02-20968. Savannah River Site High-Level Waste Tank Closure

AGENCY:

Department of Energy (DOE).

ACTION:

Record of decision.

SUMMARY:

In the Savannah River Site (SRS) High-Level Waste Tank Closure Environmental Impact Statement (Tank Closure EIS, DOE/EIS-0303) DOE considered alternatives for closure of 49 high-level radioactive waste (HLW) tanks and associated equipment such as evaporator systems, transfer pipelines, diversion boxes, and pump pits. DOE needs to close these tanks to reduce human health and safety risks at and near the HLW tanks, and to reduce the eventual introduction of contaminants into the environment. Moreover, DOE must comply with the provisions of the Wastewater Systems Operating Permit issued by the South Carolina Department of Health and Environmental Control (SCDHEC) for HLW tank operations, and with the closure schedule and provisions contained in the Industrial Wastewater Closure Plan for F- and H-Area High-Level Waste Tank Systems (the General Closure Plan) approved by SCDHEC. DOE evaluated three alternatives for closure of the tank systems: Stabilize Tanks, Clean and Remove Tanks, and No Action. The Stabilize Tanks alternative has three options—Fill with Grout (preferred alternative), Fill with Sand, and Fill with Saltstone.

DOE has selected the preferred alternative identified in the Final EIS, Stabilize Tanks—Fill with Grout, to guide development and implementation of closure of the high-level waste tanks and associated equipment at the SRS. Following bulk waste removal, DOE will clean the tanks if associated equipment at the SRS. Following bulk waste removal, DOE will clean the tanks if necessary to meet the performance objectives contained in the General Closure Plan and the tank-specific Closure Module, and then fill the tanks with grout.

In parallel with tank closures, DOE will evaluate and consult with SCDHEC on closure methods and regulatory compliance revisions that will allow accelerated closure and reduction of risk associated with the HLW tanks. DOE remains committed to closure of the HLW tanks in accordance with the approved General Closure Plan.

ADDRESSES:

Copies of the Tank Closure EIS and this Record of Decision may be obtained by calling a toll-free number (800-881-7292), by sending an e-mail request to [e-mail], or by mailing a request to: Andrew Grainger, National Environmental Policy Act (NEPA) Compliance Officer, Savannah River Operations Office, Department of Energy, Building 742A, Room 185, Aiken, SC 29808. This Record of Decision will be available on the Department of Energy NEPA Web site, tis.eh.doe.gov/nepa/whatsnew.htm.

FOR FURTHER INFORMATION CONTACT:

Questions concerning the SRS tank closure program can be submitted by calling 800-881-7292, mailing them to Mr. Andrew Grainger at the above address, or sending them electronically to the Savannah River Operations Office e-mail address, [e-mail].

For general information on the DOE NEPA process, please contact: Carol M. Borgstrom, Director, Office of NEPA Policy and Compliance, U.S. Department of Energy, 1000 Independence Avenue, SW., Washington, DC 20585, 202-586-4600 or leave a message at 800-472-2756.

SUPPLEMENTARY INFORMATION:

Background

Nuclear materials production at the SRS resulted in the generation of large quantities of HLW that is stored onsite in large underground tanks. The HLW resulted from the dissolution of spent reactor fuel and nuclear targets to recover the valuable radioactive isotopes. DOE has stored the HLW in 51 large underground storage tanks located in the F- and H-Area Tank Farms at SRS. DOE has emptied and closed two of those tanks. Approximately 37 million gallons of HLW is stored in the remaining 49 HLW tanks.

The HLW tank systems at SRS are operated under the authority of the Atomic Energy Act of 1954 (AEA) and DOE Orders issued pursuant to the AEA. The HLW tank systems also are operated in accordance with a permit issued by SCDHEC under the authority of the South Carolina Pollution Control Act for industrial wastewater treatment facilities. DOE is required to close the tank systems in accordance with AEA requirements and South Carolina Regulation R.61-82, “Proper Closeout of Wastewater Treatment Facilities.” This regulation requires that closures be carried out according to site-specific guidelines established by SCDHEC to prevent health hazards and to promote safety in and around the tank systems. DOE has adopted a general strategy for HLW tank system closure, set forth in DOE's Industrial Wastewater Closure Plan for the F- and H-Area High-Level Waste Tank Systems (March 2000), known as the General Closure Plan.^[1] The General Closure Plan has been approved by SCDHEC and DOE must gain SCDHEC's approval on any revisions to the General Closure Plan. Also, DOE has entered into an agreement, the SRS Federal Facility Agreement, with the U.S. Environmental Protection Agency (EPA) and SCDHEC to remove from service and close 24 HLW tanks that do not meet Resource Conservation and Recovery Act secondary containment requirements. The remaining 27 tanks will also be closed when they are no longer required for service. Closure of the HLW tanks will comply with DOE's responsibilities under the AEA and the General Closure Plan, and be carried out under a schedule agreed to by DOE, EPA, and SCDHEC.

