Task: Question Generation
Input (English): Passage: In 1967, Pennsylvania leased the reactor complex to the Nuclear Materials and Equipment Corporation (NUMEC), which already had a federal license to work with nuclear materials. NUMEC, which soon became a subsidiary of Atlantic-Richfield Corporation (ARCO), set up a large irradiator in what had been the reactor pool. The irradiator contained over 1 million curies of cobalt-60 to produce intense gamma rays, which were used to sterilize medical equipment and irradiate food and wood. In the spring of 1967 the state had concluded that radiation contamination at the Quehanna site "could never be completely cleaned up", and so was glad to find a tenant with nuclear experience.
A group of NUMEC employees discovered that irradiating hardwood treated with plastics produced very durable flooring. In 1978 they formed PermaGrain Products, Inc. as a separate company from ARCO, and purchased the rights to the process as well as "the main irradiator, a smaller shielded irradiator and related equipment". PermaGrain sold the flooring for use in basketball courts and gymnasiums, and was the longest occupant of the Quehanna facility, operating there from 1978 to December 2002. PermaGrain also let Neutron Products, Inc., a Maryland company, do cobalt-60 work in its hot cells, which required an amendment of their license from the Nuclear Regulatory Commission (NRC, the successor to the AEC).In 1993, strontium-90 contamination in the reactor facility led the NRC to require PermaGrain to begin decontamination work, and the Pennsylvania DEP commissioned a "site characterization study". In 1998, a firm named NES began the cleanup work; they changed their name to Scientech in 1999 and to EnergySolutions in 2006. The cleanup was originally estimated to take six months; by 2006 it had taken 8 years and cost $30 million. According to the Pennsylvania Department of Environmental Protection's (DEP) Bureau of Radiation Protection: "Inadequate characterization of the site and the presence of ongoing industrial operations resulted in many project delays and increased costs." The hot cells proved to have more radioactive sources than originally thought. In October 1998 a Scientech worker doing decontamination cut a tube in hot cell number 4, which accidentally released strontium-90 into PermaGrain's work area. As a result, a robot had to be constructed to remove 3,000 curies of cobalt-60 in two of the hot cells, dismantle cell 4, and decontaminate the rest remotely.
Output (English): How many years did the cleanup that was estimated by the company that was the longest occupant of the Quehanna facility to take six months actually take?