Nuclear Safety Commission Research Articles

What's Your “Position” on Nuclear Power? An Exploration of Conflict in Stakeholder Participation for Decision‐making about Risky Technologies

AbstractOne of the exigent issues concerning stakeholder engagement in decision‐making for nuclear power generation facilities is the manner in which conflict is acknowledged and managed. In order to manage conflict effectively, one must understand the full variability of positions on certain issues, and from perspectives of diverse stakeholders. Research to‐date on risk perception and resultant conflict has been conducted almost exclusively from the perspective of the public. This paper utilizes grounded theory methodology combined with a case study approach to explore the decision‐making processes for the re‐licensing of two local nuclear power generation facilities; Pickering ‘A’ and Bruce ‘A’ from the perspective of the nuclear industry, the Canadian Nuclear Safety Commission, government, Non‐Governmental Organizations, scientists, and public. Situational analysis is a tool utilized to generate 7 positional maps which display the diversity of viewpoints on major contested issues such as environmental, technical, and financial risk, availability of information, and satisfaction with the process for stakeholder engagement. The paper concludes that conflict can be both negative and positive, and recommends the best way to reduce the potential for conflict is by actively engaging stakeholders in facilitated discussions with ground rules for conduct of all participants, and conducting discussions over the long‐term and well before (and after) legislated public consultations take place. The results of this study provide a useful framework for future quantitative exploration of the issues illustrated in each of the 7 positional maps.

Evaluation of sediment quality guidelines derived using the screening-level concentration approach for application at uranium operations in Saskatchewan, Canada

Sediment quality guidelines (SQGs) can be derived using different approaches and are commonly used in environmental management, reclamation, and risk assessment. The screening-level concentration (SLC) approach has been used in Ontario, Canada, to derive lowest effect levels (LELs) and severe effect levels for use as SQGs. This approach was adopted by the Canadian Nuclear Safety Commission (CNSC) to set guidelines for metals (As, Cr, Cu, Pb, Mo, Ni, Se, U, and V) and radionuclides (Ra-226, Pb-210, and Po-210) in sediment at northern Saskatchewan uranium mining and milling operations. The SLC approach is based on total metal and radionuclide concentrations in sediment, and corresponding benthic community composition data for a specific sampling site. In this study, sediment chemistry (total metals and radionuclides) and benthic community data from northern Saskatchewan uranium operations were compiled and examined. Results indicate that the CNSC-derived SQGs had limited relationships to observed effects, or lack thereof, on benthic invertebrate communities near uranium operations in Saskatchewan. The LELs were found to correctly align with effects at 95% of the sites that had effects, on a general basis, but on an element-specific basis many of the elements had concentrations at effect sites below their LELs. Furthermore, concentrations of the evaluated elements exceeded at least one LEL at 60% of the no-effect sites. The high number of exceedences of LELs at reference and no-effect sites (false-positives) calls to question the appropriateness of the CNSC-derived SQGs. It is suggested that alternatives to the SLC approach be explored.

Toxicity of uranium, molybdenum, nickel, and arsenic to Hyalella azteca and Chironomus dilutus in water-only and spiked-sediment toxicity tests

