perch Creek, which drains Perch Lake into the Ottawa River, contains about 12 thousand Bq/L of tritium. Plans to phase out waste dumping activities by constructing a waste treatment facility have been delayed for a number of years owing to technical problems. AECL maintains that no remedial action is required, as "radionuclides will decay to very low levels before they could leave the CRNL site" (AECL 1987).
A "process sewer" channels about 80% of the flow from the NRU reactor's heat exchangers directly into the Ottawa River, and carries additional contaminated waste water from other facilities such as the Heavy Water Recovery Plant. This process sewer has been the source of numerous "unplanned" releases of tritium. The maximum permitted annual release of tritium from any liquid source on CRL property into the Ottawa River is 370 quadrillion Bq.
Tritium migrates very rapidly as a constituent of water. The continued dumping of high levels of tritiated wastes is progressively increasing the contamination of surface- and ground-water at the CRL property. "Area C"(20K) (chart C 16K) is composed of a series of sand trenches, much like municipal landfills, that are excavated and back filled with contaminated wastes. More than 30, 90-metre long trenches (four metres wide by three metres deep) have been filled with wastes since 1963. Medium-level liquid wastes are accumulating in drums in "Area C", with an inventory of about 90,000 litres at the end of 1993. The tritium plume from "Area C" takes only three years to reach the surface waters of Duke Stream, with a tritium concentration of around 200 thousand Bq/L. An extension to "Area C" was excavated, commissioned, and put in service in 1993. However, AECB approval was granted for only 25% of the original area of expansion requested by AECL "pending the satisfactory resolution of outstanding issues" (AECB 1994a).
"Area D" contains over 600 drums of waste oil contaminated with PCBs, uranium, tritium, and mixed fission products. AECL orginally planned to burn these PCB-contaminated wastes in a radioactive waste incinerator, but this incinerator has been closed since 1991 and other disposal options are being investigated. "Area D" is also used for above ground storage of equipment known or suspected to be contaminated, but of potential future value.
"Area B"(20K) is another currently active site, used for commercial waste disposal operations as well as for wastes generated by AECL. It has been in operation since 1953. Solid wastes were buried in unlined sand trenches until 1963, and unlined trenches are still used for lower-level wastes. In recent years, greater efforts have been made to prevent higher-level wastes from migrating off site. Trenches were first lined with asphalt, and later concrete bunkers and "tile holes" were constructed. An effluent treatment facility is run continuously to reduce the Sr-90 levels in one of the two main plumes emanating from "Area B". As of 1990, these plumes were estimated to be releasing about 4 TBq of tritium and 4 GBq of Sr-90 each year to Perch Lake (AECB 1991).
"Area E" (also known as the "Waste Tank Farm") has seven stainless steel tanks containing high-level liquid wastes from fuel experiments. Five of these are protected by placement within concrete bunkers. One of the two unprotected tanks (placed directly in soil) contains wastes, while the other is used for back-up. No leaks have been detected to date. Additional high-level liquid wastes are found in the fissile solution storage tank (FISST), which is an integral part of the process used to produce the Mo-99 feedstock for medical isotopes. This tank is about 96% full. Throughout 1993, AECL evaporated water to make room for more contaminated waste in this tank. AECB has raised concerns that this tank contains sufficient amounts of uranium to cause a criticality accident, but AECL plans a further increase in the concentration limit of uranium in the FISST (AECB 1994a).
Literally hundreds of radionuclides are produced as fission and activation products during the operation of the reactors and other research facilities at CRL. Some of these are quite short-lived and do not pose regulatory concerns. Palmer (1981) gives maximum allowed concentrations for 62 isotopes released in liquid effluents and 14 additional isotopes (noble gases) which are released only to the air. The regulatory framework for permitted releases assumes that liquid effluent streams are fully diluted into the large flow of the Ottawa River (averaging 750 m3/second) and that airborne effluents are diluted about a half-billion fold before they reach the CRL property boundary. Permitted doses are based on a 1-yr individual exposure at the property boundary. Accumulation of longer-lived radionuclides in the environment, individual exposure times greater than one year, and collective doses to downstream and downwind populations, are not taken into account in the current regulatory framework.
The most abundant isotopes in low- and medium-level wastes include tritium (H-3), C-14, P-32, S-35, Co-60, Sr-90, I-125, I-131, Cs-137, Ra-226, and Am-241. The half-lives of these isotopes vary greatly, but relatively mobile elements of concern include H-3 at 12.33 years, Co-60 at 5.27 years, Sr-90 at 28.8 years, and Cs-137 at 30.2 years. A longer-term hazard is posed by elements such as Ra-226 (half-life of 1600 years) and C-14 (5730 years). In 1986, 3298 cubic metres (m3) of wastes were placed in sand trenches, 587 m3 in bunkers, and 29 m3 in tile holes at "Area B". The tile holes received more concentrated medium-level wastes. Average concentration of C-14 was 1850 GBq/m3, Co-60 was 92,500 GBq/m3, and mixed I-125 and I-131 was 3700 GBq/m3 in the tile holes. Bunkers received lower-level wastes (H-3 at 96 GBq/m3, Am-241 at 4.8 GBq/m3, etc.), and the unlined sand trenches received wastes in the range of 0.004-0.022 GBq/m3. These figures are taken from the 1987 publication "Inventory of Waste Quantities", produced by AECL's Low-Level Radioactive Waste Management Office (AECL 1987). This publication also contains some estimates of total solid volumes in a number of the waste areas, and limited estimates for total activities (but not volumes) of liquid wastes. In most cases, only the isotope that is migrating fastest in the plume (H-3 or Sr-90) is reported.
