Abstract: The investigated object containing a source of positrons is placed into a system of n position and energy-sensitive gamma radiation detectors (Di), each having detection elements (Dijk), where one of a pair of annihilation photons interacts in the detection element (D1jk) and the other interacts in another detection element (D2jk). The detectors store the coordinates of simultaneously affected detector elements, the time of interactions and the energies E1 and E2 of the annihilation photons. The recorded events in the detection elements (D1jk) and (D2jk) leads to recognition of individual pairs of annihilation photons. An analysis is performed of the registration of the photons by the detection elements (D1jk) and (D2jk) with energies in the interval from 507 keV to 513 keV to obtain an approximate spatial depiction of positions of positron annihilation and, registration of the photons from the positron annihilation with significantly Doppler shifted energies outside of that interval.

Abstract: The investigated object containing a source of positrons is placed into a system of n position and energy-sensitive gamma radiation detectors (Di), each having detection elements (Dijk), where one of a pair of annihilation photons interacts in the detection element (D1jk) and the other interacts in another detection element (D2jk). The detectors store the coordinates of simultaneously affected detector elements, the time of interactions and the energies E1 and E2 of the annihilation photons. The recorded events in the detection elements (D1jk) and (D2jk) leads to recognition of individual pairs of annihilation photons. An analysis is performed of the registration of the photons by the detection elements (D1jk) and (D2jk) with energies in the interval from 507 keV to 513 keV to obtain an approximate spatial depiction of positions of positron annihilation and, registration of the photons from the positron annihilation with significantly Doppler shifted energies outside of that interval.

Abstract: During operation of a light water moderated and cooled nuclear reactor, rods varying the neutron energy spectrum are introduced into the core of the reactor in the course of a first phase of the cycle in order to reduce the ratio of the volume of moderator to the volume of fissile material in the core. In a second phase of the cycle the spectrum displacement rods are extracted. The rods are of a mixture of thorium energy neutrons. The rods may be of fertile material and--depleted uranium. The invention is of particular interest in PWRs.

Abstract: For operating a PWR with spectral shift during all combustion cycles and with undermoderation during some cycles only, the reactor structure is designed for receiving either one of two types of fuel assemblies, having the same geometry. All fuel assemblies have guide tubes for receiving spectral shift clusters containing fissile material but with different elements bundles so as to be able to choose the type of operation.

Abstract: A control device for a PWR includes a plurality of clusters arranged for insertion into and removal from the core and each having a plurality of rods connected to a common carrier vertically slidable in a stationary guide structure and connectable to a drive shaft. First clusters contain neutron absorbing material and are each individually associated with electromagnetic actuation means for adjusting the amount of insertion of the associated one of the first clusters. Second clusters contain a different material and are each individually associated with hydraulic actuation means controllable to cause upward and downward movement. A set of one first cluster and one second cluster is associated with some of said fuel assemblies, with the drive shafts of the two clusters in each set being arranged symmetrically with respect to the axis of a single stationary structure located above the associated fuel assembly and arranged for authorizing mutually independent movement of the first and second clusters.

Abstract: Acoustic distance measuring apparatus for measuring the distance of a vessel (N) from a vertical line through a fixed point (P) on the bottom of a body of water, the apparatus comprising: an acoustic emitter unit (I) and at least three acoustic receiver units (H1, H2, H3) disposed on the bottom of the vessel, said receiver units being disposed at the vertices of a plane polygon; at least three acoustic emitter/receiver units (A, B, C) placed on the water bottom in the vicinity of said fixed point (P), said emitter/receiver units being disposed at the vertices of a polygon; and the improvement wherein the measuring apparatus further includes a relay acoustic emitter/receiver (R) submerged close to the vessel at a depth where vessel noise is highly attenuated, said relay receiing acoustic waves (a) from the vessel's emitter and responding by emitting acoustic wave (1, 2, 3) to the vessel's receiver units thereby enabling the distances between the relay and each of the vessel's receiver units to be calculated, s

Abstract: This invention concerns an apparatus characterised in that the heat exchange surface is formed by passages with a vertical circulation, said passages being distributed in two groups, one serving for pre-heating by means of diffuse radiation and the other providing the heating action in the true sense, said two groups being connected in series in such a way that the heat-exchange liquid passes through the two groups of passages in an upward direction.

Abstract: This invention concerns an inflatable-structure apparatus for cooling a heat exchange fluid comprising a flexible cylindrical casing of plastic material which is permeable to infra-red rays, said casing being maintained in its cylindrical form by an increased internal pressure, while disposed within said casing is a wall means which is reflective in the direction of the outer casing and over which flows the heat exchange fluid to be cooled, which is supplied to the interior of the casing by way of a supply duct and is removed therefrom by way of a discharge duct to be recycled by a pump, passing through a buffer tank.

Abstract: A solar collector includes two concentric spheres or hemispheres, the outer sphere or hemisphere being translucent or transparent and the inner sphere or hemisphere being absorbent of the solar radiation. Fluid to be heated is conveyed by an inlet duct in which is inserted a pump, and sprayed by a head in an inner spherical or hemispherical chamber defined by the inner surface wall of the inner sphere or hemisphere. It flows along this inner wall, becomes heated during its passage, is collected at the base of the inner sphere or hemisphere by an outlet duct. The collector is particularly adapted for the production of hot water to heat swimming pools and the like. In its hemispherical form, when placed at the top of a support post, it can be associated with a mating hemispherical, translucent or frosted housing which houses a light bulb. In this form the structure functions as a street lamp or the like.