A series of laboratory spiked-sediment toxicity tests with the amphipod Hyalella azteca and the midge Chironomus dilutus were undertaken to determine acute and chronic toxicity thresholds for uranium (U), molybdenum (Mo), nickel (Ni), and arsenic (As) based on both whole-sediment (total) and pore water exposure concentrations. Water-only toxicity data were also generated from separate experiments to determine the toxicities of these metals/metalloids under our test conditions and to help evaluate the hypothesis that pore water metal concentrations are better correlated with sediment toxicity to benthic organisms than whole-sediment metal concentrations. The relative toxicity of the four elements tested differed depending on which test species was used and whether whole-sediment or pore water metal concentrations were correlated with effects. Based on measured whole-sediment concentrations, Ni and As were the two most acutely toxic elements to H. azteca with 10-d LC50s of 521 and 532 mg/kg d.w., respectively. Measured pore water concentrations indicated that U and Ni were the two most acutely toxic elements, with 10-d LC50s to H. azteca of 2.15 and 2.05 mg/L, respectively. Based on pore water metal concentrations, the no-observed-effect concentrations (NOECs) for growth were ( H. azteca and C. dilutus, respectively) 0.67 and 0.21 mg/L for U, <0.37 and 0.60 mg/L for Ni, and 16.43 and <0.42 mg/L for As. Pore-water lowest-observed-effect concentrations (LOECs) for growth were ( H. azteca and C. dilutus, respectively) 2.99 and 0.48 mg/L for U, 0.37 and 2.33 mg/L for Ni, and 58.99 and 0.42 mg/L for As. For U and Ni, results from 96-h water-only acute toxicity tests correlated well with pore water metal concentrations in acutely toxic metal-spiked sediment. This was not true for As where metalloid concentrations in overlying water (diffusion from sediment) may have contributed to toxicity. The lowest whole-sediment LOEC reported here for As was 6.6- and 4-fold higher than the Canadian Council of Ministers of the Environment interim sediment quality guideline and the Canadian Nuclear Safety Commission (CNSC) lowest effect level (LEL), respectively. The lowest whole-sediment LOECs reported here for Ni, U and Mo were 4-, 17.5-, and >260-fold higher, respectively, than the CNSC LELs for these metals/metalloids. Data on pore water metal concentrations in toxic sediment would be a useful addition to future Guidelines documents.

Discussions about safety criteria and guidelines for radioactive waste management

In Japan, the clearance levels for uranium-bearing waste have been established by the Nuclear Safety Commission (NSC). The criteria for uranium-bearing waste disposal are also necessary; however, the NSC has not concluded the discussion on this subject. Meanwhile, the General Administrative Group of the Radiation Council has concluded the revision of its former recommendation 'Regulatory exemption dose for radioactive solid waste disposal', the dose criteria after the institutional control period for a repository. The Standardization Committee on Radiation Protection in the Japan Health Physics Society (The Committee) also has developed the relevant safety criteria and guidelines for existing exposure situations, which are potentially applicable to uranium-bearing waste disposal. A new working group established by The Committee was initially aimed at developing criteria and guidelines specifically for uranium-bearing waste disposal; however, the aim has been shifted to broader criteria applicable to any radioactive wastes.

Preparation and application of tea to a tritium performance testing programme

A simple, but novel technique, for adjusting steeps of black tea to produce fluids, which are visually and spectroscopically similar to urine, has been developed at the National Calibration Reference Centre for Bioassay and In Vivo Monitoring in Canada. The method uses scans of absorbance versus wavelength, in the UV-VIS range (200-800 nm) to select diluted tea steeps that simulate urine. Tea solutions (1 and 10 %) were spiked with tritium and distributed to laboratories for performance testing (PT). The PT exercise was done as in a regular bioassay programme. The results showed that all samples satisfied the pass/fail conditions of the S-106 standard of the Canadian Nuclear Safety Commission, suggesting that adjusted tea successfully simulated urine for the tritium PT programmes. Also, since unlike urine whose use may increase the probability of contaminating and transmitting diseases (e.g. hepatitis C), tea is a safer alternative. When needed, it can readily be prepared for the laboratories.

Development of System Based Code (1) Reliability Target Derivation of Structures and Components

The present paper describes a new method for determining the target value of structural reliability in the framework of the System Based Code (SBC) by considering the safety point of view. This new method utilizes analysis models of a probabilistic safety assessment (PSA), and the reliability target is derived from (1) the proposal to a quantitative safety goal that was published by the nuclear safety commission (NSC) of Japan; (2) the quantitative safety design requirements on the core damage frequency (CDF) and the containment failure frequency (CFF) that were determined in the Fast Reactor Cycle Technology Development (FaCT) project by Japan Atomic Energy Agency (JAEA). This method was applied to determine the reliability target of the structures and components which constitute the reactor cooling system in the Japan sodium-cooled fast reactor (JSFR). The risk from the reactor is shown by the sum of combination of various elements in the PSA analysis model. Those elements include dynamic failures and static failures of the structures and components, and human errors. However, the present study focuses on the sequences including the static failure, and the probability of dynamic failures and human errors in those sequences is conservatively assumed as a unity. It was confirmed that the present method combined with the PSA analysis model for internal initiating events is applicable to determine the reliability target associated with a random failure of the structures and components, and also confirmed that the method related to seismic initiating events can derive the target value of the occurrence frequency at which any of the important structures and components fails due to an earthquake.

