Abstract: A variable-voltage variable-frequency power source for an electric motor that drives a re-circulation pump for a boiling water nuclear reactor. The power source has a semiconductor electric power converter and a speed controller for controlling the semiconductor electric power converter. When a part of the semiconductor electric power converter comes into an inoperative state, that part is electrically disconnected, and the variable-voltage variable-frequency power source temporarily stops outputting power, thereby idling the re-circulation pump. Thereafter, the power source re-starts outputting power before the re-circulation pump completely stops. Thus, the re-circulation pump keeps operating, without stopping.

Abstract: The invention relates to a control system for controlling an average temperature of a coolant at a reactor core outlet. The control system method detects an average temperature of the coolant at the reactor core outlet, compares the actual average temperature of the coolant at the reactor core outlet with a reference temperature thereby to generate an error signal, and adjusts the actual average temperature of the coolant at the reactor core outlet in response to the error signal. The invention extends to a cascade controller for a nuclear reactor, and to a nuclear power plant.

Abstract: A jet pump beam bolt locking assembly includes a locking sleeve having a plurality of ratchet teeth extending around the periphery of a base portion, and a lock plate having a beam bolt opening, and an integral beam spring arm having a plurality of ratchet teeth extending from at least a portion of a side of the spring arm. The spring arm ratchet teeth are sized to mesh with the locking sleeve ratchet teeth. The lock plate also includes a lip extending at least partially around the beam bolt opening which captures the locking sleeve. The spring arm is movable between a first position where a lock plate detent is positioned in a spring arm notch which permits engagement of the ratchet teeth, and a second position where the side of the spring arm is in contact with the detent which disengages the ratchet teeth to permit loosening of the beam bolt.

Abstract: A power supply system for driving reactor coolant recirculation pumps within an advanced boiling water reactor is configured in such a manner that: at least one normal-operation busbar branches off from either a main on-site power line or from a power line for auxiliary power generation that branches off from the main on-site power line, with a house transformer therebetween; at least one MG set is connected to one of these normal-operation busbars; one static adjustable-frequency power supply device is connected to each MG set; and a plurality of recirculation pumps is connected to each static adjustable-frequency power supply device.

Abstract: A reactor core coolant flow rate control system for a BWR type nuclear power plant in which electric power is generated by a turbine-driven generator driven by a steam turbine rotating under the work of a main steam generated from a cooling water recirculated through a boiling water reactor includes an internal pump driving unit comprised of an electric motor driven by an electric power generated by the turbine-driven generator, a fluid coupling for transmitting an output torque of the electric motor and a variable-frequency generator whose rotation number is changed in accordance with the torque transmitted by way of the fluid coupling, a fluid coupling control signal generating unit for generating a fluid coupling control signal for the fluid coupling in response to at least one of deviation in a load and a rotation speed of the turbine-driven generator and deviation in a rotation speed of the internal pumps, and a plurality of internal pumps for recirculating the cooling water.

Abstract: A jet pump assembly for recirculating coolant through a recirculation loop of a boiling water reactor vessel, the jet pump assembly comprises a jet pump in operative association with the recirculation loop for forcing the coolant through the recirculation loop. A beam is positioned adjacent and in operative association with the jet pump for assisting in maintaining the positional relationship of the jet pump. A bolt is inserted in the beam for resisting the hydraulic forces generated in the jet pump, and an insert is disposed in said beam for receiving and surrounding the bolt which, in turn, reduces stress on the beam.

Abstract: Elongated coolant pumps suspended under steam generators within containment in a power plant with limited access space, are removed and replaced by an elongated maintenance cart with an elongated opening along one side in which the motor is received. Rollers support the cart for conveying the elongated motor in an upright position out from under the steam generator and onto an elevator. The elevator is lowered to transfer support of the cart and motor through trunnions to saddles straddling the elevator for rotation of the cart to a generally horizontal position. The elevator then raises the horizontally disposed cart carrying the motor to a higher floor where it is rolled off the elevator and out through the auxiliary equipment hatch.

