Abstract: Given are a method and apparatus for measuring nondestructively and non-invasively (i.e., using no internal probing) the burnup, reactivity, or fissile content of any material which emits neutrons and which has fissionable components. No external neutron-emitting interrogation source or fissile material is used and no scanning is required, although if a profile is desired scanning can be used. As in active assays, here both reactivity and content of fissionable material can be measured. The assay is accomplished by altering the return flux of neutrons into the fuel assembly. The return flux is altered by changing the reflecting material. The existing passive neutron emissions in the material being assayed are used as the source of interrogating neutrons.

Abstract: A new apparatus is used to substantially instantaneously obtain a profile of an object, for example a spent fuel assembly, which profile (when normalized) has unexpectedly been found to be substantially identical to the normalized profile of the burnup monitor Cs-137 obtained with a germanium detector. That profile can be used without normalization in a new method of identifying and monitoring in order to determine for example whether any of the fuel has been removed. Alternatively, two other new methods involve calibrating that profile so as to obtain a determination of fuel burnup (which is important for complying with safeguards requirements, for utilizing fuel to an optimal extent, and for storing spent fuel in a minimal amount of space). Using either of these two methods of determining burnup, one can reduce the required measurement time significantly (by more than an order of magnitude) over existing methods, yet retain equal or only slightly reduced accuracy.

Abstract: A magnetoresistive bubble detector which includes an expander, a first and second detector element and a dummy element is disclosed. An expanded bubble is propagated from the first detector element to the second detector element. The detectors are coupled in pairs with the first element of one detector and the second element of the other detector connected in a bridge circuit with the dummy elements. Two independent streams of spaced-apart bubbles are detected within the bridge circuit.

Abstract: A magnetic memory system is provided that includes magnetic domain data chips having a block replicate organization wherein the system may include data chips having one or more defective minor loops. A dedicated minor loop is provided on the chip to store a redundancy map for locating the defective minor loops. The dedicated minor loop also provides for storing a synchronization pattern for initializing the system by having each minor loop properly addressed for transferring magnetic domains. The dedicated loop can only be accessed by a separate swap pin preventing a write operation by the user thus preserving the data stored therein.