放射性廃棄物の余裕深度処分における埋設深度の妥当性評価の考え方について

This paper describes the objectives and specific applicational issues of the document authorized by the Nuclear Safety Commission entitled “Policy of the safety assessment of subsurface disposal after the period for active control”, focusing on the policy of assessment for the appropriateness of burial depth. Concerning the burial depth of subsurface disposal, the proposal of 50-100 m from the surface has been made by the Atomic Energy Commission as a sufficient depth to avoid general usage of the underground environment, furthermore, taking into account these circumstances, the above document stipulates the new policy of assessment for the appropriateness of burial depth considering uplift/erosion noted in the safety assessment for long-lived radioactive materials. In the case of considering uplift/erosion, the isolation from the living environment planned in the original scheme will be gradually lost, the disposal facility will come close to the surface and become near-surface disposal in the long term. This paper describes the required roles of burial depth for subsurface disposal considering the long-term evolutional changes, introduces the physical protection capability to human intrusion as one of the protective functions of engineered barriers, and discusses the specific important issues related to the actual application.

Evidence of children's vulnerability to radiation in the context of radiological/nuclear events and considerations for emergency response

International organisations, such as International Atomic Energy Agency, United Nations Scientific Committee on the Effects of Atomic Radiation and World Health Organisation, together with committees of experts such as Biological Effects of Ionising Radiation and Committee on Medical Aspects of Radiation in the Environment, have assessed the effects of radiation on large exposed populations (Chernobyl accident, and Hiroshima/Nagasaki atomic bombings) and on nuclear energy workers and people living near nuclear facilities. Childhood and in utero exposure to moderate and high levels of ionizing radiation, such as those experienced during the atomic bombings of Japan, or from radiotherapy, is an established cause of leukaemia and solid cancer. There is no evidence of increase in solid cancers (excluding thyroid cancer) or leukaemia in the children from Chernobyl, and no evident link between worker's exposure to radiation and leukaemia in their offspring or with the presence of leukaemia clusters around nuclear power plants. It has also not been possible to demonstrate the evidence of radiation hereditary effects in human populations. In accordance with international guidance, Canadian Nuclear Safety Commission recommends optimisation of protection strategies to reduce doses to children. The development of credible radiological/nuclear event scenarios would assist in identifying probable sources of radioactivity and pathways of exposure for children. Such scenarios should then be used to identify protection strategies appropriate for children.

The Independence of the Nuclear Regulator

The firing of Linda Keen as President and Chief Executive Officer of the Canadian Nuclear Safety Commission provoked considerable debate within Canada and internationally about the independence of the Canadian nuclear regulator. Ms. Keen was dismissed from her position at the height of the crisis over a world-wide shortage of medical isotopes caused by the shut-down of the research reactor in Chalk River, Ontario. Under the terms of its licence, the reactor was required to have two cooling pumps connected to an emergency power supply as a backup in case of a power outage caused by an event such as an earthquake. In November 2007, after it was discovered that the pumps were not connected, the reactor was shut down. As panic over the shortage of medical isotopes grew, the government took three extraordinary measures: first, it issued a directive; second, it introduced emergency legislation in Parliament; and finally, it fired Linda Keen as President of the Commission. This paper examines those three measures and whether they constituted an unwarranted interference with the independence of the Canadian nuclear regulator.

