Abstract: A control rod is used to control the reaction of a nuclear reactor. The control rod comprises one or more internal rodlet(s) and a hafnium skin that serves as the outermost layer, rather than a stainless steel cladding. Several variations on rodlets are contemplated. The rodlets are made of hafnium or Ag—In—Cd. The resulting control rod, due to the lack of a stainless steel cladding, has a greater rod reactivity worth, increased weight, and high flexibility.

Abstract: A fast reactor has a reactivity control assembly including a reactor shutdown rod of a backup reactor shutdown system and neutron absorbers to suppress the initial surplus reactivity, a reactor shutdown rod drive mechanism for releasing the reactor shutdown rod and units of neutron absorber drive mechanism capable of moving the respective neutron absorbers up and down. The reactor shutdown rod and the neutron absorbers are arranged in a wrapper tube. The reactor shutdown rod drive mechanism causes an inner extension tube to fall and release the reactor shutdown rod by means of a gripper section at the lowermost end of an outer extension tube by turning off the power supply to a holding magnet at the time of scram. Each of the units of neutron absorber drive mechanism has a dual tube type drive shaft including an outer extension shaft and an inner extension shaft. When grasping the neutron absorbers, the outer extension shaft is pulled up to allow both of the extension shafts to be inserted.

Abstract: A method for compensating a rod position indication system for non-linearity comprises the steps of applying an excitation current to a primary of a sensor for inducing a generally linear voltage that is representative of the position of a control rod on a secondary of the sensor. The excitation current includes a first frequency which is sufficient to provide the generally linear output for the sensor. The excitation current is then modified to include a second frequency which is sufficient for providing the generally linear output when the first frequency is insufficient to provide the generally linear output.

Abstract: An expanded reactor core capacity is achieved within the constraints imposed by the diametric extent of the current advanced boiling reactor (ABWR). This enhanced core capacity is achieved through the utilization of a scalloped shroud structure in conjunction with modified control rod designs. The core diameter is expanded toward the reactor vessel interior wall to establish a minimum distance therebetween representing a minimum value thereof avoiding neutron fluence induced vessel embrittlement. The control rods servicing peripheral fuel assemblies are configured having either a T-shaped blade configuration or an L-shaped blade configuration depending upon the parallel orientations of the peripheral fuel assemblies.

Abstract: An absorber rod for nuclear reactors with a pile of spherical fuel elements, which is inserted directly into the pile, in order to affect the prevailing neutron flux by absorber material located in an annular gap between two concentric cylindrical rod elements. The absorber rod has concentric rod elements arranged in pairs, a common rod tip and common connecting pieces. The rod elements are cooled by flow of gas and the inner cylindrical rod element performs the support function, i.e., it absorbs and transmits forces and moments originating in the movements of the rod during insertion and extraction.

Abstract: A nuclear reactor installation with a high temperture, gas cooled nuclear reactor supported in a cavity on a segmented bottom plate held by a centered point of fixation. The first heat exchangers of the primary circulation loop are arranged in the cavity around the nuclear reactor, with the associated first blowers being supported in first passages of the pressure vessel roof. The second heat exchanger for the removal of the decay heat are arranged similarly, with the associated second blowers located in passages of the pressure vessel bottom. The blowers are equipped with contactless magnetic bearings for the rotors. The drives of the core rods and the reflector rods are designed for a banking operation. Simultaneously, the side reflector is supported by means of radial supports on the thermal side shield elastically and secured against rotation. The measures described provide a simplified configuration without affecting safety.

Abstract: Control regulation and shutdown of gas-cooled, high-temperature nuclear reactors require precise adjustment of core reactivity through the use of absorber rods. Fine adjustment without permanent damage to the reactor core having a bed of spherical fuel elements is accomplished by a process and arrangement of the reactor such that two groups of absorber rods are independently controlled for insertion into the reactor cavity between the roof reflector and the bed of spherical fuel elements and into the fuel element bed itself. Adjustments can be made for rapid shutdown and/or complete shutdown as well as rapid shutdown required due to water or oil penetration into the reactor core.

Abstract: A method of controlling the reactivity of a gas-cooled core reactor the core of which consists of a pile of poured balls of equal diameter of fuel material which are withdrawn from the pile in downward direction and, if desired, are again added from above in conformity with the extent to which the pile of fuel balls has burned off. The method is characterized primarily in that balls which consist of absorbing material and have a diameter shorter than the diameter D of the balls of fuel material are introduced into the poured pile, the diameter d.sub.A of the balls of absorbing material being d.sub.Z .ltoreq.d.sub.A .ltoreq.d.sub.z +xd, preferably d.sub.Z <d.sub.A <d.sub.Z <+xd.sub.Z if d.sub.Z = D(2.sqroot.3-1) and representing the diameter of the maximum possible ball which can be placed in the densest ball packing between three interengaging balls of fuel material, and when d.sub.Z +xd.sub.Z =D(.sqroot.2-1).

Abstract: A method of actuating absorber rods in pebble bed reactors, according to which the rod is moved into or out of the ball pile with limited advancing speed in a turning or rotary manner. A feeding or advancing force is transmitted onto the rod being introduced, and this force does not exceed the appropriate maximum value of the ball strength and the rod stability. The drive provided for the foregoing procedure effects both a longitudinal shifting and rotation of a rod connected therewith, and has an axially fixed advancing spindle, the spindle nut of which is rigidly connected with the absorber rod and is journalled in a rotary pipe or tube in such a way as to be axially displaceable yet fixed against rotation, with the rotary tube being driven at a constant speed. During removal or outward travel of the rod from the ball pile, a fixed transmission ratio exists between the driving mechanism and driven end, which fixed transmission is generated with the aid of a freewheel or free-running drive.

Abstract: Improvements in high temperature gas cooled nuclear reactors is effected by an arrangement of paired absorber elements, each pair comprising a rod shaped absorber element and a tubular absorber element generally surrounding the rod shaped element. With this paired combination in a reactor employing spherical fuel elements, the effective life of the absorber rods is significantly extended by protection of the rod shaped absorber element from excessive amounts of irradiation from thermal neutrons.