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Science and Technology for Environmental Cleanup at Hanford (2001)
Board on Radioactive Waste Management (BRWM)

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2 Hanford Site Background The region around the present-day Hanford Site was occupied by Native Americans for more than 10,000 years before the arrival of the first European American explorers, the Meriwether Lewis and William Clark party, in 1805. Euro-American settlement of the area was promoted by several events: the relinquishment of Indian lands to the government at the Treaty Council of 1855 and military action against Indian resistance in 1858, and the development of irrigation canals and construction of the railroad in the 1880s and 1890s the latter of which led to the founding of the towns of Kennewick and Pasco. By the early 1 940s, the region had a population of about 19,000, supported mostly by farming and ranching. In December 1942, an officer assigned to the Army Corps of Engineers Manhattan Engineering District and two DuPont engineers began a tour of the western United States to locate a site for a highly classified "atomic" project associated with the war effort. They were seeking a large tract of land with abundant cold water and electricity supplies that was also isolated from highways, railroads, and population centers. After visiting a region along the Columbia River near its confluence with the Yakima River (Figure 2.1), they reported to General Leslie R. Groves, head of the Manhattan Engineering District, that the site "was far more favorable in virtually all respects than any other' (Gerber, 1992~. By March 1943, Groves had acquired about 500,000 acres (almost 800 square molest of land at a cost of a little more than $5 million, and ground was broken for the world's first production facility to make plutonium for atomic weapons (Rhodes, 1986~. The site was first designated as Site W and later as the Hanford Engineering Works. The site design (Figure 2.1 ) called for three graphite-moderated "atomic piles," or reactors, to be built at 6-mile (about 1 O-kilometer) intervals along the Columbia River. These areas are referred to collectively as the "100 Areas" and individually by the reactor designation, for example, the "1 OO-B" Area for the B-Reactor. These reactors would irradiate fuel slugs made from natural uranium' to create plutonium-239, which had been made in minute quantities for the first time at the Radiation Laboratory (now the E.O. Lawrence Berkeley National Laboratory) in 1941. The river water was needed to cool the piles, which operated at about 200°C. Some 10 to 15 miles (16 to 24 kilometers) The graphite piles were effective neutron moderators and absorbed few neutrons, making it possible to use natural uranium to fuel the reactors. Later, slightly enriched uranium was used to fuel the reactors to increase plutonium production rates. 11

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12 Science and Technology for Environmental Cleanup Priest ~ . Vernita Bridge Rapids Dam _ - - Rattlesnal Mountain ..... r Kennew~-- _ === = _ = = _ _ . _ - , _ _~ Arid Lands Ecolotgy Reserve ~BC White Bluffs tt~hl" R''tt^_~ _ _ _ - _, - . ~ \ 1oo-K 1oo-N 1nn D ,^1co-H \ 200-West Gable Mt. - ~ I, N" ~30~ :_: IBM ~ · Vancouv~ ~ = = = 1 \ \ ;,OO-F r Old Hanford, | TO sin' 0 5 l Scale: Miles Seattle Spokane V WASHINGTON Hanford ~Tri-Cities ·Portland OREGON Figure 2.1 Plan view of the present-day Hanford Site showing locations of major plutonium production areas. SOURCE: BHI, 1999, Figure 1-1; DOE, 1998a. south, on a plateau near the center of the site behind two elevated ridges called Gable Mountain and Gable Butte, two other industrial sites were established, referred to as the 200 East Area and 200 West Area, each containing two massively shielded chemical processing plants to dissolve the irradiated uranium slugs to recover plutonium. The recovered Dlutonium would then be shipped off-site2 for orocessino to make - 2Plutonium was recovered as a nitrate paste, which was shipped to Los Alamos, New Mexico, for conversion to metallic plutonium. A facility to make metallic plutonium at the Hanford Site the Plutonium Finishing Plant was constructed in 1949.

