Science and Technology Division
OF LOW-LEVEL RADIOACTIVE
METHODS OF WASTE DISPOSAL
OF HISTORIC WASTES
The management of radioactive
waste is one of the most serious environmental problems facing Canadians.
From the early industrial uses of radioactive material in the 1930s to
the development of nuclear power reactors and the medical and experimental
use of radio-isotopes today, there has been a steady accumulation of waste
products. Although the difficulties involved in radioactive waste management
are considerable, responsible solutions are possible. This paper will
discuss low-level radioactive waste, including its production, the amounts
in storage, the rate of waste accumulation and possible strategies for
In Canada, low-level radioactive
waste is defined as all forms of radioactive waste except spent nuclear
fuel (which is high-level waste) and waste resulting from uranium mining,
milling and mill tailings. Low-level waste is produced in a number of
ways: the nuclear fuel cycle, including uranium processing, nuclear fuel
manufacturing and electricity generation; nuclear research and radioisotope
production by Atomic Energy of Canada Limited (AECL); commercial radioisotope
production and use; historical activities; and decommissioning. Each of
these activities will be discussed in turn.
The nuclear fuel cycle is
made up of uranium processing, fuel manufacturing and electricity generation.
Cameco Corporation operates Canada's only uranium refinery at Blind River,
Ontario, and the only uranium conversion facilities at Port Hope, Ontario.
The ore concentrate resulting from the uranium milling process, which
takes place at the mine site, is refined and made into fuel bundle by
General Electric and Zircatec. The low-level radioactive waste that results
from these processes includes garbage, most of which is incinerated, and
contaminated metals. The companies pay to have these wastes shipped to
AECL's Chalk River Laboratories, where they are stored for eventual disposal.(1)
The largest producer of
nuclear-generated electricity in Canada is Ontario Hydro, which has 20
reactors in operation. Most of the waste generated by Ontario Hydro is
shipped to the Radioactive Waste Operations Site at the Bruce Nuclear
Power Development in Ontario but a small volume remains at the individual
power station sites. The New Brunswick Power Corporation and Hydro-Québec
each has one operating nuclear reactor.
Nuclear research is carried
out at AECL's Chalk River and Whiteshell Laboratories. Chalk River scientists
and engineers conduct research in the nuclear sciences, produce radioisotopes
in the research reactors and manage low-level waste; work at Whiteshell
is largely focused on management of high-level waste. Both sites have
waste storage facilities, which will be discussed later.(2)
in Canada by Nordion International Inc. and AECL, are used for medical,
agricultural and pharmaceutical purposes as well as for many types of
scientific research. Waste is produced when the radioisotope is manufactured
and sometimes, as in the case of unsealed radioisotopes tracers, when
it is used. In Canada today there are approximately 4,000 licences issued
by the Atomic Energy Control Board for the use of radioisotopes. Many
radioisotope users ship their wastes to the Chalk River Laboratories where
they pay for it to be stored.
The term "historic
waste" is used to describe radioactive waste that resulted from the
processing of radium and uranium ores from the 1930s to the 1950s. In
these cases, wastes were managed in a way that does not conform to current
safety standards. Since the original producers of this waste cannot be
held responsible, the federal government has assumed responsibility for
its eventual disposal.
Finally, waste is generated
when a nuclear reactor is closed down at the end of its useful life and
decommissioned, a process that was performed on a limited basis for the
demonstration reactors Gentilly-1 in Quebec and the Douglas Point and
NPD reactors in Ontario.
OF LOW-LEVEL RADIOACTIVE
A classification system
has been developed that divides low-level radioactive waste into three
categories, depending on source. Generators are waste producers
still operating; this means they are responsible for the management of
the waste they produce and that already in storage; these are current
sources of radioactive waste. The Historical Activities category
includes former sources of waste that are not being managed acceptably
and whose originators are no longer functioning or cannot "reasonably
be held responsible for the management of the waste they generated."
Finally, the Decommissioning category includes future sources of
waste that will result from the decommissioning of facilities involved
in the nuclear fuel cycle and radioisotope applications. A small amount
of such waste already exists.(3)
The latest figures indicate
that there are about 1,300,000 cubic metres of low-level radioactive waste
currently in storage in Canada. As Figure 1 shows, nearly 90% of this
stems from historical activities, while current generators produce 10%.
Decommissioning accounts for less than 1%, as there has not yet been a
complete dismantling of any large facilities.(4)
Figure 2 shows that
waste stemming from historical activities is only a small part of all
low-level radioactive waste being generated today. Decommissioning accounts
for a larger part but remains a relatively small factor in the production
of new waste. The amount indicated, which comes from the dismantling of
research facilities and environmental remediation, will increase to an
average of 5,000 cubic metres of waste per year when commercial reactors
are dismantled, a process expected to begin around 2010. The Generator
category, as defined above, accounts for nearly 90% of new waste.
In the early days of waste
creation, little thought was given to disposing of low-level radioactive
waste. As has been discussed, since there was no real understanding of
the potential threat such waste poses to human health, it was often placed
in landfill sites or simply left in a remote area. This situation has
improved over the years, with AECL building trenches and monitoring the
spread of the waste; however, a great deal of work must still be done
to deal with the problem of low-level radioactive waste.
