Canadian Nuclear Safety Commission
Research Report Abstracts
Contractors’ reports are only available in the language in which they are submitted to CNSC.
Bilingual abstracts of the reports are available below.
Reports Issued in Fiscal Year 2005-2006
RSP-0194: Accidental Exposures in Radiotherapy Survey, NRC + Picker CanadaHighlighted below are the key findings of the Canadian Nuclear Safety Commission (CNSC) Accidental Exposures in Radiotherapy Survey (2005). The survey was administered in April 2005. Thirty-nine CNSC licensees (hereafter the radiation therapy cancer centres) across the country were asked to participate.
While all of the centres included in this study have identified and implemented some quality control protocols to detect and prevent medical events, there is no standardized systematic protocol to ensure that errors are minimized and tracked for quality improvement purposes.
RSP-0195: Applicability Review of Fuel and Fuel-Channel Models in Thermalhydraulics Computer Codes for CANFLEX 43-Element Fuel – Phase 1, Patrick J. Mills
This project was initiated to provide a critical review of the models or correlations defining the constitutive relationships in TUF and CATHENA and give an opinion as to the applicability of the use of these models or correlations for safety analysis in scenarios with CANFLEX fuel. The first task was to review the CATHENA and TUF theory manuals to glean from them a list of references thought to be required to meet the overall objectives of the contract. A reference list was provided to CNSC and as many of the documents as possible were provided. Any reference received was reviewed. Rarely did the cited reference give the information sought by this review. The references did cite many “tier‑two” references which could provide the desired information and some of these references were requested and reviewed. Time did not allow for this type of exploration to identify the empirical basis of all models or correlations in the codes.
RSP-0196: A Report on Performance Demonstration of NDR Techniques, Nuclear Safety Solutions Inc.CNSC initiated this project to determine a consistent set of requirements
for demonstrating the combined performance of inspector, inspection technique
and inspection equipment to reliably inspect CANDU plant components. CNSC
intends to use these requirements as a basis for making recommendations to
Canadian nuclear power plant licensees on strengthening inspection requirements,
fitness-for-service and plant life management.
The scope of the project included:
This report documents the results of this work. The assessment concludes an inspection qualification process based on the ENIQ approach is the method by which Canadian nuclear power plant licensees can best meet the performance demonstration requirements embodied in CSA N285.4. A consistent approach by all utilities provides for most effective use of regulatory and utility resources and increased opportunity to share qualified NDE systems amongst plant owners.Consistent with this conclusion the following recommendations are proposed:
- CNSC should endorse the adoption of the ENIQ methodology by the Canadian nuclear sector as a viable means of achieving the performance demonstration requirements in CSA N285.4.
- All parties involved in implementing the inspection qualification process should recognize that its existence will be evolutionary. It is more useful to the industry to implement a draft process soon rather than wait for the process to be thoroughly designed before implementation. As the process is utilized and experience is gained (through one or more pilot studies) in qualifying inspection systems, the process will change and evolve.
- CNSC should commission further work to assess and clarify its preferred role in the inspection qualification process. This should be done in consultation with the nuclear utilities and other interested parties and include a detailed assessment of the various regulatory frameworks for inspection qualification employed in European jurisdictions that follow the ENIQ approach.
- CNSC should endorse the creation of an Inspection Qualification Organization (IQO) by the Licensees, as described in Section 4.4.2 of this report. Inspection Qualification Bodies formed under the IQO should initially be set up in accordance with ENIQ Recommended Practice #7, “Recommended General Requirements for a Body Operating Qualification of Non-destructive Tests.” As the inspection qualification process matures, the need for certification of the IQBs to a recognized standard, such as ISO 17020, should be assessed.
- CNSC should conduct an assessment of the COG proposal for inspection qualification. The assessment should be conducted by individuals with detailed knowledge in, and experience with, the use of the ENIQ methodology.
- Several pilot studies using the ENIQ methodology have been performed by the industry. CNSC and industry should retain the services of individuals with detailed knowledge in, and experience with, the use of the ENIQ methodology to evaluate these pilot studies with a view to identifying possible improvements in the methodology used.