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Hanford Site Background plutonium metal that would form the cores of atomic bombs. Sixty-four underground storage tanks were initially constructed near these plants to store the highly radioactive liquid waste from processing operations (Figure 2.2~. Additional facilities were constructed downstream of the reactors to manufacture the uranium slugs, in the 300 Area. Given the Figure 2.2 Construction of single-shell tanks in the BX Tank Farm, 1947. The partially constructed tank in the front-right portion of the photo is filled with liquid, presumably for leak testing. After construction of the steel shells, the tanks were encased in concrete shells and domes, as shown at the left-center and left- rear of the photo. The tanks were constructed below grade (note land surface at the rear of the photo) to provide radiation shielding. SOURCE: David Briggs, Pacific Northwest National Laboratory, Negative 1313. 13

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14 Science and Technology for Environmental Cleanup large potential hazards involved with the operation of these first-of-a-kind facilities, the site design called for these reactors and processing plants to be separated by large distances to minimize potential impacts from routine radionuclide releases as well as catastrophic accidents. By May 1945, barely two years after groundbreaking, Hanford had produced enough plutonium for the first test of a plutonium bomb, which was carried out at the Trinity Site in New Mexico on July 16. After this successful test, another bomb made from Hanford plutonium (code-named "Fat Man") was dropped on Nagasaki, Japan, on August 9, 1945, thereby forcing an end to the war in the Pacific.3 By the end of the second world war, the Hanford Site contained more than 500 buildings, almost 400 miles of roadway, and about 160 miles of railroad. A nearby town (Richland) was expanded to house more than 17,000 workers and their families. The total cost of construction was about $230 million (Gerber, 1992~. The Hanford Site was expanded several times after the war to meet national security needs (Table 2.1; see DOE, 1998f, for details). After President Harry Truman's declaration of the Cold War with the Soviet Union in March 1947, Hanford embarked on a $350 million expansion that added two new reactors, a plant to produce metallic plutonium, and new underground high-level waste storage tanks. Following the Soviet Union's detonation of its first atomic bomb in August 1949, a second expansion was undertaken that added yet another reactor, the REDOX chemical processing plant, additional underground waste storage tanks, and two waste evaporators to reduce the large volumes of tank waste being produced from chemical processing operations.4 The third and final expansion of the Hanford Site occurred during the peak of Cold War tensions during the Eisenhower, Kennedy, and Johnson administrations: three more reactors were built along the Columbia River, another chemical processing plant (PUREX) went into operation, and additional underground waste storage tanks were constructed. 3An atomic bomb was dropped on Hiroshima, Japan, on August 6, 1945. This bomb, code-named "Little Boy," used uranium-235 as the nuclear explosive. The uranium was produced at the Oak Ridge Site in Tennessee, which was also established during the Manhattan Project. 4During this expansion period, many other sites were also established to aid the Cold War effort, most notably the Nevada Test Site, the Idaho Reactor Testing Station (now the Idaho National Engineering and Environmental Laboratory), the Savannah River Site in South Carolina, the Rocky Flats Site in Colorado, the Pantex Plant in Texas, the Fernald Site in Ohio, and the Paducah Plant in Kentucky.

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Hanford Site Background TABLE 2.1 Chronology of Major Production Facilities at the Hanford Site . . . Facility Operation Start Operation End Date Date Production Reactors B-Reactor 1944 1968 D-Reactor 1944 1967 F-Reactor 1945 1965 H-Reactor 1949 1965 DR-Reactor 1950 1964 C-Reactor 1952 1969 KW-Reactor 1954 1970 KE-Reactor 1955 1971 N-Reactor 1963 1987 Fuel Processing Facilities T-Plant 1944 1956 B-Plant 1945 1952 REDOX 1952 1967 U-Plant 1952 1958 PUREX 1956 1990 Materials Processing Plutonium Finishing Plant 1949 1989 Hiah-Level Waste Tanks B-Tank Farm 1945 Inactive T-Tank Farm 1945 Inactive C-Tank Farm 1946 Inactive U-Tank Farm 1946 Inactive BX-Tank Farm 1948 Inactive TX-Tank Farm 1949 Inactive BY-Tank Farm 1950 Inactive S-Tank Farm 1951 Inactive TY-Tank Farm 1953 Inactive SX-Tank Farm 1954 Inactive A-Tank Farm 1956 Inactive A)(-Tank Farm 1965 Inactive AY-Tank Farm (D) 1976 Still in service AZ-Tank Farm (D) 1976 Still in service SY-Tank Farm (D) 1977 Still in service AW-Tank Farm (D) 1980 Still in service AN-Tank Farm (D) 1981 Still in service AP-Tank Farm (D) 1986 Still in service 15 . Note: The ~inactive" tanks contain mostly saltcake, sludge, and some drainable liquids, but they are no longer being used for storage of liquid waste. (D) denotes double containment tank. SOURCES: DOE, 1998f, Table 2.3.6; tank data from Brevick, 1994, 1995a, 1995b, 1995c.

