[en] The nuclear landscape looked very promising before the Fukushima Daiichi accident. In the past five years before the accident, so-called Nuclear Rennainsance looked to be in full swing, with many countries beginning to factor nuclear energy as part of their electricity generation mix. At some point, 43 IAEA Members States confirmed their interest in launching new nuclear power programmes. Whilst only two of these nuclear new-comers have already chosen the reactor designs they would deploy in their new build, it is commonly accepted that the so-called Generation III and Generation III+ would mostly be the designs of the choice for new nuclear build. This presentation seeks to examine the current status of plans for nuclear build after Fukushima, looking into technology and safety issues that would influence the final policy decisions in new nuclear build programmes.(author).

[en] High Temperature Reactors have been designed and operated as far back as the 1970s. A number of critical facilities and test reactors such as the AVR in Germany have operated successfully and have provided scientist and engineers with an opportunity to collect valuable data regarding the performance of the reactor for example, fuel performance, materials behaviour, flow characteristics, improved understanding of neutronics and thermal hydraulics behaviour during normal and transient conditions, etc. Such data is very important for utilization in further technology development especially for modern V/HTRs currently being pursued in IAEA Member States. An assessment of how much data was collected and how it can be of use to developers of future HTGR designs has not been done in the past. This paper aims at highlighting the available data and makes proposals for use of such data for the advancement of the HTGR technology.

[en] Africa is a continent endowed in mineral resources. Among others, there are vast deposits of gold and uranium in African countries. The by-products of these minerals are in some cases radioactive and therefore exposures must be monitored. Additionally, Africa uses a lot of radioactive sources in different industries and in the health sector. Regulation of these mining activities and facilities handling these radioactive sources becomes extremely important for the protection of people, property and the environment against harmful effects of ionizing radiation. Due to the vast size of the African continent, with inequitable resources, regional cooperation becomes key to capacity-building and knowledge and information sharing. In order to achieve this, African Member States resolved to form a Forum for Nuclear Regulatory Bodies in Africa (FNRBA) in 2009. The paper will present the FNRBA, its activities, achievements and challenges in the quest to bring about effective regulation of nuclear and radiation safety in the continent. (author)

[en] In the advent of increased demand for safety and economics of nuclear power plants, nuclear engineers and designers are called upon to develop advanced computation tools. In these developments, space-time effects in the dynamics of nuclear reactors must be considered within the framework of a full 3-dimensional treatment of both neutron kinetics and thermal hydraulics. In a recent effort at the Pennsylvania State University, a time-dependent version of the discrete ordinates transport code DORT, DORT-TD was coupled to a 2-dimensional core thermal hydraulics code THERMIX-DIREKT. In the coupling process, a feedback model was developed to account for the feedback effects and was implemented into DORT-TD. During the calculation process for each spatial node of the DORT-TD core model, feedback parameters representative of this node are passed to the feedback module. Using these values, cross section tables are then interpolated for the appropriate macroscopic cross section values. The updated macroscopic cross sections are passed back to DORT-TD to perform transport core calculations, and the power distribution is transferred to THERMIX-DIREKT to obtain the relevant thermal-hydraulics data in turn, and this calculation loop continues. In this paper, DORT-TD/THERMIX is used to simulate transients of interest in the PBMR (Pebble Bed Modular Reactor) safety using established benchmark problems: load change from 100% to 40% power and fast control rod ejection (PBMR-268 benchmark problem). The results obtained are compared with those obtained using the diffusion-based module of the code. The results are only preliminary and so far show that diffusion theory is not such a bad approximation for PBMR for the prediction of integral parameters

[en] Leadership, management and culture for safety were topics that were discussed during the conference. The participants in this session included members from utilities, regulatory authorities, vendors and international organizations. The topics were discussed over three parallel sessions that consisted of a total of 12 presentations. The overall theme was: ‘The role of leaders and managers in developing, nurturing, maintaining and continuously improving the culture for safety in the organization they led’.

