The Hanford Tanks: Environmental Impacts and Policy Choices (1996)

The Hanford Site (also known as the Hanford Reservation) occupies approximately 1,450 km² (560 square miles) along the Columbia River in south-central Washington, north of the city of Richland. The site was established by the federal government in 1943 to produce plutonium for nuclear weapons. Currently, the mission of the site, under the responsibility of DOE, is management of waste generated by the weapons program and remediation of the environment contaminated by that waste. As part of that mission, DOE and the Washington State Department of Ecology prepared the Hanford Site Tank Waste Remediation System Draft Environmental Impact Statement (DEIS).

The Hanford Site DEIS was prepared under the National Environmental Policy Act (NEPA) and the Washington State Environmental Policy Act. It addresses major changes in the tank waste program that were incorporated by amendments to the Hanford Federal Facility Agreement and Consent Order (hereafter, the “Tri-Party Agreement”) entered into in 1989 by the Washington State Department of Ecology, U.S. Environmental Protection Agency, and U.S. Department of Energy (1994, with latest amendments). This NEPA analysis of a comment made under the Tri-Party Agreement represents a positive development reflecting the national significance of the decisions being proposed.

The DEIS evaluates alternative strategies for managing and disposing of radioactive, hazardous, and mixed wastes from Hanford underground storage tanks (large single- and double-shell tanks and miscellaneous small tanks), as well as cesium and strontium capsules currently stored on the site. The DEIS describes and analyzes the potential enviromental consequences and the projected impact on public and worker health and safety of various alternative approaches to waste management and remediation of the facilities. These alternatives range from no waste retrieval or treatment actions to extensive retrieval, with varying levels of treatment, and disposal of appropriate portions of the treated waste on and off site. The DEIS provides information for decision makers to consider when selecting remediation actions.

The January 28, 1994, Notice of Intent to Prepare Hanford Tank Waste Remediation System Environmental Impact Statement (59 FR 4052) states that the DEIS will (1) analyze the adoption of the most recent amendments to the Tri-Party Agreement; (2) supplement the December 1987 Hanford Defense High-Level Transuranic and Tank Wastes Final Environmental Impact Statement (hereafter, the “1987 FEIS”; U.S. Department of Energy, 1987) and the subsequent April 14, 1988, Record of Decision (53 FR 12449); and (3) reflect changes made since the 1988 Record of Decision. An additional purpose of the DEIS is to support the contracting strategy for privatization of tank farm activities (DEIS, p. 3-13).

The Tri-Party Agreement acts as a programmatic document, providing the framework for decision making and prioritization of cleanup at the Hanford Site. It is implemented by a binding, enforceable action plan with milestones that have been accepted by all parties to the agreement. Significant commitments made in the Tri-Party Agreement changed the planning approach chosen in the 1988 Record of Decision which had been based on the 1987 FEIS. Some of these commitments, as referenced in the DEIS, include (1) 99 percent removal of wastes from both single-shell and double-shell tanks, (2) termination of the planned grout project for low-level waste and adoption of a vitrified form, and (3) designation of both single-shell and double-shell tanks for waste retrieval. As far as the committee is aware, the environmental impacts, uncertainties, costs, and alternatives to these commitments were not specifically analyzed prior to the present DEIS.

DOE implements its NEPA compliance through regulations found in 10 CFR Part 1021 (NEPA Implementing Procedures), the regulations of the President's Council of Environmental Quality (CEQ; 40 CFR Parts 1500-1508), its own order (DOE Order 5440.1E, 1992, NEPA Compliance Program), and the guidelines presented in Recommendations for the

Preparation of Environmental Assessments and Environmental ImpactStatements (U.S. Department of Energy, 1993). The DEIS, though presented as a stand-alone document, is only one of a series of enviromental documents analyzing remediation activities at the Hanford Site. A 1995 unpublished DOE briefing document provided to the committee identifies other environmental impact statements, some in preparation or planned, that address DOE activities with the potential to affect remediation of the Hanford Site. A recent DOE publication, Charting the Course: The Future Use Report (U.S. Department of Energy, 1996a), makes recommendations for future land uses for 20 DOE sites, including the Hanford Site, and describes plans to prepare the Hanford Remedial Action Environmental Impact Statement for the Hanford Comprehensive Land Use Plan. The 1987 FEIS references eight other relevant environmental impact statements that had already been completed, with the earliest dated 1975.

