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Panel Report

3.0 The AECL Concept: Description, Performance Assessment Analyses and Implications

3.1 Requirements and Objectives

To guide the development of its disposal concept, AECL established four general requirements, as discussed in the EIS. [Atomic Energy of Canada Limited, Environmental Impact Statement, pp. 62-70.]

  • Protect human health and the natural environment.
  • Minimize the burden placed on future generations, taking social and economic factors into account.
  • Ensure there is scope for public involvement during all stages of implementing the concept.
  • Develop a disposal concept that is appropriate for Canada - that is, a concept that is compatible with the country's geographical features and economic factors.

AECL also instituted a number of technical objectives for the concept. [Atomic Energy of Canada Limited, Environmental Impact Statement, pp. 70-74.]

  • Develop and demonstrate the technology for siting, constructing, operating, decommissioning and closing a disposal facility in plutonic rock. The technology should:
    • not rely on long-term institutional controls as a necessary safety feature-that is, a disposal facility should be passively safe following closure;
    • be currently available or readily achievable;
    • be adaptable to a wide range of physical conditions and societal requirements and to potential changes in criteria, guidelines and standards;
    • allow for monitoring; and
    • allow for retrieving the wastes, but provisions for retrieval should not compromise passive safety.
  • Develop and demonstrate a methodology for evaluating the safety of a disposal system against established safety criteria, guidelines and standards.
  • Determine whether technically suitable disposal sites are likely to exist in Canada.

AECL derived these requirements and objectives from various initiatives undertaken since the mid-1970s by international organizations, the governments of Canada and Ontario, the AECB and AECL itself.

3.2 Concept Overview

AECL has proposed a multiple barrier containment system to dispose of nuclear fuel wastes deep within the plutonic rock of the Canadian Shield. Each of the engineered or natural barriers can retain various components of the wastes for differing durations. Their combined performance would impede the migration of radioactive and chemical contaminants to the earth's surface for several thousand to hundreds of thousands of years, by which time substantial radioactive decay will have taken place.

Options exist for each of the engineered barriers and other design components. The final choices would be made according to site-specific and other requirements, such as volume of used fuel, once a disposal site is selected. In general, the barriers, components and possible options for each are as follows.

  • The waste form - The wastes would be either used CANDU reactor fuel bundles or, should reprocessing be implemented, derived solidified high-level wastes from reprocessed used fuel. In either case, the waste form would serve as a barrier itself, due to its low solubility under anticipated groundwater conditions.
  • The container - The wastes would be encased in a container designed to isolate them from groundwater for at least 500 years and as long as over a million years, depending on which material and design are selected. Several alternatives are discussed in the EIS and in R-Barriers, one of the primary reference documents.
  • The buffer - The containers would be surrounded by a buffer material, likely clay-based, that would limit groundwater movement, container corrosion, mechanical damage, and contaminant dissolution and movement. The containers and buffer would be placed either in underground rooms or in boreholes drilled from the rooms. A horizontal network of rooms and tunnels, on one or more levels, would form the disposal vault. See the EIS and R-Facility, one of the primary reference documents, for more details on vault design.
  • The backfill and other vault seals - Each room, tunnel, shaft and exploration borehole would be filled with clay- or cement-based backfill and other seals designed to delay the transport of contaminants out of the vault. Vault seals are further described in the EIS and R-Barriers.
  • The geosphere - The vault would be excavated at a nominal depth of 500 to 1000 metres in plutonic rock of the Canadian Shield. This would protect the vault from natural or human disruptions, maintain conditions favourable for isolating wastes and retard the release of contaminants to the surface.

AECL's system is intended to be passively safe after closure-that is, safe without the need for ongoing monitoring and maintenance-as required by the AECB in its regulatory documents R-71 and R-90. [Atomic Energy Control Board, Regulatory Policy Statement, Deep Geological Disposal of Nuclear Fuel Waste: Background Information and Regulatory Requirements Regarding the Concept Assessment Phase (Atomic Energy Control Board Regulatory Document R - 71, January 29, 1985), p. 10; Regulatory Policy Statement, Policy on the Decommissioning of Nuclear Facilities (Atomic Energy Control Board Regulatory Document R-90, August 22, 1988), p. 4.] Although future generations may provide long-term care, such a facility would remain safe if they were either unwilling or unable to do so.

The cost of a facility based on the concept, estimated by AECL in 1991 dollars, would range from $8.7 billion for five million fuel bundles to $13.3 billion for 10 million bundles, excluding financing costs, taxes, non-routine activities (such as waste retrieval), transportation and any extended monitoring stages.

3.3 Implementation Stages

At the broadest level, the concept can be conceived in two phases: preclosure and postclosure.

