Patent Number: 055464351
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT In the FIGURE, 1 designates a loading machine for fuel assemblies for a pressurized-water reactor, 2 the reactor hall floor along which the loading machine is movable, 3 the reactor vessel, 4 the reactor core, 5 a pool located above the reactor vessel with reactor water, and 6 the reactor water in the reactor vessel and in the pool. The loading machine is provided with a lifting mast 7 of preferably telescopic design. The mast 7 is cylindrical and has an internal chamber wide enough to house a fuel assembly. A gripping device 8 provided at the end of a wire 8' provided inside the mast 7 is adapted to grip a lifting handle on a fuel assembly 10 which in the illustrated case is being lifted out of the reactor core and drawn well into the mast by a motor 11. The mast with the fuel assembly 9 is lifted upp into the pool 5 so that the fuel assembly comes near the upper water level, but so that the fuel assembly is surrounded by water 12. The mast counteracts that water which has passed the fuel assembly spreads to the area ouside the mast, which would mean that leaked-out fission products would be lost for the analysis. A hose 14 or other conduit extends from the upper part of the mast 7 to a little distance below the water level inside the mast but above the fuel assembly 9. The conduit 14 includes a pump 13 by means of which the water is sucked from the water 12 inside the mast 7, which is open in its lower end. The reactor water is caused to stream inside the mast 7 from below as marked by arrows and to flow around and through the fuel assembly 9 by the action of the pump 13. The fuel assembly is all the time located below the water level. Water is pumped by the pump 13 to a gas separator 22 in which gases present in the water are released therefrom by lowering the pressure and therewith decreasing the solubility of the gases in water. The gas separator 22 includes at least one gas space 23 having a small volume and one water reservoir 24. The gas space 23 and the water reservoir 24 are separated by means of a waterseal 25. In order to achieve a more effective release of the gases present in the samples in accordance with the present invention, the water is finely-divided, or atomized, with the aid of spray devices 26 mounted in the gas space 23, in conjunction with passing the water to the gas separator 22. The gases released from the water, these gases possibly containing gaseous fission products, are mixed with a working gas present in the gas separator 22 and are pumped through a gas circuit 27 to a measuring chamber 28 in which the gases are analyzed for the occurrence of gaseous fission products with the aid of a detector which functions to detect radioactivity in gases. The detection result could be presented on a display 35. The degasified water is passed to the water reservoir 24 in which any radioactivity in the water could be detected separately (not shown). Alternatively, water samples can be sent to a separate laboratory for analysis. Then the degasified water is conducted back to the pool 5 through a hose 36. In the case of low activity in the water samples, the enrichment of gaseous fission products in the detection system necessary for detection purposes is achieved by pumping large quantities of water sample through the gas separator 22 in which the water is degasified. The gas circuit 27 includes a pump 31 which functions to pump any gas present in the circuit 27 and the gas space 23 around said gas circuit 27 and the gas space 23, therewith enriching any gaseous fission products present. To ensure that dry gas is delivered to the measuring chamber 28 for detecting radioactivity in gases, the gas circuit 27 conveniently includes a moisture separator 32, a gas dryer 33 and an iodine trap 34 between the gas space 23 and the measuring chamber 28. While the invention has been described with reference to a specific embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention. In addition, modifications may be made without departing from the essential teachings of the invention as expressed in the accompanying claims.