Nuclear Science User Facilities 84 seen in Figure 2, show enrichment of Mn on the outer edges of the loop and Si enrichment on the inner edges. Sequential post irradiation annealing treatments for 1 week each were performed at temperatures between 350°C and 550°C in 25°C increments in order to track the changes in both the Cu-rich precipitates and also the solute segregation to dislocation loops. The precipitates in the 450°C and 500°C annealed samples, also shown in Figure 1, began coarsening but still had slight Mn enrichments.The Si was no longer enriched around the dislocation loops after the 450°C anneal, seen in both Figures 1 and 2, but some slight Mn segregation was still observed.After the 500°C anneal, the loops were only slightly enriched in Mn, but also significantly enriched in Mo and C.These results will be used to better calibrate hardening models and determine the hardening efficiency of dislocation loops and precipitates. In addition, they can help to better understand radiation induced segregation of various elements. Future Activities This work is part of a much larger project designed to create an RPV embrittlement prediction model for extended life fluences.These results Figure 2. Line profiles through dislocation loops showing change in solute segregation around dislocation loops under annealing.