Boilers

Dismantling Zion

Issue 6 and Volume 5.

ZionSolutions is tasked with the largest plant decommissioning project in U.S. history

By Brian Wheeler

Dismantling a nuclear power plant is a job that takes time, something EnergySolutions knows all too well. Decommissioning activities have been completed at only 10 commercial nuclear power plants in the U.S. EnergySolutions has provided decontamination and decommissioning services at six of those sites. ZionSolutions, a subsidiary of EnergySolutions, is taking on a 10-year, $1 billion project to complete the largest commercial nuclear power decommissioning project in U.S. history.

Zion Station
(1) The Zion Station on the western shore of Lake Michigan is a former nuclear power plant that has been converted into an electrical grid voltage-stabilizing facility. Photo courtesy of Exelon Corp.

The Zion Station’s two Westinghouse pressurized water reactors entered service in 1973 and 1974. After more than 20 years of operation, both units at the plant on the western shore of Lake Michigan in Zion, Ill., were permanently shut down in 1998. Commonwealth Edison, owner of the plant at the time, made the decision to close the plant, stating the continued operation of Zion was not financially feasible. The site has since been converted into an electrical grid voltage-stabilizing facility, with both units’ generators having been connected to condensers to provide stability to the grid in the northeast Illinois region.

Zion's two reactors
(2) After more than 20 years of operation, Zion’s two reactors were shut down on January 15, 1998. All other photos courtesy of EnergySolutions and ZionSolutions.

In 2008, Exelon submitted an application to the U.S. Nuclear Regulatory Commission requesting approval for a transfer of the possession license, management authorities and decommissioning trust fund to ZionSolutions. In September 2010, the NRC approved the license transfer to ZionSolutions and decommissioning activities started. ZionSolutions is now well into the project, having cut openings in both containment buildings.

“This is the first two-unit plant to be decommissioned in the country and is the largest commercial power plant to be decommissioned,” said Pat Daly, general manager for ZionSolutions. “The work takes a long time.”

Unit 2
(3) Unit 2 containment opening steel liner removal in June 2011

Daly said workers are currently segmenting the reactor vessel internals in Unit 2, while progress continues on the cutting of coolant pumps, valves and tops of steam generators in Unit 1. Construction has started on the interim spent fuel storage facility used to house spent fuel assemblies. In total, 65 casks will be built on a pad covering about half an acre at the Zion site. Sixty-one casks, about 18-feet-tall and 11 feet in diameter, will be used to store fuel while four additional casks will be used for greater-than-Class C waste. In the U.S., more than 1,400 canisters of used fuel are stored in 63 interim storage facilities.

The first shipment of low-level radioactive waste is expected to take place in November or December, Daly said. Twenty-eight gondola cars have been delivered to the site to complete the first shipment to EnergySolutions’ permanent waste storage site in Clive, Utah.

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(4) Unit 2 hatch platform segmentation.

ZionSolutions has an in-depth schedule to complete set milestones in the near future. In2013, Daly said ZionSolutions will finish reactor vessel internal segmentation on Unit 2, begin internal segmentation on Unit 1 and begin moving spent fuel from the spent fuel pool to the recently-constructed casks. The fuel campaign is expected to be complete in 2014, as well as all reactor vessel work.

All equipment and residual contamination in the buildings will be removed. After removal of all equipment, the final phase is demolition of all on-site buildings.

“Then we complete a final status survey where we verify that the cleanup is up to the standard of the NRC,” said Daly.

First greater-than Class C
(5) First greater-than Class C (GTCC) canister arrival in August 2011.

Throughout the 10-year decommissioning process, Exelon will remain owner of the plant’s used fuel. ZionSolutions cannot comment as to how long the fuel will stay on-site. Once the decommissioning project is complete in the 2020-timeframe, the spent fuel facility will be turned back over to Exelon. The agreement ZionSolutions has with Exelon gives ZionSolutions ownership of the plant, liabilities and trust fund, but Exelon still owns the land and the spent fuel placed in storage.

“(Exelon) could use the land for other uses if they decide to do that,” said Daly.

Exelon said the two-acre site will be available for other unrestricted commercial uses in the future.

Unit 2 containment hatch
(6) Unit 2 containment hatch removal in March 2011.

An existing switchyard and related equipment will also be housed on site as it is of importance to the electricity supply in northern Illinois, according to Exelon.