Mitsuru Kambe

Design and Development of Fast Breeder Reactor Passive Reactivity Control Systems: LEM and LIM

AbstractTo enhance the inherent safety of the fast breeder reactor (FBR), unique attempts are being made in reactivity control systems design to achieve maintenance-free and reliable performance at the Central Research Institute of the Electric Power Industry. The design involves the lithium expansion module (LEM) for inherent reactivity feedback and the lithium injection module (LIM) for inherent ultimate shutdown. Reactor physics calculation revealed the reactivity worth of LEM and LIM in a 60-MW(electric), metal-fueled FBR and a 1000-MW(electric) mixed-oxide-fueled FBR. The system dynamics analyses revealed that LEM and LIM are effective to avoid sodium boiling in unprotected transient overpower and unprotected loss-of-flow transients. Reliability, maintainability, and real-time monitoring for LEM and LIM are also discussed.

Development of the High Performance Thermoelectric Modules for High Temperature Heat Sources

In recent years, power generating systems using thermoelectric elements have become attractive as an effective method of using industrial waste heat, at a temperature of around 773K, to produce energy. However, in order to develop a module usable under such a high temperature, certain concerns have to be overcome, e.g. thermal stress, diffusion of the connecting interfaces, etc. In this research, using an FeSi2 with diffusion barrier layers and a SiGe element produced by a powder metallurgy process, the module structure and installation method were optimized for application in PM sintering furnaces. As a result, from a viewpoint of heat stress at high temperatures and contact thermal resistance, it is confirmed that the optimal structure is the skeleton structure using Cu substrate on the cooling side, which has excellent heat conductivity and the optimal installation method is to adopt a carbon sheet and a mica sheet to the high temperature side, where Si grease is applied to the low temperature side, under pressurized condition. The power of the developed modules indicated 0.5W in an FeSi2 module and 3.8 W with a SiGe module at 827K, respectively. Moreover, neither breakage nor deterioration were observed after 30 heat cycles test simulating sintering furnace.

Intensive energy density thermoelectric energy conversion system by using FGM compliant pads

Abstract In order to provide increasingly large amounts of electrical power to space and terrestrial systems with a sufficient reliability at a reasonable cost, thermoelectric energy conversion system by using Functionally Graded Material (FGM) compliant pads has been focused. To achieve high thermal energy density in thermoelectric (TE) power conversion systems, conductively coupling the TE module to the hot and cold heat exchangers is the most effective configuration. This is accomplished by two sets of FGM compliant pads. This design strategy provides (1) a high flux, direct conduction path to heat source and heat sink, (2) the structural flexibility to protect the cell from high stress due to thermal expansion, (3) an extended durability by a simple FGM structure, and (4) manufacturing cost reduction by spark plasma sintering. High thermal energy density of more than twice as much as conventional conduction coupling TE generator is expected. TE energy conversion systems combined with FGM compliant pads for space and terrestrial design options are proposed in this paper.

Rapid-L Operator-Free Fast Reactor Concept Without Any Control Rods

Abstract The 200-kW(electric) uranium-nitride-fueled lithium-cooled fast reactor concept “RAPID-L” to achieve highly automated reactor operation has been demonstrated. RAPID-L is designed for a lunar base power system. It is one of the variants of the RAPID (Refueling by All Pins Integrated Design) fast reactor concept, which enables quick and simplified refueling. The essential feature of the RAPID concept is that the reactor core consists of an integrated fuel assembly instead of conventional fuel subassemblies. In this small-size reactor core, 2700 fuel pins are integrated and encased in a fuel cartridge. Refueling is conducted by replacing a fuel cartridge. The reactor can be operated without refueling for up to 10 yr. Unique challenges in reactivity control systems design have been addressed in the RAPID-L concept. The reactor has no control rod but involves the following innovative reactivity control systems: lithium expansion modules (LEM) for inherent reactivity feedback, lithium injection modules (LIM) for inherent ultimate shutdown, and lithium release modules (LRM) for automated reactor startup. All these systems adopt 6Li as a liquid poison instead of B4C rods. In combination with LEMs, LIMs, and LRMs, RAPID-L can be operated without an operator. This reactor concept is also applicable to the terrestrial fast reactors. In this paper, the RAPID-L reactor concept and its transient characteristics are presented.