[en] This paper presents an overview of the safety analysis of the pebble-bed reactor using the advanced coupled-code NEM-THERMIX. This coupled code is a combination of the Nodal Expansion Method code (NEM), a 3-D neutronics code developed at Penn State, and THERMIX-DIREKT, a 2-D HTR thermal-hydraulics code. The coupled code is used in this work to illustrate the importance of coupled neutronics/thermal-hydraulics calculations when analyzing the safety of high temperature gas-cooled reactors. Using this code, it is demonstrated that the neutronics behavior is sensitive to cross section changes due to temperature and spectrum feedback effects. The spatial dependence of these effects is very important to be modeled and hence, coupled calculations are inevitable in establishing and building a safety case for the high temperature gas-cooled reactors of a pebble-bed type like the PBMR. (authors)

[en] The principal responsibility for a nuclear regulator is to assure compliance with regulations and safety standards by operators. One of these requirements is demonstration of, and adherence to, nuclear safety culture by the operators. At the same time, the regulators themselves are expected to live the talk and practice what they preach, i.e., demonstrate highest levels of nuclear safety culture within their organizations. Consequently, it is recognised that leadership is important in the creation of a culture that supports and promotes a strong nuclear safety performance of an organization. The leaders of a regulatory body are vital in inspiring employees to a higher level of safety and productivity, which means that they must apply good leadership attributes on a daily basis. This paper will attempt to bring forth and share attributes for strong leadership role in promoting a safety culture within a nuclear regulatory body by surveying world-wide practices and examples in developing and advanced nuclear countries. (author)

[en] Full text: Regulatory bodies must maintain the highest levels of competence to provide regulatory oversight to the operating organizations. In building up that competency, regulators amongst others develop safety regulations and authorization processes, review and assess the safety and design documentation provided by the operating organization and inspect the facility, the vendors and manufacturers of safety related components. Over the years, regulators have seen an exodus of skills due to several reasons such as natural attrition, poaching by industry due to new nuclear build opportunities, etc. Regulatory knowledge and experience loss becomes the biggest risk to many regulators. Intervention strategies must be devised to mitigate this risk, and knowledge management is one of them. The presentation will highlight and conjecture ways and means by which nuclear knowledge management can enable a regulator to be both effective and efficient. (author

[en] The verification and validation of computer codes used in the analysis of high temperature gas cooled pebble bed reactor systems has not been an easy goal to achieve. A limited amount of tests and operating reactor measurements are available. Code-to-code comparisons for realistic pebble bed reactor designs often exhibit differences that are difficult to explain and are often blamed on the complexity of the core models or the variety of analysis methods and cross section data sets employed. For this reason, within the framework of the IAEA CRP5, the 'Pebble Box' benchmark was formulated as a simple way to compare various treatments of neutronics phenomena. The problem is comprised of six test cases which were designed to investigate the treatments and effects of leakage and heterogeneity. This paper presents the preliminary results of the benchmark exercise as received during the CRP and suggests possible future steps towards the resolution of discrepancies between the results. Although few participants took part in the benchmarking exercise, the results presented here show that there is still a need for further evaluation and in-depth understanding in order to build the confidence that all the different methods, codes and cross-section data sets have the capability to handle the various neutronics effects for such systems. (authors)

[en] This paper presents an overview of the investigations on the need for deterministic transport methods for the analysis of pebble-bed reactors. To account for the transport effects present in the PBMR design that cannot be modeled accurately with the diffusion theory, a two-dimensional neutronics solver based on transport theory is implemented in the Penn State NEM-THERMIX code system. The necessity of equipping neutronics analysis codes with neutron transport theory capability is investigated along with the challenges to accomplish this in an efficient and versatile manner. For this purpose a time-dependent version of the two-dimensional neutron transport code DORT is utilized as a first step. The developed benchmark test cases, based on the PBMR 268 MW design, are used for this work, and results from the comparative analyses of these test cases are presented. The results show clearly that even in steady-state calculations, the differences between diffusion and transport-based methods in analyzing the PBMR are observed and need to be addressed. (authors)