Demolition of Hanford’s Plutonium Finishing Plant halted Monday after a spread of radioactive contamination outside the plant Friday afternoon.
The cause is being investigated but demolition is expected to restart this week.
About 4:45 p.m. Friday a radiation monitor alarm sounded near the part of the plant where demolition had been underway earlier but had stopped for the day. A work crew was outside applying fixative to contain any radioactive contamination on a waste pile.
Workers at the plant took cover as a precaution as the alarm was confirmed as valid about 10 minutes after it sounded.
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“Workers acted safely and appropriately when contamination higher that expected was discovered,” contractor CH2M Hill Plateau Remediation said in a statement released Monday.
Contamination was found beyond the outdoor zone where it was planned to be contained during the open air demolition, but still close to the demolition project. It did not spread beyond the boundary surrounding the plant.
Radiological surveys found low levels of contamination on workers’ protective clothing, but no contamination on the street clothing they wore underneath or their skin. Nasal smears found no evidence of inhaled contamination.
CH2M Hill is continuing to investigate how the contamination spread and then will use information to reduce the risk of recurrence, it said. Extensive air monitoring is done during demolition to protect workers and the environment.
Demolition of the plant began at the beginning of November, with tear down starting on the Plutonium Reclamation Facility built onto one end of the main plant. Demolition continued on the Plutonium Reclamation Facility on Friday.
Demolition already had halted in the first half of January when temperatures dropped down to about 20 degrees, which was too cold for some equipment.
Demolition workers were assigned then to the continuing clean out of the main part of the plant, where preparations still are being made for demolition. More asbestos than expected has been found in some areas and DOE said earlier this month that its contractor would hire 20 more workers to help clean it up.
The tear down has started only on the Plutonium Reclamation Facility and the McCluskey Room, which connects the Plutonium Reclamation Facility to the main plant.
DOE expects to have the Plutonium Reclamation Facility torn down in late April and the fan house — with the exception of the explosive demolition of the stack — down in August, it said earlier this month.
The goal is to have the entire plant torn down to slab on grade by September 2017 to meet a legal deadline.
The plant processed almost two-thirds of the plutonium for the nation’s nuclear weapons program during the Cold War.