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16 Science and Technology for Environmental Cleanup Production at the Hanford Site began to decline after 1965 in response to decreased national needs for plutonium and other nuclear materials. By 1972, all but one plutonium production reactor was shut down. The last reactor operated until 1987, mainly to produce electricity for the regional power grid.5 Twenty-eight additional underground waste storage tanks, each having a storage capacity of between 1.0 million and 1.1 million gallons, were constructed and began receiving waste between 1976 and 1986. These tanks have a double-shell design and are used to hold newly generated waste, as well as waste pumped out of older single-containment tanks, some of which had started leaking in the late 1 950s. At present, all plutonium production reactors and reprocessing plants are permanently shut down. Most facilities have been deactivated, and some are now being torn down. As noted later in this chapter, the Department of Energy (DOE) has also started to remediate contaminated soil and groundwater at the site and to ship transuranic solid waste to the Waste Isolation Pilot Plant (WIPP) in New Mexico. During its roughly 40 years of operation, Hanford produced about 67 metric tons of plutonium—approximately two-thirds of the nation's plutonium stockpile (DOE, 1 99Bg). In the process, large areas of the site around the production facilities, from the surface to the groundwater, were contaminated with radioactivity and hazardous chemicals. The United States is now spending more than $1 billion per year at Hanford alone to manage residual waste and nuclear materials at the site and to clean up contaminated soil and grounclwater, reactors, tanks, chemical processing plants, and ancillary facilities. WASTE PRODUCTION AND MANAGEMENT The production of plutonium and other nuclear materials at Hanford consumed more than 95,000 metric tons of uranium fuel and created large volumes of liquid and solid wastes. In the press of the effort to win the Second World War and then to accelerate production during the ensuing Cold War, production of plutonium and other nuclear materials at the site took priority over environmental protection. Most of the high-activity waste produced contains actinides and fission products and is stored in the 200 Area tank farms. In addition, large amounts of radioactive and chemical contaminants were also released into the 5Eight of the nine reactors at the Hanford site were designed only to produce plutonium. The ninth reactor, designated UN-Reactor," was built with an isolated cooling loop and could produce both plutonium and electricity.

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Hanford Site Background 17 atmosphere, the Columbia River, and the subsurface during the site's 40- year operational history. Until the 1970s, relatively poor records were kept for many of these releases. Some waste continues to be released to the environment today from waste management and cleanup operations at the site. These controlled environmental releases are now regulated by the Environmental Protection Agency and Washington State. Although plutonium production took priority at the site, there was a concern about potential environmental impacts even from the earliest days of site operations. Programs were established to monitor and limit worker exposures and make environmental measurements of the Columbia River and its aquatic life, site vegetation, wildlife, and groundwater. Extensive studies of the Columbia River ecosystem concentrated on both radionuclide and thermal (heat) releases (e.g., Vaughan and Hebling, 1975; Becker, 1990~. After the war, additional studies were made of site sediments to determine their capacity to retard the migration of radionuclides, which were being released into the subsurface along with large volumes of water. As noted elsewhere in this section, some operational practices were modified to reduce waste releases based on these monitoring programs. Because of incomplete record keeping, an exact mass balance of historical releases of radioactivity and chemicals to the environment at the site does not exist. The Integration Project has established a program to obtain such an estimate, as described in Chapter 5 of this report. The following sections summarize what is currently known about contaminant releases at the site, organized by environmental medium as illustrated in Figure 2.3. More detailed discussions of waste releases can be found on the Hanford web site; see especially the History of the Plutonium Production Facilities at the Hanford Site Historic District (DOE, 1 997a; http:llwww. hanford.gov/docs/rl-97-1 047/index.htm) and many of the references cited therein. Releases to the Atmosphere The operation of production reactors resulted in the release of about 12 million curies of volatile fission products to the atmosphere (Heeb, 1994~. Volatile radioisotopes were also released during chemical processing of the fuel to recover plutonium,6 especially during the war years (Napier, 1992~. Emissions from the chemical processing plants were reduced after the war through the use of scrubbers and filters and 6The chemical processing plants had 200-foot-high vent stacks to disperse these releases.

