[en] International standards from nuclear power plant operation area are being frequently upgraded and revised in accordance with the continuous improvement philosophy. This philosophy applies also to the area of Quality Assurance, which has also undergone significant improvement since the early 1950s. Besides just nuclear industry, there are also other international quality standards that are being continuously developed and revised, bringing needs for upgrades also in the nuclear application. Since the beginning of Krsko NPP construction, the overall Quality Assurance program and its applicable procedures were in place to assure that all planned and systematic actions necessary to provide adequate confidence that an item or service will satisfy given requirements to quality, are in place. The overall requirements for quality as one of the major objectives for Krsko NPP operation are also set forth in the Updated Safety Analyses Report, the document that serves as a base for operating license. During more than 30 years of Krsko NPP operation, the quality requirements and related documents were revised and upgraded in several attempts. The latest revision 6 of QD-1, Quality Assurance Plan was issued during the year 2011. The bases for the revision were: Changes of the Slovenian regulatory requirements (ZVISJV, JV5, JV9?), Changes of Krsko NPP licensing documents (USAR section 13?), SNSA inspection requirements, Changes of international standards (IAEA, ISO?), Conclusions of first PSR, Implementation of ISO standards in Krsko NPP (ISO14001, ISO17025), Changes of plant procedures, etc. One of the most obvious changes was the enlargement of the QA Plan scope to cover interdisciplinary areas defined in the plant management program MD-1, such as Safety culture, Self-assessment, Human performance, Industrial Safety etc. The attachment of the QA Plan defining relationships between certain standards was also updated to provide matrix for better correlation of requirements of various standards: 10CFR50 App. B, IAEA GS-R-3, JV5 and ISO9001. Krsko NPP will continue to develop its internal quality assurance processes and requirements also in the future. The most important objective of the entire organization - to protect the safe and efficient power plant operation, will continue to be also the most important goal to the quality assurance program.(author).

[en] The system code ATHLET is being developed at Gesellschaft fuer Anlagen-und Reaktorsicherheit (GRS) in Germany. In 1996, the NPP Krsko (NEK) input deck for ATHLET Mod 1.1 Cycle C has been developed at Faculty of Electrical Engineering (FER), University of Zagreb. The input deck was tested by analyzing the realistic plant event 'Main Steam Isolation Valve Closure' and the results were assessed against the measured data. The input deck was established before plant modernization that took place in 2000 and included the power uprate and SG replacement. The released ATHLET version (Mod 2.2 Cycle A) is now being available at FER Zagreb. Accordingly, the NEK input deck for ATHLET Mod 2.2 Cycle A has been developed. A completely new input deck has been created taking into account the large number of changes due to power uprate and SG replacement as well as taking advantage of developmental work on NEK data base performed at FER. The new NEK input deck for ATHLET code has been tested by analyzing the Rod Withdrawal Power (RWAP) accident and the results were assessed against the analysis performed by RELAP5/mod 3.3 code. The RWAP accident can be either Departure from Nucleate Boiling (DNB) ratio or overpower limiting accident depending on initial power and reactivity insertion rate. Since the automatic rod control system is assumed unavailable, the only negative reactivity is due to Doppler and moderator feedback. Consequently, the nuclear power and the transferred heat in the steam generators (SGs) increase. Since the steam flow to the turbine and the extracted power from the SGs remain constant, the SG secondary pressure and the temperatures on the primary side increase. Unless terminated by manual or automatic action, the power mismatch between primary and secondary side and the resultant coolant temperature rise could eventually result in DNB ratio and/or fuel centreline melt. In order to avoid core damage, the reactor protection system is designed to automatically terminate the transient before the DNB ratio falls below the limit value, or the fuel rod power density limit (kW/m) is reached. For both ATHLET and RELAP5 analysis, the steady state calculation has been performed for the first 1000 seconds. The RWAP accident is simulated by constant reactivity insertion rate equal to 2.4 pcm/sec.(author).

