Final shutdown for Fort Calhoun

25 October 2016

Operators have taken the Fort Calhoun nuclear power plant in Nebraska offline for the final time, Omaha Public Power District (OPPD) announced yesterday. The company said in June that the single-unit pressurized water reactor would be shut down by the end of this year.

Fort Calhoun control room - 460 (Andrew Roger - OPPD)
Reactor operators in the control room shut down Fort Calhoun (Image: Andrew Roger/OPPD)

Senior management at OPPD recommended the plant's closure in May. Extensive modelling conducted by a third party had found ceasing operations at Fort Calhoun and "rebalancing" OPPD's energy portfolio would result in savings of between $735 million and $994 million over the next 20 years. In mid-June, the company's board of directors confirmed the decision to shut the plant. OPPD cited market conditions, including historically low natural gas prices and lower energy consumption, as a major factor behind the board's decision.

At around 8.00am yesterday, when the reactor was operating at about 77% capacity, workers made the first addition of boric acid to the reactor's primary circuit to start the shutdown process. The reactor was down-powered at a rate of 10% per hour. When power output reached 50% at about 11.00am, operators shut down the pumps feeding the steam generator from the condenser. At 12.55pm, when the reactor reached 30% output, the operators initiated a manual reactor trip, which inserted the control rods and shut down the reactor for the final time.

OPPD said the next step involved setting up plant conditions to begin the 36-hour chemical hold, which began at 6.00pm. This involves pumping in high levels of boric acid into the reactor's primary circuit to create a more acidic solution rather than a base solution. This will significantly reduce radioactivity levels and make for safer conditions once the core is offloaded in the next three to five years.

OPPD president and CEO Tim Burke said, "This is an historic and sombre day for everyone at OPPD, past and present. For more than 40 years, the men and women who have worked here have done so with a passion to serve that reflects the very best in our company and our community. I want to acknowledge the work, especially over these last few months, under really tough conditions."

He added, "Employees have remained focused on doing their jobs safely and with the highest levels of professionalism. Everyone should be assured that dedication will continue in the coming months and years as Fort Calhoun Station completes its defueling and begins the decommissioning process."

OPPD has previously said it will use the Safestor decommissioning option for Fort Calhoun, a deferred dismantling strategy where residual radioactivity is allowed to naturally decay over a period of up to 60 years, after which the plant is dismantled. It will cost an estimated $1.2 billion to decommission Fort Calhoun.

At 478 MWe (net), Fort Calhoun was the smallest operating nuclear unit in the USA in terms of its accredited capacity and, unlike larger and multi-unit nuclear plants, cannot spread costs over high levels of production. The plant provided about one-third of OPPD's total electricity generation.

Marvin Fertel, president and chief executive officer of the Nuclear Energy Institute, said in a statement, "The premature closing of Fort Calhoun illustrates the situation in which well operating nuclear facilities are forced to shut down as a result of weak market conditions. This is especially the case with smaller, single-unit facilities in unregulated markets such as in Nebraska where economies of scale make it challenging to generate electricity at a competitive price."

He added, "Fort Calhoun was licensed to operate until 2033. The negative impacts of its untimely closing make it clear there is an urgent need to prevent this from happening to other nuclear plants at risk of premature retirement. Without change, there will be more plant closings resulting in similar negative economic and environmental consequences."

Fort Calhoun had been in commercial operation since September 1973 and the unit underwent extensive operating and safety systems upgrades during an extended outage between 2011 and 2013. The plant is owned and licensed to OPPD, and has been operated by Exelon since 2012. Closure of Fort Calhoun will leave the state of Nebraska with one operating nuclear power plant, Nebraska Public Power District's Cooper 768 MWe (net) boiling water reactor.

Researched and written
by World Nuclear News