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The capability of natural circulation for core cooling has been evaluated in detail for a station blackout (SBO) event induced by an earthquake and a subsequent tsunami hit. The evaluation was prom...

A small modular fast reactor is thought to be one of the solutions to meet future energy security with low research and development (R&D) risk. In the present study, a new small reactor concept for a modular power source is proposed. A minimum configuration with a compact reactor vessel, one-loop main cooling system, and simple fuel-handling system is adopted, enhancing cost reduction. In the present one-loop main cooling system, there are double electromagnetic pumps in series considering pump failure. To show the reliability of the one-loop main cooling system, pipe-break transient analyses have been carried out. In addition, the construction cost of a set of a first-of-a-kind reactor and small fuel cycle plant is evaluated to show the economical potential at the demonstration stage. A major advantage of the present concept is that the demonstration reactor and fuel cycle plant can be directly appropriated for first commercial modules and the power plant can easily increase its capacity adding reactor and electrorefiner modules. Commercialization of the nuclear fuel cycle fusing the present modular concept is thought to reduce R&D risk since the total budget for demonstration is small and the facilities for demonstration are directly appropriated to commercial use.

It is of vital importance for commercialized fast reactor to achieve component design with excellent integrity and economics. In the phase II of feasibility study till 2005, a system design for commercialized fast reactor for sodium cooling was achieved. For economical improvement, the system design was undertaken along the guideline including innovative technology for system simplification and new material development. In this paper, the results from the design for shortening of cooling pipings, new components and three dimensional seismic isolation are described, which are design challenges for the sodium cooled fast reactor. Furthermore, in-service inspection and repair is mentioned. Finally, economics for the simplification and the mass reduction employing above technologies are examined.

This paper describes a 50MWe Small Modular Fast Reactor (SMFR) design that has been developed jointly by Argonne National Laboratory (ANL), Commissariat a l'Energie Atomique (CEA), and Japan Atomic Energy Agency (JAEA) as an international collaborative effort. Key design innovations include a metallic fueled core with 30-year lifetime and supercritical carbon dioxide Brayton cycle.

An innovative concept of sodium-cooled fast reactor, named JAEA Sodium Cooled FR (JSFR) has been created and modified through the Feasibility Study on Commercialized FR Cycle System, aiming at full satisfaction of the development targets. A modified concept of JSFR applied double-wall straight tube type steam generator (SG) which is excelling in safety for sodium-water reaction has been developed. In addition, decay heat removal system suitable for the straight tube SG has been selected and in-service inspection and repair capabilities have been improved. As the result of this study, the potential to realize this plant concept has been obtained through evaluation concerning safety and economics.

A small reactor has the potential to be utilized as a power source to meet diverse social needs and reduce capital risks. In remote areas, populations tend to be small, and an economic power grid may not be available. In such situations, a small power source with a capacity of less than 50 MW(electric) without refueling is attractive since the costs for fuel transfer to such a site are expensive. In the present study, a metal fuel core with a lifetime of 30 yr and a simple reactor plant design has been proposed. The local burnup reactivity change in every core region is minimized by adjusting the zirconium content and the smear density of the three-core region to achieve a 550°C core outlet temperature. At the end of the cycle, the burnup reactivity is evaluated to be 1.1% of (dk/kk'), achieving a 30-yr core life. The reactor vessel is dramatically simplified by eliminating a fuel-handling system. The number of main cooling loops is reduced to one by installing dual electromagnetic pumps in the primary sodium circuit. The nuclear steam supply system mass, at 309 tonnes, shows that the present loop-type concept can more dramatically reduce material mass than that of the previous pool-type concept of 484 tonnes. The rough estimation of the electricity cost shows that this concept will be competitive for remote sites. Transient analyses show that a self-actuated shutdown system enhances the passive safety features, thus ensuring reactor integrity in anticipated transient without scram events.

Hydrogen production with a fast breeder reactor (FBR) may be attractive as a long-term energy source with nuclear fuel breeding. The thermochemical and electrolytic hybrid process is one of the hyd...