RSP-0197 Assessment of LBB Applicability to CANDU Primary Heat Transport Piping, B. Jarman
OPG’s reliance on leak-before-break (LBB) for Darlington was the first
and only time that a licensee has used the technology in support of application
for a license. CNSC staff has expressed its views on LBB in memos, letters,
and license conditions. This report recommends that CNSC needs documents
that are more formal.
CNSC first permitted leak before break in the licensing of Darlington,
to relieve the requirements for protection against pipe whip. This was the
first time it had been used to license a reactor anywhere in the world. That
application identified certain key elements in the process, the most important
of which is the ability to detect and react to leaks. Its use, and in particular,
the fracture analysis, has spread to include fitness for service of a number
of degrading components such as pressure tubes, feeders, steam generators,
erosion/corrosion of piping, and IGSCC in stainless steel welds. In the future,
licensees will likely use it to justify the reuse of old pressure boundary
equipment for plant life extension.
With degrading components, the issues for using leak before break as a part
of regulation are different. Ageing can change material properties, not only
in the sense of uniform behaviour such as strain ageing or embrittlement but
also in a localised way such as with IGSCC, pitting, and FAC near discontinuities.
The use of leak before break to justify continued operation with ageing components
is more difficult to regulate, because degradation inevitably leads to increasing
risk. Unless the regulator accepts leaking as a tolerable end to the degradation
regulatory control must be based on some assumed risk. Determining levels of
risk for leaking and rupture is complicated and highly speculative.
In this report, I examined the governance. How LBB has been used worldwide
to relax the requirements of regulatory bodies; and suggest how these can be
integrated into the rules for pressure boundary integrity, of CNSC.
RSP-0198 Development of Regulatory Guidelines on the Effectiveness of NPP Ageing Management Programs, Pachner Associates
This project required the contractor to: perform a survey of international
practices for effective ageing management of nuclear power plant systems,
structures, or components (SSC); identify and summarize fundamental components
of ageing management strategies and programs; and recommend possible regulatory
guidelines to facilitate CNSC evaluations of the effectiveness of NPP AMPs
within the framework of CNSC’s compliance program.
The report is organized in parts according to the scope. Part I presents a
survey of international practices on aging management consisting of a review
of guidance provided by international organizations and a review of regulatory
and utility approaches to aging management of nuclear power plants. Part II
recommends regulatory requirements for NPP ageing management programs supplemented
by recommendations for meeting these requirements presented in Annex A. In
addition, the report identifies and discusses interfaces with related technical
areas, i.e. equipment qualification, design basis reconstitution, and long
term operation. Finally, the report provides for consideration recommendations
for future follow up work.
In March 2004, the Canadian Nuclear Safety Commission (CNSC) commissioned
Ipsos-Reid to conduct a telephone survey to assess Canadians’ general knowledge,
perceptions and attitudes towards nuclear regulation and safety. The primary
objective of the present study is to build on the Ipsos-Reid research by
targeting the research towards populations most affected, economically
and environmentally, by their proximity to large nuclear operations.
Decima conducted a telephone survey with 2,006 respondents between September
21st and 26th, 2005, targeting six geographical areas located near nuclear
power plants and substantial mining operations in Canada: Point Lepreau, NB;
Becancour, QC; Chalk River, ON; Darlington/Pickering, ON; Port Elgin, ON; and
North Saskatchewan.
Research Results - Comparisons to 2004 General Population Data
Opinions of residents in the six communities is similar to the opinions of
Canadians in general in 2004:
2005 Issues
Three quarters (75%) of residents (outside of North Saskatchewan) are either ‘very
confident’ (30%) or ‘somewhat confident’ (45%) in the safety of the nuclear
plant closest to them. A slightly lower proportion (69%) feels that they live
either ‘very close’ (26%) or ‘somewhat close’ (43%) to a nuclear power plant.
Familiarity with a local plant issue is highest in Point Lepreau, where three
quarters (76%) of residents are either ‘very’ (23%) or ‘somewhat’ (53%) familiar
with the issue presented. It is lowest in Chalk River (34%) and Becancour (36%).
Familiarity levels in Northern Saskatchewan are relatively similar across the
three issues presented to these residents, with roughly four in ten indicating
they are familiar with each topic.
