Abstract: A segmented electromagnetic coil assembly for use in a magnetic jack type of drive mechanism used to move control rods within a nuclear reactor. The coil assembly has a plurality of individual magnetic coils spaced around and against the non-magnetic housing which contains the control rod drive shaft.

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: High velocity reactor coolant water in a boiling water reactor or a pressurized water reactor transports radioactive ions and particles from a nuclear reactor vessel to the balance of the reactor coolant system where they deposit on chromium (III) oxide-containing surfaces. These radioactive deposits are removed in a dilute chemical decontamination process wherein permanganate ion-containing reactor coolant water is circulated throughout a reactor coolant system to oxidize chromium (III) oxide surfaces of the system to chromium (IV) oxide. Formic acid is added to the permanganate ion-containing reactor coolant water and then the formic acid-containing water is circulated throughout the reactor coolant system to reduce unreacted permanganate ions in the reactor coolant water to manganous ions.

Abstract: A forced-circulation boiling-water reactor includes fluidic diodes in the coolant fluid return path between the pump deck and the core inlet plenum. The fluidic diodes permit a downstream flow to proceed relatively freely, but substantially resist upstream flow. When pumps are shut down, the fluidic diodes serve to augment natural circulation, thus enhancing core stability. When the pumps are operating, the fluidic diodes serve to resist backflow, minimizing any loss of pump efficiency. This direction-flow asymmetry imposed by the fluidic diodes is achieved without moving parts, so as to achieve a high level of reliability.

Abstract: A process is presented for fabricating a fuel rod including an elongated fuel tube, a lower end plug for sealing one of the openings, and an upper end plug for sealing an opposite opening. The steps include sealing an opening of the aperture by melting the lead portion of the upper end plug in such way that welding is carried out along the lead portion and a welded portion formed by the welding is disposed below the lower portion of the chamfer. The elongated fuel tube has openings at opposite end thereof, and a plurality of fuel pellets inserted therein. The upper end plug has an end face and an outer peripheral surface, a chamfer formed at an intersection between the end face and the outer peripheral surface, an aperture formed in the center of the upper end plug, a groove formed around the aperture, and a lead portion formed between the aperture and the groove.

Abstract: A fuel assembly supporting structure for a nuclear reactor fuel assembly which comprises a two-way shape-memory alloy. A shape-memory alloy is selected which has an overall transition temperature range substantially above atmospheric temperature and substantially below a temperature experienced by the shape-memory alloy under reactor operating conditions. By using a shape-memory alloy in the design, the support structure assumes a first configuration for securely supporting one or a plurality of nuclear reactor components at a temperature above the overall transition temperature range and assumes a second configuration for loosely engaging the reactor components below the transition temperature range.

Abstract: A method of decommissioning a nuclear reactor is provided in which radiation exposure is minimized. The method includes the steps of encapsulating portions of the reactor vessel and reactor internals into a solid reactor capsule and then converting this reactor capsule into a plurality of decommissioned segments. The encapsulating step preferably includes the step of forming a matrix within the chamber which integrally attaches to the vessel and integrally embeds the reactor internals to create a solid reactor capsule. Such a reactor capsule has an outer shell which is formed from the vessel and which substantially encases the matrix and thus the reactor internals. More particularly, this encapsulating is preferably accomplished by providing a fluidized matrix-creating material, preferably concrete, which may be predictably solidified and which functions as a radioactive shield in its solid state.

Abstract: A safety system grade dropped rod detection system for a pressurized water reactor (PWR) utilizes core exit thermocouples arranged in multiple trains and hot and cold leg RTDs to generate a safety system grade rod stop signal. The system generates from the temperature signals a relative power deviation (RD) and a curvature index (CI), which is the spatial second derivative of RD for each fuel assembly. The CI signatures not only provide rapid, reliable detection of dropped control rods, but also clearly identify failed and failing thermocouples.

Abstract: A reactor containment facility having a reactor pressure vessel containing a core; a dry well in which the reactor pressure vessel is arranged; a suppression chamber holding suppression-pool water and forming above the suppression-pool water a wet well; and a plurality of vent pipes allowing the dry well to communicate with the suppression-pool water; a steel wall which is in contact with the suppression-pool water of the suppression chamber and which surrounds at least the pool water so as to form a containment vessel which houses the dry well and the suppression chamber; and an outer peripheral pool containing cooling water in contact with the outer peripheral surface of the steel wall.

Abstract: A recirculation system for driving reactor coolant water in a downcomer within a reactor pressure vessel includes a jet pump disposed in the downcomer and having a suction inlet at the top thereof and an outlet at the bottom thereof. A reactor internal pump is joined directly to the pressure vessel at an access nozzle thereof and includes a housing sealingly joined to the access nozzle, and in serial flow communication an inlet channel, an impeller, an outlet channel, and an injector nozzle. The inlet channel carries coolant water from the pressure vessel to the impeller which pressurizes the coolant water and returns it through the outlet channel and the injector nozzle for injection into the jet pump inlet. The water injected from the internal pump into the jet pump drives the jet pump for effecting recirculation flow within the pressure vessel.

Abstract: A neutron generator, comprising:(i) an ion source comprising an anode and a thermionic cathode disposed in an ionizable gas environment (e.g. hydrogen isotope);(ii) means for heating the cathode so that the latter emits electrons which, when colliding with the gas atoms, generate ions;(iii) a target;(iv) an electrical gap to accelerate ions from the ion source towards the target upon impingement of the ions; and(v) control means for applying voltages to the anode, cathode and electrical gap.The cathode is of the dispenser type or volume type, and preferably comprises one block of material comprised of a substrate impregnated with an electron emitting material.

