Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Mikio Sakurai

Yuichiro Yoshimoto

Takao Igarashi

Shiro Nakamura

Hiroshi Sasaki

Yasuhiro Aizawa

Hiromasa Hirakawa

Tsutomu Hayashi

Masayuki Izumi

Hiroshi Kodama

Koki Yamauchi

Mutsuo Konno

Mishihiro Ozawa

Toshimitsu Ishikawa

Thoru Satho

Kazuo Owada

The present invention relates to a decontamination method in which an object to be decontaminated is immersed in a liquid, bubbles are produced by blowing vapor in the liquid, and these bubbles are caused to burst on a solid surface which constitutes the object to be decontaminated which is brought into contact with the liquid, whereby substances adhered to the solid surface are separated and removed by the impulsive force produced when the bubbles burst. Also provided is a method of decontaminating solid surfaces which exhibits a high degree of efficiency and a high level of safety.

Decontaminating solid surfaces

A fuel assembly has a fuel spacer consisting of a water rod having an outer diameter greater than that of fuel rods and a large number of circular sleeves into which the fuel rods are inserted. The fuel spacer has four bridge members. Both ends of these bridge members are fitted to two of eight circular sleeves which are adjacent one another in the diagonal direction of the fuel spacer. Both ends of each bridge member are bent so that its center projects outwardly away from the water rod.

Fuel assembly

A nuclear reactor having a reactor vessel adapted to be supplied with a coolant, a reactor core disposed in the reactor vessel and including a plurality of fuel assemblies, a plurality of control rods adapted to be inserted into the reactor core and a plurality of control rod driving devices for driving the control rods into and out of the reactor core. A plurality of tubular coolant passage members are disposed above the fuel assemblies so as to receive the heated coolant discharged from the fuel assemblies, so that the heated coolant flows upwardly through the tubular coolant passage members. The tubular coolant passage members provide a chimney effect which enhances the upward flow of the coolant and, hence, increases the flow rate of coolant flowing through the reactor core. In consequence, a greater cooling effect is obtained and the range of power controllable by the control rods is widened. In consequence, the construction of the reactor is simplified and the size is decreased due to elimination of coolant recycling system in the reactor vessel.

Nuclear reactor

A nuclear reactor power monitoring system for monitoring the power level of a reactor and preventing an excessive rise thereof attributable to a transient increase in the core coolant flow rate before the reactor is scrammed. The system include an operating region monitor (ORM) for blocking the increase in the core coolant flow rate or running-back the flow rate when the power level exceeds a predetermined coolant block threshold power level which is a function of the core coolant flow rate.

Nuclear reactor power monitoring system

System for preventing erroneous operation of control rods for securing a safety control of a nuclear reactor. The erroneous operation preventing system is comprised of a control rod objective position setting means for setting an objective position of a control rod, a control rod position detector for detecting a position of the control rod, and an operation means which operates a difference between the objective position set up and the detected position of the control rod being operated and produces a signal for blocking the control rod operation when the control rod is operated so that the difference goes away from zero. The erroneous operation blocking system stops the control rod at the first possible control rod stopping position. The erroneous operation preventing system includes a return operation commanding unit for compensating for erroneous operation of the control rod when the control rod is erroneously operated.

System for preventing erroneous operation of control rods

Growing community of inventors

Mito, Japan

Mikio Sakurai