We are pleased to report that the U.S. Patent and Trademark Office (USPTO) has issued patent number 8,158,962B1 to Holtec’s engineers for the design and method of installing the DREAM (acronym for “Device For REActivity Mitigation”) insert technology for used fuel storage racks. The DREAM insert serves to replace the neutron attenuation function of the degraded neutron absorber material in the host rack allowing the nuclear plant to recover the lost storage cells and also increase the criticality safety margins in the pool. DREAM inserts consist of precisely formed shapes of Metamic™ with remote handling features. Metamic is a porosityfree metal matrix composite of aluminum and boron carbide widely used for reactivity control in high density fuel storage racks and dry used fuel storage casks.
Holtec’s long term customer, NextEra Energy (formerly Florida Power & Light) has been the most proactive in exploiting the benefits of the DREAM insert technology having installed over 1000 in Turkey Point Units 3 & 4 pools and an additional 1000 in the twin pools at the Port St. Lucie Plant. The photo (bottom right) shows a typical DREAM insert being installed at a NextEra Energy Plant. According to NextEra Energy, the DREAM insert installation operation was extremely smooth, resulting in successful installation in 100% of storage cells as planned. Commenting on the project, Mr. Richard Pearson, Project Manager, PSL Extended Power Uprate Project stated, “Holtec was a pleasure to work with throughout our project. All documentation and equipment were provided on time or ahead of time. The Metamic inserts and associated tooling to support handling and installation were manufactured at a very high quality level and worked perfectly. The Metamic inserts all installed in the fuel rack cells as designed without any issues.”
Another nuclear plant located in the southern U.S. has 480 DREAM inserts installed in its fuel storage racks, bringing the total number of Holtec supplied inserts to over 2500. Holtec International designed, manufactured, and supported licensing of the inserts for all five plants, including performing the required criticality analyses.
In addition to the removable insert design configuration employed at the NextEra Energy plants, Holtec offers other variations including inserts that are permanently affixed to the fuel pool storage cells and the tubular type that are directly installed in the fuel assembly. All Holtec DREAM inserts are manufactured at the Company’s Nanotec Metals Division located in Lakeland, Florida.
“Holtec has designed, licensed, and fabricated fuel storage racks for over 100 operating reactors world-wide since the mid-1980’s and has pioneered the development of wet storage rack insert technologies. I am confident that there is a DREAM insert design in our technology inventory suitable for every fuel rack design out there,” says Holtec’s Vice President, Corporate Business Development, Ms. Joy Russell.