Development of passive safety systems for Next Generation PWR in Japan

Our country’s energy demand is expected to increase steadily into the future. When the situation of our country, which is not rich in energy resources, is taken into account, it seems that the importance of nuclear power generation will be heightened. Based on such a background, the basic policy for nuclear power generation is ‘from light water reactors to fast breeder reactors’. However, considering that light water reactors have become common, the recent outlook for the supply and demand for uranium resources, development trends of fast breeder reactor technology, etc., the light water reactor is expected to remain dominant in our country until at least the second half of the 21st century. Therefore, five PWR utilities in Japan (Hokkaido, Kansai, Shikoku, Kyushu, and Japan Atomic Power), Mitsubishi Heavy Industries Ltd and Westinghouse Electric Corporation have jointly started researching the Next Generation PWR (N.G.P) which is expected to be the leading nuclear power plant, taking place of APWR [T. Magari, Development of Next Generation PWR in Japan, Proceedings of the 10th Pacific Basin Nuclear Conference, 1996; K. Fujimura, et al., Proceedings of the Second International Symposium on Global Environment and Nuclear Energy Systems, 1996]. In this program, construction is targeted to start from 2010 based on expected future environmental conditions. Now, the capacity of more than 1500 MWe class PWR concept is investigated and a plant concept which has innovative features of a hybrid safety systems, i.e. an optimum combination of active and passive safety systems, and horizontal steam generators for core cooling at the accidents is developed as a promising candidate. The plant concept and the results of the investigation are presented in this paper.     

Safety Aspects of Long-term Dry Interim Storage Of Type-b Spent Fuel and Hlw Transport Casks

Abstract

Based on the German decision to minimise transport of spent fuel casks between nuclear power plants, reprocessing plants and central storage facilities several on-site storage facilities were licensed until the end of 2003. Because of the large amount of Type B(U) transport casks which are going to be used for long-term interim storage the question of timelimited Type B(U) licence maintenance during the storage period of up to 40 years has been discussed under different aspects. This paper describes present technical aspects of the discussion. A main aspect of qualification of transport casks for interim storage is the long-term behaviour of the metallic seal–lid system. Here results are presented from current long-term experimental tests with metallic 'Helicoflex' seals in which pool water is enclosed. This series of tests has been performed by the Federal Institute for Materials Research and Testing (BAM) on behalf of the Federal Office for Radiation Protection (BfS) since 2001. Finally, the paper presents a German concept for an exchange of experience, know-how and state-of-the-art between authorities and technical experts with regard to cask dispatch in nuclear facilities. BAM has taken over a central role in this so-called 'coordinating institution for cask dispatching information' ('KOBAF') which entails management of an online database of cask-specific documents and a technical working group meeting twice a year. The goal is to keep comparable technical standards for all nuclear sites and storage facilities which are going to load and dispatch casks of the same or similar types under the responsibility of different German state governments for the coming decades.     

German approach and feedback on experience of transportability of SNF packages after interim storage

In Germany, the concept of dry interim storage of spent fuel in dual purpose metal casks is implemented, currently for periods of up to 40 years. The casks being used have an approved package design in accordance with the international transport regulations. The license for dry storage is granted on the German Atomic Energy Act with respect to the recently revised ‘Guidelines for dry interim storage of irradiated fuel assemblies and heat-generating radioactive waste in casks’ by the German Waste management Commission. For transport on public routes between or after long term interim storage periods, it has to be ensured that the transport and storage casks fulfil the specifications of the transport approval or other sufficient properties, which satisfy the proofs for the compliance of the safety objectives at that time. In recent years, the validation period of transport approval certificates for manufactured, loaded and stored packages were discussed among authorities and applicants. A case dependent system of 3, 5 and 10 years was established. There are consequences for the safety cases in the Package Design Safety Report, including evaluation of long term behaviour of components and specific operating procedures of the package. The present research and knowledge concerning the long term behaviour of transport and storage cask components have to be consulted as well as experiences from interim cask storage operations. Challenges in the safety assessment are e.g. the behaviour of aged metal and elastomeric gaskets under IAEA test conditions to ensure that the results of drop tests can be transferred to the compliance of the safety objectives at the time of transport after the interim storage period. Assessment methods for the material compatibility, the behaviour of fuel assemblies and the aging behaviour of shielding parts are issues as well. This paper describes the state of the art technology in Germany, explains recent experience on transport preparation after interim storage and points out arising prospective challenges.     