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~8 Since and ~chno~ far e~nmen~/ Bang ~~'~;!'~'~~!~.~!~' . ,_ . ~ ! .. ~ Fag ~ ...- -~.._- ~..~. ~"~_~$~.~<'?~1'S#~,~^ ~ ,_~.-~ 3,,,,, ,. .; ?~/,:`~.~-~- , gu[e2.3 Boor contain and subsurface release pathways in the (A) 100 and 300 Areas and (B) 200 Area at the Hanford Site. SOURCE: DOE, 19988, Figures 1-5 and 1-6.

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Hanford Site Background by allowing more time for the fuel to "cool" after irradiation to allow short- lived radionuclides to decay. 19 Once released into the atmosphere, radionuclides were dispersed by atmospheric mixing. The impacts of atmospheric releases of radionuclides at Hanford on human health have been assessed in the Hanford Environmental Dose Reconstruction Project and the Hanford Thyroid Disease Study (National Research Council, 1994a, 1995, 2000b). These studies have shown that iodine-131 (half-life-8 days) contributed most of the radiation dose received by members of the public from atmospheric releases at Hanford. Releases to the Ground The release of radionuclides and hazardous chemicals to the ground at the Hanford Site occurred at all of the major production areas. These contaminants are among the most significant potential environmental hazards that exist at the site today in addition to the spent nuclear fuel, high-level waste, and other nuclear materials under active management at Hanford. These releases can, for convenience, be grouped into the following three categories: (1 ) solid waste disposal, (2) liquid waste disposal, and (3) accidental releases and discharges. Solid Waste Disposal Radioactive and chemically contaminated solid waste has been disposed of in shallow land burial grounds around all of Hanford's production facilities. Almost 70 burial sites containing more than 650,000 cubic meters of waste are known to exist (DOE, 1 997d, 2000h). Solid waste was placed in unlined trenches, lined excavations, and underground vaults and consisted of a wide variety of materials, including failed hardware, construction and demolition waste, soil contaminated by spills and leaks, contaminated clothing, and various kinds of process waste. During the first two decades of site operation, burial grounds were built in close proximity to production facilities, and both chemical and radioactive wastes were disposed with little or no segregation. Moreover, no detailed records were kept of the kinds or amounts of waste disposed. By the 1960s, the burial grounds were centralized, mostly in the 200 Area, and waste segregation and better record-keeping practices were implemented. By the 1970s, all radioactive solid waste was being disposed of in the 200 Area, and transuranic waste was being segregated

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20 Science and Technology for Environmental Cleanup and stored.7 Additionally, computerized databases began to be used to track inventories of waste disposed of in the burial grounds. In 1995, the Environmental Restoration Disposal Facility (ERDF)9 was established between the 200 East Area and the 200 West Area (see Figure 2.1~. It now receives most of the solid radioactive and mixed wasted generated by cleanup and waste management activities at the site. The burial grounds in the 200 Area also hold waste generated off- site by other DOE sites and laboratories, universities, the military, and private companies. Most notable, perhaps, is the burial ground in the 200 East Area that holds more than 80 reactor compartments from decommissioned U.S. nuclear submarines. A private-sector organization (U.S. Ecology) also operates a commercial low-level waste disposal facility on land owned by Washington State. Liquid Waste Disposal Liquid radioactive and chemical wastes were discharged to the ground at all operating facilities on the Hanford Site. In terms of volume and toxicity, the most significant releases occurred in the 200 Area from chemical processing operations. After irradiation, the fuel was brought to the 200 Area by train, where it was dissolved and chemically processed to recover plutonium, uranium, and sometimes neptunium. These processing operations produced 26 distinct waste streams containing actinides and fission products and a wide range of chemicals, including nitric acid, bismuth phosphate, potassium permanganate, methyl isobutyl ketone, aluminum nitrate, tributyl phosphate, kerosene, ammonium fluoride, and sodium hydroxide. 7A 1970 Atomic Energy Commission directive required the segregation of transuranic waste and also required that it be placed in retrievable storage. That stored waste is now being shipped to the WIPP in New Mexico for disposal. 8The database is now referred to as the Solid Waste Tracking System (see Chapter 5~. The ERDF is a Resource Conservation and Recovery Act- and Comprehensive Environmental Response, Compensation, and Liability Act- compliant land disposal facility for disposal of waste from Hanford cleanup operations. It comprises a series of disposal cells, each measuring about 500 feet on a side and 70 feet deep, with a combined capacity of almost 12 million cubic yards. '°Mixed waste contains both radionuclides and hazardous chemicals. Neptunium was used to make plutonium-238 for radioisotope thermoelectric generators (also known as RTGs) for space applications.

