Patent Number: 041727606
Section: claims

1. A method of determining the neutron transmission characteristics of the wings of a cruciform shaped control rod positioned in a nuclear reactor core wherein each of the four wings of said control rod is normally located between a pair of fuel assemblies, each of said fuel assemblies including a surrounding flow channel, comprising the steps of: (1) removing a pair of said fuel assemblies from said core to provide access to one wing of said control rod; (2) positioning a neutron shielding source enclosure containing a neutron source on one side of said one wing, a side of said source enclosure being adjacent said one wing and having an opening therein for passage of a continuous stream of neutrons into said one wing from said source; (3) positioning a neutron shielding detector enclosure containing neutron detector means on the opposite side of said one wing, a side of said detector enclosure being adjacent said one wing and having at least one opening for passage of neutrons from said one wing to said detector means for detection of neutrons that pass through said one wing from said source; (4) monitoring the signals from said detector means to determine the relative number of neutrons transmitted from said source through said one wing to said detector means; and (5) moving said source and detector enclosures in unison along the length of said one wing and registering a record of the signals from said detector means during said moving. 2. The method of claim 1 including the steps of placing dummy flow channels in the positions of said removed fuel assemblies and positioning said source and detector means enclosures within respective ones of said dummy flow channels. 3. The method of claim 1 including the further steps of generating a position signal indicative of the position of said source and detector enclosures along the length of said control rod and recording a record of said position signal. 4. Portable apparatus for remotely determining the neutron transmission characteristics of a control rod located in a pool of water for shielding operating personnel from radiation comprising: a neutron source removably contained in a shielding cask in said pool; a carriage positioned adjacent said control rod and adapted for movement therealong; a neutron source enclosure formed of a neutron shielding material and supported on said carriage adjacent one side of said control rod, said enclosure containing a receptacle for receiving said neutron source, said enclosure having at least one opening for passage of neutrons in the side of said enclosure adjacent said control rod; remotely manipulatable means for moving said neutron source from said cask into said receptacle in said enclosure whereby a continuous stream of neutrons from said source is directed through said opening into said control rod; neutron detection means supported on said carriage adjacent a side of said control rod opposite from said one side for detecting neutrons transmitted through said control rod from said source whereby signals produced by said detection means are proportional to the quantity of neutrons transmitted from said source through said control rod; remotely manipulatable means for moving said carriage along the length of said control rod; and recording means responsive to the signals from said neutron detection means for registering said signals as said carriage is moved along the length of said control rod. 5. Apparatus according to claim 4 further including position indicating means coupled to said moving means and responsive to said movement to produce a position signal indicative of the position of said neutron detector means with respect to the distance along the length of said control rod and means for recording said position signal in synchronism with the recording of the signals from said detector means. 6. Apparatus according to claim 4 wherein said detector means includes a neutron shielding enclosure. 7. Apparatus according to claim 4 including guiding means for guiding said carriage means along said control rod.