Fitness for service assessment of degraded CANDU feeder piping—Canadian regulatory expectations

Allowance for the continued operation of feeder piping at some Canadian CANDU stations, which is experiencing active degradation mechanisms, has been based primarily on augmented inspection practices and conservative fitness for service assessments. The major degradation mechanisms identified to date are: pipe wall thinning due to Flow Accelerated Corrosion (FAC) and service induced cracking due to Intergranular Cracking due to Stress Corrosion Cracking (SCC) and potentially Low Temperature Creep Cracking (LTCC) mechanisms. Given that currently available industry codes and standards do not provide sufficient guidelines/criteria for assessing the degradation of feeder pipes, the Canadian Nuclear Safety Commission (CNSC) has asked the utilities to establish feeder pipe specific procedures to provide reasonable assurance that the risk associated with the feeder degradation is maintained at an acceptably low level. In response to this requirement, the Canadian CANDU industry has developed and continued to update feeder fitness for service guidelines to provide evaluation procedures and industry standard acceptance criteria for assessing the structural integrity of the feeder pipes. The scope and frequency of inspections are determined based on the results of the fitness for service assessments taking into account the relative susceptibility of feeder pipes to each specific degradation mechanism. While industry practices for the management of degraded feeder pipes have, in general, been complied with the regulatory expectations, outstanding issues still remain. Major regulatory concerns include uncertainties associated with limitations in both the inspection techniques and the mechanistic understanding of the degradation processes, which can impede inspection planning and fitness for service assessments.This paper presents the regulator's view of the current situation with respect to degradation of feeder piping, its implications for nuclear safety and the regulatory expectations on industry's management of the critical ageing phenomena.

Special Symposium on Draft Reports of Radiation Council and Nuclear Safety Commission

Special Symposium on Draft Reports of Radiation Council and Nuclear Safety Commission

The Logical Framework Approach-Millennium

The Logical Framework Approach (LFA) has proved to be a valuable tool for project approval, design, and evaluation. However, a few pitfalls make it hard to use within today's project management framework and to integrate with other project management tools. This article proposes an updated version of the LFA to improve its compatibility with today's corporate culture, project management framework, and tools. We propose to call the updated tool the Logical Framework Approach-Millennium (LFA-M). The LFA-M is a seven-step approach leading to the development of the Logframe-Millennium (LF-M), a five-column and four-line matrix describing major project commitments and providing an overall understanding of the project. It was successfully implemented at the Canadian Space Agency and the Canadian Nuclear Safety Commission. The LFA-M fits well within today's project management framework and corporate culture and leads easily to other project management tools.

Case Law

By decision dated 7 April 2009, Mr. Justice Hughes of the Federal Court of Canada denied an application for judicial review submitted by Linda Keen, the former President of the Canadian Nuclear Safety Commission (CNSC), by which she challenged the legality of the Order in Council which removed her as President. The court dismissed the application,2 finding that the decision had been lawful.

Assessment of Steam Generator Tube Flaw Size and Leak Rate Models

The Canadian Nuclear Safety Commission recently developed the CANTIA (CANDUTM Tube Inspection Assessment) methodology for probabilistic assessment of inspection strategies for steam generator (SG) tubes as a direct effect on the early detection and prevention of tube failure and primary-to-secondary leak of reactor coolant. In an effort to improve CANTIA, an SG tube integrity assessment code, a relevant survey of the literature on the discharge of subcooled water from cracks and critical flow models, SG tube cracks, leakage, and probabilistic assessment methodologies was carried out. The original CANTIA and ANL/CANTIA code models for the flaw opening area and flow leakage rate were reviewed. The predictions from the crack opening area and the leakage flow rate models were compared with experimental measured data from cracked SG tubes.

Is Thyroid Screening Necessary for Nuclear Medicine Personnel Receiving and Administering Capsules Containing Large Doses of 131I?

The cost-effectiveness of a thyroid screening procedure for the detection of internal contamination of personnel working with large doses of encapsulated iodine-131 ( 131I) was examined by reviewing the results of screening measurements performed during 1 year. Thyroid burdens were measured by self-assessment using a sodium iodide (NaI) probe. Of 113 screening measurements, 101 indicated a negative thyroid content of 131I. The largest burden observed was statistically not different from zero. The count rate corresponding to the largest observed burden would represent an 131I content of 23 Bq, which is approximately 0.2% of the level at which results have to be reported to the Canadian Nuclear Safety Commission. Negative count rates arose because of a small overestimation of the background contribution that was measured with a neck phantom positioned in front of the thyroid probe. The cost of a thyroid screening program for personnel who handle encapsulated 131I is considerable, especially when the need for such measurements is questionable.