The preclosure period is expected to last about 100 years. AECL proposes the following preclosure stages, as illustrated in Figure 4, with possible extended monitoring either before or after decommissioning:

  • siting (at least 20 years);
  • construction (5 years);
  • operation (from 20 to 80 or more years);
  • decommissioning (10 years); and
  • closure (at least 2 years).

Public involvement would be ongoing, founded on the principles of safety and environmental protection, voluntarism, shared decision-making, openness and fairness. Chapter 5 of the EIS, R-Siting (one of the primary reference documents) and Chapter 6 of this report discuss public participation in more detail.

Before beginning each stage of preclosure after siting, the implementing organization would have to obtain a licence from the AECB, as well as other approvals. While no implementing organization has yet been identified, the Panel makes recommendations on this subject in Chapter 6 of this report.

During the siting stage, governments and waste owners would probably identify broad siting territories of plutonic rock, which would not necessarily be contiguous. Within these, the implementing organization would identify willing host communities and one or more candidate sites. The implementing organization would consult with governments and potential host communities to develop criteria to exclude sites and, if necessary, processes to rank sites. Using the criteria and increasingly detailed site characterization methods, the implementing organization would select a preferred candidate site. The organizations responsible for transportation, in consultation with affected communities, would choose transportation routes and modes.

In this stage, the implementing organization would begin characterizing and monitoring the biophysical environ-ment and affected communities, modifying the design, and assessing and managing environmental effects. These tasks would continue, as necessary, through subsequent stages. By the end of siting, the design would be fully adapted to the site conditions. A list of AECL's proposed siting steps can be found in Appendix M. The availability of potential sites and the methodology used to characterize sites are described more fully in the next sections.

Depending on the design chosen, the construction stage would involve building transportation facilities and equipment, access routes, utilities and surface facilities, including a used-fuel packaging plant; excavating shafts, tunnels and some of the disposal rooms; building underground ancillary facilities; and testing all systems.

The operation stage would involve transporting wastes from storage at reactor sites to the facility, as well as preparing for and carrying out underground emplacement. Its duration, estimated to range between 20 and 80 years, would depend on the quantity of used fuel to be transported and on whether limited demonstration disposal would be done first. Used fuel would be transported in specialized casks along the chosen transportation route by road, rail, water or some combination of these. The number of annual shipments would be determined by the waste quantity, transport mode and cask capacity. On-site activities would include transferring the wastes from transportation casks to sealed disposal containers, transporting the containers to the vault, and sealing them in with buffer and backfill. Operations would cease once all the wastes were emplaced and approvals were granted to proceed to decommissioning.

Decommissioning would include sealing remaining excavations (such as shafts, tunnels and boreholes), dismantling surface facilities, decontaminating and remediating the site, and, possibly, installing location markers. Extended monitoring could be done either immediately before or after decommissioning, to obtain performance data sufficient to secure approvals to proceed.

Figure 4: Implementation Schedule (Source: AECL)

Figure 4: Implementation Schedule (Source: AECL)

Closure, the last part of the preclosure phase, would occur when the repository no longer depended on human intervention to perform its function. While limited types of monitoring could be done during the postclosure phase, closure would entail removing any monitoring equipment and sealing associated boreholes that could compromise safety if left in place. AECL proposes that the closure stage would end once the regulatory agencies, the host community and the implementing organization agreed that the facility could be safely abandoned.

Although the concept does not include plans for retrieving wastes, such retrieval would be feasible during both the operation stage and after decommissioning. It would be more complex and expensive during the latter period. A design-specific description for retrieving wastes during the operation phase is given inR-Facility; a similar description for the phase after decommissioning is given in one of the additional information documents reviewed during the autumn of 1996.

More detailed discussions of concept implementation can be found in Chapter 5 of the EIS, as well as in R-Siting andR-Facility.

3.3.1 Availability and Characterization of Sites

Since site selection will not take place until a disposal concept has been accepted as safe, the Panel shall not consider any specific potential sites. However, the Panel may review the methodology required to characterize sites and the potential availability of sites in Canada. It may also review general criteria for site selection . . .

Terms of Reference Potential Availability of Sites

AECL's concept is designed for plutonic rock of the Canadian Shield. As illustrated in Figure 5, the Canadian Shield extends through much of the Northwest Territories, roughly the northern halves of Saskatchewan and Manitoba, and most of Ontario, Quebec and Labrador.

Figure 5: Potential Availability of Sites in Canada (source: AECL, afterR-Siting, page 45) Suggested exclusion areas: seismic zones 2 and above Canadian Shield

Figure 5: Potential Availability of Sites in Canada (source: AECL, afterR-Siting, page 45) Suggested exclusion areas: seismic zones 2 and above Canadian Shield

Plutonic rock such as granite, otherwise known as crystalline or igneous intrusive rock, was formed deep in the earth by the crystallization of magma and by chemical alteration. It is widely distributed on the Canadian Shield and elsewhere in Canada. In 1981, 1,365 plutons (large individual bodies of plutonic rock) were documented within the Canadian Shield in Ontario alone.

