The Department of Energy needs to do a better job of evaluating and controlling safety risks in hazardous cleanup work at Hanford, the Defense Nuclear Facilities Safety Board said after a review of safety systems at the Plutonium Finishing Plant.
Work at the Hanford Plutonium Finishing Plant is nearly done as DOE faces a legal deadline to have the contaminated plant cleaned out and torn down to ground level by Sept. 30, 2016, acknowledged safety board vice chairman Jessie Roberson in a letter to DOE.
But DOE has more hazardous cleanup work ahead at Hanford that could be made safer by the findings at the Plutonium Finishing Plant, said the defense board.
DOE contractor CH2M Hill Plateau Remediation Co. developed a plan to secure and downgrade the systems in place to ensure safety at the Plutonium Finishing Plant as cleanup work there has progressed.
Major milestones have been reached to reduce some of the hazards there, including stabilizing 20 tons of plutonium-bearing materials and shipping it off site and removing 90 percent of the large pieces of processing equipment.
The safety board staff reviewed the plan to make sure it provided an adequate strategy for decommissioning safety controls, particularly in the ventilation system because of reliability issues of its aging fans and its importance to safety.
The Plutonium Finishing Plant’s safety plans rely on the ventilation system to prevent the release of radioactive material in the event of accidents, such as a fire, explosion or spill of radiological material.
The review team found that significant improvements had been made to replace aging fan components and in maintenance to prevent failures. But it was concerned with Hanford officials’ evaluation and acceptance of safety risks at the plant.
DOE has accepted some high risk accident scenarios, such as facility fires, equipment explosions, earthquakes and an airplane crash, because the plant will not be left standing much longer and no cost effective way to control such risks, the review team said.
Such scenarios would not put the public at risk miles away from the plant, but would pose a radiation risk to workers.
The review team concluded some simple and cost-effective controls were available. For instance, it could put formal limits on the amount of waste contaminated with plutonium stored in Building 242-Z.
In response, CH2M Hill officials agreed to review high risk scenarios for additional controls that would reduce risk.
In another case, the air pressure maintained in a low contamination zone in one of the plant’s buildings may not prevent an unfiltered release of some radiological materials during an accident, the team found. The pressure had been set to control air flow to protect some vital equipment from contamination.
CH2M Hill officials told the safety board staff they would evaluate changing the pressure requirement, although they could not guarantee a schedule for the evaluation because of a tight budget.
In a third case, Hanford officials had not maintained a high enough safety classification for electrical power, instrument air and building zone pressure controls for the ventilation system that is vital to safety, the review team found.
Failure of those support systems could prevent the ventilation system from performing its safety function.
A higher safety classification would have required enhanced inspections and maintenance to detect degradation of systems, including detecting leaks in the instrument air system.
Hanford workers had not completed inspections and repairs of potential leaks in the instrument air system detected in late 2013, the review found. The system operates pressure transmitters and dampers to control airflow and building pressure as part of the ventilation system.
DOE officials agreed to investigate the issue.
The review team also found that adequate surveillance was not required for confirming that HEPA filters were protective, leading to the potential for diluted radioactive releases from the plant’s stacks during an accident.
Hanford contractor and DOE officials said they would review previous technical analyses related to the issue and provide results to safety board staff.