Approximately one quarter (24%) of respondents are familiar with the Canadian
Nuclear Safety Commission. Among those who are familiar (n=477), nearly eight
in ten (77%) have a positive impression (58%).
A generic action item (GAI) on the Canadian nuclear sector (AECL, Hydro-Québec,
New Brunswick Power, Bruce Power, and Ontario Power Generation) has been
raised by the Canadian Nuclear Safety Commission (CNSC), on the issue of
potential Molten Fuel Moderator Interactions under some postulated accidents
in CANDU reactors. The action arises from a long-standing difference
between the Canadian nuclear sector and CNSC. The industry’s licensing
analysis is based on a model developed by its consultant. The model treats
the molten fuel as being finely fragmented as it is ejected at 10 MPa from
a ruptured fuel channel, and evaluates the energy transfer from the fine
molten particles to the moderator to derive the pressurization inside the
calandria vessel. This model is commonly termed the "forced interaction" model.
CNSC staff, however, have noted that it is conceivable not all the
ejected melt will be finely fragmented as postulated in the forced interaction
model. This position was supported by CNSC’s consultant, who contended
a steam explosion (i.e., thermal detonation) cannot be ruled out.
To resolve this difference, the Canadian nuclear sector has proposed an experimental
program with the objective to confirm the dominant mode of molten fuel-moderator
interaction following a severe flow blockage accident in a CANDU reactor.
Data collected over the period 1990-2004 have been used to assess selenium
bioaccumulation in fish of the Athabasca basin of northern Saskatchewan,
in particular for sites that are thought to be affected by uranium mining,
milling and waste management operations. A dataset comprised of 358 co-located
water and fish tissue selenium records has been screened, pre-processed,
and statistically analyzed to develop a statistical regression model for
setting site-specific water quality objectives. The data have been analyzed
for species and site effects and for representativeness. Fourteen recommendations
for future sampling have been made. Real-world complexities that affect
model predictive power are identified and discussed.
The model projects the water selenium concentration required at a specific
site to meet a tissue selenium concentration threshold. The distribution of
tissue selenium concentrations measured at project area reference sites has
been derived. The upper tail of the reference site distribution (99th percentile
=7.2 mg/kgdry wt) or the maximum concentration in the reference site dataset
(10.9 mg/kgdry wt) are possible values for the tissue selenium concentration
threshold. Alternatively a toxicologically based threshold (e.g., the US EPA
draft criterion of 7.91 mg/kgdry wt) or a tissue threshold selected by other
means could be used. The water selenium concentration required at a specific
site to meet a tissue selenium concentration threshold is referred to as a “site-specific
water quality objective.” A lower limit of 0.5g/L has been set for
the site-specific water quality objective based on evidence of selenium homeostasis
at lower concentrations.
The model has been used to produce a look-up table and automated lookup tool.
Either of these tools can be used, with site-specific water and tissue selenium
concentration data, to project site-specific water quality objectives. The
lookup tool will automatically account for any future updates to the database,
model or tissue threshold. The look-up table would require manual updating
to account for model or threshold changes.
Key assumptions in the model for projecting site-specific water quality objectives
are (1) that site-specific data accurately reflect the site’s sensitivity to
selenium bioaccumulation in fish, and (2) that site sensitivity will remain
constant over time. If actions taken to help meet the tissue selenium concentration
threshold reduce the site’s sensitivity to selenium bioaccumulation – i.e.,
by reducing selenium bioavailability or exposure of organisms in the aquatic
food chain to bioavailable selenium – the model will set the site-specific
water quality objective at a lower concentration than would be needed to meet
the tissue selenium concentration threshold. The accuracy of site-specific
bioaccumulation estimates hinges on sampling design issues, addressed through
sampling recommendations provided in this report.
Four key technical management issues are identified and discussed at the end
of the report. They are: (1) establishing the tissue threshold selenium concentration,
(2) selecting the fish species to be sampled for comparing sites to the tissue
threshold, (3) choosing a sampling statistic to use for estimating site sensitivity
to selenium bioaccumulation, and (4) anticipating and managing for changes
over time in site sensitivity to selenium bioaccumulation.