[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] The task of reducing CO₂ emission in order to keep the global temperature increase below 2⁰C requires staggering changes in energy consumption and production. It appears, unfortunately, that before obvious and drastic effects of climate change occur, few governments have the strength to implement the energy strategies called for. However, by the time climate change becomes evident to wide public it may be too late or much more difficult. Energy policy is heavily politicized which creates another obstacle to timely action, as witnessed by backlash against nuclear energy following Fukushima accidents. Post Fukushima arguments for nuclear energy should concentrate on the features which give it a secure place in the 21st century energy strategy, with highest safety standards understood. Its modern relevance comes from the, at present, unique ability, independent on external conditions, to produce large amounts of energy without emission of carbon dioxide. How long will this unique position last cannot be predicted with precision, but from the dynamics of their developments, large scale CCS is unlikely to be available before 2060/65 and nuclear fusion later still. We discuss the feasibility and desirability of the future without nuclear energy. Our recent study (EP 2010) has shown that nuclear energy, even subject to stringent safety and technology constraints, can give substantial contribution to carbon emission reduction until 2065, thus providing time for a large scale introduction of renewable sources, CCS and possibly nuclear fusion. Maximum nuclear strategy limited by uranium resources and with conventional reactor technology without reprocessing we assumed in period 2025-2065, would contribute in 2065 with about 25.2 Gt CO₂ emission reduction, respectively with 39% of the reduction needed to reduce emission from business as usual strategy (WEO 2009) to the level required to limit global temperature increase below 2⁰C. Remaining reduction of 38.4 Gt C0₂ eq, respectively 61% would have to be covered by new energy sources, energy efficiency and reduction of consumption. To achieve this by 2065 is a task requiring brave assumptions on development of new energy sources. Prediction on renewable sources development are given by several organizations such as EREC, GWEC, Solar Energy Council, and others. However, accepting their optimistic forecasts about wind and solar energy contribution in the years up to 2060/65, we show that renewable sources would not suffice to replace both coal and nuclear power plants. We do not see that it would be feasible and wise to enlarge the task by abandonment of nuclear contribution, especially in EU.(author).

[en] The presentation analyses some issues which are of particular importance for future nuclear power application. These include duration of uranium reserves and high level radioactive waste decay period in function of uranium reserves (determined, assumed and speculative) and type of fuel cycle used. Public acceptance during essential historical milestones of nuclear power use, influence of safety and compatibility evaluations, quantified risk, externalities and nuclear accidents. Short review of major accidents, causes, consequences, impact of LNT and hormesis hypothesis. Particular problem for future of nuclear power is potential shortage of experienced personnel due to long period without plants construction. To address some of problems which may face future investors a brief review of specific events experienced during construction of NPP Krsko is presented. Such events could be of interest to countries planning to construct nuclear power plant.(author).

