[en] Short communication

[en] The computer codes RFSP-IST, WIMS-IST and DRAGON-IST were used to pre-simulate the Bruce A Nuclear Generating Station Unit 4 Restart Phase B commissioning physics tests. Comparisons between calculations and measurements have validated all Bruce A Restart accident analyses, previously done with the same computer codes and modelling methodologies. Post-simulations of Phase B commissioning physics tests were also performed, which differ from the pre-simulations mainly in the use of an improved methodology, the side-step method, for calculating the incremental cross-sections for reactivity devices. The post-simulation results showed better agreement with measurements than those of the pre-simulations, particularly for the reactivity worth of the liquid zone controllers. (author)

[en] In this paper we look respectively at three specific examples showing program strategies for maintenance management, organization and planning. Starting with preventive maintenance optimization, we will look at one Bruce B Predefined task on the Reactor Regulating System to illustrate reduced maintenance requirement, a maintenance management strategy. Next discussed is the organizational strategy at Darlington to have an engineering program meet the jurisdictional requirements for maintaining certification for TSSA registered pressure vessels. The last look-see will show the earned value of the planning for the first Pickering A unit to be returned to service. Finally all the above is tied together in a compare and contrast of what works and what could be improved upon. (author)

[en] The radiation-resistant polymer developed by the Savannah River National Laboratory is adaptable for multiple applications to enhance polymer endurance and effectiveness in radiation environments. SRNL offers to collaborate with TEPCO in evaluation, testing, and utilization of SRNL's radiation-resistant polymer in the D&D of the Fukushima Daiichi NPS. Refinement of the scope and associated costs will be conducted in consultation with TECPO.

[en] Risk comparison is essential for effective societal and individual decision-making. After the Fukushima disaster, studies compared radiation and other disaster-related risks to determine the effective prioritizing of measures for response. Evaluating the value of risk comparison information can enable effective risk communication. In this review, the value of risk comparison after the Fukushima disaster for societal and individual decision-making is discussed while clarifying the concept of radiation risk assessment at low doses. The objectives of radiation risk assessment are explained within a regulatory science framework, including the historical adoption of the linear non-threshold theory. An example of risk comparison (i.e. radiation risk versus evacuation-related risk in nursing homes) is used to discuss the prioritization of pre-disaster measures. The effective communication of risk information by authorities is discussed with respect to group-based and face-to-face approaches. Furthermore, future perspectives regarding radiation risk comparisons are discussed.

[en] As electronic components of nuclear power plants age, their reliability decreases. With this decreased mean time between failures, there is increased cost. The increased costs are associated with replacing or repairing components and with the increased risk of production loss.To compound these problems there are issues of obsolescence. The impact of these effects on the area of instrumentation and control electronics is especially severe. By utilizing digital technology that is relatively cheap and readily available, one can achieve improved reliability in complex control loops. The deaerator level control loop in a nuclear power plant is a complex control loop. The control of the loop is achieved using a feed-forward control scheme. A station-specific implementation of this control scheme is achieved using several analog electronic components. A modification was performed to achieve increased reliability while implementing the same control algorithm by using digital components, an improved component arrangement and increased redundancy. This paper will describe how the improved reliability was achieved. (author)

[en] Physics simulations in safety analyses are generally performed using a bundle irradiation distribution that is consistent with an approximate time-average configuration. In this paper, three assessments of a spurious adjuster withdrawal event at Darlington are performed with RFSP. The simulations are performed using a time-average irradiation distribution and the SORO predicted irradiation distribution just prior to the actual event. In all three of the assessments it is shown that the results are quite insensitive to the assumed irradiation distribution. This supports the approach of assuming a time-average irradiation distribution in safety analyses. (author)

[en] This paper describes the major results of the recently-completed Bruce B Risk Assessment (BBRA). The results are presented in the form of the frequencies of various fuel damage categories (FDCs) and ex-plant release categories (EPRCs). Some of the dominant sequences leading to these categories are discussed. Also discussed are the key conclusions of the assessment. The paper also discusses how the products of the study have been used to support decision-making at the plant. Some specific examples are included. The paper concludes by describing the work undertaken to develop an on-line risk model that is being used on a regular basis by plant personnel to assess the risk impact of changes in plant configuration. (author)

[en] This paper presents the results of a large study of 1340 articles published by two major newspapers in six European countries (Belgium, Italy, Norway, Slovenia, Spain and Russia) in the first 2 months after the Fukushima Daiichi nuclear disaster. The focus of the analysis is on the application and overall impact of protective actions, both during the emergency phase and later, how the newspapers describe those actions, which differences were apparent between countries and what recommendations can be extracted in order to improve general communication about these issues. A clear lesson is that, even under uncertainty and recognising limitations, responsible authorities need to provide transparent, clear and understandable information to the public and the mass media right from the beginning of the early phase of any nuclear emergency. Clear, concise messages should be given. Mass media could play a key role in reassuring the public if the countermeasures are clearly explained. (authors)

[en] The Canadian Nuclear Safety Commission (CNSC) guidance documents related to human factors do not specify design implementation as a specific aspect requiring review, as is done in NUREG-0711. However, even without being separately identified, it is clearly understood by any Human Factors specialist that issues arising from the implementation of a design need to be carefully reviewed and addressed. One of the key areas where implementation issues become a concern is the area of technological changes. This can be of particular concern in multi-unit control rooms, such as are used on many CANDU stations, as periods will exist where different designs and technologies are in use for the same purpose in the same control room. This paper will look at the techniques used by the Bruce Power Human Factors section to ensure that the existence of multiple technologies does not have a negative performance impact for the personnel operating and maintaining the station. This will be done using examples from past Bruce Power experience. Lessons learned will also be discussed. (author)