Nondestructive determination of nuclear fuel burnup

Apparatus for remotely measuring the burnup of freshly irradiated nuclear fuel comprising:

• a containment capsule;
• a support member removably disposed within the containment capsule, said member carrying thereon a solid state track recorder material and a layer of fissile material adjacent said recorder material;
• and
• means on the exterior of the capsule adapted to be remotely grasped, for positioning the capsule adjacent to the fuel.

A method for measuring the burnup of nuclear fuel during refueling of a nuclear reactor, comprising:

• removing the fuel from the reactor;
• locating the fuel in an area accessible from above;
• lowering a measurement capsule into close proximity to the fuel, said capsule including a metal container, a central support member removably supported within the container, a recording member carried by the support member, said recording member including a layer of solid state track recorder material adjacent to the support member and a coating of fissile material on the exterior of the recorder material;
• positioning said capsule at a predetermined location for a period of time between approximately one hour and one day;
• removing the capsule from the fuel and recording the time interval during which the capsule was positioned in close proximity to the fuel;
• removing the support member and recording member from the capsule;
• removing the recording member from the support member,
• processing the recording member including the steps of removing the fissile coating, etching the solid state track recorder material, and counting the density of the number of tracks per unit area of track recorder material;
• relating the neutron flux required to produce the track density counted, to the plutonium content of the fuel, to determine the fuel burnup.