Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Kotaro Inoue

Yuichiro Yoshimoto

Yasuhiro Masuhara

Osamu Yokomizo

Yoshiyuki Kataoka

Akihito Orii

Katsuyuki Kawashima

Sadao Uchikawa

Takaaki Mochida

Tatsuo Hayashi

Ken Amano

Shinichi Kashiwai

Akio Tomiyama

Motoo Aoyama

Kikuo Umegaki

Junichi Yamashita

Koji Nishida

Koji Hashimoto

Hiromasa Hirakawa

Isao Sumida

Michio Murase

Hiroaki Suzuki

Ryuhei Kawabe

Tetsuo Yasuda

Yoshihiko Sato

Shin-ichi Kashiwai

Masaki Matsumoto

Shozo Yamanari

Shigehiro Shimoyashiki

Shigeto Murata

Yasuo Tachi

Kazuo Azekura

Atsushi Zukeran

Satoshi Miura

Yojiro Hayashi

Soamu Yokomizo

A resistance member (e.g., fuel holding portion of the lower tie plate) is provided at the lower end of the fuel assembly. Provision is made of a coolant ascending path in which said water rods have coolant inlet ports that are open in a region lower than the resistance member to upwardly guide the coolant, and a coolant descending path which has a coolant delivery port that is open in a region higher than the resistance member to downwardly guide the coolant. The coolant ascending path and the coolant descending path are communicated with each other at their upper end portions.

Fuel assembly and nuclear reactor

In a fuel assembly having fuel rods inserted into regularly arranged cells of a fuel spacer which keeps the fuel rods correctly spaced from one another and has spacer elements disposed in a plurality of stages in the longitudinal direction of the fuel rods, the fuel spacer comprises vanes formed on the cells in such a manner that each vane is bent from a cut formed in a part of the side wall of the cell. The vanes obliquely project into the corresponding spaces between adjacent fuel rods and allow a coolant flowing through the spaces and forming two-phase flows to generate swirling flows toward the fuel rods. The fuel spacer may alternatively comprise either thin-walled cylinders having built-in vanes or spiral vanes, which are fixed to the spacer that has not been subjected to any direct machining. Also disclosed is a fuel assembly provided with any of the above-described fuel spacers. The arrangement of the present invention enables, while assuring a sufficient strength for maintaining fuel rods in their correct position, the transfer of heat from the fuel rods to the coolant to be promoted so as to raise the allowable power level of the fuel assembly, and enables the void ratio to be lowered so as to increase the reactivity.

Fuel assembly and fuel spacer

Of the components making up the pump, one part including the bearing is removably assembled into the other part so that the bearing is received in the other part. This structure allows easy removal of the first part of the pump components from the second part for disassembly and for maintenance and inspection of the pump. The pump can also be reassembled with ease by inserting the first part into the other part.

Mechanical pump equipment

A fuel assembly including a plurality of fuel rods and water rods. The fuel rods are arranged with a predetermined pitch and two water rods are disposed adjacent to each other in a diagonal direction of the fuel assembly. More particularly, the fuel rods are arranged in a lattice of nine rows by nine columns and the two water rods are disposed inside a region corresponding to a space sufficient for disposing seven fuel rods at the center of the fuel assembly. Each of the water rods has an outer diameter greater than the pitch of the fuel rods.

Fuel assembly

A natural circulation reactor includes a reactor pressure vessel, a cylindrical shroud disposed within the reactor pressure vessel to surround a reactor core and to extend to a position above the reactor core, and a coolant descending passage defined between the reactor pressure vessel and the shroud for allowing the coolant discharged from the top of the reactor core to be again supplied to the bottom of the reactor core. In such a natural circulation reactor, a liquid level of coolant in the coolant descending passage is adjusted on the basis of a reactor power request signal at a position below a liquid level of coolant in the shroud, and thus reactor power is controlled so that it may reach a predetermined reactor power by adjusting the liquid level of coolant in the coolant descending passage.

Method of and apparatus for controlling power of natural circulation

A fast breeder incorporating a core having a driver core region containing an enriched fissile material, an external blanket region surrounding the core region and containing a fertile material and an internal blanket region disposed within the driver core region and containing a fertile material. The internal blanket region has a thickness or axial height greater at the central portion thereof than at the peripheral portion thereof. The peripheral end of the internal blanket region opposes to the inner peripheral surface of the external radial blanket region with a portion of the core region interposed therebetween.

Fast breeder

In the fast breeder reactor according to this invention, a medium-pressure plenum and a high-pressure plenum are disposed, in the mentioned order from above in a reactor core. Sodium is filled in the medium- and high-pressure plenums. The pressure in the medium-pressure plenum is lower than that in the high-pressure plenum. The lower ends of the entrance nozzles of a multiplicity of fuel assemblies loaded in the reactor core are supported by a supporting plate which forms a boundary between the medium- and high-pressure plenums. The entrance nozzles of control rod guide pipes disposed among the multiplicity of fuel assemblies are also supported by said supporting plate. The sodium in the medium-pressure plenum is supplied into each control rod guide pipe through a first opening provided in the lateral surface of the entrance nozzle of each control rod guide pipe. The sodium in the high-pressure plenum is supplied into each fuel assembly from the lower end of the entrance nozzle of each fuel assembly through a second opening provided piercing through the supporting plate. The sodium in the high-pressure plenum is supplied to the medium-pressure plenum through a pressure-reducing orifice.

Fast breeder reactor

A fast breeder which is formed with a driver core region having an enriched nuclear fuel substance and allowing liquid metal acting as a coolant to pass therethrough and with a blanket region surrounding the periphery of the driver core region. A reactor stopping control rod to be inserted downward into the driver core region has an axially uniform density of boron-10. A reactor power adjusting control to be inserted downward into the driver core region has a lower density of boron-10 in a lower region than that in an upper region.

This invention relates to a fuel assembly for fast reactors and aims to reduce stresses induced in fuel pins by interaction between a wrapper tube and a bundle of fuel elements each of which consists of the fuel pin and a wire spacer wound around the fuel pin. The fuel elements consists of two kinds of fuel elements, one of them consists of conventional fuel pins and wire spacers and the other fuel pins of smaller diameter than the conventional fuel pins and wire spacers of larger diameter than the conventional wire spacers whereby the fuel assembly is provided with larger space therein.

Fuel assembly for fast reactors

An initial charge core of a fast breeder and a method of renewing fuel in the initial charge core. The initial charge core comprises a driver core region containing a fissile material, an external blanket region containing a fertile material and surrounding the driver core region, and an internal blanket region disposed within the driver core region and containing a fertile material. The axial thickness of the internal blanket region is greater at its central portion that at the peripheral portion thereof. The internal blanket region is enriched with the fissile material. The degree of enrichment in the internal blanket region is greater than that in the driver core region.

Initial charge core of fast breeder and method of charging the core with

A fast breeder has a driver core region enriched with a fissile material and a blanket core region containing mainly a fertile material. The driver core region includes an inner core region and an outer core region surrounding the inner core region. The volume of the inner core region is selected to range between 30 and 70% of the volume of the driver core region. The enhancement of the fissile material in the inner core region ranges between 30 and 80% of the fissile material in the outer core region.

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Toukai-mura, Japan

Kotaro Inoue