AECL stipulates that a suitable site, as well as being located within plutonic rock of the Canadian Shield, must have two main features: characteristics permitting construction of a safe, environmentally acceptable disposal system; and a willing host community.

AECB Regulatory Document R-72 discusses the requirements for a geologically acceptable site and host rock. Such a site must:

  • have combined properties that significantly retard the movement or release of radionuclides;
  • be an unlikely candidate for exploitation as a natural resource;
  • be geologically stable; and
  • be large enough so that the repository can be built deep underground and far away from geological discontinuities.

To meet some of these requirements, AECL specified that the following areas should be excluded from siting:

  • those near operating and abandoned mines;
  • those near known or inferred mineral deposits with future economic potential;
  • those outside of the relatively stable seismic zones 0 and 1 (this would exclude eastern Ontario, southern Quebec and almost all of New Brunswick, as shown in Figure 5); and
  • those with ancient rifts or clustering of historic earth-quake activity.

The concept requires a volume of suitable plutonic rock large enough to contain a vault at a nominal depth of between 500 and 1000 metres. AECL established that an area at vault depth of roughly 9 square kilometres would likely be needed for the reference case study facility. Of 373 plutons in a sample area of north central Ontario, 75 per cent had an area exceeding 9 square kilometres, 50 per cent exceeded 35 square kilometres, and about 10 per cent exceeded 400 square kilometres. On the surface, the site boundary would encompass about 25 square kilometres, and access would be required to at least the surrounding 400 square kilometres to characterize the hydrogeological setting.

AECL points out that plutonic rock of the Canadian Shield has many properties favourable for disposal, including potentially large areas of low permeability. However, it stresses that the latter is not required to ensure long-term safety-rather, the combined effect of engineered and geosphere barriers must be considered. With the options available for the engineered barriers, AECL believes that technically suitable disposal sites are widely available in Canada.

Since AECL proposes that communities should volunteer to host a site, the second major requirement for a suitable site is a willing host community with jurisdiction over the area. If such jurisdiction is lacking-for instance, if the site is located on Crown land-a willing government with jurisdiction is necessary. On Crown land, the implementing organization would encourage the government to identify a potential host community. Neither AECL nor any other organization has been asked to investigate the potential availability of a willing host community. Methodology for Characterizing Sites

The proposed approach to characterizing sites is to study increasingly smaller areas in increasingly greater detail. AECL divides the process into two stages: site screening, which would last about 3 to 5 years, and site evaluation, which would last about 15 to 20 years. The last 6 years of site evaluation would involve work underground.

During site screening, the implementing organization would use readily available information and exclusion criteria to map out potential siting regions within siting territories identified by governments and waste owners. The pre-existing information would include satellite images, air photos, reports, records, maps and data from a variety of sources. To map the siting regions, the information and exclusion criteria would be integrated using a geographic information system.

At this stage, communities within those regions would be invited to volunteer as potential hosts for the facility. Within those areas permitted by potential host communities or governments with jurisdiction, the implementing organization would then conduct reconnaissance-level remote sensing and surface studies. These would make it possible to do preliminary modelling of the conditions at up to two or three potential candidate areas of roughly 25 square kilometres each.

During the site evaluation stage, the implementing organization would identify a preferred vault location, develop a preliminary design for each potential candidate area and, ultimately, select a preferred candidate site. Site evaluation would entail several tasks:

  • a more thorough analysis of pre-existing information;
  • additional reconnaissance studies;
  • more detailed and expensive aerial, surface and borehole investigations of potential vault locations and at least 400 square kilometres surrounding them; and
  • integration of all the information into three-dimensional regional groundwater flow and contaminant movement models.

Once an engineering conceptual design for the candidate sites had been developed, the implementing organization would use modelling to assess potential environmental effects. If more than one candidate site passed scrutiny, they would be ranked to select one on which to excavate exploratory shafts and tunnels.

At this point, the organizations responsible for transportation would study conditions along potential transportation routes to select a route, mode and detailed design, and to evaluate their potential effects.

Finally, at the preferred candidate site, the implementing organization would employ comprehensive underground studies to confirm site suitability, prepare a detailed design and complete the environmental assessment. If this site did not meet all requirements, the latter steps would be repeated for the second-ranked candidate site.

Appendix J of the EIS, and the primary reference documentsR-Siting and R-Preclosure, describe site characterization in detail. Even though this process would involve state-of-the-art technology, the investigation of large areas and the integration of copious quantities of data, AECL is confident that the methods are currently available and sufficiently well developed to allow siting to proceed.