[en] Our civilization is witnessing about century of nuclear age mixed with enormous promises and cataclysmic threats. Nuclear energy seems to encapsulate both potential for pure good and evil or at least we humans are able to perceive that. These images are continuously with us and they are both helping and distracting from making best of nuclear potentials for civilization. Today with nuclear use significantly present and with huge potential to further improve our life with energy and medical use it is of enormous importance to try to have calmed, rational, and objective view on potential risks and certain benefits. Because all use of nuclear energy proved that their immediate risks are negligible (i.e., Three Mile Island and Fukushima) or much smaller than from the other alternatives (i.e., Chernobyl) it seems that the most important issue is the amount of risk from the long term effects to people from exposure to small doses of radiation. A similar issue is present in the increased use of modern computational tomography and other radiation sources use in medicine for examination and therapy. Finally, extreme natural exposures are third such potential risk sources. Definition of low doses varies depending on the way of delivery (i.e., single, multiple or continuous exposures), and for this paper usual dose of 100 mSv is selected as yearly upper amount. There are three very different scientifically supported views on the potential risks from the low doses exposure. The most conservative theory is that all radiation is harmful, and even small increments from background levels (i.e., 2-3 mSv) present additional risk. This view is called linear no threshold theory (LNT) and it is accepted as a regulatory conservative simple approach which guarantees safety. Risk is derived from the extrapolation of the measured effects of high levels of radiation. Opposite theory to LNT is hormesis which assumes that in fact small doses of radiation are helpful and they are improving our health. This view is supported with numerous evidences, and explained with beneficial effects from the increased activity of immune system activated with small radiation exposures. Finally, theory in between is that small doses are less than linearly proportionally harmful and that they are presenting a much smaller risks than according to the LNT. This view is derived from the use of different evidences. Difficulties to find one single theory about effects of small radiation doses are related to existence of huge variability and uncertainty in the evidence data. This is very hard experimental and theoretical problem. It will require lots of additional research to reduce these uncertainties and find final theory. This might be too late for the number of people affected in different ways with current single most conservative LNT approach. The problem with the conservative LNT regulatory approach is resulting in enormous additional costs of nuclear energy and medical applications. Which is reasonable and acceptable during the regular operation when source is high and concentrated. But, this becomes unreasonable huge economic burden after accidents and for cleanups with nuclear facilities. Similar problem arises with restriction of medical examinations and treatments based on over conservative risk estimate. Special circumstances are with evacuated people from contaminated areas where they are on the one side saved from small radiation exposures, and on the other side exposed to years of life away from their home and with numerous direct and indirect additional risks (i.e., stress, social problems, etc.). It seems reasonable that some alternative (total) risk management approach might be much more suitable for this situation. Evacuation of people from contaminated area with small doses sources should not be done when that induces larger risks from even what is expected from radiation based on LNT. Similar total risk management could be also applied for with medical examination and treatments. This paper is proposing estimate of all potential additional evacuations related risks in order to implement total risk management. A preliminary illustrative estimate with uncertainties stands against evacuation. Much further work is needed to make this risk management approach applicable. However, preliminary illustrative results are clearly showing that much of the long term evacuation is not justified. This approach seems appropriate before scientific uncertainty is reduced and better decision base is established. With additionally more honest, transparent and scientific approach to risk communication and management small doses of radiation might not be used any more as fuel for anti-nuclear activism. Without proper understanding of priorities we are not just wasting our limited resources but also missing great opportunities and increasing total risk.(author).

[en] Uncertainty evaluation constitutes a key feature of BEPU (Best Estimate Plus Uncertainty) process. The uncertainty can be the result of a Monte Carlo type analysis involving input uncertainty parameters or the outcome of a process involving the use of experimental data and connected code calculations. Those uncertainty methods are discussed in several papers and guidelines (IAEA-SRS-52, OECD/NEA BEMUSE reports). The present paper aims at discussing the role and the depth of the analysis required for merging from one side suitable experimental data and on the other side qualified code calculation results. This aspect is mostly connected with the second approach for uncertainty mentioned above, but it can be used also in the framework of the first approach. Namely, the paper discusses the features and structure of the database that includes the following kinds of documents: 1. The 'RDS-facility' (Reference Data Set for the selected facility): this includes the description of the facility, the geometrical characterization of any component of the facility, the instrumentations, the data acquisition system, the evaluation of pressure losses, the physical properties of the material and the characterization of pumps, valves and heat losses; 2. The 'RDS-test' (Reference Data Set for the selected test of the facility): this includes the description of the main phenomena investigated during the test, the configuration of the facility for the selected test (possible new evaluation of pressure and heat losses if needed) and the specific boundary and initial conditions; 3. The 'QP' (Qualification Report) of the code calculation results: this includes the description of the nodalization developed following a set of homogeneous techniques, the achievement of the steady state conditions and the qualitative and quantitative analysis of the transient with the characterization of the Relevant Thermal-Hydraulics Aspects (RTA); 4. The EH (Engineering Handbook) of the input nodalization: this includes the rationale adopted for each part of the nodalization, the user choices, and the systematic derivation and justification of any value present in the code input respect to the values as indicated in the RDS-facility and in the RDS-test.(author).

[en] The fascinating topic of small nuclear is becoming more prevalent on the nuclear agenda. The discussions are generally focused within the country of technical origin. In this presentation 'The global outlook for small reactors' Rolls-Royce along with energy business analysts Douglas-Westwood present their shared views on the global opportunities for Small Reactor deployment in the context of the wider energy market. The presentation will: provide a compressive overview of trends and dynamics relating to Small Reactors in the context of the current world energy market, identify specific Small Reactor opportunities and areas of interest, address the challenges and potential solutions for Small Reactor deployment and operation.(author).