The sandy soils of the CRL property permit rapid surface movement of contaminated wastes. In addition, the underlying shallow and intermediate depth bedrock is moderately- to highly-fractured, with average fluid velocities of 10 to 100 metres per year (Raven Beck Environmental Ltd. 1994a,b). Radioactive waste contamination at CRL is therefore not limited to the surface streams, lakes, swamps, and bogs, but extends to depths of 100 metres or more in the bedrock. This makes full site remediation impossible and greatly complicates the regulatory process of decommissioning older waste areas.
Direct drainage to the Ottawa River occurs in 20% of the CRL property, and Maskinonge Lake drains about 35% of the area. Although the development of regional groundwater flow systems beneath the CRL site is largely unknown, both the Ottawa River and Maskinonge Lake are thought to be regional discharge locations for groundwater flow from the west (Raven Beck Environmental Ltd. 1994b). CRL clearly represents a long-term source of contamination for the Ottawa and St. Lawrence Rivers. Downstream communities at risk include Petawawa, Pembroke, Ottawa, and Montreal.
The 1993 Report of the Auditor General of Canada to the House of Commons noted a
Failure to record obligations for decommissioning and site remediation in the financial statements of Atomic Energy of Canada Limited for the year ended 31 March 1993.
The Report also pointed out that this failure "was a departure from generally accepted accounting principles", and that "the recording of liabilities is important to maintain accountability for obligations that will result in claims on public resources".
AECL clearly intends to avoid dealing with the radioactive waste contamination problems created by its past and current actions, and is concealing the magnitude of these waste problems and their public health consequences. It is generally supported in this strategy by staff of the Atomic Energy Control Board. In recent years the AECB has asserted greater control over ongoing facilities operations, but has not required that AECL decommission and rehabilitate leaking waste sites that are now closed.
Although AECL is a crown corporation and is financially responsible for the CRL property, it has received Parliamentary appropriations for past remedial actions and apparently intends to take no future action unless additional public funds are provided (AECL 1993). AECL has never prepared a detailed site remediation plan for the CRL property. There is no publicly available document that provides a comprehensive overview of contaminated areas and clean-up priorities. The 1993 Auditor General's report notes that AECL has not determined the overall estimated costs of remedial activities to be carried out over the next four to five decades.
The AECB grants periodic "site licenses" to AECL, and AECB staff has proposed that the Board grant a two-year renewal of the current licence when it expires in fall 1994. The proposed new license as currently written by AECB staff (AECB 1994b) does not address the need for a comprehensive site remediation program. Unless the Board responds to public or political pressures, there will be additional and costly delays in forcing AECL to address the CRL waste problem described in this report.
References.
AECB. 1991. A general overview of operations at the Chalk River and Whiteshell Laboratories. Atomic Energy Control Board BMD 91-198.
AECB. 1994a. AECB staff annual review of the operation of Chalk River Laboratories and Whiteshell Laboratories for the year 1993. Atomic Energy Control Board. BMD 94-107.
AECB. 1994b. Chalk River Laboratories and Whiteshell Laboratories renewal of operation license. Atomic Energy Control Board. BMD 94-117.
AECL. 1987. Inventory of waste quantities. Report to the Siting Process Task Force on Low-Level Radioactive Waste Disposal. Prepared by the Low-Level Radioactive Waste Management Office, AECL Research Company Head Office. ISBN 0-662-15760-5.
AECL. 1993. AECL Annual Report, 1993. Atomic Energy of Canada Limited. Ottawa, Ontario.
Minister of Supply and Services Canada. 1993. Report of the Auditor General of Canada to the House of Commons, 1993. ISBN 0-662-211001-4.
Palmer, J.F. 1981. Derived release limits (DRL's) for airborne and liquid effluents from the Chalk River Nuclear Laboratories during normal operations. Chalk River Nuclear Laboratories, Chalk River, Ontario. AECL -7243.
Raven Beck Environmental Ltd. 1994a. Bedrock geological mapping and studies of the Chalk River Laboratories property, Deep River, Ontario. Report to the Siting Task Force Secretariat, Ottawa, Ontario. STF Tech. Bibl. No. 338.
Raven Beck Environmental Ltd. 1994b. Regional hydrologic characterization of the Chalk River Laboratories property, Deep River, Ontario. Report to the Siting Task Force Secretariat, Ottawa, Ontario. STF Tech. Bibl. No. 344.