3.4 Concept Performance Assessment Analyses

AECL presented assessments of the preclosure and postclosure performance of the concept and its environmental and safety effects, as directed by the panel's EIS guidelines and the AECB's regulatory documents. Ontario Hydro, which provided technical assistance to AECL and studied interim storage and transportation, did the preclosure assessment. Given the absence of a specific site, there was neither a known environmental setting nor a site-specific facility design. Therefore, to meet the AECB requirements for quantitative estimates of risk, AECL and Ontario Hydro adopted a case study approach; they specified and evaluated hypothetical reference disposal systems.

Although the reference case studies were hypothetical, they incorporated data from extensive research and engineering studies, both laboratory- and field-based. Since conservative assumptions were used, AECL and Ontario Hydro believe that the results should over-estimate the potential effects of any eventual implementation of the concept.

One case study was presented for preclosure and for postclosure in the EIS and primary reference documents. AECL introduced a second postclosure case study in its May 1996 Response to Request for Information and presented it during the phase II technical hearings.

3.4.1 Preclosure Performance Assessment Analyses

Ontario Hydro based its preclosure assessment on a hypothetical facility and transportation system designed to dispose of 10 million used CANDU fuel bundles. The designs are described in the EIS, R-Preclosure and R-Facility. Three regions of the Canadian Shield in Ontario-northern, central and southern-were selected as alternative environments.

Transportation was analyzed separately from other operation stage activities. The utility examined three projected modes of transportation (road, rail and water), along with eight possible transportation routes originating from the three nuclear generating stations in Ontario.

Ontario Hydro used a combination of information and techniques, including real case studies, existing data, interaction matrices, contaminant pathways analysis, deterministic mathematical modelling, and scenario and sensitivity analyses. It described and, where possible, quantified potential effects on human health, the natural environment and the socio-economic environment, for both normal and accident conditions, and for each implementation stage.

To estimate radiological risk to the public during operation, Ontario Hydro used a hypothetical "critical group" living on a farm at the facility boundary, whose members consumed contaminated farm products, water and fish. A hypothetical generic freshwater fish, plant, mammal and bird were used to estimate doses to non-human biota. Ontario Hydro suggested measures to mitigate and compensate for adverse effects. It gauged the significance of effects by comparing results with appropriate federal and provincial regulatory limits, guidelines, standards, background conditions or threshold values, as documented in Appendix B of the EIS and in R-Preclosure.

The findings of the preclosure assessment, which are summarized in Chapter 6 of the EIS and detailed in R-Preclosure, are briefly reviewed here.

Although a facility of this type has never been constructed, Ontario Hydro concluded that its preclosure effects would be comparable to those associated with other large industrial projects, such as nuclear generating stations. Hence, existing experience in managing the effects of such projects, as well as in transporting radioactive materials, could be applied.

Radiological doses to the public from facility operations and transportation, during both normal and accident conditions, were estimated to be below the AECB limits for existing nuclear facilities and to be a small fraction of the annual exposure from natural background radiation. Exposure to workers was estimated to be well below AECB limits for atomic radiation workers under normal and accident conditions. Radionuclide concentrations in the natural environment and radiological doses to non-human biota were estimated to be a small proportion of background levels. Ontario Hydro found that potential non-radiological effects were either negligible or small, and that they could be mitigated using known technologies and practices.

While it estimated that potential radiological effects would be below existing limits, Ontario Hydro recognized that they would likely concern people living near the facility and along transportation routes, and that this concern could potentially cause significant socio-economic effects. Aboriginal and northern communities would be more susceptible than others to the effects of construction and operation, including transportation. The most positive socio-economic effects were identified as permanent waste isolation, employment and local economic growth. The amounts of raw and manufactured materials required for implementation were anticipated to be small in comparison to those available in Canada or elsewhere, yet the estimated cost of the case study facility would be substantial.

Ontario Hydro concluded that the precision of the preclosure assessment was limited by its generic nature, and that it was impossible to evaluate the significance of the socio-economic effects without consulting the people who would be affected.

Included in the additional information reviewed during the autumn of 1996 was a selective probabilistic analysis of the effects of preclosure operations. [Sean B. Russell, "Preclosure Probabilistic Assessment of the Canadian Concept for Used Fuel Disposal Focussing on Key Radionuclides and Exposure Pathways for Routine Emissions," Proceedings of the International Conference on Deep Geologic Disposal of Radioactive Waste, Canadian Nuclear Society, September 16-19, 1996 (Lac du Bonnet: Canadian Nuclear Society, 1996, Undertaking 96 and Additional Information 75).] The estimates of mean dose and radionuclide concentrations in the natural environment at the end of routine operations (after 41 years) were roughly comparable to those presented in the EIS, and declined thereafter. The author therefore concluded that long-term effects from operations are expected to be negligible.