Interim storage of power reactor spent nuclear fuel (SNF) and its potential application to SNF separations and closed fuel cycle

Interim, centralized, engineered (dry cask) storage facilities for USA light water power reactor spent nuclear fuel (SNF) should be implemented to complement and to offer much needed flexibility while the Nuclear Regulatory Commission is funded to complete its evaluation of the Yucca Mountain License and to subject it to public hearings. The interim sites should use the credo reproduced in Table 1 [Bunn, M., 2001. Interim Storage of Spent Nuclear Fuel. Harvard University and University of Tokyo] and involve both the industry and government. The sites will help settle the 50 pending lawsuits against the government and the $11 billion of potential additional liabilities for SNF delay damages if Yucca Mountain does not being operation in 2020 [DOE, 2008a. Report to Congress on the Demonstration of the Interim Storage of Spent Nuclear Fuel from Decommissioned Nuclear Power Stations (December)].Under the developing consensus to proceed with closed fuel cycles, it will be necessary to develop SNF separation facilities with stringent requirements upon separation processes and upon generation of only highly resistant waste forms. The location of such facilities at the interim storage sites would offer great benefits to those sites and assure their long term viability by returning them to their original status.The switch from once-through to closed fuel cycle will require extensive time and development work as illustrated in “The Path to Sustainable Nuclear Energy” [DOE, 2005. The Path to Sustainable Nuclear Energy. Basic and Applied Research Opportunities for Advanced Fuel Cycles. DOE (September)]. A carefully crafted long term program, funded for at least 5 years, managed by a strong joint government–industry team, and subjected to regular independent reviews should be considered to assure the program stability and success.The new uncertainty about Yucca Mountain role raises two key issues: (a) what to do with the weapons and other high level government wastes committed to be moved to Yucca Mountain by specified dates? And (b) can the $13.6 billion invested at Yucca Mountain be salvaged if the NRC approves the license submittal and the opposition relents after contentious hearings? Or will it take contingent actions, or, a switch to a partial closed fuel cycle with its reduced risks and earlier timing of their peak risk value? Only time will tell if any of these alternates will be acceptable but, they all reinforce the need for interim storage for commercial SNF.If the decision is to go to a new repository one wonders whether the time has not come to change the safety evaluation process for geological repositories by characterizing two to three sites and subjecting them to an arbitrary release of the fission products in the HLW to be stored and considering the forms of some of the HLW to reduce their peak risks. It would allow the proper choice to be made among the selected sites and to have a basis for convincing the local committee to accept the repository location. It may even decide whether the CONFU fuel assembly [MIT, 2006. Implications of alternative strategies for transition to sustainable fuel cycles. Nucl. Sci. Eng., 154 (September)] for pressurized water reactors can be accommodated in a once-through fuel cycle as suggested by Levy [Levy, S., 2008. Yucca backup plan. Nucl. Eng. Int., 24–28]. A similar configuration is possible in boiling water reactors.     

Description of the German Concept of Final Storage Cask

Abstract

The German storage concept for the direct final storage of spent fuel assemblies from LWR reactors is described. The final storage concept is designed in such a way that it encompasses the whole spectrum of fuel elements to be stored from German reactors, Le. U fuel assemblies and MOX fuel assemblies with a mean bumup of 55 GW.d.t^?1 heavy metal were considered. The further design requirements are defined in such a way that the cask concept satisfies the conditions for type B(U) transport, interim storage and fmal storage. The safe long-term containment of the activity is guaranteed by an inner cask welded leak-tight; the sufficient shielding and the transport packaging are ensured by a shielding cask.     

Considering the next generation of nuclear power plants

Nuclear power will be needed for future energy demands, which are expected to grow at different rates around the world. The opportunities for building new nuclear power plants around the world will be depend on need, energy demand growth, and issues related to global warming and climate change. However, four major barriers exist for the expansion of nuclear power: economics, proliferation, safety, and wate. These issues must be addressed in the ongoing research and development of nuclear energy technology and applications. The evolution of nuclear power plant technology is presented as four distinct design generations: (1) prototypes, (2) current operating plants, (3) advanced light water reactor technology, and (4) revolutionary design concepts (i.e., Generation IV) that are now under development. The U.S. DOE Nuclear Energy Research Initiative (NERI) program is focused on the research and development of Generation IV designs that are safe, economic, proliferation-resistant, and will address current waste issues. NERI provides grants for independently peer-reviewed proposals from universities, national laboratories and industry for advanced nuclear research and development. Several NERI projects awarded in 1999 are described in terms of how they remove barriers to nuclear power plant expansion. Another DOE effort, the Accelerator Transmutation of Waste program, will seek to reduce and ameliorate civilian reactor waste. The Accelerator Transmutation of Waste program will involve a six-year science-based research plan to define key technical issues. Finally, the need for international collaboration is stressed for fourth-generation nuclear power technology development.     

