Frequently Asked Questions (FAQs)

Hanford’s 177 underground waste tanks contain a complex mixture of radioactive materials and hazardous chemicals. In fact, more than 1,800 chemicals have been identified in the tank waste. Of these, about 1,500 chemicals are present in the headspace of the tanks, which need to be vented to the atmosphere to prevent potentially flammable concentrations of gases in the tanks. The vapors are filtered to remove radioactive contaminants, but chemical vapors have the potential to enter workers’ breathing space.

Chemicals are routinely monitored in the tank farms. When a Personal Ammonia Monitor alarm occurs the TF-AOP-015 (Tank farm - Abnormal operating procedure - #015) is initiated.

In the event of an AOP-015, the affected area is evacuated and employees are moved upwind. Other workers in adjacent areas are notified. Access to the area is restricted. Employees who exhibit symptoms are sent to the onsite medical provider for an evaluation. Medical evaluation is also offered to employees who don’t have symptoms.

Washington River Protection Solutions has continued to improve its tank farm industrial hygiene program with additional staff, new equipment, updated procedures, and improved worker training.

• 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.

The foundation for the Hanford tank farms Chemical Vapor Program is a Technical Basis established by an independent panel of experts. The Technical Basis integrated the results of waste characterization, toxicology, field monitoring, personal sampling, environmental modeling, and chemical process data for the tank farms. The Technical Basis characterized the chemicals in the tank waste and the tank headspaces, identified the 61 chemicals of potential concern and established occupational exposure limits for the COPCs. The Technical Basis has been reviewed by outside experts and determined to be appropriate for Hanford’s tank farms. Using accepted industry data and independent experts, Occupational Exposure Limits (OELs) were established for all of the COPCs. Federal law mandates that worker exposures be kept below 50 percent of the OELs. Administrative limits for Hanford tank farm workers were set at 10 percent of the federal OELs. The tank farms industrial hygiene program meets National Institute for Occupational Safety and Health (NIOSH) protocols. For a complete list of the COPCs, click here.

Occupational Exposure Limits (OELs) protect workers and prevent long-term health effects. OELs have been established for all 61 Chemicals of Potential Concern (COPCs). Federal law mandates that worker exposures be kept below 50 percent of the OELs. WRPS has instituted Administrative Control Levels for COPCs at 10 percent of the OELs.

WRPS uses a hierarchy of controls to manage chemical vapors in Hanford’s tank farms.

1. Eliminate vapor sources
2. Establish administrative controls
3. Install engineered controls
4. Provide personal protective equipment

There are high concentrations of chemicals in the headspace of Hanford’s underground waste tanks. The headspace is the area inside the tank between the surface of the waste and the domed top of the tank. Openings to the 75-foot diameter headspace, called risers, protrude through the soil above the tanks. “Fugitive vapors” – chemical vapors that migrate from the tank headspace into the work areas through openings in the tank dome for pipes, instrument cables and openings in valve pits – are controlled by sealing the pathways with foam. Periodic monitoring is conducted to discover and control fugitive vapors in an ongoing effort to keep them out of the workers’ breathing space.

Respiratory protection is another component of the Industrial Hygiene program. Tank farm workers are supplied with a variety of respiratory protection equipment, including use of supplied air. Due to an ongoing Stop Work order, any work conducted within a tank farm requires the use of a supplied-air respirator. Workers wear a self-contained breathing apparatus, or SCBA, that provides fresh air from a bottle on the worker’s back. Bottles typically have a 30- to 60-minute supply of air. SCBA units provide fresh air through a regulator that is attached to a mask that seals to the user’s face. SCBA is the respiratory protection prescribed for situations that require the most protection.

The Tank Vapor Assessment Team, or TVAT, report was issued by a team of independent experts led by the Savannah River National Laboratory. The TVAT has 10 overarching recommendations and 47 specific recommendations to enhance the WRPS Industrial Hygiene program. WRPS established a TVAT Implementation Plan that addresses all the recommendations in the report. The plan is a multi-year, phased project.

• 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.

Workers are protected from potential effects of airborne chemicals by wearing the minimum level of respiratory Personal Protective Equipment (PPE) that still provides adequate health protection. The selection of the APR as respiratory protection is made by the Industrial Hygienist (IH) based collectively on personal, source, and area sampling data, as well as available monitoring data. The level of protection and the designated filter cartridge are prescribed by the WRPS IH program on the Respiratory Protection Form (RPF). The personal, area, and source data are considered because of the Direct Reading Instrumentation (DRI) limitations to detect some of the COPCs 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.