Mamoru Konomura

An Innovative Concept of the Sodium-Cooled Reactor to Pursue High Economic Competitiveness

Abstract 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 200 000 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.

Resistance and Fluctuating Pressures of a Large Elbow in High Reynolds Numbers

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 Feasibility Study of a Steam Methane Reforming Hydrogen Production Plant with a Sodium-Cooled Fast Reactor

Abstract 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 ~500°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

A system design study of a fast breeder reactor hydrogen production plant using thermochemical and electrolytic hybrid process

1.67/kg, achieving the economic target of

Flow-Induced Vibration of a Large-Diameter Elbow Piping Based on Random Force Measurement Caused by Conveying Fluid: Visualization Test Results

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.

Development of Natural Circulation Analytical Model in Super-COPD Code and Evaluation of Core Cooling Capability in Monju During a Station Blackout

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 hydrogen production methods using a sulfuric acid cycle with the maximum temperature at 500°C, which can be supplied by a sodium-cooled FBR. In this study, a hydrogen production plant with the thermochemical and electrolytic hybrid process has been designed, and the hydrogen production efficiency has been evaluated. The structural materials of the components in the system are steels such as high-Si cast iron, which has good toughness against sulfuric acid. High hydrogen production efficiency of 44% (high heating value) is achieved assuming development of high-efficiency electrolysis.

A modular metal-fuel fast reactor with one-loop main cooling system

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

A Compact Loop-Type Fast Reactor Without Refueling for a Remote Area Power Source

Abstract 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 prompted by the accident at the Fukushima Daiichi nuclear power station of Tokyo Electric Power Company. The plant dynamics computer code Super-COPD was used for the evaluation, which has been validated by analyses of preliminary test results on the natural circulation in Monju. As a result, it was concluded that natural circulation of the sodium coolant will enable the decay heat from the core to be removed under such an SBO condition.

A conceptual design study of a small natural convection lead-bismuth-cooled reactor without refueling for 30 years

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.

HLMC Fast Reactor With Complete Natural Circulation

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.