Repatriation of Vinča RA reactor spent fuel

Abstract

The RA research reactor is located at the Vin?a Institute of Nuclear Sciences near Belgrade, Serbia. The reactor is a 6·5 MW, tank-type, heavy water moderated and cooled reactor of Russian design which commenced operation in 1959. After being temporarily shut down in 1984 for refurbishment, a final shutdown decision was made in 2002. Operations are underway to safely remove and repatriate the spent nuclear fuel (SNF) to the Russian Federation (RF), as well as to improve waste management throughout the Vin?a site and prepare a plan for reactor decommissioning. As a major activity within the Vin?a Institute Nuclear Decommissioning (VIND) Programme, the repatriation of over 8000 SNF elements containing 2·5 tons of uranium metal will significantly reduce nuclear proliferation and environmental safety risks confronting the current facility. Poor water quality in the SNF storage basins and degraded fuel integrity significantly challenge efforts to repackage and transport the SNF. This paper will focus on the activities related to SNF repackaging and shipment, report on progress, detail significant challenges and provide an overview of the fully integrated VIND project.     

The global nuclear liability regime post Fukushima Daiichi

Nuclear liability regimes are important as they ensure that potential victims will be compensated promptly and efficiently after a nuclear accident. The accident at Fukushima Daiichi in Japan in 2011 prompted a review of the global nuclear liability regime that remains on-going. Progress has been slow, but over the next few years the European Union is set to announce its new proposals. Meanwhile, in 2015, another global nuclear liability regime, the Convention on Supplementary Compensation for Nuclear Damage, has entered into force. This paper aims to move the debate in the literature on nuclear liability and focuses on the four following major issues: (1) reviews third-party nuclear liability regimes currently in operation around the world; (2) analyses the international nuclear liability regime following the accident at Fukushima Daiichi; (3) comparatively assesses the liability regimes for nuclear energy and the non-nuclear energy sector; and (4) presents the future outlook for possible developments in the global nuclear liability regime.     

U.S. regulatory perspectives on the back end of the fuel cycle: EUROSAFE 2013 proceeding

For the United States Nuclear Regulatory Commission and the reactor licensees it regulates, there are a number of contemporary issues associated with the back end of the fuel cycle including, the agency's revision to its “Waste Confidence” decision and the path-forward for high-level waste disposal. Additionally, the 2012 Blue Ribbon Commission on America's Nuclear Future recommendations, the future of reprocessing, consolidated interim spent fuel storage, and maintaining technical competence within the NRC in challenging budgetary conditions are addressed. I conclude that there is confidence in the feasibility of safe storage of spent nuclear fuel following the licensed operational life of a reactor and any change in high-level waste policy will require Congressional action to amend the Nuclear Waste Policy Act.     

Adaptation of Approved Transport and Storage Cask Lines to Individual Customer Requirements

Abstract

Within the decommissioning programmes of the Italian nuclear power plants, the Italian multi-utility company ENEL decided to rely on on-site dry storage while waiting for the availability of the national interim storage site. SOGIN (Società Gestione Impianti Nucleari SpA, Rome, Italy), now in charge of all nuclear power plant (NPP) decommissioning activities was created in the ENEL group but is now owned by the Italian government. In 2000 it ordered 30 CASTOR® casks for the storage of its spent fuel not covered by existing or future reprocessing contracts. Ten CASTOR X/A17 casks will contain the Trino pressurised water reactor (PWR) fuel and the Garigliano boiling water reactor (BWR) fuel currently stored in pools at the nuclear power plant Trino and the Avogadro nuclear facility at Saluggia. Additionally 20 CASTOR X/B52 casks will contain the BWR fuel assemblies, which are stored in the pool at the Caorso nuclear power plant. GNB (Gesellschaft fuer Nuklear-Behaelter mbH, Essen, Germany) has completed detailed studies for the design of both types of cask. The tailored cask design is based on the well-established and proven design features of CASTOR reference casks and is responsive to the needs and requirements of the Italian fuel and handling conditions. The design of the CASTOR X/A17 for up to 17 Trino PWR fuel assemblies or 17 Garigliano BWR fuel assemblies and the CASTOR X/B52 cask holding up to 52 Caorso BWR fuel assemblies is suitable for the following conditions of use: loading of the casks in the fuel pools of the nuclear installations at Trino, Caorso and Avogadro; no upgrading of the Current on-site crane capacities; transport of the fuel assemblies, which are currently stored at the Saluggia facility to the nuclear power plant Trino; on-site storage in a vertical or horizontal position with the possibility of transfer to another temporary storage or a final repository, even after a number of years; the partial loading of mixed oxide (MOX) and failed fuel; loading and drying of bottled Garigliano fuel assemblies. On the basis of the CASTOR V/19 and CASTOR V/52 cask lines, the design of the CASTOR X/A17 and X/B52 casks aims at optimising safety and economics under the given boundary conditions. The long time for which fuel is kept in intermediate wet storage results in a reduced shielding and thermal-conduction requirement. This is used to meet the tight mass and geometry restrictions while allowing for the largest cask capacity possible.     