[en] According to current projections of economic development of Ukraine, domestic consumption of electricity will grow from the present level of 190 billion kWh / year to about 280 billion kWh / year in 2030, which determines the prospects of the electricity industry development. Alternative ''green'' energy sources - solar, wind and small hydropower can develop only within a commercially reasonable considering temporary ''green'' tariff, which is far above the rates for traditional sources. According to prognoses the share of ''green'' energy sources in Ukraine in 2030 will not exceed 10-15% regardless of their environmental appeal. The updated nuclear energy development strategy by 2030 will save the share of nuclear electricity generation at the achieved level about half of total domestic electricity production. Development of nuclear power generation in the period to 2030 provides: increase the safety of the operating NPP; efficiency increase of existing nuclear power plants (up to 85% in terms of the basic mode of operation); continued of NPP units operation for 20 years over time, provided the original design; completion of the units 3,4 Khmelnitsky nuclear power plant in 2017; construction and commissioning prior to 2027 three new nuclear power units the total capacity to 3.5 GW on new NPP site; beginning in 2022-2029 years construction of new nuclear reactors at sites of existing nuclear power plants to replace existing units that will be decommissioned after 2030; implementation of the units preparation to decommissioning after an additional period of operation; improvement of infrastructure support and development of nuclear power generation. In the article analyzes the necessity, advantages and disadvantages of nuclear energy in Ukraine in the Updated Energy Strategy of Ukraine until 2030.(author).

[en] In all operating modes of a nuclear power plant a lot of activities take place, including maintenance, surveillance testing and plant modifications. Some of these activities can impose temporary increase in risk level, as they may change the status of equipment important to plant safety. Such risk increases are usually controlled by risk monitoring, which considers changes in risk due to changes in the status (e.g. availability) of plant systems and functions. Risk monitors are, in many cases, designed and operated to be system-oriented (or function-oriented), as they focus on ''measuring'' the risk associated with different system configurations (from where comes the often used term ''configuration risk management''). On the other hand, components of plant systems are placed in various locations and at various floors (elevations) of plant buildings. Piping, as well as cabling, is routed through one or more buildings. Equipment performing different functions is, sometimes, located near each other due to architectural limitations. Where required, barriers are applied in order to ensure physical separation and independency. Due to these reasons, a particular plant area (compartment, room, part of a large room, ...) can contain a variety of mechanical, electrical and / or other equipment with different safety implications. As well as system components, plant areas are also related to each other, with different degrees of relative importance. Since activities performed in different plant areas can imply changes, actual or potential, in the status of associated equipment, structures and / or barriers, there is also a need that risk monitoring considers the area-oriented aspects, beside considering those which are system-oriented or function-oriented. Risk impact of an activity taking place in a particular plant area can be considered in terms of changes (potential or actual) to its three components: 1) likelihood of initiators which can be triggered by equipment in the area (but which are not mitigated by any of the equipment in the same area); 2) mitigating capability regarding the initiators which are not triggered in this area; 3) likelihood of initiators triggered in this area and mitigating capability regarding the same initiators. Activity in a particular plant area may be related to none or to any combination of the three risk impact components. Normally, risk impact under 3) is limited by the architectural engineering principles (because it may become very large risk contributor). However, it may be present in some residual form and it cannot be excluded (as demonstrated by area-related risk studies performed in the past, such as internal fire and internal flooding analyses). With activity taking place in a particular area, the relevant importance of any other plant area (and, hence, potential risk impact of any activity that may be planned to go on at the same time) is then considered in terms of, respectively: 1) whether it contains the equipment relevant for mitigation of initiators that can be triggered in the considered area; 2) whether it includes the potential for triggering an initiator which is mitigated by the equipment located in the considered area; 3) whether it contains the relevant mitigation equipment or include the potential for relevant initiators. The paper will discuss these and other related issues and will describe basic concepts for the area-oriented risk management.(author).