ICONE11-36599 Conceptual Design of a Small Lead-bismuth Cooled Reactor
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概要
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Small sized fast reactors have a potential to use a power source applicable to diversified social needs. In the feasibility studies on commercialized fast breeder reactor cycle system of Japan nuclear cycle development institute (JNC), we will make a concept of small sized fast reactor with various requirements of economical competitiveness, reactor safety, very long lived core, etc. The design requirements for a small lead-bismuth cooled fast reactor which is one of promising concepts are defined as follows; -electric power : 50 MWe, -fuel type : mixed nitride fuel, -reactor type : tank type (elimination of secondary cooling system), -coolant circulation system : natural circulation, -fuel exchanging system : handling of each fuel subassembly, and -core life : 30 years. In this design, the reactor type was tank type and the steam generator is placed inside the reactor vessel, because there is no high reactivity between lead-bismuth and steam. The heat mass balance and the steam pressure for the turbine are chosen to minimize the total mass of the reactor vessel and the steam generator. The reactor coolant outlet and inlet temperature are 505 and 335 degree-C and the reactor vessel height becomes rather high (18.5m) to keep natural circulation force. The steam temperature (400 degree-C) and pressure (6 MPa) are designed to make the steam generator compact and the reactor vessel diameter is achieved to be 3.85m. Passive safety is enhanced to avoid a core disruptive accident even at anticipated transient without scram. The constitution of a decay heat removal system is chosen which is a system of one PRACS and one reactor vessel air cooling system (RVACS) driven by natural circulation. Protection from corrosion of metallic alloys in liquid lead-bismuth is ensured with using 9Cr steel and control of oxide composition in coolant. But further elemental studies are needed. The construction cost of the plant is estimated at 800,000 yen/k We which is much higher than the target value, that is, 350,000 yen/kWe (5.5 yen/kWh), because of a scale demerit coming from a low power and a usage of heavy reactor components for lead-bismuth coolant. But it would have some possibility to reduce the construction cost with a improvement of core efficiency, an increasing of a reactor power, a common use of some BOP components among reactors and a learning effect of construction.
著者
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Chikazawa Yoshitaka
O-arai Engineering Center Japan Nuclear Cycle Development Institute
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Hori Toru
O-arai Engineering Center Japan Nuclear Cycle Development Institute
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Konomura Mamoru
O-arai Engineering Center Japan Nuclear Cycle Development institute