We are pleased to announce that Southern California Edison (SCE) has awarded an Engineering, Procurement, Construction (EPC) contract to Holtec to place the used fuel inventory of the two retired San Onofre Nuclear Generating Station (SONGS) reactors into dry storage. Under the contract, Holtec will construct a HI-STORM UMAX underground storage facility to store 2,668 used fuel assemblies in the MPC-37 multi-purpose canister, each containing 37 used fuel assemblies. HI-STORM UMAX is an acronym for Underground and MAXimum Safety and Security. Holtec will also perform pool-to-pad loading services for all used fuel and non-fuel waste stored in the spent fuel pools of SONGS Unit 2 and 3. To insure a long service life in the site’s salt air environment, SCE has selected the most corrosion resistant grade of stainless steel, 316L grade austenitic stainless steel, for the confinement boundary of the MPC in lieu of the commonly used 304 grade. Likewise, all external surfaces of the storage cavity in contact with the ambient air will be upgraded from carbon steel to stainless steel to minimize in-service maintenance requirements.

Designed for the post-9/11 age, the HI-STORM UMAX’s large subterranean stainless steel lined concrete monolith will store the MPCs in fortified cavities designed to withstand any conceivable threats to its integrity; including tsunamis and earthquakes of intensities exceeding any recorded on earth. Other threats considered in the system design include hypothetical events such as impact from a crashing aircraft, a severe fire (from the burning jet fuel), and a long lasting massive flood.

The low profile of the HI-STORM UMAX storage system will non-obtrusively blend with the environment. The SONGS underground used fuel storage facility defense-in-depth features will also include a state-of-the-art aging management system designed to predict the potential onset of corrosion damage to the integrity of the MPCs decades before any indications are seen.

Another HI-STORM UMAX ISFSI, at the Callaway Nuclear Plant in Missouri, is under construction under a turnkey contract between Ameren and Holtec and is scheduled to be commissioned in 2015. The HI-STORM UMAX ISFSIs at SONGS and Callaway are successors to the first underground storage system devised and implemented by Holtec for PG&E’s Humboldt Bay site in 2007.

The underground storage technology pioneered by Holtec in the past decade is covered by U.S. patents assigned to the Company, which are listed below:

  • 61/625,869 (provisional)
  • US 7,068,748 B2
  • US 7,590,213 B1
  • US 7,330,526 B2
  • US 8,098,790 B1
  • US 7,933,374 B2
  • US 8,351,562 B2
  • US 2014/0226777A1/WO/2013036970 (pending)
  • US 7,676,016 B2
  • US 2011/0286567 (pending)
  • US 2010/0150297 (pending)
  • US 8,625,732

In our view, selection of the underground storage system at SONGS, together with the use of underground storage at Humboldt Bay and the HI-STORM UMAX at Callaway are validation that either the HI-STORM UMAX or a densified version of the underground storage system called HI-STORM Subterra, (if the land area use is to be further minimized) are ideally configured to serve as the storage technology for the consolidated interim storage facility(ies) contemplated by the U.S. government. Holtec’s underground used fuel dry storage technologies present robust solutions for storing the nation’s used fuel in interim storage pending the construction of a repository.

Holtec International is a global leader in used nuclear fuel dry storage technologies. Holtec has supplied over 700 dry storage systems worldwide. Holtec’s dry storage systems are currently in use at over 70 nuclear units across nine countries.


Media Files: HH 29.22