The General Closure Plan identifies the resources (e.g., groundwater, air) potentially affected by contaminants remaining in the tanks after waste removal and closure; describes how the tanks will be cleaned and how the tank systems and residual wastes will be stabilized; and identifies Federal and State regulations and guidance that apply to the closures. The Plan describes the use of fate and transport models to calculate potential environmental exposure concentrations or radiological dose rates from the residual waste left in the tank systems. The General Closure Plan describes the method DOE will use to make sure the impacts of closure of individual tank systems do not exceed the environmental standards that apply to the entire F- and H-Area Tank Farms.

Several issues related to the HLW tank closure program will be resolved as DOE implements this Record of Decision. These issues will be addressed during tank-by-tank closure and include: (1) Performance objectives for each tank that allow the cumulative closure to meet the overall performance standard; (2) the regulatory status of residual waste in the tanks, through a determination whether they are “waste incidental to reprocessing;” and (3) use of cleaning methods such as spray water washing or oxalic acid cleaning, if needed to meet tank-specific performance objectives.

Performance Objectives

In implementing this Record of Decision, DOE will establish performance objectives for closure of each HLW tank. Each performance objective will correspond to an overall performance standard identified in the General Closure Plan and will ensure that the overall performance standard can be met. For example, if the performance standard for drinking water in the receiving stream is 4 millirem per year, the combined contribution from contaminants from all tanks will not exceed the 4 millirem-per-year limit. DOE will evaluate closure for specific tanks to determine whether use of a specific closure option will allow DOE to meet the overall performance standard. Based on this analysis, DOE will develop a Closure Module (a tank-specific closure plan) for each HLW tank such that the performance objectives for the tank can be met. The Closure Module must be approved by SCDHEC before tank closure can begin.

Waste Incidental to Reprocessing

Before bulk waste removal, the content of the tanks is HLW. The goal of the bulk waste removal and, if needed, subsequent cleaning of the tanks, is to meet DOE's criteria for Waste Incidental to Reprocessing. DOE Manual 435.1-1, which implements DOE Order 435.1, Radioactive Waste Management, describes two processes, citation and evaluation, for determining that HLW can be considered “waste incidental to reprocessing” and can therefore be managed under DOE's regulatory authority in accordance with requirements for transuranic waste or low-level waste. In implementing this Record of Decision, DOE will perform a waste incidental to reprocessing determination by evaluation on each HLW tank as part of the analysis used to prepare the Closure Module.

HLW Tank Cleaning

Following bulk waste removal, DOE will clean the tanks, if necessary, to meet the performance objectives contained in the General Closure Plan and in the tank-specific Closure Module, which includes DOE's criteria for Waste Incidental to Reprocessing. In accordance with the General Closure Plan, the need for and the extent of any tank cleaning will be determined based on the analysis presented in the tank-specific Closure Module.

If necessary tank cleaning by spray water washing will initially be performed. If performance objectives could not be met using spray water washing, other cleaning techniques would be employed. These techniques include mechanical methods, oxalic acid cleaning, or other chemical cleaning methods. Potential criticality safety concerns and interference with downstream waste processing activities such as Defense Waste Processing Facility glass quality could arise with the use of chemical cleaning methods and would have to be addressed.

Alternatives Considered

In the EIS DOE evaluated three alternatives for tank closure, each of which begins when bulk waste removal from the tank has been completed. Under each alternative except No Action, DOE would close 49 HLW tanks and associated waste handling equipment including evaporators, pumps, diversion boxes, and transfer lines.