The DEIS relates most directly to the 1987 FEIS, which led to the 1988 Record of Decision to begin processing the double-shell tank wastes but to defer action on the single-shell tanks. In 1989 a policy shift occurred, and the Tri-Party Agreement was entered into. This agreement gave priority to joint removal and processing of the single-shell and double-shell tank wastes. Preparation of the DEIS, in effect, represents an implementation step of the Tri-Party Agreement.

The DEIS addresses the management and disposal of radioactive and mixed wastes stored or to be stored in underground tanks at the Hanford Site. In addition, it addresses the management and disposal of capsules of cesium and strontium, and of waste in miscellaneous underground storage tanks.

At the Hanford Site there are approximately 216,000 m³ (57 million gallons) of waste stored in 177 large tanks, of which 149 are single-shell tanks ranging in capacity from 210 m³ (55,400 gallons) to 3,800 m³ (1 million gallons), and 28 are double-shell tanks with capacities ranging from 606 m³

(160,000 gallons) to 3,800 m³. The wastes were highly acidic when generated, but they were neutralized with sodium hydroxide or calcium carbonate to permit storage in carbon steel tanks. As a result, most of the chemicals present in the waste precipitated. In the liquid remaining in the tanks, the primary dissolved chemicals are nonradioactive sodium nitrate, nitrite, and hydroxide, with much smaller mounts of other chemicals. Major radioisotopes include ¹³⁷Cs and ⁹⁰Sr.

During the years since the tanks were filled, some of the single-shell tanks have failed and leaked. There are presently 67 tanks (all single-shell) known or assumed to have leaked (Hanlon, 1996, p. 1). To forestall further leakage, all single-shell tank contents were processed further to reduce the liquid content as much as possible, given other safety considerations. This resulted in the precipitation of many soluble salts from the oversaturated liquid. There are now four distinct types of material—liquid, saltcake, sludge, and slurry—in at least some of the Hanford tanks (DEIS, Table A.2.1.1):

• Liquid (63,000 m³) includes the supernatant and drainable interstitial liquid in the tanks, containing substantial amounts of dissolved chemicals, especially sodium salts such as hydroxide and nitrate/nitrite, often near or at their respective solubility limits.

• Saltcake (91,000 m³) is a crystalline mixture of chemical salts that precipitated when neutralized liquids were concentrated to reduce storage volume or potential waste mobility; in general, it is composed of the same mix of chemicals as is dissolved in the liquid.

• Sludge (54,000 m³) is a generally viscous, amorphous mixture of relatively insoluble chemicals that precipitated in the tanks as a result of neutralization; iron and aluminum compounds are typically important components, but sludges are usually heterogeneous and contain a wide variety of cations and anions as well as interstitial salt cake or liquid; phosphate ion forms a gelatinous precipitate in the sludge with a variety of cations.

• Slurry (7,700 m³) epresents tank waste comprising solid, generally crystalline particles suspended in a liquid; most of the solids are alkaline nitrate salts that crystallized in the tanks when liquid wastes were concentrated, but some solids similar to sludges are also present; slurry is found only in double-shell tanks at Hanford.

It is notable that although the radioactive components of the tank wastes represent a small fraction of the total mass of chemicals in the tanks, they nonetheless are the source of a large amount of radioactivity. There are approximately 104 million curies (Ci) in the single-shell tanks and 73 million Ci in the double-shell tanks (DEIS, Table A.2.1.3). The radioisotopes ¹³⁷Cs (with a half-life of 30 years) and ⁹⁰Sr (with a half-life of 28.5 years), which account for essentially all of the total radioactivity in both types of tanks, will remain the primary individual contributors to the total radioactivity over the next 150 to 200 years.