The Canadian Nuclear Safety Commission (CNSC) is responsible for regulating
nuclear power plants in Canada. There are eight Canadian nuclear power
facilities located in Ontario, Quebec and New Brunswick. Each facility
uses once-through cooling water to discharge waste heat from power production.
Thermal effluent, caused by condenser cooling water discharge, is subject
to Canadian and provincial laws and regulations (e.g., it may considered
to be a deleterious substance under the Fisheries Act or may cause an adverse
environmental effect under the Canadian Environmental Assessment Act).
Thermal effluent discharge and technology options to control thermal discharges
have recently emerged as regulatory considerations for CNSC staff.
Consequently, CNSC has determined that it requires an independent source
of information that can be used as an evaluation tool to support its regulatory
position regarding discharge of thermal effluent and potential technologies
that could be used to avoid or mitigate potential effects. Golder Associates
Ltd. was retained to prepare this report, intended to be a reference document,
which could be used as a tool to evaluate licensee submissions on proposed
mitigation measures for thermal discharges from Canadian nuclear facilities.
A preliminary identification of potential remediation technologies was completed
in the initial literature search conducted prior to the site visits. In the
next phase of the project, a more detailed literature search and review was
conducted to provide further information into each of the potential remediation
technologies. One outcome of the site visits and meetings was identification
of relevant laws and regulations applicable to the various facilities. Golder
staff obtained copies of the various laws and regulations, and reviewed this
material. The findings from the review are presented in Section 4 of this report.
More detailed information on potential technologies was obtained by literature
searches on the internet and from Golder contacts. This information was used
to prepare the evaluation contained in Section 5 of this report. Golder staff
in the United States provided references, data and information regarding thermal
control technologies and U.S. regulatory requirements. Similarly, information
was collected to provide an overview of experience at facilities internationally
and presented in Section 6 of this report.
A comparative evaluation matrix was developed (see Table 7.3.4-1, for example)
to compare and identify best available technologies for the remediation of
thermal discharges at Canadian nuclear facilities. Based on an understanding
of site-specific conditions, regulatory requirements, potential environmental
effects and potential remediation technologies, the authors first identified
a long list of potential remediation options. Next a screening was conducted
to eliminate options that were not considered to be technically or economically
feasible. Next the authors conducted a comparative evaluation of potential
remediation options for each of the eight facilities. Using technical, environmental
and economic criteria, the authors rated each identified option for suitability
at each facility. Criteria were rated “High”, “Medium” or “Low”. Finally, the
best available technologies were identified based on the above-mentioned rating.
The overall objective of this project was to provide the basis of a regulatory
framework to enable the Canadian Nuclear Safety Commission (CNSC) to assess
the adequacy of licensee’s Human Performance Programs (HPPs), and their
effectiveness in implementing these programs. To meet this objective, definitions
were drafted of Human Performance and Human Factors, suitable for use by
CNSC.
A literature survey was conducted regarding Human Performance Programs implemented
by the nuclear sector and other high reliability industries, regulatory frameworks
and international best practices used to regulate Human Performance Programs
for nuclear facilities, and to identify elements of a Human Performance Program
that are suitable for nuclear facilities. Structured interviews were also carried
out with Subject Matter Experts (SMEs) in the definition or administration
of Human Performance Programs.
Based on the literature survey and the structured interviews, recommendations were made regarding Human Performance and Human Factors definitions, HPP elements, a suitable regulatory framework, and an approach for developing Human Performance indicators. Fifteen HPP elements were recommended, categorized by four functional groupings:
Policy and Organisation
Human Performance Monitoring and Response
Human Performance Traps and Tools
Organisational Learning and Knowledge Management
For each of the fifteen HPP elements, it was recommended that anchored rating scales be developed to evaluate the elements of human performance programs where each scale value is described by specific examples of relevance to the element under consideration. Anchored rating scales have been successfully used to assess Capability Maturity, e.g. of Software development processes, Safety Culture and Human Factors, whereby increasing maturity is characterised by increasing rigour, depth and consistency of practice and performance. These anchored rating scales will need to undergo verification and the framework should undergo validation by field testing. RSP-0204 Uranium in Effluent Treatment Process, SENES Consultants LimitedTechnologies for removal of uranium from uranium mine and mill effluents
have been reviewed. The results of current practice and the potential for
process and technology improvements are discussed.