Innovative fast breeder reactor concept 'RAPID' for improvement of reactor performance and proliferation resistance

Abstract The 60 MWe metal fueled fast breeder reactor concept ‘RAPID’ to improve reactor performance and proliferation resistance has been demonstrated. The reactor can be operated without refueling for up to 5 years. The essential feature of RAPID concept is that the reactor core consists of an integrated fuel assembly (IFA) instead of conventional fuel subassemblies. RAPID concept enables quick and simplified refueling by replacing an IFA in which all the core and blanket fuel elements are comprised. An on-site storage cask achieves on-site decay heat removal of an IFA. After 3 years of on-site storage, an IFA together with an on-site storage cask can be transported directly to the reprocessing plant without any intermediate steps. Significant improvement of inherent safety features and plant availability has been discussed. Decay heat removal capability, safety consideration on criticality of the IFA and shielding design of the on-site storage cask has been confirmed. The RAPID refueling concept possesses high resistance to state-supported removal of plutonium for nuclear weapons production.

RAPID Operator-Free Fast Reactor Concept without Any Control Rods Reactor Concept and Plant Dynamics Analyses

The 1,000kWe metal fueled sodium-cooled fast reactor concept “RAPID” to achieve highly automated reactor operation has been demonstrated. RAPID (Refueling by All Pins Integrated Design) is designed for a terrestrial power system which enables quick and simplified refueling. It is one of the successors of the RAPID-L, the operator-free fast reactor concept designed for lunar base power system. The essential feature of the RAPID concept is that the reactor core consists of an integrated fuel assembly instead of conventional fuel subassemblies. In this small-size reactor core, 14,000 fuel pins are integrated and encased in a fuel cartridge. Refueling is conducted by replacing a fuel cartridge. The reactor can be operated without refueling for up to 10 years. Unique challenges in reactivity control systems design have been addressed in the RAPID concept. The reactor has no control rod but involves the following innovative reactivity control systems: lithium expansion modules (LEM) for inherent reactivity feedback, lithium injection modules (LIM) for inherent ultimate shutdown, and lithium release modules (LRM) for automated reactor startup. All these systems adopt 6Li as a liquid poison instead of B4C rods. In combination with LEMs, LIMs and LRMs, RAPID can be operated without an operator. In this paper, the RAPID reactor concept and its transient characteristics are presented.

Long lifetime fast spectrum reactor for lunar surface power system

In the framework of innovative reactor research activities, a conceptual design study of fast spectrum reactor and primary system for 800 kWe lunar surface power system to be combined with potassium Rankine cycle power conversion has been conducted to meet the power requirements of the lunar base activities in the next century. The reactor subsystem is characterized by RAPID (Refueling by All Pins Integrated Design) concept to enhance inherent safety and to enable quick and simplifed refueling in every 10 years. RAPID concept affords power plant design lifetime of up to 30 years. Integrity of the reactor structure and replacement of failed primary circuits are also discussed. Substantial reduction in per‐kWh cost on considering launch, emplacement, and final disposition can be expected by a long system lifetime.

Rapid-A fast reactor concept without any control rods

A 60-MW (electric) fast reactor concept, RAPID-A, without any control rods has been shown to achieve inherent safety and highly automated reactor operation and to provide reactivity control systems with maintenance-free and reliable performance over the plant design life-time. RAPID-A is one of the variants of the refueling by all pins integrated design (RAPID), fast reactor concept, which enables quick and simplified refueling 2 months after reactor shutdown. In addition to the aforementioned advantages, unique challenges in reactivity control system design have been attempted in the RAPID-A concept. The design involves the following innovative reactivity control systems: lithium expansion modules for inherent reactivity feedback, lithium injection modules for inherent ultimate shutdown, and lithium release modules for automated reactor startup.

Experimental and Analytical Investigation of the Fast Reactor Passive Shutdown System: LIM

To enhance the inherent safety of the fast reactors, the lithium injection module (LIM) is proposed for inherent ultimate shutdown instead of conventional scram rod. LIM is composed of a refractory metal envelope in which 95% enriched 6Li is enclosed. In case the core outlet temperature exceeds the melting point of the freeze seal, 6Li is injected by a pneumatic mechanism from the top to bottom chamber to achieve negative reactivity insertion. This concept is attractive because the actuator has no moving parts and depends on the reliable physical property. In this paper, experimental and analytical verification of the LIM performance are presented. Real-time monitoring of LIM during reactor operation has been discussed as well.

Conceptual design of a modular island core fast breeder reactor RAPID-M

A metal fueled modular island core sodium cooled fast breeder reactor concept RAPID-M to improve reactor performance and proliferation resistance and to accommodate various power requirements has been demonstrated. The essential feature of the RAPID-M concept is that the reactor core consists of integrated fuel assemblies (IFAs) instead of conventional fuel subassemblies. The RAPID concept enables quick and simplified refueling by replacing IFAs in which all the core and blanket fuel elements are comprised. In this paper, the 600 MWe RAPID-M design consists of 7 IFAs is presented. Significant reactor mass savings and the improvement of inherent safety features are discussed. Plant dynamics analyses using the multi-point reactor kinetics equations to accommodate the modular core configuration demonstrated a favorable transient response in case of unprotected transient over power (UTOP).