Hitachi, Ltd.

Toshitaka Suzuki

Takao Sasayama

Sadayasu Ueno

Masayuki Miki

Akira Ikegami

Nobuo Sato

Seiko Suzuki

Tsutomu Omae

Taro Iwamoto

Sho Kusumoto

Shimon Ando

Takaichi Koyama

Kazuhiro Yoshida

Masatake Takidera

Seikoh Suzuki

Kunio Hamada

An oxygen sensor is disclosed in which an airtight reference chamber isolated from a surrounding space is formed on one main surface of a solid electrolyte, a current is supplied to the solid electrolyte to pump out oxygen from the reference chamber in such a manner that oxygen in the reference chamber is ionized and then passes through the solid electrolyte, means is provided for transferring oxygen from the surrounding space to the reference chamber in such a manner that oxygen in the surrounding space is ionized and then passes through the solid electrolyte, and the oxygen concentration in the surrounding space is detected on the basis of the current supplied to the solid electrolyte.

Oxygen sensor

An air-fuel ratio in the lean range is detected by measuring a limiting current when oxygen diffused to a first electrode is pumped to a second electrode via a solid electrolyte. A stoichiometric air-fuel ratio is detected from electromotive force between first and third electrodes when oxygen is pumped from the first electrode to the third electrode. The invention is characterized by use of such three electrodes. Furthermore, an air-fuel ratio in a rich range is detected by either sending oxygen from the first electrode to the third electrode via the solid electrolyte and measuring a current when the electromotive force between the first and third electrodes is controlled to be constant, or measuring a current when the air-fuel ratio range is judged as 'rich' from this electromotive force and the polarity of the impressed voltage at the time of lean detection is reversed.

Air-fuel ratio detector

In a method and a system for inspection of the inside of a nuclear reactor vessel in which an inspection device for inspecting a defect in a nuclear reactor vessel is so moved by a drive/control device as to permit inspection of a part to be inspected in the reactor vessel, and the presence or absence of defect in the reactor vessel is judged based upon information from the inspection device in the course of the above-mentioned movement of the inspection device; the movement of the inspection device is pursued and monitored by monitor means, and the movement of the inspection device is suppressed when an abnormality in the movement of the inspection device is judged based upon information from the monitor means, to avoid the abnormal movement.

Method and system for inspection of inside of nuclear reactor vessel

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Hitachi, Japan

Toshitaka Suzuki