Treatment & Immobilization of Hanford Radioactive Tank Waste
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Report to
Congress Treatment & Immobilization of Hanford Radioactive Tank Waste |
2.0 Background—The Importance of Tank Waste Treatment
The Hanford Site in the southeastern part of the state of Washington is the location of one of the greatest concentrations of radioactive waste in the world. That waste is the legacy of nearly 50 years of chemical processing to produce plutonium for nuclear weapons, which began with the Manhattan Project in the 1940s and continued through most of the Cold War. The 54 million gallons of tank waste at Hanford exist in three forms—sludge, salt cake, and liquid supernatant—and are stored in 177 underground, steel-lined, concrete tanks (see Figure 2-1), most with capacity of a half-million to a million gallons.
Figure 2-1. Current Hanford Tank Waste Volume (127 Kb)
Of the 177 tanks, 149 are older, single-shell tanks (SSTs), the last one being placed in service in 1964. Figure 2-2 illustrates that all of the SSTs have exceeded their 20-year design life. Sixty-seven of these SSTs are known to have leaked high-level radioactive waste into the ground. DOE is currently investigating several additional tanks to assess the liquid levels and determine the potential for leaks. DOE operates an ongoing process of pumping liquids out of SSTs to minimize chances of additional leaks.
The remainder of the waste is contained in 28 newer double-shell tanks (DSTs), which were placed in service from 1971 to 1986. Although none of these DSTs has leaked, a number will reach the end of their design life prior to waste being retrieved and treated, as shown also in Figure 2-2.
Figure 2-2. Delay of Tank Waste Disposal Poses Risk of Tank Failures (16 Kb)
Cleanup of the Hanford tank waste is of major importance for Hanford regulatory agencies and regional stakeholders. The Hanford Advisory Board, representing a cross section of stakeholders, has made tank cleanup, and specifically the privatization project, one of its top priorities.
2.1 Description of the Problem
Hanford’s tank wastes present a serious safety concern to the environment, specifically the Columbia River, and, at the same time, to public and worker health and safety. These concerns exist because the tanks were intended for interim storage when they were constructed and were not designed to be permanent disposal facilities for the waste. To date, tank leaks already have resulted in nearly a million gallons of HLW entering the soil at the Hanford Site, and there is a constant threat of new leaks.
The Washington State Department of Ecology (Ecology) and other stakeholders have emphasized the need to address the threat to the environment caused by contamination of the groundwater and the need to protect the Columbia River. In November 1997, DOE confirmed that contaminants from past tank leaks have moved further into the vadose zone toward the groundwater than previously believed and have undoubtedly reached the groundwater. The vadose zone is the soil and rock that lies between the Hanford tank farms and the groundwater. The vadose zone itself is heavily contaminated by previous disposal of low-level radioactive and hazardous liquid chemicals from plutonium processing, which were discharged into cribs, ditches, and ponds, as well as the leaks from SSTs. This contamination is illustrated in Figure 2-3.
The leaking of these SSTs and the aging of all of the tanks represent problems that compound with time until actions are carried out to eliminate the source of the problems. Even though no DSTs are known to have leaked as yet, they also will be soon exceeding their design life. DSTs represent the last available safe storage location for Hanford’s tank waste, particularly for the liquid supernatant. Under current regulatory milestones, all waste, solid and liquid, is scheduled to be transferred from SSTs to DSTs by 2018. To achieve this schedule, some waste in the DSTs must be processed to provide space for SST waste. If DSTs begin to develop leaks, the urgency and magnitude of Hanford’s tank waste management problem increase dramatically.
To prevent further releases to the soil, Hanford is currently carrying out a process of removing pumpable liquids from the SSTs. To date, 119 of 149 SSTs have had the pumpable liquids removed and transferred to safer DSTs. However, this pumping does not remove all of the liquid waste from the tanks, nor does it remove the waste solids from the SSTs. It will take several more years to pump the remaining 30 tanks, at which time all will be several decades beyond their design lives.
Figure 2-3. Tank Waste as a Source of Vadose Zone and Groundwater Contamination (25 Kb)
The highly radioactive tank waste is viewed regionally as a long-term threat that requires near-term actions to be initiated to provide a permanent solution. The preferred solution is to remove the source of the problem by retrieving and immobilizing the waste, as currently planned in TWRS Phase I. Phase I has been designed to retrieve, treat, and immobilize approximately 10% by mass (and as much as 25% by radioactivity) of the tank waste, which will free up valuable tank space to transfer SST waste to DSTs.
2.2 Compliance Agreements
With regard to environmental and public safety issues, there are specific legal requirements that DOE must satisfy, as well as compliance agreements that DOE has signed, concerning the Hanford tanks. DOE, the U.S. Environmental Protection Agency (EPA), and Ecology have entered into the Hanford Federal Facility Agreement and Consent Order (also called the Tri-Party Agreement [TPA]). This agreement is intended to ensure compliance with the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation, and Liability Act, as amended. The TPA sets forth certain requirements and milestones for cleanup activities at the Hanford Site, including cleanup of the tank waste. The major project milestones and their respective completion dates will be discussed in Section 5.4.
In providing waste treatment and immobilization services in Phase I, the contractors also are required to assure that treated HLW meets Nuclear Waste Policy Act requirements for deep geologic disposal. Additional requirements for LAW require that the treated LAW meets RCRA requirements for near surface land disposal. Treatment facilities also must meet state and federal requirements for public and worker health and safety.
