Methods and devices to improve performances of RCCA and CEA to mitigate clad strain in the high fluence region

A Rod Cluster Control Assembly (RCCA) for mitigating clad strain, the RCCA comprising:

• a control rod comprising:
• a clad tube comprising an upper section and a lower section, wherein the clad tube defines an inner wall;
• an upper absorber material housed inside the upper section of the clad tube;
• and
• a lower absorber material housed inside the lower section of the clad tube;
• wherein the control rod is configured to have a first annular gap between the upper absorber material and the inner wall of the clad tube and a second annular gap between the lower absorber material and the inner wall of the clad tube;
• and
• a device positioned inside the clad tube between the upper absorber material and the lower absorber material, the device comprising:
• a garter spring configured to exert an outward force against the inner wall of the clad tube, wherein the garter spring comprises coils configured to prevent powder generated from the upper absorber material from passing to the lower section of the clad tube, and wherein the coils are further configured to allow gases to pass between the upper section of the clad tube and the lower section of the clad tube;
• and
• a spacer configured to retain the garter spring, wherein the spacer is further configured to provide a bearing surface for the upper absorber material, and wherein the spacer defines axial openings for collecting the powder generated by the upper absorber material.