Information about the contents of the tanks is based primarily on historical records of transfers of radioactive and chemical wastes from processing facilities, supplemented by recent analyses of samples collected from some of the tanks. The data are suspect on a tank-by-tank basis, but the overall inventory of tank wastes is considered to be more accurate. The total mass of nonradioactive chemical components in the tanks is estimated as approximately 357,000 metric tons (approximately 224,000 metric tons in the single-shell tanks and 133,000 metric tons in the double-shell tanks; DEIS, Table A.2.1.2).

As a result of the various plutonium production processes and tank waste processing methods used at the Hanford Site, the tanks contain a wide variety of minor chemical constituents. Some of these constituents have caused safety concerns apart from the issue of leaking tanks. The most important of these risks are explosions resulting from the presence of unstable chemicals (e.g., ferrocyanides and organic chemicals) or from hydrogen produced by the radiolytic degradation of organic chemicals. One tank has a high heat output and requires the addition of water to maintain an acceptably low temperature. In total, 54 large Hanford Site tanks are on a “watch list” because of safety concerns (Hanlon, 1996, p. 1).

There are approximately 60 so-called miscellaneous underground storage tanks (MUST), with capacities ranging from 3.4 m³ (900 gallons) to 190 m³ (50,000 gallons), on the Hanford Site. These tanks were used for a variety of purposes such as settling, processing, and waste transfer. Of these, 40 are now inactive and part of the TWRS project. The total waste volume in

these tanks is approximately 400 m³ (100,000 gallons), a small fraction of the total waste volume in the single-shell and double-shell tanks. The composition of the waste in the MUST is thought to be similar to the waste in the single-shell and double-shell tanks. The design and construction features of the MUST are not described in the DEIS.

During the 1970s much of the heat-generating radioisotopes of cesium (primarily ¹³⁷Cs, with a half-life of 30 years) and strontium (primarily ⁹⁰Sr, with a half-life of 29 years) was removed from the Hanford tank waste to provide for safer storage of the remaining, less radioactive waste. Between 1974 and 1980 this material was purified and encapsulated in double-walled cylindrical containers approximately 7 cm (3 inches) in diameter by 51 cm (20 inches) long. Some of the encapsulated radioisotopes were subsequently recovered for beneficial uses and are not part of the TWRS program. The cesium capsules emit intense penetrating gamma radiation and have been used in beneficial applications such as sterilization of medical equipment. Strontium capsules emit relatively little penetrating radiation and have been used as heat sources.

What remains as a TWRS responsibility are 1,329 capsules of concentrated fused cesium chloride (CsCl) salt and 601 capsules of strontium fluoride (SrF₂) powder. If the materials in the heat-generating capsules could be closely packed, their total volume would be approximately 2 m ³ (DEIS, p. 3-17). As of January 1995, each cesium capsule contains approximately 40,000 Ci of ¹³⁷Cs (half-life of 30 years) plus an unspecified amount of ¹³⁵Cs (half-life of 2.3 million years), estimated to be 0.7 Ci; each capsule emits approximately 190 watts (W) of heat. Each strontium capsule contains approximately 39,000 Ci of ⁹⁰Sr and emits approximately 260 W of heat. The capsules are stored in water pools on the Hanford Site.

The main subject of the DEIS is remediation of the contents of large waste tanks, a number of which are known to have leaked significant portions of their contents to the underlying environment. However, the DEIS does not

address remediation of the tanks themselves, waste that cannot be removed from them, or the soil and ground water contaminated by leakage from the tanks. In addition, the DEIS does not address other sites of environmental contamination at the Hanford Site, such as production reactors, cribs, low-level waste disposal sites, and reprocessing facilities. The standards that must be met for tank closure, that is, the process of declaring remediation of the tanks to be complete under applicable federal and state laws, also are not addressed in the DEIS.

The DEIS presents and discusses a range of separate alternatives for remediation of the high-level waste tanks, the miscellaneous underground storage tanks, and the encapsulated cesium and strontium. In Table 1 the essential features of the alternatives and implementation sections of the DEIS are summarized. For the reader's convenience, a brief summary from the DEIS of the descriptions and analyses each of the tank waste remediation alternatives is contained in Appendix B.