At the panel's request, AECL and Ontario Hydro provided a brief qualitative analysis of the preclosure implications of a 10-million-bundle disposal vault using in-room emplacement, rather than in-borehole emplacement. [Atomic Energy of Canada Limited, Response to Undertaking 100, Preclosure Implications of a Disposal Vault using the In-room Emplacement Method (Undertaking 100, November 15, 1996).] In general, they said that the implications were within the scope of the reference case study and sensitivity analyses documented in the EIS and R-Preclosure, which was based on in-borehole emplacement. However, there were a few notable differences.

Due to the need to reduce container loading density (for worker radiation shielding purposes), the plan area of the vault would roughly double to about 7.25 square kilo-metres, thus requiring a larger volume of suitable host rock and a somewhat larger site surface area. While the required volume of backfill material would be approximately halved, that of bentonite buffer would be doubled. Used fuel transportation, radioactive emissions from the surface facilities and their potential effects would remain unchanged. [Kurt Johansen, in Nuclear Fuel Waste Environmental Assessment Panel Public Hearing Transcripts, November 20, 1996, p. 15.] The estimated cost of in-room emplacement would be about 15 per cent to 20 per cent more per fuel bundle than in-borehole emplacement.

3.4.2 Postclosure Performance Assessment Analyses

AECL's postclosure assessment is documented in Chapter 7 of the EIS and in four of the primary reference documents (R-Postclosure, R-Vault, R-Geosphere and R-Biosphere). It includes a qualitative discussion of long-term disposal system conditions and performance, a quantitative estimate of the performance of a hypothetical disposal system during the first 10,000 years and a qualitative treatment thereafter.

AECL intended the quantitative performance assessment to demonstrate that this methodology could be applied to a real facility, and that the facility could achieve safety indefinitely using available or readily achievable technology. The assessment includes scenario and sensitivity analyses and an explanation of the sources of and treatment of uncertainty. It also uses extensive field, laboratory and engineering study results; expert judgment; contaminant pathways analysis; and deterministic and probabilistic mathematical modelling. AECL evaluated models by comparing them with natural analogue case studies, actual observations and independent model predictions.

The qualitative description of the postclosure disposal system focuses on the processes and assumptions critical to assessments of long-term system performance. AECL concludes that a series of engineered barriers designed and placed to take advantage of a well-chosen site would effectively contain the wastes.

For the quantitative analysis, AECL represented the hypothetical reference disposal system by using linked mathematical models consisting of biosphere, geosphere and vault components. The biosphere and geosphere models were based on information obtained from AECL's Whiteshell Research Area. The geosphere model also embodied data from surface investigations for the underground research laboratory, and specified a context of low-permeability, sparsely fractured plutonic rock for the vault. The vault component was based on a capacity of 8.6 million fuel bundles, titanium-shell packed-particulate containers, emplacement in boreholes in the floors of vault rooms, and a depth of 500 metres.

AECL simulated a number of processes: changes in radionuclide inventories over time; container corrosion; contaminant release from the wastes and migration through the vault, geosphere and biosphere, including food chains; and exposure of organisms to internal and external radiation. It defined the "critical group" as a self-sufficient rural household residing in the vault ground-water discharge area and obtaining all its food, supplies and water nearby. As in the preclosure analysis, hypothetical organisms representing a plant, a mammal, a bird and a fish were used.

AECL excluded a number of scenarios from the modelling process, including criticality, earthquakes, biosphere evolution and climate change, because it judged them to be highly unlikely or implicitly accounted for by the data used. In the general system model, it included a scenario in which the critical group accidentally drilled a water supply well into the centre of the contaminant plume in a permeable fracture zone near the vault, and used the contaminated water for drinking and irrigation. Separately, AECL analyzed four additional inadvertent intrusion scenarios in which a drilling operation penetrated a waste container in a sealed vault, bringing wastes to the surface. Depending on the scenario, the wastes either expose a drill crew member or a laboratory technician to radiation, or are dispersed at the site and later expose a construction worker or a resident to radiation.

To account for and quantify the uncertainty inherent in modelling complex systems over long time frames, AECL used a probabilistic approach. Each of the modelled system characteristics was represented by a parameter which, depending on the nature of the characteristic, would take on a "constant" value, a "switch" value chosen from two or more alternatives, or a value selected from a probability distribution of possible values.