2.3 Regulatory Context
The regulatory framework for the TWRS Phase I project requires compliance with existing laws and regulations and relies on, to the extent possible, established external regulatory authorities. The regulatory framework for execution of Phase I addresses a variety of objectives, including the following:
Except where regulatory authority is specifically reserved for DOE, or where regulatory compliance responsibility is established for DOE, DOE will not serve as the regulator or enforce regulatory compliance requirements. Where an external regulator assigns joint responsibility for regulatory compliance to DOE and the contractor, the contractor has primary responsibility and accountability to the external regulator. Where joint responsibility does not exist, the contractor has full responsibility and accountability to the external regulator. Based on the scope of work and the applicable regulatory authorities, the planned regulators for this project include Ecology, the Washington State Department of Health, and the U.S. Department of Transportation, the EPA, as well as DOE. Continued participation by the U.S. Nuclear Regulatory Commission (NRC) is planned, and involvement of the U.S. Department of Labor’s Occupational Safety and Health Administration (OSHA) is currently being addressed. The regulatory framework is outlined below.
2.3.1 External Regulation
For environmental protection, federal and state agencies will regulate the contractor in a manner similar to other facilities on the Hanford Site.
The external regulatory agencies and their specific roles are described below.
The OSHA, or DOE under its authority, will be responsible for regulating non-radiological safety and health concerns. If OSHA does not assume regulatory authority (per letter of May 13, 1998 from the OSHA Administrator to DOE), oversight of the contractor’s non-radiological safety and health will be provided by DOE.
2.3.2 Regulation by DOE
DOE will regulate the radiological, nuclear, and process safety of the TWRS Phase I facilities through the DOE Office of Radiological, Nuclear, and Process Safety for TWRS Privatization (Regulatory Unit). This is a DOE organization that reports directly to the DOE Richland Operations Office (DOE-RL) manager with DOE Headquarters oversight. As such, the Regulatory Unit is independent of the TWRS program and is essentially autonomous within its range of regulatory authority.
Pursuant to the Atomic Energy Act, either DOE or the NRC serves as regulator for all radiological and nuclear safety regulation in the United States. External regulation by the NRC was desired by prospective Phase I private contractors and stakeholders as it was viewed as capable of providing more certainty and more predictable regulation than the traditional DOE order-based approach to safety. However, discussions with NRC confirmed that the Commission could not provide independent regulation as quickly as needed under the DOE privatization planning. Furthermore, it appeared that NRC regulation required legislative action to confirm NRC authority to regulate the Hanford tank waste treatment.
To allow the project to proceed under a stable regulatory regime for nuclear and process safety, DOE established the Regulatory Unit; a staff of 17 full-time federal employees at Hanford. Additional support for the Unit is provided by DOE Headquarters and, in an advisory role, the Nuclear Regulatory Commission (NRC). This support is formalized by Memoranda of Agreement and Understanding between the cognizant DOE and NRC officers, specifically, the DOE Assistant Secretaries for Environment, Safety and Health; and Environmental Management; and the Director of Nuclear Materials Safety and Safeguards of the NRC.
Pursuant to the Memorandum of Understanding (MOU) between DOE and NRC (62 FR 12861), the NRC’s participation during Phase I is primarily of a cooperative nature for the purposes of information transfer and assisting DOE in establishing a regulatory program that is consistent with the NRC’s regulatory approach for protecting the workers, the general public, and the environment. To further this goal, NRC has formally assigned staff to coordinate with the Regulatory Unit of TWRS.
Accordingly, DOE arrived at a radiological, nuclear, and process safety oversight program to ensure maximum NRC involvement in accordance with the cited MOU. Under this approach:
To facilitate the regulatory transition to Phase II, the Memorandum of Understanding between NRC and DOE for Phase I calls for prompt identification and elevation of issues that could impact the design, construction, or operation of the Phase II plants. In addition, during this period, NRC is expected to issue its new draft 10 CFR 70 Rule, that would ultimately apply to the TWRS facilities, if NRC assumed regulatory oversight. DOE and its contractors will comment on this draft rule. The comment resolution process is expected to settle many areas of potential disagreement. The lead time for Phase II will allow the NRC to have the necessary legislative and regulatory framework to assume regulatory oversight.
Other DOE regulation will be for the protection of government assets (including waste to be processed) from theft or sabotage, and for the protection of classified information. Oversight of the contractor’s safeguards and security program will be provided by the DOE-RL Safeguards and Security Division. The scope of the safeguards and security program includes physical protection, nuclear material control and accountability, information and personnel security, and government property protection.
2.4 TWRS Environmental Impact Statement
DOE issued an Environmental Impact Statement (EIS) (DOE 1996a) for the TWRS program and a subsequent Record of Decision (62 FR 8693) under the National Environmental Policy Act. In view of the complexity and remaining uncertainties of the TWRS program as a whole, DOE decided on a path of "phased implementation," whereby forward movement on the program would be in well-defined phases. This incremental approach allows for learning in each increment and for development of new information and new technologies. It also allows for refining program plans as new information is incorporated.
The phased approach being used to define the TWRS Phase I project, as well as subsequent work on TWRS, is consistent with the TWRS EIS and Record of Decision. Details on the implementation of this approach are provided in Section 5.
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