Radioactive particles have been measured at elevated levels for the first time in the outer safety space of the Hanford double-shell tank known as AY-101. The contractor that manages the tank told employees "we recently discovered higher-than-expected radioactivity readings" from filters that are part of the tank’s continuous air monitor (CAM).
"The filter contained traces of radioactive americium, cesium and plutonium, raising the possibility that the material is from tank waste that has escaped from the primary shell of the double-shell tank," wrote Rob Gregory, chief operating officer of Washington River Protection Solutions.
Sources tell KING 5 that alarms went off last week to alert staff of the presence of “hot” (radioactive) particles trapped in filters of the tank’s continuous air monitor (CAM). The sources say this is the first time readings of this sort have been detected in AY-101.
The U.S. Department of Energy confirmed to the state that radioactive particles had been detected by filters circulating air from inside AY-101, according to officials with the Washington Department of Ecology.
But DOE's Office of River Protection, which oversees the tank farms at Hanford, said no alarms went off indicating radioactive particles had been detected. On Twitter, ORP said: "Note that the elevated readings were found during routine inspection of annulus ventilation; no alarms went off." WRPS's Gregory said "readings were well below alarm levels" in his email to staff.
DOE added, "Leak-detection instruments, located throughout the annulus, are monitored to detect any liquid on the floor of the annulus space. No liquid has been detected in the AY-101 annulus."
AY-101 is one of 28 underground double-shell tanks at Hanford that store millions of gallons of the most radioactive and chemically contaminated nuclear waste at the site. AY-101 has the same design as AY-102, a tank that was found to be leaking five years ago and was at the center of a year-long KING 5 investigation, “Hanford’s Dirty Secrets.”
The DOE office, again via Twitter, said: "For perspective, AY-101 was built with thicker steel and improved construction methods than AY-102."
Related story: Leak worsens in massive Hanford tank holding nuclear waste (April 18, 2016)
The citizen watchdog group Hanford Challenge also said sources of its own confirmed the detection of elevated radiation levels outside the primary liner of AY-101. The group’s sources say the by-products confirmed include Cesium-137, plutonium, and a high-beta emitter (most likely Strontium-90) that are all constituents commonly found in Hanford’s underground tanks.
The executive director of Hanford Challenge, Tom Carpenter, said this recent event has “serious implications” for the Hanford Site.
“Simply put, Hanford is nearly out of double-shell tank space, especially after pumping out AY-102 and emptying some of the shakier single-shell tanks…This is no other realistic option but to begin building new tanks immediately,” said Carpenter.
Elevated radiation and radioactive materials found in the CAM filters was the first indication that AY-102 was leaking. This was a red flag for the Department of Energy (DOE), which owns Hanford, 15 years before confirmation of the leak. Those high CAM filter readings in the 1990s were dismissed by DOE and its contractors at the time.
WRPS's Gregory said a visual inspection of the AY-101 annulus showed no signs of a leak. But he said other explanations for the presence of radioactive particles include: "cross contamination between the primary and annulus ventilation systems, contamination from a transfer line that runs through the annulus, or contamination brought into the annulus through the ventilation air supply."
The nuclear waste stored at Hanford, near Richland, is the result of decades of plutonium production for the country’s weapons defense program. Plutonium from Hanford fueled the bomb dropped on Nagasaki and then was used to build up the U.S. nuclear arsenal throughout the Cold War.
AY-101 is a 45-year-old tank that was not designed to hold hot, nuclear waste for this long.
Read full statement from U.S. Dept. of Energy:
Hanford tank farms contractor Washington River Protection Solutions (WRPS) routinely samples air in the annulus, the space between the primary and outer shells, of Hanford's double-shell tanks. During routine filter inspections, higher than normal readings for contamination were found on filter paper installed on a continuous air monitor for Hanford's double-shell tank AY-101 annulus. While these readings were higher than normal, they were well below the alarm level.
Leak-detection instruments, located throughout the annulus, are monitored to detect any liquid on the floor of the annulus space. No liquid has been detected in the AY-101 annulus. Following confirmation of the filter sample readings, workers completed a video inspection of the AY-101 annulus and the results showed no visual change from previously conducted inspections and no indication of a leak. DOE is conducting engineering analysis and assessments to determine potential causes of the readings.
We continue inspections of the continuous air monitor, as well as video surveillance of the annulus.
DOE and WRPS are committed to ensuring the safety of the Hanford workforce, the public and the environment.