AECL used a computer program called SYVAC (SYstems Variability Analysis Code) to select the values for each of the vault, geosphere and biosphere model parameters. SYVAC randomly samples the parameter values from input probability distributions, and then calculates the outcome for that combination of values. The variability in parameter values was based primarily on expert input. The sampling process for the seven most influential radionuclides was repeated over more than 40,000 simulations to produce a frequency distribution of estimated radiological dose rates to a member of the critical group, plotted as trends versus time up to 100,000 years. The frequency distributions illustrate the range of possible doses and their probabilities of occurrence. SYVAC also calculated average concentrations of contaminants in the environment, as well as average dose rates to the four hypothetical organisms.

AECL compared the SYVAC simulation results with the appropriate federal and provincial regulatory criteria, guidelines, standards and background levels to establish their significance. The mean of the annual total dose estimates at 10,000 years for the 40,000 simulations was found to be 300 million times below that of natural background radiation. Its associated risk was five million times below the AECB Regulatory Document R-104 individual risk criterion of one in a million fatal cancers and serious genetic effects in a year. The maximum annual dose estimate calculated from these analyses for times up to 10,000 years was 81,000 times below natural background levels and its associated risk was 1,350 times below the regulatory criterion. The inadvertent human intrusion scenarios analyzed separately were estimated to increase the risk to about 3333 times below the AECB criterion. AECL expected that chemical toxicity and radiation effects on the natural environment would be insignificant, as demonstrated by the model. It concluded that while uncertainty cannot be entirely eliminated, their approach met the AECB R-104 requirements that the predicted risk should be "sufficiently low so as to allow for uncertainties in exposure scenarios and their consequences." [Atomic Energy of Canada Limited, Environmental Impact Statement, p. 317.]

Since predicted doses did not peak before 10,000 years-the limit for quantitative analyses required by AECB R-104-AECL furnished a qualitative discussion of effects anticipated thereafter. Iodine-129, with a half-life of 15.7 million years, is the major contributor to the estimated dose within the first 100,000 years. Its contribution does not peak in that period. Other radionuclides that are unimportant before 100,000 years could potentially increase in influence thereafter. AECL argues that any radionuclide releases beyond 10,000 years would be gradual, that resulting doses would be of the same order as natural background ones and that no major effects would occur.

As noted earlier, a second postclosure case study was introduced during the technical hearings. [A.G. Wikjord, P. Baumgartner, L.H. Johnson, F.W. Stanchell, R. Zach and B.W. Goodwin, The Disposal of Canada's Nuclear Fuel Waste: A Study of Postclosure Safety of In-Room Emplacement of Used CANDU Fuel in Copper Containers in Permeable Plutonic Rock, Volume 1: Summary (Atomic Energy of Canada Limited Report AECL - 11494 - 1, COG - 95 - 552 - 1, 1996, Part of Undertaking 58, Additional Information 60).] AECL maintains that adequate evidence for the safety and acceptability of the concept had been presented in the EIS and primary reference documents. However, it explains that the second case study shows that the concept and the assessment and modelling methods are flexible enough to adapt to differing site characteristics, designs and safety requirements. Thus, the second case study responds to a number of criticisms of the concept and of the EIS case study.

While the EIS case study was based on titanium containers emplaced in boreholes in low-permeability, sparsely fractured rock, the second case study is based on copper containers emplaced in rooms in permeable rock. The dominant safety feature in the first instance is the nature of the rock; in the second, it is the long-lasting copper container. Because it is more difficult to shield workers from radiation during in-room emplacement, the density of container placement in the second case study is reduced by 50 per cent from that used in the EIS case study. This entails a comparable reduction of the vault capacity from 8.6 to 4.3 million fuel bundles for vaults of roughly the same area.

Although the assessment methodology used for the second case study is similar to that used for the first, it is selective because it is based on only 14,000 simulations, and it examines only the most likely contaminant transport scenario, the 16 most influential radionuclides, and a restricted water-supply well depth. In addition, it does not evaluate the effects of chemically toxic elements. Furthermore, it uses, among other changes, a significantly modified vault model, hypothetical and unfavourable geosphere parameter values, and a prototype computer code that has not undergone the same degree of quality assurance as previous ones.

Due to the contrast in container materials and their expected lifetimes, contaminant release from containers is modelled to occur only through undetected pinhole-sized fabrication defects rather than through container failure by corrosion, as in the EIS. Since the containers are placed within rooms, they are surrounded by backfill materials, which is not the case in in-borehole emplacement. The conditions assigned to the geosphere model are less favourable than those observed below 500 metres depth at any of AECL's research areas, producing greatly increased rates of groundwater flow from the vault to the surface.

The results show that radiological effects occur relatively early compared to the EIS case study. AECL attributes this to the reduced groundwater flow times and consequent contributions from radionuclides with shorter half-lives and greater specific activities. The average dose rate reaches a maximum at 10,000 years and is 25 times below the dose rate associated with the AECB radiological risk criterion and 1500 times below the background dose rate for Ontario. AECL infers that the maximum radiological risk is not necessarily larger than that of the EIS case study, but it is shifted to an earlier time. As in the EIS case study, dose rates to non-human biota were estimated to be below the lower range of background levels, leading to the conclusion that there would be no significant radiological effects on them.