When discussing the responsibility
for the waste's management, a clear distinction must be made between historic
waste and waste still being generated on an ongoing basis. The latter
remains the responsibility of its producers, while the former is the responsibility
of the federal government. In 1982, AECL created the Low-Level Radioactive
Waste Management Office and gave it the mandate to resolve the historic
waste problem. This office operates as a distinct unit within AECL and
takes advantage of that company's technical expertise while remaining
independent of its other roles.(5) The
office also answers public information questions about low-level radioactive
waste, and is developing a user-pay service for disposing of the waste
created on an ongoing basis. Funding for the office comes from Energy,
Mines and Resources Canada, the department responsible for establishing
a national policy for low-level radioactive waste management.
All low-level radioactive
waste in Canada today is in storage, with the method of storage varying
considerably, depending upon when and where the waste was created.
Historic waste, created
in the years before there was a clear understanding of its dangers, has
been poorly managed. At first, it was deposited in municipal landfill
sites and vacant land near the Eldorado refinery in Port Hope, Ontario,
with Eldorado later placing its refinery wastes on land it owned. Contamination
led to the closure of the site near Welcome, Ontario, and its relocation
near Port Granby. Eldorado routinely used near-surface burial for its
waste disposal, a method now considered unacceptable.
In addition to radioactivity,
historic wastes are of concern because they contain a number of toxic
heavy metals that will remain hazardous for a very long time. Most of
the low-level radioactive waste produced today contains radionuclides
arising from the nuclear fission process. This waste has a higher level
of radioactivity than historic waste but, because the half-lives are shorter,
will not remain hazardous as long. Thus, it can be disposed of in facilities
using man-made materials such as concrete, whereas historic waste must
use natural and geological media for long term containment of radioactive
and toxic materials.(6)
A significant proportion
of the low-level waste is generated at the 20 nuclear power reactors operated
by Ontario Hydro and from the research laboratories of AECL. All of this
waste has been stored at Ontario Hydro's Bruce Nuclear Power Development
site or the Chalk River Laboratory site of AECL, to avoid the problem
of having many small sites.
For 20 years, Ontario Hydro
has stored its low-level waste from all three power plants at the Bruce
Nuclear Power Development site, located 200 kilometres north-west of Toronto.
In storing the waste, four basic principles are followed. The facilities
are designed to last a maximum of 50 years and materials must be retrievable
from them. Radioactive materials cannot be placed directly in the earth
but must be in an engineered structure. Only solids are placed in storage;
liquids must first be immobilized to ensure they do not spread into the
environment. Finally, waste storage is recognized as temporary; no permanent
disposal method for low-level radioactive waste has yet been implemented.(7)
Depending on the radioactivity
of the waste, a variety of different types of storage facilities are in
use today. Ontario Hydro places almost all of its low-level waste in "above-ground
modular warehouse type structures, each with a storage capacity of approximately
280,000 cubic feet."(8) The concrete
walls, roof and floor of the building provide shielding and the waste
is placed to maximize storage capacity. A further advantage of these buildings
is that waste can be "cascaded"; that is, it can be stored elsewhere
until its activity level drops, when it can be transferred to a storage
building. The first such structure was put in place in 1982. Another type
of above-ground facility are quadricells: reinforced concrete modules
consisting of two independent envelopes with a monitored interspace, designed
to hold resins from storage tanks.
Concrete trenches were one
of the early methods of storing low-level waste. Trenches, approximately
130 feet long, 23 feet wide and 10 feet deep, are placed in
areas where the soil has low permeability to ensure the slow migration
of any radionuclides that escape. When full, the trenches are covered
by one-foot thick concrete lids. The concrete tile hole, another type
of in-ground structure, is formed by excavating a hole, and placing a
section of precast pipe sections on a concrete base. After these are carefully
attached, the excavation is backfilled and paved over. Steel liners were
introduced to deal with early problems of water leakage.(9)
At Chalk River, where low-level
waste has been stored since 1946, many of the same disposal methods are
used. Concrete bunkers contain waste that can be handled safely without
protective shielding and in-ground concrete pipes are used for wastes
with a higher level of radioactivity. The main aim is to advance from
this type of temporary storage to a permanent disposal system.
At the Chalk River Laboratories
a number of storage concepts are in use. Sand trenches are used for storage
of low-hazard material. Both in-ground and above-ground cylindrical concrete
structures, similar to those used by Ontario Hydro, are used for higher
activity materials that require radioactive shielding.
Scientists at Chalk River
are also developing methods to assess and deal with the problem of waste
disposal at old storage sites that do not meet today's safety standards.
At these sites, which are extensively monitored, contamination is spread
over large areas, which must now be dealt with.
