Patent Number: 051924919
Section: description

Referring now to the figures of the drawing in detail and first, particularly, to FIGS. 1 and 2 thereof, there is seen a cross-sectional view of a cross-shaped control element 1 of a boiling water reactor. The control element 1 receives tubes 2 containing absorber material that extend along the longitudinal axis of the control element. The control element, which is disposed in a water pond or pool 3, has a can be brought to various test positions with the aid of a non-illustrated hoist and which is kept free of water by means of a compressed air connection 5. A collimator system 6 is integrated into the hood 4 in such a way that two vanes of the control element 1 are always exposed to a divergent collimator 7, as shown by phantom lines in FIG. 2. The collimator 7 has an inlet opening with a neutron source 8. In each case, a film cassette 9 which contains an image recorder is situated opposite the collimator 7 in the same measurement plane. The film cassette 9 is disposed in a holding device 10 which has a construction and relationship to the hood 4 that is explained below in connection with FIG. 3. As can be seen from FIG. 3 which is on an enlarged scale, the hood 4 has a wall with an opening 11 therein adjacent the film cassette. The opening 11 is disposed in a common measurement plane of the neutron source 8, the collimator system 6 and the film cassette 9 and its cross section corresponds to the cross section of the image recorder used in the film cassette 9. The holding device 10 fits over the opening 11 and is joined to the wall of the hood 4 through a sheet-metal casing 12 in such a way that a housing is produced which only has an opening 27 in its lower surface 13. The sheet-metal casing 12 has side walls 28 extended perpendicular to the wall of the hood 4, with which the sheet-metal casing 12 forms a form-locking guide channel for the film cassette 9. A form-locking connection is one which connects two elements together due to the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together by force external to the elements. The holding device 10 is consequently in communication with the internal space of the hood 4 through the opening 11 and is a part of the hood which is also kept free of water through the compressed air connection 5. The sheet-metal casing 12 of the holding device 10 is drawn downwards to such an extent that it terminates at about one height measurement of the film cassette below the lower edge of the opening 11. Projecting from the film cassette 9 is a coupling piece 14 which extends downwards at an angle and which enters into a detachable coupling link 15 with a coupling rod 16 extended approximately parallel to the hood 4. The length of the coupling rod 16 is dimensioned in such a way that it can be moved from outside the water pond 3 by manual actuation. The film cassette can therefore be introduced through the opening 27 into the water-free space of the holding device 10 by remote control. In order to reliably reach the measuring position, the holding device 10 has a centering piece 17 with a guide surface 18 that adjoins a stop 19 for the film cassette 9. The stop 19 has a truncated conical construction and receives an upper part 20 of the film cassette 9, which is likewise constructed with regard to its shape, in such a way as to center it. In the limit position, the film cassette 9 is centered by its lower frame part 22 on a projection 23. The projection 23 is a component of a guide piece 24 which extends below the opening 27. The film cassette 9 is held in the measuring position by at least one locking device 21 which comes out of a recess 29 in the guide piece 24 in such a way as to rest against a stop pin 30 provided on the coupling piece 14 with the aid of a non-illustrated pneumatic cylinder. The guide piece 24 carries a skimmer 25 which is already disposed in the water-free space of the holding device 10 and removes water residues from the surface of the film cassette 9 adjacent the opening 11. The skimmer 25 consequently assists the action of an air current flowing in the direction of an arrow 26, which also contributes to the removal of residual water. In order to ensure that no water can penetrate into the internal space of the cassette during the transport of the film cassette 9 through the water pond 3 to the hood 4, the part of the coupling piece 14 which is of tubular construction has a non-illustrated compressed air connection, so that air can pass through a hole 31 in the cassette 9 into its internal space.