Drilling apparatus for working on tubes in a radioactive environment

A drilling instrument for machining tubes in tube sheets of heat exchangers in a radioactive environment, comprising:

• a support device;
• a transport device having retaining elements;
• and
• a drilling device having retaining fingers and a resting plate;
• wherein the transport device, and the drilling device are located proximate to each other and are each connected to the support device, such that the retaining elements and the retaining fingers are arranged on a common first side of the transport device and of the drilling device,
• wherein the support device has a support plate and wherein the resting plate is located proximate to and supported by the support plate,
• wherein the support plate is connected to the resting plate by at least one connecting element that is movable between a first position and a second position,
• wherein the resting plate is fixed in position relative to the support plate when the at least one connecting element is in the first position, and
• wherein the resting plate is movable relative to the support plate when the at least one connecting element is in the second position.