3.5 Implications of a Facility Based on the AECL Concept

It should also examine the social, economic and environmental implications of a possible nuclear fuel waste management facility . . . in addition to examining, in general terms, the costs and benefits to potential host communities.

In addition, the impact of transportation of nuclear fuel wastes to a generic site will also be examined.

Terms of Reference

The Panel examined the various implications of a facility and its associated transportation. This section highlights the implications, while Appendix N presents them in greater detail. Some of these implications could also apply to other options for managing nuclear fuel wastes. Appendix L outlines some implications of other options, but the Panel did not have sufficient information to examine them fully.

The discussion in this section is divided into subsections covering human health, environmental, economic, social and transportation implications. The Panel recognizes, of course, that these implications are greatly interrelated. Discussion of the costs and benefits to potential host communities is integrated throughout. While human health and transportation implications were well developed in the EIS and supporting documents, the other subject areas were not. Therefore, most review participants did not discuss them in any detail.

Many implications of the proposed facility relate to the fact that it will be a relatively large, long-term, technologically complex project, and that it is intended for nuclear waste disposal. These implications would, in many ways, be relevant in discussing a nuclear power plant, a uranium mine or a large facility for managing hazardous wastes. We also know that the proposed location lies within the relatively sensitive Canadian Shield. Nevertheless, the types and magnitudes of effects depend on factors that are unknown at this conceptual stage. As one gets closer to site selection and later phases of implementation, these factors will be known with a greater degree of certainty.

Perhaps the most critical of these unknown factors is the social setting of the facility. According to the proponent, one cannot know whether the potential socio-economic effects will be positive or negative, or even whether they will be significant, without knowing two things about the people who will experience them: how will these people perceive these effects, and can they manage the effects? Small, northern or Aboriginal communities may be especially vulnerable to adverse impacts.

Another uncertain factor is the capacity of the facility. This will control not only its cost, but also the number of fuel bundle and other shipments, the duration of the project and other elements. For example, AECL estimates that a 5-million-bundle facility would cost $8.7 billion (1991 dollars) and take 63 years to implement. A 10-million-bundle facility, on the other hand, would cost $13.3 billion (1991 dollars) and take 89 years. [Atomic Energy of Canada Limited, Environmental Impact Statement, p. 233.] While the AECL reference case facility was intended to accommodate 10 million spent fuel bundles, only about one third of this quantity was forecast to be produced by the time the existing Canadian reactors were taken out of service.

All the factors controlling the implications of the proposed facility are interdependent. As long as they remain indefinite, the best that can be done is to sketch out some of the possibilities.

3.5.1 Human Health Implications

The AECB licensing requirements for the 10,000 years following the closure of a facility set a maximum radiation risk to the most exposed individuals living in the vicinity of the site of one in a million fatal cancers and serious genetic effects each year. If these licensing requirements are met, it is clear that transport and storage plant workers will experience the greatest radiation risk during the lifetime of the facility. This risk will be limited to the maximum permissible dose for occupationally exposed workers. During the public hearings, participants repeatedly noted that current AECB regulations for occupational exposures do not reflect the latest recommendations of the ICRP. However, AECB limits are being amended to comply with the latest international recommendations. The Panel expects amended limits will be in place before any disposal facility becomes operational.

A more serious concern was raised in several presentations. Several participants were concerned that even the latest ICRP estimate for the numerical risk associated with unit radiation dose is too low. The Panel reviewed this matter carefully (see Appendix H). It concluded that the current ICRP estimate for numerical risk adequately protects public health. However, apart from the health effects on workers resulting from exposure to radiation, a significant number of normal industrial and transportation accidents will inevitably affect a substantial number of individuals during the operation of the facility.

If one assumes that 10 million bundles of used fuel would be placed in a facility at a remote northern Ontario site, and that all transport would be by truck, one can use data provided by Ontario Hydro to estimate a ceiling or "highest volume projection" value for the number of health effects likely to occur over the operational lifetime of the facility. Based on the data presented in Appendix N, the panel's view is that the normal industrial risks associated with transportation, construction and mining activities would greatly exceed those associated with the radiation exposures that either workers or the general public would likely incur. Furthermore, these risks are not unusual for such a large and extended operation.

The Panel recognizes, however, that concerns about radiological risks will lead to high levels of stress in some individuals. Moreover, the size of the project may strain the social cohesion of a given community. This in turn adds to the stress on individuals, and may manifest itself in behaviour detrimental to a healthy community. Many Aboriginal participants expressed concern that a project that would disrupt a community's social and cultural fabric would have a devastating impact on their lifestyles.

