Hitachi, Ltd.

Yukihisa Fukasawa

Akira Nishimura

Junichi Yamashita

Kanji Kato

Yoshiyuki Miyamoto

Koji Nishida

Junjiro Nakajima

Yasunori Bessho

Tatsuo Hayashi

Takaharu Fukuzaki

Hideo Soneda

Michihiro Ozawa

Mitsuo Kinoshita

Koji Kurokawa

Yuichi Higashikawa

Kazuo Asami

Taro Ueki

Sadayuki Izutsu

Kenichi Takeuchi

A method of controlling a nuclear power plant includes determining a first maximum linear heat generation rate and a first minimum critical power ratio by a core monitoring system, and determining a second maximum linear heat generation rate and a second minimum critical power ratio by utilizing the first maximum linear heat generation rate and the first minimum critical power ratio determined by the core monitoring system and plant data. The second maximum linear heat generation rate and the second minimum critical power ratio are compared with predetermined thermal limit values and a control signal outputted from an automatic power regulator system to a re-circulation flow control system and to a control rod control system is held when at least one of the second maximum linear heat generation rate and the second minimum critical power ratio exceeds the predetermined thermal limit values.

Control system of nuclear power plant, and control method thereof

A control system, and a control method, of a nuclear power plant capable of easily executing automatic output regulation by an automatic power regulator system even when a lower-accuracy maximum linear heat generation rate and a lower-accuracy minimum critical power ratio are determined in a short cycle by using brief calculation. While a core monitoring system does not calculate a maximum linear heat generation rate and a minimum critical power ratio, they are determined by utilizing the maximum linear heat generation rate and the minimum critical power ratio calculated by the core monitoring system as well as plant data, and the lower-accuracy maximum linear heat generation rate and the lower-accuracy minimum critical power ratio so determined are compared with predetermined thermal limit values. The automatic power regulator system holds a control signal when at least one of the lower-accuracy maximum linear heat generation rate and the lower-accuracy minimum critical power ratio exceeds the predetermined thermal limit values.

A fuel assembly is provided with a coolant ascending path for making coolant rise and a water rod having a coolant descending path for conducting the coolant. A ratio of a flow area in a coolant inlet port of the smallest in coolant ascending path 13 on the downstream side than large diameter tube portion 3E to a flow area of the largest in the axial direction of coolant ascending path 13 in large diameter tube portion 3E is set to be 0.2-20%. In the normal operation, the declination degree from the liquid level in the coolant ascending path, corresponding to the coolant flow rate of the liquid level formed in the coolant ascending path can be controlled. Further, at the time of the excess the change speed of the liquid level can also be controlled.

Fuel assembly

This invention relates to an automation system for nuclear power plants. This system comprises operation plan making means, supervisory control means, and control means for controlling controlled objects. The operation plan making means makes a new operation plan to restore a normal operating condition which existed before the plant condition deviated from the normal operation range. The supervisory control means outputs control commands according to an operation plan under abnormal condition when the plant operating condition deviates from the normal operation range. Furthermore, the supervisory control means outputs control commands according a new operation plan prepared by the operation plan making means after an operation according to an operation plan under abnormal condition has been finished. The control means for controlling controlled objects controls the controlled objects according to control commands output from the supervisory control means.

Automation system for nuclear power plants

A storage 14 of a unit 13 constituting a gang control-rod operating unit stores an A type pattern sequence for configuring an A type control rod pattern, a B type pattern sequence for configuring a B type control rod pattern, and a control rod pattern exchange sequence. The control rod pattern exchange sequence comprises groups subsequent to 5 in the A type sequence and groups subsequent to 5 in the B type sequence. A control panel includes a sequence select switch 12a, a control rod group select switch 12b, and an insert/withdraw select switch 12c. In exchanging the control rod pattern, an operator actuates the sequence select switch 12a to select the control rod pattern exchange sequence, and then actuates the control rod group select switch 12b and the insert/withdraw select switch 12c to operate a plurality of control rods at the same time for carrying out the pattern exchange. The operation of exchanging the control rod pattern is facilitated and reliability is improved. Selection of the control rod pattern exchange sequence is allowed only when reactor power is above a set value at which an RWM 17 is to be released.

Gang control-rod controlling system and reactor operation method

The fuel assembly has fuel arrangement of a square lattice of 10 lines by 10 rows. Four water rods having a large diameter are arranged in central region of horizontal cross section wherein arrangement of 12 fuel rods is possible. The four water rods having a large diameter are so arranged adjacently in a circle as to form an internal between each other. First coolant flow path which is extended toward axial direction is formed by surrounded with the water rods having a large diameter. The first coolant flow path leads to third coolant flow path which is formed around the fuel rods through second coolant flow path which is the interval between the water rods having a large diameter. The fuel assembly is able to optimize the moderator to fuel atom number density ratio and to reduce the pressure loss because a portion to be an excessively moderated region is utilized as the first coolant flow path.

Fuel assembly and upper tie plate thereof

Reactor core, fuel assembly and fuel spacer

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Hitachi, Japan

Yukihisa Fukasawa