Uranium was identified in the 2003 Environmental and Health Canada Priority
Substance List report as having the potential for environmental effect at the
reported concentrations in discharges from some of the older operating mine
facilities in Canada. CNSC has initiated investigations to determine whether
it is possible to lower release concentrations.
Uranium removal has not typically been a specific target of water treatment
strategies in the uranium industry. The focus has been on radium-226, acidity,
and with the development of the high-grade mines in Saskatchewan, on nickel,
cobalt, molybdenum and arsenic. The reduction of uranium in process and waste
management streams to lower levels in effluents has been a side benefit of
the lime neutralisation of acidity, the use of ferric ion to remove arsenic
and the removal of suspended solids.
Control at source is a key strategy in achieving low levels in effluents. Uranium
in mill process discharge is reduced to a level as low as economically achievable
by reducing “soluble losses” to a minimum. Soluble losses primarily originate
from two process streams – (1) unrecovered soluble uranium from CCD (counter
current decantation) circuits and (2) residual uranium in the solvent extraction
(SX) barren. Both streams typically contain uranium in the range of µg/L to
mg/L. Further reduction in uranium levels in either stream would involve the
installation of additional stages in the CCD and SX circuits and that is usually
not economical or physically feasible.
Other potential sources of uranium in final effluents – mine water, tailings
drainage, and waste rock seepage can contain mg/L levels of uranium (and other
contaminants) but there are few opportunities to reduce the uranium content
at source.
This study reviewed the available information from Canada and from selected
foreign uranium mine facilities in order to gauge uranium-in-effluent levels
and what technology has been developed and applied to remove uranium. The potential
target concentrations of uranium-specific technologies are undefined at this
time, but as a reference point for this study, it was assumed that the total
measured uranium in effluents should be reduced to less than 100 µg/L U or
as low as reasonably achievable (ALARA) given technical and economic considerations.
It has been determined that use of calcium hydroxide (lime) in combination
with ferric sulphate and flocculants offers the best basis for achieving a
consistently low level of uranium in mine effluents. For each mine facility,
the process would be adapted to local conditions, the presence of carbonate
and/or bicarbonate, suspended solids and other constituents to be removed – such
as radium-226, nickel, molybdenum, arsenic and ammonia.
For low dissolved salts streams, reverse osmosis (RO) can be used to produce
very low levels of uranium in discharges. This technology is in place at Key
Lake treating water containing uranium and nickel from mine perimeter dewatering
wells. Ion exchange (IX) offers a treatment option for water streams containing
mg/L levels of uranium and containing difficult to treat uranyl carbonate complexes.
Cameco is currently investigating the potential of IX to remove uranium at
the Rabbit Lake facility. However, lime and ferric sulphate treatment technology
will also be needed at the same mine site to treat acidity and remove other
contaminants.
Reports of results from other unconventional (to the mining industry) treatment
technology such as sorption, reductive and biological precipitation do not
appear to indicate significant potential for these technologies at present.
RSP-0205 Eldorado Nuclear Epidemiology Study Update - Eldorado Uranium Miners' Cohort: Part I of the Saskatchewan Uranium Miners' Cohort Study, Dr. G. Howe, Columbia University
A cohort study has been completed in which records for uranium miners
and processors who worked for Eldorado Nuclear Limited have been linked
to national mortality records (1950–1999) and national cancer incidence
records (1969–1999). This study, thus, updates an earlier study in which
mortality in the cohort between 1950 and 1980 was ascertained.
This report presents the results of the statistical analysis of a cohort of
17,660 individuals known to have worked for Eldorado somewhere between 1930
and 1999. Based on a total of 5,332 deaths between 1950 and 1999, and 2,355
individuals who developed at least one cancer between 1969 and 1999, several
types of analyses have been conducted.
