[en] Ontario Hydro operates 20 AECL designed CANDU nuclear power reactors, some of which have been in service for 20 years. These pressurized heavy water, natural uranium fuelled reactors, ranging in size from 540 to 900 MWe, have continuously provided high capacity factors and low total electricity production costs, among the world's leaders in performance. CANDU's inherently have large cores and utilize a large number of diverse types of Reactivity Control Devices (RCDs) for fully automatic, continuous measurement and regulation of bulk power level as well as spatial uniformity of fission power in the core. The devices also control start-up and power manoeuvering. Other RCDs provide two independent systems of measurement and neutron absorber insertion for fast reactor shutdown. The continuous proper operation of RCDs obviously has significant influence on plant performance and availability, yet Ontario Hydro (OH) experience is that no significant loss of capacity factor has been attributed to the RCDs. This paper focuses on these Ontario Hydro replacement practices as they apply to RCD equipment in CANDU plants. The particular practices described relate to some extent to the unique aspects of CANDU plants, but the concepts of thorough planning, operational quality and teamwork are universally valid. Practicing safe, efficient component replacements contributes to reliable, cost effective plant operation. (author)

[en] KEPCO (Korea Electric Power Corporation) opened its HWR program in 1977 by starting the construction of Wolsong 1 (CANDU-6). Wolsong 1 completed its construction in 1983 and has been operated successfully achieving an average lifetime capacity factor of 85%. As far as PHWR technology is concerned, KEPCO did not have self reliance program like PWR but for the PHWR technology development of Korea, KEPCO and AECL made technology transfer agreement for the CANDU-6 NSSS design at the time of Wolsong 3 and 4 contracts. Under this agreement, AECL has provided the CANDU-6 design technology and it is contributing to the development of Korean PHWR design technology. In the field of fuel, KAERI (Korea Atomic Energy Research Institute) is carrying out the feasibility study of CANFLEX and DUPIC. Planning of future CANDU projects in Korea as well as type and capacity if constructed is under study by KEPCO. The economic aspects of CANDU-6, the future prospects of CANDU-9 technology development and availability of construction site will be the important points of study and it will be finished next year. The result of study will be reflected to the new Korean electric power development plan, which will extend Korean power plant construction schedule until 2010

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[en] The design of the CANDU NPP control centre and the associated control centre design process has evolved considerably over several generations of plants, from Douglas Point through Darlington, and beyond, to new designs like CANDU 3. In the early plants, the control centre configuration had to be based on designers' projections of control interface requirements. With succeeding generations of designs, along with the introduction of advancing computer control technology, a larger based of operational experience has been factored into the control interface design, and increasing attention has been given to more formal requirements definition, and more systematic consideration of human factors aspects of the design

[en] Integrated programs for plant design and construction (IPPDC) is a 5-yr program at Ontario Hydro to optimize engineering and construction productivity through better use of computer technology. The proportion of computer programs operating with data derived from an integrated common data base is very low. IPPDC, on the other hand, is greatly concerned with this common data base. The goals of the IPPDC include improvement of the information flow for a project, minimization of site-discovered interferences, and compression of the entire project life cycle through the intelligent use of computer technology. This program focuses on the development of an integrated data base for plant design software systems to service a multi discipline engineering environment as required by a large-scale megaproject. To achieve the goals of IPPDC, there are three basic elements of computer technology that must be in place before a totally integrated data base system can be achieved: (1) data management; (2) networking; and (3) three-dimensional modeling

[en] An analytical model for the dynamics of an articulated string of fuel bundles in axial flow is described each bundle being composed of many fuel elements held between end plates, and the bundles being held together by a central support tube running through the whole assembly, as for example, in the CANDU-BLW design. The mathematical formulation will be given first, followed by the derivation of the equations of motion and their solution, and then by typical results and their interpretation

[en] The ACR-1000 design is the next evolution of the proven CANDU reactor design. One of the key objectives for this project was to improve station environmental performance based on the As Low As Reasonably Achievable (ALARA) principle, and station operating experience, feedback from owners of CANDU stations, and industry best available techniques. Design improvements, based on these concepts to improve the environmental performance of the ACR-1000 reactor and protect workers, the public, and the environment, are presented in this paper. (author)

[en] This report describes a method and results establishing the weighting factors for plant's functions and threshold value for screening the safety-significant structures, systems, and components(SSCs) to implement the Maintenance Rule (MR) to CANDU Reactor by using the Delphi Process. In implementing the MR, it is required to screen the SSCs that are significant contributors to safety as identified through a blended risk-informed process that uses Probabilistic Safety Assessment(PSA) insights, operating experience and new technical information using an expert panel evaluations. Decision making through an expert panel is an important part of implementing the MR because we cannot obtain all of the necessary information from PSA results. In this study, we used the Delphi process for elicitation of the expert opinions. Hence, we established the weighting factors for the plant's functions and estimated the threshold value to screen out the low safety-significant SSCs

[en] RBGSS technology may provide another way to approach guaranteed shut- down state for CANDU6 reactor. This paper introduces the technical scheme of RBGSS, asses the advantages of RBGSS. Combining with operating practices of Qinshan CANDU reactor, it discusses the proces for RBGSS to applied in long-time outage and short-time outage, and assess the safety and economy of RBGSS. Finally it discuss the possible problem of RBGSS. (authors)

[en] Good neutron economy is the basis of the fuel cycle flexibility in the CANDU reactor. This paper describes the fuel cycle options available to the CANDU owner with special emphasis on resource conservation and waste management. CANDU fuel cycles with low initial fissile content operate with relatively high conversion ratio. The natural uranium cycle provides over 55 % of energy from the plutonium that is created during fuel life. Resource utilization is over 7 MWd/kg NU. This can be improved by slight enrichment (between 0.9 and 1.2 wt % U235) of the fuel. Resource utilization increases to 11 MWd/kg NU with the Slightly Enriched Uranium cycle. Thorium based cycles in CANDU operate at near-breeder efficiency. Obey provide attractive options when used with natural uranium or separated (reactor grade and weapons grade) plutonium as driver fuels. In the latter case, the energy from the U233 plus the initial plutonium content amounts to 3.4 GW(th).d/kg Pu-fissile. The same utilization is expected from the use of FBR plutonium in a CANDU thorium cycle. Extension of natural resource is achieved by the use of spent fuels in CANDU. The LWR/CANDU Tandem cycle leads to an additional 77 % of energy through the use of reprocessed LWR fuel (which has a fissile content of 1.6 wt %) in CANDU. Dry reprocessing of LWR fuel with the OREOX process (a more safeguardable alternative to the PUREX process) provides an additional 50 % energy. Uranium recovered (RU) from separation of plutonium contained in spent LWR fuel provides an additional 15 MWd/kg RU. CANDU's low fissile requirement provides the possibility, through the use of non-fertile targets, of extracting energy from the minor actinides contained in spent fuel. In addition to the resource utilization advantage described above, there is a corresponding reduction in waste arisings with such cycles. This is especially significant when separated plutonium is available as a fissile resource. (author)