Meeting the energy challenge for the environment: The role of safety

Nuclear power has an overwhelming potential to meet the demands of an energy hungry world while protecting the environment. However, the renaissance of nuclear energy will only become true when the public can be convinced that nuclear power plants are safe and that a strong safety culture exists around the globe. While the overall safety performance of the world's power plants had been steadily improved after the shock of Chernobyl, unfortunately, the overall plant availability has levelled off in the last few years. The main reason for this is found in a complacency toward nuclear safety issues which can be linked to the arrival of new CEOs in the nuclear industry who – all too often – have no nuclear background and who manage nuclear power plants in the same way they would manage any other industrial plants – being not at all aware of the necessity of a very special and very sensitive safety culture of nuclear installations.     

Development of new transportable storage casks for interim dry storage

Abstract

We have started a programme to design a new type of transportable storage cask (Hitz casks) for both boiling water reactor (BWR) and pressurised water reactor (PWR) fuels for use in the new interim dry spent fuel storage project in Japan. The basic policy of this development is to use proven technology to realize a safe and cost-effective design with a high transport and storage capacity and a low fabrication cost. Since it is not permissible to change the lid gaskets at the storage facility, the double-lid system is designed to be able to use double metallic gaskets as the containment boundary for transport after the storage period; this is one of the new design features used in the casks. With the basket design we tried to achieve a capacity of 69 fuel assemblies for BWR fuel and 26 fuel assemblies for PWR fuel. Further details about these and other topics are discussed.     

Packaging for the Transport and Storage of Spent Sealed Sources in Brazil

Abstract

Since mid-1994, the Centro de Desenvolvimento da Tecnologia Nuclear has been assigned the task of receiving and safely conditioning spent sealed sources until a federal disposal site is available. At the moment (October 1995) there are approximately 1300 sources in the CDTN interim storage hall. As part of the measures taken to accomplish this task, the transport group has developed a simple and low cost packaging, which consists of an outer 200 litre drum surrounding a cylindrical lead shielding, the intermediate space being filled with concrete. In the primary concept a concrete internal lid allowed the sources to be retrieved for future re-encapsulation. In view of a failure in the drop test, a modification was introduced to gather additional information about the ultimate packaging strength, although the resulting concept does not allow future recovery of the contents. The next improvement to be introduced will be the use of a shell-type shock absorber to protect the packaging closing system.     

Effect of addition of corrosion inhibitors on corrosion behaviors of PCV material under diluted artificial seawater environment

ABSTRACT

Fukushima Daiichi nuclear power plants (1F) were damaged by unprecedented severe accident in the great east Japan earthquake, and seawater and freshwater had been injected as an emergency countermeasure for the core cooling. Although, the primary containment vessel (PCV) was not supposed to be exposed to diluted seawater, the PCV will be exposed to diluted seawater environment until fuel debris removal is completed. Therefore, it is necessary to establish a countermeasure of corrosion for the PCVs made of carbon steel. In this study, the effect of the addition of corrosion inhibitor, which is one of the corrosion countermeasures, was investigated by two types of corrosion tests. As a result of the immersion corrosion test, it was found that any of the three kinds of corrosion inhibitor could suppress corrosion of carbon steel. In addition, as a result of the inhibitor interim addition test, it was found that corrosion of carbon steel covered with corrosion products could be suppressed by optimizing the additive amount of corrosion inhibitor in the cooling water.     

