SHAPED BURNABLE POISON DEVELOPMENT PROGRAM UNDER THE EURATOM PROGRAM. Quarterly Progress Report, July 1, 1963-September 30, 1963

The number and size of Gd/sub 2/O/sub 3/ poison cylinders were computed for a large boiling water reactor with H/sub 2/O-toUO/sub 2/ ratio of 2.6, a U/ sup 235/ enrichment of 3.3 wt%, and Zr clad. The excess reactivity of the poisoned core was computed for the cold-clean, hot-clean non-voided, and hot full- power condition as a function of Mwd/t. For comparison, these calculations were repeated for B/sub 4/C as the burnable poison element for the same reactor. The use of Gd rather than B/sup 10/ as the burnable poison reduces the moderator and void defect and provides a better match to the poison demand curve. For reactors in the lifetime range of 10,000 Mwd/t, the use of Gd results in a smaller poison residual. However, for lifetimes of approximately 20,000 Mwd/t, B/sup 10/ and Gd are comparable. Methods were developed to account for the netron interaction among clusters of Gd/sub 2/O/sub 3/ poison cylinders. Gadolinia cylinders in Al/ sub 2/O/sub 3/ rods were formed and sintered to 3100 deg F. A reaction between Gd/ sub 2/O/sub 3/ and Al/sub 2/O/sub 3/ begins at 2650 deg F. At 3000 deg F the reaction is complete with the integrity of the cylinders destroyed. The compound GdAlO/sub 3/ is formed. Gadolinia cylinders in UO/sub 2/ rods were formed and sintered to 3100 deg F. A reaction between Gd2O/sub 3/ and UO/sub 2/ begins at 2850 deg F. At 3100 deg F the reaction is complete with the Gd2O/sub 3/ diffused out of its original site and dispersed throughout the UO/sub 2/ matrix. Investigations were begun of the reaction between UO/sub 2/ and Gd2O/sub 3/ mixed with other oxides such as Al2O/sub 3/ in the form of the compound GdAlO/sub 3/. Twenty capsules were loaded with homogeneous mixtures of Al/sub 2/O/sub 3/, B2O/ sub 3/, and Gd/sub 2/O/sub 3/. Initial danger coefficient measurements were performed on the samples in the University of Wisconsin Reactor. (auth