3.5.2 Environmental Implications

The Panel concurs with the SRG that the greatest environmental impact of a disposal facility based on the AECL concept is expected to take place during the preclosure phase. [Scientific Review Group, An Evaluation of the Environmental Impact Statement on Atomic Energy of Canada Limited's Concept for the Disposal of Canada's Nuclear Fuel Waste (Hull: Canadian Environmental Assessment Agency, October 6, 1995), p. 3.] Like any major project built in a natural environment, the construction of surface facilities and access corridors could have implications for terrestrial, wetland and fresh water habitats. The potential contamination of waterways and alteration of wildlife migration patterns due to project activities could have implications for Aboriginal and northern people who depend on them for their survival. However, if proper regulations are applied and good engineering and management practices are followed, it should be possible to mitigate adverse environmental impacts.

Radionuclides circulate within the biosphere through defined pathways and complex processes of geological, biological and chemical cycling. Since radionuclides are subject to these complex natural pathways, they do not follow a linear hydrological flow-through to the surface. Attempts to model the movement of radionuclides within the biosphere will have to account for these constant movements within the ecosystem.

3.5.3 Economic Implications

The economic effects of a nuclear fuel waste disposal facility on a community or region depend on the size and nature of the existing economy and the views of residents. From one viewpoint, a facility would offer local employment and business opportunities over a relatively long period. Viewed from a different perspective, a disposal facility could overwhelm or displace the existing economies of small communities. Property values may increase or decrease, depending on their proximity to the facility or its transportation routes, altered accessibility and housing demand.

Attention during the review also focused on availability of the non-renewable resources required to construct and operate a disposal facility. Will there be an adequate supply of these materials, and would the needed amounts represent a disproportionate consumption of resources in local, regional, national or international terms? Many participants were also very concerned about the availability of the financial resources needed to construct and operate a facility.

3.5.4 Social Implications

As stated earlier, the type and magnitude of social impacts cannot be determined with precision in the absence of a known social setting. These impacts would depend on such factors as: the types of potential host and affected communities; the values, needs and desires of these communities and their ability to manage the effects of the project; as well as the relationships between individuals, communities and their natural environment.

During the siting stage, even a voluntary process embodying AECL's principles of shared decision-making, openness and fairness could initiate widespread division among those living in the siting territories. Consequently, communities could experience a variety of political repercussions arising from conflicting values, opinions and interests, and either increased cohesion or conflict as a result. During construction and operation, many of the socio-economic effects will hinge on the size, demography, place of residence and other characteristics of the workforce and their families, relative to the size of the host community and its ability to supply workers and assimilate non-local workers and, possibly, their families. A collective stress could result from either a rapid population increase or, at the decommissioning stage, a population decrease, and the social and cultural changes that accompany them. Furthermore, introducing a non-Aboriginal population into traditional Aboriginal territory may conflict with Aboriginal values, culture and language, and with the traditional way of life. Special measures conforming to the wishes of the community would be needed to avoid or minimize such impacts.

Experience in past similar projects shows that one of the most significant socio-economic impacts would be any forced relocation of residents to acquire property for a facility. [L. Grondin et al, R-Preclosure, p. 6-140.] Residents may also perceive that a large portion of their physical environment is being modified and dedicated to high-risk activities. This could alter community land use patterns and traditional, recreational or economic activities that depend upon them.

3.5.5 Transportation Implications

The potential effects of transporting nuclear fuel wastes depend on many factors that remain to be determined. Some factors include the location of the facility, the distance from reactor sites, and shipping modes and routes. Except for the highly radioactive nature of the cargo and its implications, the effects would be similar to those of transporting materials and supplies to build and operate the facility. In many respects, transportation of spent nuclear fuel would be no different than transportation of radioactive or other hazardous substances, which occurs frequently.

The unusual level of fear associated with the transportation of nuclear fuel wastes is one of the most important implications of the proposed facility. Predominant concerns raised during the review included highway safety; cask integrity; security threats; emergency response capabilities; liability and insurance; and public consultation. For example, some participants were concerned that an accident in a remote area, especially one involving a release of radioactive materials, would cause long blockages of the only available highway. This could subject local communities to long periods of isolation. Participants also expressed concern that cargo might be stolen or sabotaged, especially along remote sections of the transportation routes. These issues stress the importance of developing a comprehensive emergency response plan in consultation with communities along the transportation routes.

Related to transportation accidents and emergency response are the issues of responsibility, liability and insurance. The various acts and regulations governing transportation of nuclear fuel wastes are unclear as they pertain to the implications of these issues for the utilities and a waste management agency.