METHODS OF WASTE DISPOSAL
The main difference between
storage and disposal is one of intent. Waste in storage is monitored,
with the possibility that it could be retrieved; waste in a disposal facility
remains there for the indefinite future, without surveillance. No decision
has been made on the type of disposal facility that will be used for low-level
radioactive waste but AECL has developed and demonstrated a few methods
and has studied three concepts. The Improved Sand Trench would be used
for wastes that need isolation for up to 150 years. The Intrusion Resistant
Underground Structure (IRUS), in which most of the waste will be stored,
could hold wastes for up to 500 years and the Shallow Rock Cavity could
contain wastes that should be isolated for even longer.(10)
Scientists and engineers
at the Chalk River laboratories started the IRUS development and demonstration
program. The facility will be made up of an underground concrete vault
located above the water table in a sand formation on AECL property at
Chalk River.(11) The concrete vault
will provide approximately 4,000 cubic metres of space for waste and backfill.
To ensure that nobody inadvertently breaks into the facility, it will
have a thick concrete cover, which, tests indicate, will remain intact
for over 500 years. Drainage barriers will be put in place to direct water
away from the disposal unit. Water that does seep into IRUS will pass
through a porous bottom layer, which will remove the radionuclides.
Much background work has
gone into the development of IRUS in order to ensure that the facility,
once it is finished, will receive a licence from the Atomic Energy Control
Board (AECB). The regulatory requirement is that "serious health
risks to individuals be less than one in a million per year as a result
of migration of nuclides from the waste through pathways in the environment,
or by inadvertent intrusion into the waste."(12)
The IRUS design is currently under regulatory review by the AECB.
Any low-level radioactive
waste facility constructed in Canada must be be regulated by the Atomic
Energy Control Board. This federal agency issues licences and regulates
all nuclear-related facilities. Having issued the regulations and associated
documents, however, the AECB makes the licensee responsible for the safety
of the facility and establishes a number of guidelines to which the operator
of the facility must adhere. In general, it is the responsibility of the
licensee to explain to the AECB how it plans to meet its performance criteria,
and how safety will be assured. Considerable effort will be needed to
ensure that the public has input into decisions, both on the type of waste
facility needed and where it should be located.
OF HISTORIC WASTES
Determining the location
of the long-term disposal site for low-level radioactive waste continues
to be the most difficult issue. For example, in 1980 the Atomic Energy
Control Board directed Eldorado Nuclear, the Crown company that processed
uranium in the Port Hope area from 1948 to 1955, to decommission the nearby
Port Granby site in order to prevent waste at this site from eventually
eroding into Lake Ontario. Community opposition led the government to
cancel an attempt to find a permanent disposal site in the Port Hope area,
and instead establish an independent task force (the Siting Process Task
Force on Low-Level Radioactive Waste Disposal) to develop a process to
resolve the siting problem for most of the historic waste.
The Task Force's final report,
Opting for Cooperation, recommended that communities should have
greater participation in determining where the waste should be placed.
The process would include joint planning, information sharing and community
participation in decision-making. The community would also be compensated
both for participating in the process and for housing the waste facility.(13)
In response to this report,
the federal government appointed a second task force, the Siting Task
Force on Low-Level Radioactive Waste Management, to work towards finding
a solution to the problem of historic waste. Since its work began in 1988,
the task force has consulted with 14 communities; of the six that at first
decided to go on with the process, two, at Geraldton, Ontario, and at
Deep River, Ontario, are continuing to do so. The remaining phases include
a technical review and environmental assessment of the management options,
which, it is hoped, will lead to having one community hosting the historic
waste facility. The disposal of the waste still being generated remains
the responsibility of the producers. No disposal site has yet been determined
by AECL and Ontario Hydro, the largest generators of low-level radioactive
The search to find a safe
and acceptable low-level radioactive waste management facility continues
in this country. Although a great deal of scientific work must be carried
out to develop the optimum long-term disposal system, the most difficult
outstanding problem is to determine its site. For historic waste, a careful
process is being followed to try to ensure wide community involvement
in choosing the type of facility and its location. Much work remains to
be done, however, in how to dispose of waste still being produced.
Low-level Radioactive Waste Management Office, Inventory of Low-Level
Radioactive Waste in Canada, Annual Report, Ottawa, 1991, p. 4.
Ibid., p. 5.
L. Pabitra De and Robert C. Barker, An Update of a National Database
of Low-level Radioactive Waste in Canada, presented at the 14th Annual
DOE Low-level Radioactive Waste Management Conference, 18-20 November
Ibid., p. 3.
Ibid., p. 2.
Energy, Mines and Resources Canada, Siting Process Task Force on Low-Level
Radioactive Waste Disposal, Opting for Co-operation, 1987, p. 1;
De and Barker (1992), p. 7.
Pollock and Zelmer, Canadian Experience with Storage of Low-Level Radioactive
Waste, presented at the Thirteenth Annual U.S. DOE Low-Level Waste
Management Conference, November 1991, p. 5.
Ibid., p. 6.
L.P. Buckley and D.H. Charlesworth, "AECL Experience with Low-Level
Radioactive Waste Technologies," AECL-9787, August 1988, p.
International Atomic Energy Agency, Review of Available Options for
Low Level Radioactive Waste Disposal, July 1992, p. 41.
R.W. Morrison and P.A. Brown, Radioactive Waste Management in Canada,
presented at the Uranium Institute Sixteenth Annual Symposium, September
1991, p. 9; see also Opting for Cooperation (1987).