Stabilize Tanks Alternative

Following bulk waste removal and any required cleaning, DOE would fill the tanks with a material that would bind up remaining residual waste and prevent future collapse of the tanks. In the EIS DOE considered three options for tank stabilization under this alternative: Fill with Grout (preferred alternative), Fill with Sand, and Fill with Saltstone. Each tank system or group of tank systems would be evaluated to determine the inventory of radiological and nonradiological contaminants remaining after bulk waste removal. This information would be used to conduct a performance evaluation as part of the preparation of a Closure Module. In the evaluation DOE would consider (1) the types of contamination in the tank and the configuration of the tank system, and (2) the hydrogeologic conditions at and near the tank location, such as distance from the water table and distance to nearby streams. The performance evaluation would include modeling the projected contamination pathways for selected closure methods, and comparing the modeling results with the performance objectives developed in the General Closure Plan. If the modeling shows that performance objectives would be met, the Closure Module would be submitted to SCDHEC for approval. If the modeling shows that the performance objectives would not be met, then tank cleaning steps would be taken until sufficient waste had been removed that the objectives could be met. Therefore the closure configuration for each tank or group of tanks would be determined on a case-by-case basis through development of the Closure Module.

Following approval of a Closure Module by SCDHEC, the tank stabilization process would begin. DOE's preferred option is to use grout, a concrete-like material, as backfill. The fill material would be high enough in pH to be compatible with the carbon steel walls of the tank. The grout would be formulated with chemical properties that would retard the movement of radionuclides in the residual waste in the closed tank. The grout would be poured in three distinct layers. The bottom-most layer would be specially formulated reducing grout to retard the migration of important contaminants. The middle layer would be a low-strength material designed to fill most of the volume of the tank interior. The final layer would be a high-strength grout to deter inadvertent intrusion from drilling. DOE is also considering an all-in-one grout that would provide the same performance as the three separate layers of grout. If this all-in-one grout would provide the same performance and protection at a lesser cost, DOE would use it.

Other fill options that DOE considered in the EIS are sand and saltstone. For these options, all other aspects of the closure process, including the determination that performance objectives could be met and approval of the Closure Module by SCDHEC, would be the same as described for the Fill with Grout option. Sand is readily available and inexpensive. However, it would be more difficult to completely fill void spaces with sand than with grout, and sand could not be formulated to retard the migration of radionuclides. Expected contamination levels in groundwater and surface water resulting from migration of residual contaminants would be higher than the levels for the preferred option. Saltstone, which is the low-radioactivity fraction of HLW mixed with cement, flyash, and slag, could also be used as fill material. Saltstone is normally disposed of as low-level waste in the SRS Saltstone Disposal Facility. This alternative would have the advantage of reducing the amount of Saltstone Disposal Facility area that would be required. Filling the tank with a grout mixture that is contaminated with radionuclides, like saltstone, would considerably complicate the project and increase worker radiation exposure. In addition, the saltstone would contain large quantities of nitrate that would not be present in the tank residual waste. Because nitrates are very mobile in the environment, these large quantities of nitrate would adversely impact the groundwater near the tank farms over the long term.

Following the use of any of the stabilization options, four tanks in F-Area and four tanks in H-Area would require backfill soil to be placed over the top of the tanks to bring the ground surface at these tanks up to the surrounding surface elevation. The action would prevent ponding conditions that could accelerate degradation of the tank structure.

Clean and Remove Tanks Alternative

The Clean and Remove Tanks alternative would involve cleaning the tanks, cutting them up in situ, removing them from the ground, and transporting tank components for disposal in an engineered disposal facility at another location on the SRS. For this alternative DOE would have to clean the tanks until they were clean enough to be safely removed and could meet waste acceptance criteria at SRS low-level waste disposal facilities. Cleaning techniques such as oxalic acid cleaning, mechanical cleaning and additional steps as yet undefined might be required. Worker exposure would have to be As Low As Reasonably Achievable to ensure protection of the individual workers required to perform the tank removal operations.

Following bulk waste removal and tank cleaning, the steel components of the tank would be cut up, removed, placed in radioactive waste transport containers, (approximately 3,900 SRS low-level waste disposal boxes per tank), and transported to SRS radioactive waste disposal facilities for disposal. This alternative would require the construction of approximately 16 new low-activity waste vaults at SRS for disposal of the tank components. With removal of the tanks, backfilling of the excavations left after the removal would be required.

No Action Alternative

The No Action alternative would involve leaving the tank systems in place after bulk waste removal has been accomplished. After bulk waste removal, each tank would contain residual waste, and, in those tanks that reside in the water table, ballast water. The tanks would not be backfilled.

After some period of time (probably hundreds of years), the reinforcing bar in the roof of the tank would rust and the roof would fail, causing the structural integrity of the tank to degrade. Similarly, the floor and walls of the tank would degrade over time. Rainwater would enter the exposed tank, flushing contaminants from the residual waste in the tanks and eventually carrying these contaminants into the groundwater. Contamination of the groundwater would be much greater and occur much more quickly than it would if the tank were backfilled and the residual waste bound with the backfill material.

