Callaway’s HI-STORM UMAX Underground Storage Facility Rises Above its Subterranean Base Mat

We are pleased to report on the progress of the HI-STORM UMAX construction at Ameren’s Callaway Nuclear Plant. The HI-STORM UMAX support foundation pad (base mat), founded on the bottom of a 25 feet deep pit, now holds 48 Cavity Enclosure Canisters (CECs) (see photo below).

Base Mat Holding 48 CECs, Founded on the Bottom of 25 Feet Deep Pit

The CECs, which provide an all-welded steel enclosure for storage of the multi-purpose canisters (MPC), were manufactured at Holtec Manufacturing Division in Pittsburgh, PA. Each CEC will hold one MPC-37 canister (capacity=37 PWR assemblies) giving the Callaway ISFSI an initial installed capacity of 1776 fuel assemblies. The MPCs were co-produced by HMD and Orrvilon, Inc. (Holtec’s wholly owned subsidiary located in Orrville, Ohio).

All 48 CECs are set, verticality checked, and grouting of each is complete. The Holtec Site Services team averaged 7 CECs set/day vs. the goal of 4-6/day. The team finished setting the CECs in 7 days vs. the anticipated 12 days. The photo below shows the CECs with the biological lid placed on each silo.

CECs with Biological Lids Placed on Each Silo

Backfill and controlled low-strength material (CLSM) placement around the CECs is ongoing. The current schedule, weather permitting, is the completion of CLSM placement by year end.

Controlled Low-Strength Material (CLSM) Placement Around the CECs

Final construction steps include imbedment of each CEC top flange in the ISFSI pad situated at grade level. A massive shop fabricated steel/concrete lid designed to withstand severe environmental phenomena and beyond design basis threats will protect the MPC stored inside each CEC.

The forerunner of the Callaway HI-STORM UMAX ISFSI, the six non-ventilated underground storage facility (for low heat loads) at PG&E’s Humboldt Bay, installed and operating since 2007 (see photo below).

Non-ventilated Underground Storage Facility for Low Heat Loads at PG&E’s Humboldt Bay

The pool to pad loading dry run at Callaway is scheduled for March-April, 2015 with the first loading campaign, consisting of six MPC-37 canisters, scheduled to begin in early May, 2015.

Ameren Missouri is the owner and operator of Callaway Energy Center located near Reform, Missouri. Callaway consists of a 1284 MW Pressurized Water Reactor of the Standardized Nuclear Unit Power Plant System (SNUPPS) type design. In the late 1990s, Callaway was equipped under a turnkey contract with Holtec’s “Mixed Zone Three Region Storage Racks”, a Holtec innovation which maximizes the possible storage density in PWR Pools.

Media Files: HH 29.21

Written by Amy Grant

Amy Grant is a graphic designer and web developer. She is the founder of the Southwark Historical Society, a volunteer based group that studies the Southwark Historical District located in Philadelphia, Pennsylvania.