Workers investigating the radiological release in the underground Waste Isolation Pilot Plant (WIPP) in New Mexico have found no evidence of a roof collapse but could not explain the discovery of damage to several bags of backfill.
|Waste packages topped with bags of magnesium oxide (Image: WIPP)
The WIPP plant is owned by the US Department of Energy and operated by Nuclear Waste Partnership LLC. The facility disposes of transuranic waste packages from the US military in an underground salt formation. The waste is placed in panels within the facility, each divided into seven rooms. An underground monitor detected airborne radiation within the plant on 14 February.
On 30 April, workers entered room 7 of panel 7, the area of the facility confirmed as the location of the radiological event. By using cameras with telescopic extensions, they were able to view deeper into the room than on earlier entries.
"Eyewitness accounts from employees and video documentation confirmed there are no issues with the roof or walls in the disposal room," WIPP said. While the cause of the release remains unknown, this appears to dispel earlier suspicions that it was the result of a roof collapse within the facility.
However, the workers discovered that several large bags of magnesium oxide within the room had been damaged. Images showed several piles of loose powder on top of waste containers. The cause of the damage to the bags is "still unknown," WIPP said.
|Piles of loose magnesium oxide remain on waste containers at the rear of this photo with no sign of the bags in which it should have been contained (Image: WIPP)
Bags of magnesium oxide - each weighing between 1.4 and 1.9 tonnes - are placed on top of and around the transuranic waste containers to serve as backfill. In addition, if water is present in the repository, the magnesium oxide will react with it to form a compact material that will encapsulate the waste, controlling the solubility of radionuclides.
Operations at WIPP were suspended following the release and only essential staff have since been allowed on site.
Some 90 workers have now returned to WIPP having completed required training at Carlsbad facilities in preparation for resuming their duties. WIPP said, "Upon returning to the site, workers will perform plant and equipment maintenance and restoration, radiological checks, sampling activities, and support work procedure revisions."
No shipments of waste have been delivered to the plant. However, some waste has been taken to Waste Control Specialists' facility in Andrews County, Texas, for temporary storage until operations at WIPP resume.
Researched and written
by World Nuclear News