Appts for sealing neutron flux detector lance within a reactor - at position where it extends from housing tube, thus ensuring that no radioactive deposits are collected internally

摘要

Appts. for the sealing of a lance (2) has a housing tube (5), from whose forward end (5a) the lance (2) extends, using a collar (6). The collar (6) is welded to the lance (2) and overlaps the forward end of the housing tube (5a). Within the collar (6) is a ring (9), which is connected to the collar by a spring (10), thereby pressed down to cover the annular space (8) between the forward side (5a) of the housing tube (6) and the lance (2) and hence preventing entry of any impurities into the lance. The lance (2) comprises a number of neutron detectors and their connecting cables (12) for the accurate determination of the neutron flux within a nuclear reactor. Pref. the ring (9) is made up of two parts, the first part (9a) narrowly surrounds the lance (2), the second part (9b) a flanged shaped extension of the first part is forced down by the spring (10) to cover the space (8) between lance (2) and housing tube (5). USE/ADVANTAGE - The sealing of the top of the housing tube with the lance ensures that no radioactive deposits can collect in the lance or the housing tube. During servicing of the lance no expensive cleaning out of the radioactive deposits is required. The lances do not need to be changed so often. Excess radioactivity in the bottom region of the lances beneath the reactor pressure vessel is avoided.