- During waste-disturbing activities, such as when waste is retrieved from tanks, additional controls are put in place to protect workers.
- Vapor Control Zones are established and workers inside them are required to wear a self-contained breathing apparatus with a bottled-air supply.
- More than 1,500 chemicals were identified in the tank headspaces, with a Technical Basis identifying 61 as Chemicals of Potential Concern to workers.
- Eliminate vapor sources
- Establish administrative controls
- Install engineered controls
- Provide personal protective equipment
- Phase 1— Program enhancement; data collection & testing; R&D; recommendations for Phase 2
- Phase 2 — Complete R&D; deploy new technology/equipment; institutionalize controls To read the TVAT report in its entirety, click here.
Subsequently, a number of expert panels have evaluated WRPS programs and the work being performed at the tank farms. These included: DOE EA-32, Center for Disease Control, National Institute for Occupational Safety and Health (NIOSH) and the Hanford Vapors Expert panel, amongst others. Additionally, Stoneturn Consultants (STC), third-party independent consultant representing the Hanford Atomic Metal Trades Council under the HAMTC/WRPS Memorandum of Agreement, reviewed the IH program with a specific focus on cartridge testing. Later, STC reviews took a broader, more holistic approach to the tank farms work to evaluate the effectiveness of engineering controls and other methods. The combined assessments resulted in 371 recommendations this culminated with the Comprehensive Vapor Action Plan and its implementation. link here.
How are we going to protect workers wearing Air Purifying Respirators (APR's) from COPC's with OEL's that are lower than the ability of DRI's to detect in real time?
The APR filter cartridges currently in use have been tested for breakthrough against levels of headspace vapors that have been measured in the tank farms. The test results have shown that the results meet the manufacturers recommendations. Those reports can be reviewed at this link.
Let’s look at how DRI information is used by the IH in real time. When the headspace vapors are emitted from inside the tank to the tank farm air, all of the individual chemicals in the mixture are diluted to the same extent. Although they each dilute to far lower concentrations once outside of the tank, the ratio of one chemical to another is the same as it was in the tank headspace. This relationship allows us to use DRI to monitor one or more of the TVIS compounds to determine when an upset condition occurs. This is the basis of leading indicator(s) principles. Here is a link to the leading indicators report.
An example will illustrate how this works: Imagine a tank headspace with only two compounds: 100 ppm ammonia and 5 ppb n-nitrosodimethylamine (NDMA). The rest of the headspace is made up of plain air.
When these gases exit the stack or breather filter, they are both diluted equally. To simplify the math for our example, let’s assume a dilution factor of 100. That results in a tank farm air concentration of 1 ppm ammonia and 0.05 ppb NDMA. Even though we cannot measure the 0.05 ppb (which is below the OEL) of NDMA with DRI, we can easily measure the 1 ppm of ammonia which comes along with it.
Now let’s imagine that the DRI reading for ammonia changed from around 1 ppm up to, say, 10 ppm. The IHT would know something in the farm area or inside the tank had changed. At that point, the work area would be put into a safe condition, and personnel would exit until IH had either determined the cause of the upset, or that conditions had returned to normal, at which time work could re-commence.
In this case, we do not need to know the NDMA level in real time to be assured that the workers are still safe. We understand that NDMA would increase in the same ratio as ammonia. Although it would be at about 0.500 ppb (above the 8-hour time-weight average OEL level), the IH action would quickly remove everyone from the area. Thus, workers would be in air containing NDMA for just seconds or minutes before they are evacuated, far less than the 8 hours on which the acceptable limit is based. So, if the APR cartridges worn by the workers have been shown to filter out headspace levels of NDMA for hours at a time, and the workers leave the area after just minutes of being in NDMA above the OEL level, then we are confident that there is no risk to the workers of adverse effects from these headspace vapors.
This is an in-progress document providing answers to employee questions raised in 2015. Q&As have been placed in general categories for ease of use. Answers may be updated as new information is developed or when evaluations of the item are completed.
This is an in-progress document providing answers to employee questions. Q&As have been placed in general categories for ease of use. Answers may be updated as new information is developed or when evaluations of the item are completed.