Transport of large nuclear power plant components: experiences in mechanical design assessment

Abstract

In the course of decommissioning of power plants in Germany large nuclear components (steam generator, reactor pressure vessel) must be transported over public traffic routes to interim storage facilities, where they are dismantled or stored temporarily. Since it concerns surface contaminated objects or low specific activity materials, a safety evaluation considering the IAEA transport regulations mainly for industrial packages (type IP-2) is necessary. For these types of industrial packages the requirements from normal transport conditions are to be covered for the mechanical proof. For example, a free drop of the package from a defined height, in dependence of its mass, onto an unyielding target, and a stacking test are required. Since physical drop tests are impossible generally due to the singularity of such 'packages', a calculation has to be performed, preferably by a complex numerical analysis. The assessment of the loads takes place on the basis of local stress distributions, also with consideration of radiation induced brittleness of the material and with consideration of recent scientific investigation results. Large nuclear components have typically been transported in an unpackaged manner, so that the external shell of the component provides the packaging wall. The investigation must consider the entire component including all penetration areas such as manholes or nozzles. According to the present IAEA regulations the drop position is to be examined, which causes the maximum damage to the package. In the case of a transport under special arrangement a drop only in an attitude representing the usual handling position (administratively controlled) is necessary. If dose rate values of the package are higher than maximum allowable values for a public transport, then it is necessary that additional shielding construction units are attached to the large component.     

The comprehensive nuclear promotion plan of the Republic of Korea

Access to economic and sustainable energy is essential in every country. Rep. of Korea has insufficient supply of energy resource. Accordingly, Rep. of Korea has considered nuclear energy as the main energy source since 1970’s oil crises. In 1994, Rep. of Korea declared “Direction to Long-term Nuclear Energy Policy towards the Year 2030” and revised the Atomic Energy Act to promote the safe and peaceful use of nuclear energy.According to this Act, the government made the CNEPP (comprehensive nuclear energy promotion plan) for every 5 years since 1997. This CNEPP shall include the analysis of current status and prospect, policy targets, implementation tasks, plan to invest, and other matters for the nuclear utilization and safety. National nuclear technology has advanced a lot by 1st (1997–2001), 2nd (2002–2007), and 3rd CNEPP (2007–2011). Through these previous plans, Rep. of Korea designed its own nuclear reactor, Korea Standard Nuclear Power Plant (KSNP) and became the fifth nuclear reactor exporter after the United States, France, Russia and Canada.The Rep. of Korea has been preparing for the 4th CNEPP to advance further stage and to harmonize with the long-term policy direction. In this study, detailed process of the establishment of the 4th CNEPP was analyzed. By the analysis of the domestic and international environmental change, the achievement of the 3rd CNEPP and the major issue of the 4th CNEPP were proposed. Six promotion areas were set in the 4th CNEPP as nuclear utilization, sustainability, export/growth force, radiation, safety/public acceptance, and infra/international cooperation. It will be discussed by various social, economic, political, cultural, and technical professionals to harmonize with the national vision for the future, short- and long-term plans. By doing this, it will help to improve the nuclear safety, transparency, and effectiveness in the promotion of national nuclear technology.     

BWR spent fuel transport and storage with TN9/4 and TN24BH casks

Abstract

In 2001 the Swiss nuclear utilities started to store spent fuel in dry metallic dual purpose casks at ZWILAG, the Swiss interim storage facility. BKW FMB Energy Ltd, as the owner of the Mühleberg nuclear power plant, is involved in this process and has selected to store the spent fuel in a new high capacity dual purpose cask, the TN24BH. For the transport Cogema Logistics has developed a new medium size cask, the TN9/4, to replace the NTL9 cask, which has performed numerous shipments of BWR spent fuel in past decades. Licensed by the IAEA 1996, the TN9/4 is a 40 t transport cask, for seven BWR high burnup spent fuel assemblies. The spent fuel assemblies can be transferred to the ZWILAG hot cell in the TN24BH cask. These casks were first used in 2003. Ten TN9/4 shipments were made, and one TN24BH was loaded. After a brief presentation of the operational aspects, the paper will focus on the TN24BH high capacity dual purpose cask and the TN9/4 transport cask and describe in detail their characteristics and possibilities.     

Nuclear energy strategy in the environment of utility business deregulation

Nuclear power has contributed to the reduction and stabilization of electricity rate in Japan. However, its economic competitiveness has been eroding since mid 80's. Deregulation is hitting nuclear power just at the time its competitiveness is declining, and it poses a threat to drive short-sighted market orientation and precludes long term focus on achieving a balance between “environmental agenda” and “competitiveness in market”. Lowering the electricity rate is one of the important agenda to improve the nation's industrial competitiveness in the global market. However, it will be very difficult to win the competition of gas and oil prices with other developed countries in Europe and North America due to a handicap of long transportation distance. Only nuclear power and natural energy have no relation to such a handicap of economic distance from resources. Without securing economic superiority of those energy sources, Japan will not be able to clear the handicap of energy costs. The Japanese utilities are trying hard to regain the competitive edge of nuclear power. We have established short-term strategies for both existing and new LWRs as well as a long-term strategy for technological development. With these strategies we will be able to regain the competitiveness of nuclear power.