Periscope having telescoping sections for viewing reactor interior

Claim 1

A PERISCOPE FOR OBSERVING THE EXTERIOR OF A PRESSURE VESSEL COMPRISING FIRST TUBULAR MEANS EXTENDING FROM AN APERTURE IN A WALL OF SAID PRESSURE VESSEL AND DEFINING SAID APERTURE, SAID FIRST TUBULAR MEANS RIGIDLY ATTACHED TO SAID WALL WITH A PRESSURE-TIGHT CONNECTION, SECOND TUBULAR MEANS SLIDEABLE WITHIN SAID FIRST TUBULAR MEANS FROM A FULLY RETRACTED POSITION IN WHICH A FIRST END OF SAID SECOND TUBULAR MEANS IS WITHDRAWN INTO SAID FIRST TUBULAR MEANS BEYOND SAID APERTURE AND SAID PRESSURE VESSEL, TO A FULLY EXTENDED POSITION IN WHICH SAID FIRST END IS EXTENDED THROUGH SAID APERTURE AND INSIDE SAID PRESSURE VESSEL, SAID SECOND TUBULAR MEANS CARRYING AN OBJECT LENS IN THE END WHICH IS PROTRUDED INSIDE SAID PRESSURE VESSEL, SEALING MEANS, SAID SEALING MEANS SUSTAINING THE PRESSURE IN SAID VESSEL AGAINST LEAKAGE WHEN SAID SECOND TUBULAR MEANS IS IN THE FULLY RETRACTED POSITION AND ALLOWING A SMALL LEAK WHEN SAID SECOND TUBE IS MOVED AWAY FROM SAID FULLY RETRACTED POSITION SO THAT PRESSURE FLUCTUATIONS IN SAID PRESSURE VESSEL DO NOT MOVE SAID SECOND TUBULAR MEANS.