A small fast reactor has the potential to be utilized as a power source applicable to diversified social needs and to reduce capital risks. At remote sites where the population is small and plants ...

For the Japan Atomic Energy Agency sodium-cooled fast reactor, an experimental study on the fluctuating pressure of the hot legs was carried out with tests in a 1/3-scale model. The total resistance coefficient is consistent with published data, and, additionally, our research has given data up to the Reynolds number of 8.0×106. The flow visualization and velocity measurement confirmed the independence of the flow on the Reynolds number. Pressures on the pipe wall were statistically examined to predict the characteristics of fluctuating pressures of the hot legs. It reveals that generation of fluctuating pressure is dominant on the boundary of flow separation and reattachment.

A thermal source for hydrogen production is an attractive utilization of nuclear energy. Hydrogen production from natural gas is a promising method in an early stage of hydrogen society, though hydrogen production with water splitting without carbon dioxide emission is the final goal. Steam methane reforming is a well-known method for producing hydrogen from natural gas. A hydrogen separation membrane makes the reforming temperature much lower than that of the equilibrium condition, and a sodium-cooled fast reactor, which supplies heat at {approx}500 deg. C, can be used as a heat source for hydrogen production.In this study, a hydrogen production plant with the membrane reforming method using a sodium-cooled reactor as a thermal source has been designed, and its economic potential is roughly evaluated. The hydrogen production cost is estimated to be about $1.67/kg, achieving the economic target of $1.7/kg. The construction cost is largely shared by the reformers' cost, and it can be decreased using a more efficient hydrogen separation membrane. This shows that steam methane reforming hydrogen production with a sodium-cooled reactor has high economical potential.

An innovative concept of a sodium-cooled reactor (the Advanced Loop-Type Fast Reactor) to pursue high economic competitiveness has been developed. Measures to reduce cost adopted in the design are compact design of reactor structure, shortening of piping, reduction of loop number, and integration of components. These design measures are expected to be realized by introducing some innovative technologies (12Cr steel with high strength, advanced elevated temperature structural design standards, three-dimensional seismic isolation, and recriticality free technology), which have the potential to be put to practical use by 2015, and by taking into account the desirable characteristics of sodium coolant (operability in a low-pressure system and excellent heat transfer characteristics). By drastically decreasing the amount of materials through these measures, it is expected that the construction cost will be reduced to below 200000 yen/ kW(electric), i.e., below two-thirds times that of light water reactors at present. The potential to realize this plant concept has been obtained through evaluations of major design issues concerning safety, structural integrity, and thermal hydraulics.

This report summarizes the evaluation method, the development schedule and the result of the test. A conceptual design study of the Japanese sodium-cooled fast reactor (JSFR) is in progress of “Feasibility Study on Commercialized Fast Reactor Cycle Systems.” In this study we have proposed a component which integrated IHX (Intermediate heat exchanger) with primary pump into one vessel (integrated IHX/Pump) as one of advanced concepts for the plant economy. By development this component, the amount of material (steel) of the primary cooling system can be reduced and the maintenance performance of IHX can be improved. In order to confirm its feasibility, it is important to avoid the resonant vibration caused by integrating of the pump into the static IHX and to prevent excessive wear-out of the heat exchange tubes caused by contact with the tube support plates. Therefore, the vibration evaluation method has been developed and a lot of examinations were carried out to confirm the feasibility of this concept. The pump is arranged at the center of the IHX and heat exchange tubes are arranged concentrically. This component consists of the multiple cylindrical layers. Tube support plates are installed and they support the tube bundle with 0.1–0.3mm gaps. The 1/4-scale model was selected for vibration tests. The first step test with an internal vibration exciter which simulated the pump was performed, and the test with the pump installed into IHX was done. This test model has been installed at Takasago R&D center of Mitsubishi Heavy Industries, Ltd. The vibration caused by the pump was measured. As a result of data analysis, the character of frequency response was acquired. The analysis code called as “FINAS” can directly handle the vibration behavior of complex multi-cylinders with fluid between the cylinders. The eigenvalue analysis and response analysis were performed using a detailed model and the results were compared with the test results. Vibration evaluation methods of the integrated IHX/Pump have been studied. The 1/4-scale vibration test was performed and the results were compared with the analysis.Copyright © 2006 by ASME