Abstract: A BWR coolant recirculation system includes a pump deck disposed in a downcomer and fixedly joined to a reactor pressure vessel and reactor core shroud. A plurality of circumferentially spaced reactor internal pumps (RIPs) are joined to the deck and operable in a pumping mode for pumping downwardly a reactor coolant from the downcomer and into a core inlet. In a pump inoperable mode, a portion of the coolant bypasses the RIPs for allowing increased natural recirculation of the coolant from the downcomer and into the core inlet.

Abstract: A recirculation system is disclosed for driving reactor coolant water contained in an annular downcomer defined between a reactor vessel and a reactor core spaced radially inwardly therefrom. The system includes a plurality of circumferentially spaced pumps disposed in the downcomer, each pump including an inlet for receiving coolant water from the downcomer as pump inlet flow, and an outlet for discharging the pressurized water. The recirculation system firstly increases the pressure of the pump inlet flow at the pump inlet before being sucked into the pump for being further pressurized by the pump.

Abstract: A natural circulation boiling-water reactor system using free-surface steam separation incorporates a steam separator near the inner wall of its reaction vessel and extending into a downcomer. Steam so collected supplements the main steam flow from the reactor vessel to drive a turbine, which in turn drives a generator. A flow controller opens and closes a valve to adjust the flow of steam from the steam collector to the turbine. The flow controller can be programmed to implement a predetermined power output level or to adjust power output as a function of load or time. When this level is exceeded, as indicated by feedback from the generator, the flow controller valve is constricted. The auxiliary steam flow to the turbine is directly decreased, reducing power output. Concomitantly, less steam is removed from the steam collector, and thus from the downcomer. As a result there is more carryunder steam, which reduces the power generated at the reactor core.

Abstract: A natural circulation type boiling light-water reactor comprises a pressure vessel, a reactor core disposed within said pressure vessel to heat light water so as to generate main steam, a steam outlet provided in a wall of said pressure vessel for drawing out the main steam therethrough to supply the same to a turbine system, and a steam path along which the main steam flows from the reactor core to the steam outlet. The reactor further comprises a steam guide for prolonging the steam path and/or a radially increased chimney for reducing the velocity of the main steam flowing through the steam path. These causes radioactive isotope .sup.16 N contained in the main steam to flow within the pressure vessel for a time period exceeding its own half-life, so that the inventory of .sup.16 N in the main steam directed towards the turbine system is reduced remarkably. In consequence, shield structures for piping and turbine systems can be reduced in size and weight.

Abstract: Coolant recirculation arrangement for a nuclear reactor including a plurality of vertically oriented tubular conduits arranged in spaced relation between an unshrouded nuclear core and the inner pressure vessel wall for conducting coolant from an upper plenum above the core to a lower plenum below the core.

Abstract: The present invention is related to nuclear reactors. More specifically, this invention is directed to a means for venting pressurized water reactors.

Abstract: The pressure P.sub.R in the reactor pressure vessel, the flow rate W.sub.c of the cooling water flowing through the core in the reactor pressure vessel, and the flow rate W.sub.STM of the steam supplied from the reactor pressure vessel to the turbine are detected. The enthalpy H.sub.f of the saturated cooling water is determined on the basis of the pressure P.sub.R. The values of the cooling water flow rate W.sub.c, the steam flow rate W.sub.STM, the enthalpy H.sub.f of the saturated cooling water and a predetermined enthalpy H.sub.IN of the cooling water at the core inlet are substituted into the equation below thereby to obtain the enthalpy H.sub.fw of the feed water. ##EQU1## An error is determined between the feed-water enthalpy H.sub.fw thus obtained and the enthalpy T.sub.

Abstract: Disclosed is an angled gas conduit for a gas flowing under high pressure and at an elevated temperature which comprises a first conduit part and second conduit part connected at an angle forming an area of deflection for gas flowing within said conduit parts, an apertured plate arranged at an oblique angle within said conduit in the area of deflection, the apertured plate having a plurality of circular passages for directing the flow of gas in the conduit. A mounting arrangement for the apertured plate is also disclosed.