Environmentally Preferable Alternative

Overall, the Stabilize Tanks—Fill with Grout alternative is the environmentally preferable alternative. Review of the data presented in the Tank Closure EIS shows that in the near term the impacts of the Stabilize Tanks—Fill with Grout alternative are similar to or less than those of the Stabilize Tanks—Fill with Sand and the Stabilize Tanks—Fill with Saltstone alternatives.

Waste removal and, if necessary, cleaning activities would be similar for each of these alternatives, although worker exposures and resultant latent cancer fatalities would be slightly higher for the Stabilize Tanks—Fill with Saltstone alternative due to the radionuclide content of the saltstone. In the short term the Clean and Remove Tanks alternative would have substantially greater impacts than any of the Stabilize Tanks options, as a result of the worker exposures that would be required to clean and remove the tanks and tank systems. The No Action alternative has the least short-term impacts.

In the long term, the impacts of the Clean and Remove Tanks alternative would be the least of all the alternatives, because the groundwater contaminant source term would have been removed. Some small long-term impacts would result from release of contaminants from the disposal facility that would receive the tank systems after removal. Long-term impacts of the preferred alternative, Stabilize Tanks—Fill with Grout, would be greater than those of the Clean and Remove Tanks Alternative, although very small; no latent cancer fatalities would result from implementation of the Stabilize Tanks—Fill with Grout alternative. The No Action alternative has the greatest long-term impacts.

Decision

DOE has selected the preferred alternative identified in the Final EIS, Stabilize Tanks—Fill with Grout, to guide development and implementation of closure of the high-level waste tanks and associated equipment at SRS. Following bulk waste removal, DOE will clean the tanks if necessary to meet the performance objectives contained in the General Closure Plan and the tank-specific Closure Module and then fill the tanks with grout.

In parallel with tank closures, DOE will evaluate and consult with SCDHEC on closure methods and regulatory revisions that will allow accelerated closure and reduction of risk associated with the HLW tanks. DOE remains committed to closure of the HLW tanks in accordance with the approved General Closure Plan.

DOE has selected the Stabilize Tanks—Fill with Grout alternative for several reasons. First, DOE has confidence in the method due to the demonstrated performance of the reducing grout and the successful waste removal and closure process employed for Tanks 17 and 20. On the basis of the analysis in the EIS, the selected alternative is superior to the Fill with Sand and Fill with Saltstone options in terms of binding residual waste in the tanks and thereby preventing future environmental contamination. This alternative would likely require the least tank cleaning of any alternative and would therefore minimize worker exposures and waste management concerns while meeting the performance objectives. In addition, this alternative was found to be the environmentally preferable alternative.

As described in the EIS, bulk waste removal has been demonstrated to remove about 97 percent of the radioactive material content, measured in curies, from a HLW tank. Spray water washing has been shown to remove slightly less than an additional one percent and generates additional wastewater that requires processing. DOE will employ spray water washing or an enhanced cleaning method only if it is necessary to meet the performance objectives.

In accordance with the General Closure Plan, DOE must demonstrate whether residual waste (that is, waste that will remain in the tank following any necessary cleaning, and that will be immobilized in the grout used to stabilize the tank) is low-level or transuranic waste in accordance with the Waste Incidental to Reprocessing provision in DOE Order 435.1. However, because DOE must meet overall performance standards in any case, the regulatory status of the residual waste does not affect the assessment of environmental impacts.

Mitigation

DOE is committed to environmental stewardship and to operating the SRS in compliance with all applicable laws, regulations, DOE Orders, permits, and compliance agreements. In addition to good engineering practice, closure of the HLW tanks will follow the approved Industrial Wastewater Closure Plan for the F- and H-Area High-Level Waste Tank Systems, known as the General Closure Plan, and the individual Tank Closure Modules required by the General Closure Plan. This process will serve to ensure that risks are minimized and the environmental and health and safety impacts of tank closure are within the bounds described in the Final EIS. DOE considers this process to be standard operating procedures that do not require a mitigation action plan under 10 CFR 1021.331(a).

Issued at Washington, DC, August 9th, 2002.

Paul M. Golan,

Acting Assistant Secretary for Environmental Management.

Footnotes

1.  Although the Final Environmental Impact Statement reflected the 2000 Closure Plan, the Statement incorrectly cited the 1996 Closure Plan.