Canadian national internal dosimetry performance testing programme: results of the pilot programme

This paper describes the design and construction of a new performance testing programme that was implemented in Canada in 2008. The Canadian Regulator (Canadian Nuclear Safety Commission) had determined that their licensees, in addition to participating in the existing in vivo and in vitro performance tests, needed to demonstrate their ability in interpreting bioassay results to obtain intakes and resulting doses. The new programme is administered by the Canadian National Calibration Reference Center for Bioassay and In Vivo Monitoring (NCRC). Currently, the NCRC carries out the performance testing for the in vitro and in vivo. At the time of writing, the first round has been completed and the results for (3)H and (nat)U exposures were very consistent, while the committed effective dose from (137)Cs intake varied by a factor of two.

2 原子力の現状と技術的課題

This paper describes present status of nuclear power and current technical issues based on the activities of the Japan Nuclear Energy Safety Organization (JNES) which was established on October 1 of 2003. Currently one of the major issues in Japanese nuclear power plants is seismic issue covering Niigata-Chuetsu-oki earthquake two years' ago and re-evaluation of the operating plants in compliance with the new guideline established by Nuclear Safety Commission in 2006. New inspection system has been introduced from this year. Many issues regarding safety regulation have been addressed or under investigation such as ageing, risk application, safety culture, plant uprating, sump clogging, severe accident. Present status of nuclear fuel cycle facilities such as MONJU and the reprocessing plant at Rokkasho is also explained. International activities have been promoted by the globalization and the Multinational Design Evaluation Program (MDEP) is one of them. Role of the technical support organizations (TSO) for regulatory body is attracting more importance.

Verification of Validity of Isotope-Specific Exemption Levels for Surface Contamination Using Monte Carlo Calculation

Current surface contamination density standards are conservatively determined not for each nuclide but by the type of emitter. In the previous studies, isotope-specific exemption levels for surface contamination for representative nuclides were originally derived by developing a deterministic dose assessment model that can be applied throughout radiation, transport and waste safety fields. In this study, the effects of uncertainty in assumed parameters on the derived exemption levels were examined by developing a probabilistic dose assessment model using the Monte Carlo calculation. The criteria for the judgment of validities of the derived exemption levels were decided applying the concept of the representative person given by the International Commission on Radiological Protection (ICRP), the set of minimum dose constraint for the optimization of the radiological protection of the public revealed in a recent study and the probabilistic dose assessment model developed by the Nuclear Safety Commission (NSC) of Japan. Moreover, the effects of correlation in parameters on the results of probabilistic dose assessment are probabilistically examined by developing the function of specifying the random seeds independently for each parameter in the Monte Carlo calculation. These results verify the validity of the deterministically derived isotopespecific exemption levels for surface contamination.

Problems and Study of Regulations on Nuclear Power Plants

The purpose of this paper is to extract problems of the regulations on nuclear power plants in Japan in order to indicate the direction of the solution as much as possible. This paper includes problems about the duplicated application of Nuclear Reactor Regulation Law and Electricity Utility Law, the examination criteria of nuclear reactor establishment permission, the relation between the establishment permission and the regulations, the double check evaluation system by the Minister of Economy, Trade and Industry, and Nuclear Safety Commission, fuel inspection and in-service inspection, management of the information about insignificant events, and so on.

Radiation Safety Program: Principles and Regulations

Radiation safety principles are important to medical radiation technologists in the radiography, nuclear medicine, and radiation therapy disciplines. A combination of both federal and provincial regulations makes up the radiation safety program for a facility. The provincial governments, through the Ministry of Health and the Ministry of Labour, and the federal government through the Canadian Nuclear Safety Commission, provide guidelines of what a radiation safety program should entail for a facility. Programs will be designed and implemented by internal radiation safety specialists, based on the needs of the users of radioactive materials or radiation emitting devices. This article will explain the differences in the provincial and federal regulatory requirements and provide an overview for each, as well as outline the workers' responsibilities in regard to the specific regulations.