The U.S. Department of Energy is responsible for one of the largest nuclear cleanup efforts in the world, managing the legacy of five decades of nuclear weapons production. At its peak, this national weapons complex consisted of 16 major facilities, including vast reservations of land in the States of Idaho, Nevada, South Carolina, Tennessee, and Washington.
Nowhere in the DOE Complex is cleanup more challenging than at the Hanford Site in southeastern Washington. Hanford made more than 20 million pieces of uranium metal fuel for nine nuclear reactors along the Columbia River. Five huge plants in the center of the Hanford Site processed 110,000 tons of fuel from the reactors, discharging an estimated 450 billion gallons of liquids to soil disposal sites and 53 million gallons of radioactive waste to 177 large underground tanks.
Plutonium production ended in the late 1980s. Hanford cleanup began in 1989, when a landmark agreement was reached between DOE, the U.S. Environmental Protection Agency, and Washington State. Known as the Tri-Party Agreement, the accord established hundreds of milestones for bringing the Hanford site into compliance with federal and state environmental regulations.
After more than two decades of cleanup, considerable progress has been made at Hanford, reducing the risk the site poses to the health and safety of workers, the public, and the environment.
For more than forty years, reactors located at Hanford produced plutonium for America's defense program. The process of making plutonium is extremely "inefficient" in that a massive amount of liquid and solid waste is generated while only a small amount of plutonium is produced. Additionally, all of the facilities and structures that were associated with Hanford's defense mission must also be deactivated, decommissioned, decontaminated, and demolished. That environmental cleanup project is the work that approximately 11,000 Hanford employees are involved with today.
Crews responsible for Site cleanup are dealing with several different kinds of waste in a number of different forms, with many of the wastes being potentially harmful to people and the environment. Precautions have been taken so that the waste does not contaminate the air, the ground, the water table underneath the ground, the Columbia River, the people who are doing the cleanup work, or the people and environment near the Hanford Site.
Solid waste can be everything from broken reactor equipment and tools to contaminated clothing that a worker wore during the plutonium production activities. The solid wastes were buried in the ground in pits or trenches. Some of the waste was placed in steel drums or wooden boxes before being buried while some of the other waste was placed in the ground without a container to hold it. Depending on when the waste was buried, records about what was buried and where it was buried can be either very good, or in some cases, very bad.
Besides the millions of tons of solid waste, hundreds of billions of gallons of liquid waste was also generated during the plutonium production days. These liquid wastes were disposed of by pouring them onto the ground or into trenches or holding ponds. Unintentional spills of liquids also took place. Liquid wastes generated during the process of extracting plutonium from the uranium "fuel rods" were put into underground storage tanks. Just like with the solid wastes, while some records accurately describe the kinds of liquid wastes that were generated and where they went, some of the spills and the volume of the spills went undocumented.
Reactor buildings, support facilities, and auxiliary structures needed during the plutonium production days must also be cleaned up. For many of these buildings, the work requires crews to come in with bulldozers and other heavy equipment to bring them down. As some of these structures are either contaminated or were built using materials like asbestos, crews must take precautions to avoid being contaminated themselves or to avoid releasing contamination into the ground, the air, or the groundwater.
During cleanup operations, where the waste will end up after it is removed from the ground is based upon the kind of waste it is. A majority of the solid wastes, contaminated soil, and building debris will be taken to the Environmental Restoration Disposal Facility located on the Hanford Site. This facility, known as ERDF, is regulated by the United States Environmental Protection Agency and is basically a huge landfill. ERDF accepts waste in disposal areas called "cells". Cells are built two at a time, with each pair of cells measuring 70-feet deep, and 500-feet by 1000-feet at the base. 2.8 million tons of waste can be disposed of in each pair of cells at ERDF, and once each pair of cells is filled up the waste is covered with clean dirt and a soil fixative to ensure that the waste will safely and permanently remain in the landfill.
Some of the more hazardous chemical or radioactive solid wastes are not taken to ERDF. For example, the fuel rods that came out of the reactors but never had their plutonium extracted are stored in a facility called the Canister Storage Building at Hanford. Ultimately, these fuel rods will be sent for permanent burial at a national repository designed to accept these kinds of materials.
Solid transuranic waste is the debris that is contaminated with plutonium or other materials that may remain radioactive for hundreds of thousands of years. This waste, referred to as TRU waste, is securely packaged and is shipped to the Waste Isolation Pilot Plant in New Mexico where it will be permanently and safely buried.
Of the liquid wastes generated at Hanford, much of the waste that is currently stored in the underground tanks on the Site will ultimately be transformed into a stable, glass product in a process called vitrification. In order to vitrify the waste, it is mixed with glass forming materials and then introduced to high heat in order for the waste to bond with the glass. A facility is being constructed at Hanford which will perform this vitrification work. Once the vitrification process has taken place, the molten, glass-like material is poured into cylinders where it will cool and become solid. Ultimately, cylinders containing the most hazardous vitrified waste will be taken to a national repository for permanent burial. The cylinders with less hazardous waste are candidates for disposal in an Integrated Disposal Facility, or IDF. The development of an IDF at Hanford is currently being evaluated in the Draft Tank Closure & Waste Management (TC&WM) Environmental Impact Statement. Alternatives in the EIS evaluate the potential environmental impacts associated with locating an IDF in the 200-West Area of the Hanford Site, or alternatively in the 200-East Area. No final decision will be made on the IDF (and no wastes will be disposed there) until after the final EIS has been issued and a Record of Decision (ROD) is published. The IDF would be regulated by the State of Washington Department of Ecology and/or US Environmental Protection Agency, based on the types of wastes that would be managed there to ensure that any waste disposed of at the IDF would not pose unacceptable impacts to the environment.
The liquid waste that had been poured onto the ground or held in ponds or trenches has long since evaporated or soaked into the soil on the Site. In doing so, the waste did contaminate some of the soil and is thought to have also created underground "plumes" of contaminants. A "plume" is kind of like an underground river where the contaminants join with the water that exists beneath the surface of the Earth. Many of these plumes move in varying speeds and move toward the Columbia River. Hanford employees are actively involved in projects designed to prevent any more of the contamination from reaching the river. Several different strategies are being used in that effort.
One strategy is simply to block the groundwater contamination from getting to the Columbia. Various kinds of barriers are placed in the ground which allows the clean groundwater to move through, while chemically altering any harmful contamination into a non-toxic form as it passes through. Another strategy is called "pump and treat". Through this process, contaminated groundwater is pumped out of the ground and treated with chemicals. These chemicals serve to change the chemical makeup of the contaminants which render them harmless to the environment. Once the treatment of the groundwater is complete, the cleansed water is pumped back into the ground. Yet another strategy in dealing with groundwater contamination is called "biostimulation". This is a new technology where crews pump materials like molasses and vegetable oil into the ground where tiny microorganisms in the soil eat the molasses and vegetable oil. The microorganisms then reproduce, and in doing so, they alter the chemistry of the groundwater and render the contaminants harmless to the environment. The process also prevents the contamination from moving any closer to the river.