Abstract: Decreasing the speed of a pump supplying cooling water to the core in the boiling water type nuclear reactor based on a trip signal that is generated when a pump supplying feed water is tripped. This performs a first operation to decrease the nuclear reactor power to a first fixed value. A second operation lowers the nuclear reactor power to a second fixed value that is lower than the first fixed value and that prevents run-out of other first pumps in operation. The first fixed value is lower than the reactor power at the moment when the first pump is tripped. The steam flow is decreased substantially simultaneously with the decrease of the feed water flow. Thereby, the decrease of the steam flow is carried out in an early stage when the feed water pump is tripped and the possibility of nuclear reactor scram is reduced.

Abstract: A nuclear reactor plant is provided in which the reactor coolant system contains a dissolved solution of enriched boric acid. The boron-10 to boron-11 atomic isotope ratio of the enriched boric acid solution is greater than 19.8:80.2 at the start of the reactor core cycle. The nuclear reactor plant design provides for minimal mixing between the reactor coolant solution containing the enriched boric acid solution and the natural boric acid solution used during refueling operations.

Abstract: A gap between a foot part and a channel of a boiling water fuel assembly is sealed against a coolant flow by a spring being supported by a central part thereof against the channel and by sides thereof against the foot part and being clipped and/or clamped on at that location even when all of the fuel rods are removed. For this purpose, the upper edge can extend around the foot part edge or the spring may be constructed as a spring band running entirely around the foot part and being fitted into a lateral groove.

Abstract: A remote control apparatus for maintaining a tokamak type nuclear fusion reactor comprises a rail having a plurality of arcuated links to be extended in a circumferential direction and a plurality of joints for pivotally connecting the adjacent arcuated links, a vehicle running on the rail extended so as to form a continuous arc with its center substantially coinciding with the center of the torus space, and at least one handling device mounted on the vehicle, for handling the in-vessel components. The remote control apparatus is further provided with a rail housing device for receiving the arcuated links in a folded state when they are not in use, a rail mounting device for sending out said arcuated links in succession into the torus space, extending them so that they form a continuous arc and supporting the arcuated link on the proximal end of the rail, and a rail supporting device for supporting the central portion of the rail extended in the torus space.

Abstract: A main steam isolation valve of a reactor power plant comprises a valve body provided with inlet and outlet portions through which a steam flows, a cylindrical valve disk accommodated in the valve body to be reciprocatingly movable therein along an inner peripheral surface of the valve body for opening and closing the steam flow inlet portion and a driving mechanism secured to the valve body and operatively connected to the valve disk for reciprocatingly moving the valve disk in the valve body. A coupling member is applied to an end opening of the valve body for holding the valve disk when the valve disk is shifted to a position fully opening the inlet portion. A tubular wall member is integrally formed with the valve body so as to surround the valve disk with a gap therebetween when the valve disk is fully opened. A guide rib is further disposed to the valve body for causing asymmetric steam flow in the inlet portion of the steam flow of the valve body.

Abstract: This invention relates to a method and apparatus for the generation of isotopes, and in particular radioisotopes, from a target material which is not normally a solid and which, when bombarded by selected high energy particles, produces the selected isotope. A surface is provided which is preferably of a thermally-conductive material, which surface is cooled to a temperature below the freezing temperature of the target material. A thin layer of target material is then frozen on the surface and the target material is bombarded with the high energy particles. The beam of high energy particles is preferably at an angle to the surface such that the particles pass through a thickness of the target material greater than the thickness of the layer before reaching the surface. When the desired quantity of isotope has been produced from the target material, the target material, which has now been altered nuclearly to contain the selected isotope, is removed from the surface.

Abstract: An alkaline-permanganate process for chemically decontaminating oxidized metal surfaces wetted by primary water circulating in cooling loops of nuclear reactors maintains permanganate-containing primary water at a temperature of about 90.degree. C. and at a pH of 9-12 to oxidize the wetted surfaces. Oxalic acid is then added to the water and the oxalic acid-containing primary water is maintained at a temperature of at least about 90.degree. C. and at a pH of about 5-7 while it is circulated to destroy the permanganate ions and manganese dioxide.

Abstract: A stabilized alpha metal matrix provides an improved ductility, creep strength, and corrosion resistance against irradiation in a zirconium alloy containing on a weight percentage basis tin in a range of 0.4 to 1.0 percent and typically 0.5; iron in a range of 0.3 to 0.6 percent, and typically 0.46 percent; chromium in a range of 0.2 to 0.4 percent, and typically 0.23 percent; silicon in a range of 50 to 200 ppm, and typically 100 ppm; and oxygen in a range 1200 to 2500 ppm, typically 1800 to 2200 ppm. The high oxygen level assists in reducing hydrogen uptake of the alloy compared to Zircaloy-4, for example.

Abstract: A process for dismantling equipment that is buried, unsheltered, at risk of contamination and possibly is irradiating, and a vessel for implementing this process. According to the invention, buried equipment at risk of contamination, for example, an off-line effluent pipe, is dismantled in sections under cover of a movable vessel (124) placed above the section to be dismantled (12, 14). The invention also concerns a vessel (124) that has a self-supporting structure built around a deck (126) equipped with an elongated central opening (148) giving access to the section to be dismantled (12, 14).