US nuclear power company Exelon Corp plans to retire four Pennsylvania generation units due to a fall in profitability.

In connection with the shutdowns, 280 jobs will be cut by late 2011, Chicago-based Exelon announced in a public filing.

The four units are 50 years old and are located at the Cromby and Eddystone power stations in suburban Philadelphia, according to the company.

Three of the units being closed are powered by coal and the fourth operates on natural gas or fuel oil, Exelon said.

The shut downs will be effective from 31 May 2011.

Exelon also announced 500 job cuts and a freeze on executive pay in June, as part of plans to cut operating costs by $350m next year, writes Bloomberg.