A seismic analysis has been performed showing that the seismic interaction between the UIS and the FHM can be avoided eliminating the internal clearance of bearing at the FHM arm joint. An angular contact ball bearing is suitable for the new FHM since it can eliminate gaps by preload pressure. A major problem of the FHM bearings is lubrication since the contact pressure between the steel rings and ball of the ball bearing is larger than that of the roller bearing used in the previous design. Additionally, FHM operating temperature is about 200 deg-C and normal grease is not applicable under argon gas with sodium vapor to prevent contamination of grease in the primary sodium coolant. An endurance test with 1/10 scale bearings in the air has been performed to show applicability of angular contact ball bearings to the FHM arm joint. The results with 20,000 cycle showed that bearings with combination of MoS{sub 2} coating steel rings and ceramics balls can be tolerable as the FHM operating condition. A full-scale bearing test in argon gas with sodium vapor has also been demonstrated to reveal bearing size and sodium vapor effects. (authors)

A 1/3 scale flow-induced vibration test facility that simulates the hot-leg piping of the JNC sodium-cooled fast reactor (JSFR) is used to investigate the pressure fluctuations of the pipe, where the high velocity fluid flows inside the piping. By the measurement of the pressure drop in the elbow piping while changing the Reynolds number, the similarity law of this model is confirmed. To evaluate the flow-induced vibrations for the hot-leg and cold-leg pipes, the random force distributions along the pipe and their correlations are measured with pressure sensors in a water loop. It is found that a flow velocity-dependent periodic phenomenon in the rear region of the elbow, and the maximum flow-induced random vibration force in the pipe are observed in the region of flow separation downstream the elbow. Finally, a design method is proposed with power spectral densities of the pressure fluctuations classified into four sections, correlation lengths in the axial direction divided into three sections, and with correlation lengths in the tangential direction into four sections.Copyright © 2005 by ASME

In phase II of a feasibility study on commercialized fast reactor cycle system of Japan Nuclear Cycle Development Institute, we are finding a concept of a multi-purpose small sized fast reactor with various requirements, such as, safety and improved economical competitiveness. In this study, a membrane reforming hydrogen production plant using a small sized sodium cooled reactor was designed as one of promising concepts. In the membrane reformer, methane and steam are reformed into carbon dioxide and hydrogen with sodium heat at a temperature 500deg-C. In the equilibrium condition, steam reforming proceeds with catalyst at a temperature more than 800deg-C. Using membrane reformers, the steam reforming temperature can be decreased from 800 to 500deg-C because the hydrogen separation membrane remove hydrogen selectively from catalyst area and the partial pressure of hydrogen is kept much lower than equilibrium condition. In this study, a hydrogen and electric co-production plant has been designed. The reactor thermal output is 375MW and 25% of the thermal output is used for hydrogen production (70000Nm3 /h). The hydrogen production cost is estimated but it is still higher than the economical goal. The major reason of the high cost comes from the large size of hydrogen separation reformers because of the limit of hydrogen separation efficiency of palladium membrane. A new highly efficient hydrogen separation membrane is needed to reduce the cost of hydrogen production using membrane reformers. There is possibility of multi-tube failure in the membrane reformers. In future study, a design of measures against tube failure and elemental experiments of reaction between sodium and reforming gas will be needed.Copyright © 2004 by JSME

To seek for a promising concept of a heavy liquid metal coolant (HLMC) fast reactor plant, Japan Nuclear Cycle Development Institute (JNC) and the electric utilities conducted conceptual design study on various types of plant concepts and compared these concepts based on technical feasibility and economical perspective. The Pb-Bi cooled complete natural circulation reactor concept may attain high safety level and construction cost goal (¥200,000/kWe).Copyright © 2002 by ASME