Hitachi, Ltd.

Toshitsugu Nakao

Yoshiyuki Kataoka

Yasuhiro Masuhara

Masataka Hidaka

Shigeto Murata

Shigeo Hatamiya

Osamu Yokomizo

Isao Sumida

Masanori Naitoh

Hiroaki Suzuki

Tsuyoshi Niino

Shin-ichi Kashiwai

Akio Tomiyama

Tohru Fukui

Motoaki Utamura

Junichi Yamashita

Koji Nishida

Kenji Tominaga

Hiromasa Hirakawa

Tatsuo Hayashi

Michio Murase

Ryuhei Kawabe

Tadashi Fujii

Kanehiro Ochiai

Shinichi Kashiwai

Yoshishige Kawada

Iwao Yokoyama

Shoichiro Kinoshita

Akihiko Minato

Yuichiro Maeda

There is disclosed a nuclear reactor installation. An accumulator-type emergency core cooling system, a gravity-driven core cooling system and an equalizing system for submerging a reactor core are provided within a primary containment vessel containing a reactor pressure vessel in which the reactor core is disposed. These cooling systems are automatically operated sequentially in accordance with the pressure in the reactor pressure vessel without the need for any particular powered source. The primary containment vessel is made of steel, and the interior of this containment vessel is divided into a space containing the reactor pressure vessel and a space containing an operation floor in such a manner that the two spaces are isolated from each other. An opening device is provided between the two spaces so as to communicate the two spaces with each other in the event of an accident, the upper portion of the primary containment vessel being air-cooled while the lower portion of this containment vessel being water-cooled.

Nuclear reactor installation

In a boiling water nuclear reactor, a reactor primary cooling water line is filled with water at the start-up time, and the inside of a pressure vessel is pressurized by a pressurized tank and at the same time control rods are withdrawn to thereby heat cooling water in a state of single-phase flow to high temperature. Succeedingly, the pressurization is released and the pressure of the pressure vessel is gradually approximated to the saturation pressure corresponding to the cooling water temperature to thereby make the cooling water transit into a state of two-phase flow, and thereafter the cooling water is heated by nuclear reaction in the state of two-phase flow to thereby obtain predetermined reactor running temperature and pressure. This prevents the flow fluctuation and the reduction of stability of core due to occurrence of unstable phenomena of low temperature two-phase flow at the start-up time of the reactor to thereby make it possible to perform stable starting-up of the reactor and to shorten the start-up time of the reactor to thereby realize improvement in economy as well as reliability.

Boiling water nuclear reactor and start-up process thereof

A pressure control chamber of a reactor containment vessel for receiving the atmosphere of the reactor containment vessel containing leakage steam developing in the event of an accident includes a pressure control pool, and a wet well disposed above the pressure control pool. The wet well is divided into an inner peripheral portion and an outer peripheral portion. The inner and outer peripheral portions are communicated with each other via the pressure control pool. An outlet port for flowing the atmosphere of the reactor containment vessel containing the leakage steam is provided at the inner peripheral side of the pressure control pool. When the atmosphere of the reactor containment vessel containing the leakage steam is introduced into the pressure control pool in the event of the accident, this atmosphere is condensed by the water in the pressure control pool, and the gas of this atmosphere not condensed is accumulated in the inner peripheral portion of the wet well. As a result, the pressure within the inner peripheral portion is increased to increase the water level of the pressure control pool at the outer peripheral portion, so that the area of contact of a reactor containment vessel wall with the pressure control pool water is increased, thereby enhancing a heat radiation performance of the reactor containment vessel.

Reactor containment vessel

A fuel assembly has a water rod which consists of a coolant ascending path and a coolant descending path, the coolant ascending path opening below a fuel support of a lower tie plate, the coolant descending path opening above the fuel support and adapted to guide downwardly the coolant that has flowed up the coolant ascending path to the upper portion of the water rod. The lateral cross section of the coolant ascending path is more than 25 times that of the coolant descending path. The nuclear reactor with these fuel assemblies loaded in the core is operated as follows. After startup of the reactor when the reactor power is low, all the control rods inserted in the core are withdrawn completely. Then, the reactor power is controlled by regulating a liquid level formed in the water rods. This reactor operation method prolongs the lifetime of the control rods, thereby reducing the number of times they have to be replaced.

Nuclear reactor having an ascending cooling path much greater than the

A fuel assembly according to the present invention is formed in such a manner that the small diameter portion of an upper end plug of a fuel rod is inserted into a boss of an upper tie-plate. The upper end plug includes a small diameter portion and a large diameter portion which is disposed below the former. An expansion spring in disposed in the small diameter portion of the upper end plug. A cover member surrounding this expansion spring is disposed in the large diameter portion of the upper end plug, and extends upwardly. Since the cover member surrounds the expansion spring, pressure loss caused by the expansion spring can be reduced.

Fuel assembly

A nuclear reactor is equipped with a cooling water circulation system which includes a water-feed conduit and a drain conduit to circulate the cooling water to and from a pressure vessel which surrounds a reactor core, the cooling water having a free liquid level maintained above the reactor core. The drain conduit is inserted in the pressure vessel from the upper side toward the lower side relative to the free liquid level. A double tube consisting of an inner tube and an outer tube maintaining a gap therebetween is formed in the end portion of the drain conduit. The inner tube and outer tube being continuous with the drain conduit, the opening at the lower end of the inner tube is located below said free liquid level but above the reactor core. The opening at the upper end of the outer tube is located above the free liquid level. The opening at the lower end of said outer tube is located below the reactor core.

Nuclear reactor

Growing community of inventors

Hitachi, Japan

Toshitsugu Nakao