Retrieval of double-shell tank AY-102 is now complete, with workers removing more than 725,000 gallons of waste from the tank. Read more about the effort.
This last phase of retrieval used extended-reach sluicer technology to complete the work before March 4, 2017, an important Settlement Agreement deadline with the State of Washington.
A tank chemical vapor controls and monitoring plan was implemented to protect worker safety and health. Progress on the project and results of vapor monitoring have been communicated broadly to employees and other stakeholders throughout this phase of retrieval.
In late 2012, a small leak of high-level radioactive waste was discovered from the inner shell of double-shell tank AY-102 into the annulus, the space between the inner and outer shells of the tank. The waste is contained in the 30-inch wide annulus and does not threaten the environment.
Tank AY-102, the oldest of Hanford’s double-shell tanks that began operating in 1970, held 850,000 gallons of waste.
Waste Retrieval & Worker Safety
Protecting tank farm workers from industrial, radiological and chemical hazards is WRPS’ highest priority.
Plans are in place to mitigate and control the present hazards, including chemical vapors.
These controls may include:
- Work conducted on nights and weekends when fewer workers are present
- Vapor Control Zones established where supplied air respirators are required
- Restricted access to areas near the work zone
- And state-of-the-art industrial hygiene monitoring and sampling to detect and prevent exposures
Sampling during the AY102 to AP-102 retrieval consisted of Industrial Hygiene direct reading instruments, the Vapor Monitoring Detection System (VDMS), and the RJ Lee Mobile Laboratory.
During this period two area readings were detected above an Action Limit. The first occurred during a urethane scraping operation in the AX-103A pit, where the personnel involved would have been adequately protected from VOCs by the use of respiratory protection (e.g. SCBA). The second detection was the result of a malfunctioning AreaRAE that was removed from service and replaced with another. No other detections were seen after the instrument was replaced with a functioning AreaREA.
The Mobile Lab takes measurements every two seconds. During this time, nine compounds were detected. None of these detections were sustained, and were similar to those found while the mobile lab was sampling offsite.
The AP Stack showed consistent readings for ammonia throughout the retrieval and non-retrieval periods. IH DRI readings did show elevated levels of ammonia as expected, however, elevated ammonia levels were not found in the farms during or after retrieval operations.
A total count of over 83 million measurements were taken throughout this time period.
The analysis of the data shows there does not appear to be a measureable increase in tank farm vapor concentrations either during or after the retrieval periods inside the tank farms, along the AP fence line, or around the A Complex. See below for more detail.