The first analysis was a comparison of the mortality of the cohort with the
mortality of the general Canadian population between 1950 and 1999. Lung cancer
was elevated not only in the whole cohort, but in various sub-cohorts defined
by gender, site of working, underground and mill workers and sub-cohorts defined
by first working date for Eldorado. There can be no doubt that much of this
excess is attributable to exposure to radioactive radon decay products (RDP)
as discussed in more detail subsequently.
For most other the causes of death, the cohort as a whole and the various sub-cohorts had reduced risks relative to the population. This probably represents the healthy worker effect, a supposition which is supported, for example, by the major decrease in ischaemic heart disease to reflect the fact that the risk of heart disease is lower in the cohort being studied than in the population at large. The latter condition would probably prevent people working in a strenuous physical occupation such as mining.
The most notable exceptions for causes
of death where rates in the Eldorado cohort were elevated relative to the
population include hypertensive causes,
and external causes such as homicides, suicides and both traffic and non-traffic-related
accidents.
Comparisons of the cohort with the general Canadian population with respect
to cancer incidence rates between 1969 and 1999 are also reported. The only
cancer that is consistently elevated is lung cancer, thus, mirroring the mortality
results discussed above.
The second analysis presented in the present report is that of mortality
from lung cancer with respect to RDP exposure. This is primarily based
on 618 lung
cancer deaths amongst men in the cohort. This compares with previous analyses
of the Eldorado cohort when the total number of such deaths was 122. Thus,
the present analysis represents a substantial increase in the power of the
study and, thus, should produce more precise estimates.
There is a strong positive monotonic increase in risk of lung cancer death
with increasing RDP exposure which is highly statistically significant. This
increase generally manifests itself for the three main sites (Port Hope, Port
Radium and Beaverlodge sites), although it is likely that the exposure of the “Port
Hope” sub-cohort comes primarily from exposure received at other sites. However,
fitting a simple linear excess relative risk model to the data although, again,
demonstrating a strong relationship with RDP exposure does provide excess relative
risk estimates that are inconsistent across the sites.
Application of the BEIR VI-type risk model which allows for effect modification
by time since exposure, exposure rate and age at risk reduces this statistical
heterogeneity in terms of the RDP effect and it is clear that these modifying
factors contribute to the apparent heterogeneity seen in the simple linear
excess relative risk model. Using the same parameterization as chosen by the
BEIR VI Committee leads to coefficient estimates that are very similar in the
present study as reported by the BEIR VI Committee.
The lung cancer mortality analysis detected no effect of gamma ray exposure
on risk of lung cancer mortality and all estimates did not change by including
or excluding those with non-Eldorado work histories or those with zero exposure
to RDP.
An analysis of lung cancer incidence amongst males was also conducted.
The results mirror those of the mortality analysis and as relative measures
are
used, this is hardly surprising. It should also be noted that the two analyses
are not independent in that a substantial proportion of cancer cases contributed
to the corresponding death analysis.
The final type of analysis conducted was that examining mortality and cancer
incidence for diseases other than lung cancer with RDP exposure and gamma ray
exposure. In summary, there is no meaningful evidence of any causal relationship
between RDP exposure and increased risk of any of these other diseases, nor
was there any meaningful evidence of a relationship with gamma ray dose.
Several limitations should be borne in mind when considering the above
results. No data were available on smoking or other possible carcinogens
among the cohort.
Further, measurement error in exposure estimates could not be taken into account.
The implication of these limitations is also discussed in the report.
Exposure to RDP is one of the best-studied carcinogenic phenomena in epidemiology.
The results obtained from these studies, primarily of underground miners, are
very consistent in showing increases in lung cancer risk from such exposure,
but no increase in any other disease.
The present study (which is essentially independent of the data set used
by the BEIR VI Committee) further supports these conclusions based on 50
years’ mortality
experience and 31 years of cancer incidence experience. They certainly support
the use of BEIR VI-type models to predict any group’s future risk of lung cancer
from RDP exposure either from past or current such exposure.
Finally, it is worth noting that as yet only about 25% of the cohort has
died. Future follow-up and analysis of this cohort with respect to both
mortality
and cancer incidence should shed further light on our knowledge on the effects
of uranium mining and processing in both Saskatchewan and other provinces upon
the resulting health of those employed in such occupations.
