WIPP: Full air filtration mode a 'conservative decision' to protect environment, workers
Air in the underground facility of the Waste Isolation Pilot Plant continues to be heavily filtered to prevent radioactive particles from reaching the outside air, despite research that suggests it is not longer needed.
Filtration reduces the amount of work that can be done in the underground nuclear waste repository – now emplacing waste and mining simultaneously – about 2,000 feet underground.
The filtration is used to ensure air released by WIPP is not contaminated, after a drum of transuranic waste ruptured in portions of the facility in 2014 and released radiation into the outside air, resulting in the facility's closure for three years.
WIPP reopened in January 2017, and it was deemed safe to resume underground activities, but officials at the U.S. Department of Energy said continued filtration is a “conservative” measure to prevent contamination of the air released by WIPP.
“Based on where we are now, we are choosing to still operate in filtration mode,” said Todd Shrader, manager at the DOE’s Carlsbad Field Office. “We concede it does limit our air, but it’s a conservative decision.”
But at the Carlsbad Environmental Monitoring and Research Center (CEMRC), a DOE-funded watchdog lab that continuously studies WIPP activities, research suggested air filtration is unnecessary to keep radiation out of the air on the surface.
CEMRC Director Russell Hardy said if air was released by WIPP without filtration, levels of radiation would be below federal standards for nuclear exhaust.
“Most of the contamination has been cleaned up by their decontamination efforts,” Hardy said. “If they were to resume unfiltered release, they would be below the EPA’s (U.S. Environmental Protection Agency) requirements for a nuclear facility.”
Although Hardy contended it could be safe to release the air into the environment, he said filtration also protects workers operating in contaminated areas.
CEMRC does not measure radiation levels of the air at contamination zones, measuring levels from air directly before and after it passes through the HEPA filters.
A March 2017 paper published by CMERC and presented that month at the DOE’s annual Waste Management Conference in Phoenix suggested ceasing air filtration was not only possible, but needed to ensure efficient operations at WIPP.
The paper cited two years of data taken from measurements of radioactive elements in the air released by WIPP, concluding complete filtration is not necessary to ensure levels are safe.
Radiation levels consistently declined since a spike resulting from the 2014 release, Hardy said, and remained safe as of May.
If higher, dangerous levels are detected, an alert system will notify the DOE.
“Unfortunately, reduced airflow in the WIPP underground poses a significant challenge to the recovery efforts and has exacerbated the inherent safety issues of working underground,” read the paper. “Instead, a potential way to improve ventilation of the WIPP underground may be to simply resume the unfiltered discharge of underground exhaust directly to the environment.”
The paper argued that WIPP’s current air flow levels only allow two pieces of diesel equipment in the underground at a given time, sharply reducing the amount of activity possible.
“The current limited ventilation rates at the WIPP underground pose a significant challenge in the recovery and resumption of waste disposal operations at WIPP,” read the paper.
“Increasing ventilation capacity is a principal requirement in the reopening and resumption of waste disposal operations at WIPP,” read the paper. “The installation of additional (and) new ventilation systems in several stages is planned to enable WIPP underground operations to return to full operation capacity such as those that existed prior to the underground radiation event.”
But Don Hancock, director of the Nuclear Waste Program at the Southwest Research and Information Center said he doesn't envision WIPP could ever operate without filtering its air.
"There's no upside, and the downside is there is still contamination in there. You need filtration for that," Hancock said. "The lack of ventilation clearly slows them down some, but they (the DOE) themselves say they have room in Panel 7 until 2021. So what's the point?"
He said the contamination in Panel 7 will continue to put workers and the outside environment at risk for the foreseeable future, and that the facility is several years from sealing the panel.
Worker safety, he said, should be a higher priority than increasing emplacements.
"If you say worker safety is the No.1 priority, then all these benefits are not the top priority," Hancock said. "The lack of ventilation and contamination is a bad thing, but the biggest concern is workers in the underground."
Air is filtered at WIPP using the Underground Ventilation Filtration System (UVFS), which uses high-filtration particulate air (HEPA) filters to cleanse exhaust air from the underground, drawing the air through an exhaust shaft before releasing into the atmosphere.
The HEPA filters are housed in WIPP’s Exhaust Filter Building, pulling 60,000 cubic feet per minute (CFM) of air by each of three fans.
Two interim, skid-mounted HEPA filters and fan units can also be used to add about 54,000 cfm to underground air flow.
"This system also draws potential airborne contamination away from normally occupied locations in the underground,” said Donavan Mager, spokesman for the Nuclear Waste Partnership. “These features reduce the consequences to the facility worker by drawing potential contamination away from normally occupied areas of the underground.”
The maximum airflow at WIPP was currently reported at about 140,000 cfm, but before the 2014 incident when the air was unfiltered, air flow reached up to 425,000 cfm.
The reduction in airflow means a reduction in the diesel-powered equipment needed for mining and emplacement activities.
“The number of workers allowed underground is not affected by the air filtration status,” Mager said. “An increase in total airflow would increase the amount of diesel powered equipment that could be operated underground and the areas of the underground that could be fully utilized.”
He said air at WIPP flows from mining areas toward waste emplacement and then into exhaust, leaving the amount of air unaffected by the simultaneous salt mining and waste emplacement, but more air flow is required to add equipment.
The incident in 2014 happened in Panel 7, contaminating several portions of the area where waste is being emplaced.
When Panel 8 is fully mined, and Panel 7 is full, Mager said the contaminated area will be sealed off, and air filtration might not be needed.
Currently, anyone working in a contaminated portion of WIPP, where waste is being emplaced, must wear protective breathing equipment.
“There may be an opportunity in the future to move away from filtering the exhaust 100 percent of the time after we fill Panel 7, which is radioactively contaminated from the 2014 events,” Mager said. “We plan to revisit this issue after we complete disposal operations in Panel 7."
Panel 8 was expected to be fully mined by 2020, but in the meantime a safety significant confinement ventilation system (SSCVS) is being developed to rebuild WIPP’s air flow system.
The $273 million project will provide up to 540,000 cfm, either filtered or unfiltered, into the underground.
The SSCVS was designed, Mager said, to remain operational during maintenance activities, allowing more operations in the underground.
The SSCVS was expected to go online in 2021, and multiple bids were received for the contract, Mager said, with groundbreaking planned for mid-May.
Hancock said the new system could allay some air-quality concerns, but argued workers should always wear protective gear when near contaminated areas.
"Anything that improves ventilation in the underground is a good thing," Hancock said. "(The SSCVS) will add additional air for workers in the underground. I agree with the decision to keep workers in protective equipment."
Read the paper from CMERC:
Adrian Hedden can be reached at 575-628-5516, firstname.lastname@example.org or @AdrianHedden on Twitter.