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Hanford Site Background 21 Table 2.2 provides an inventory of the high-level waste produced by chemical processing operations between 1944 and 1988.42 The numbers given in Table 2.2 are rough estimates only43 and are based on process knowledge supplemented with records where available. Detailed records of soil discharges were not kept, and even the current high-level waste inventory of specific radionuclides and chemicals in the tanks is not well known.44 As noted previously, an effort is under way at the site to obtain better estimates of historical releases to aid the long-term cleanup effort. The following discussion is based on the inventory estimates given in Table 2.2. Chemical processing operations generated more than 500 million gallons of high-level waste with a radionuclide content of about 800 million curies.~5 This waste was transferred to the waste storage tanks by underground transfer lines. Once in the tanks, the waste was subjected to additional treatment to reduce its volume by more than 90 percent, to the 54 million gallons that exist in the tanks today (Table 2.2~. This was done using the following processes: 1. Beginning in about 1948, when tank space was in short supply,. gravity separation of the solid and liquid fractions of the high-level waste was accomplished using multiple tanks connected in series. Waste was introduced into the upstream tank, and as it cascaded through successive tanks, the solid fraction, which contained most of the actinide elements and strontium, would settle out, leaving a liquid supernate that contained cesium and other soluble fission products such as technetium. At the end of the cascacle, the supernate was discharged to soil. 2. After cascading was discontinued in the 1 950s, the supernate in some tanks was treated with potassium ferrocyanide to precipitate cesium. Once the cesium was removed, the remaining liquid was discharged to soil. 42The committee is indebted to Roy Gephart, Pacific Northwest National Laboratory (PNNL), who provided some of the background material used in this section and in Table 2.2 and who reviewed a draft of this chapter. 43The committee cannot evaluate the accuracy of the estimates given in Table 2.2 but believes that they are likely to be highly uncertain. The numerical ranges shown for some entries in the table represent differences in estimating procedures and do not necessarily represent the uncertainty ranges of the estimates themselves, which have not been determined, in part because the quality of the estimates is unknown. ~ The waste tanks are highly heterogeneous, and not all of the tanks have been sampled. 45This estimate is based on a rough calculation and was provided by Roy Gephart (PNNL).

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Hanford Site Background (B) r r r r - ~_ 100 H #_ Area I r Ares r 10~8~ i) J _ _ _ }< ' Area ~ ~F; HI TEDF ~Oid RiversJ~s salt Above Water Table ~ Chromium {MCL 100 ug/L) ~ Nitrate (20 mg/L) ~ Nitrate (MCL 45 mg/L) ~ Carbon Tetrachlondo (MCL 5 uo/O 29 Canto \ Landfill \ Supp y \ 6t8-10 Crowds 400 Ares that Flux Ted Facility) ·5 . ~ Tr~chloroe~ylene {MCL S us) 5 ~ Q;_~l._~ Dashed Where Inferred ` - Area i 2 0 1 2406~ n ~ p~as024f~yt9,'~1~~ . E98~082.215

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30 Science and Technology for Environmental Cleanup ; SIDEBAR,:(j1 ~ ~~ ~~ ~~ Th Range and lacustrIr~e :Group, or -.~-n~.~}ie Columbia .P t ~O Rome MUDS - basa.lts ~ And. ~~.~ ~ Panic ,~ die .p~a.ii of We Gil about ~ I.. and.6 .n n.an~d northern O Irks of the Ellen ~illio~ri~eai~if' - i, . - ~ ~ ~ ~ ~ it. ~ ~ . ~ ~ ~ ~ ~ ~ . ~ ~ ~ ~ ~ ~ ~ ~ ~ . . Arnold cataclysm east-we~se `~ :~.'na~ ,. ~ ~ ~~-~.~.~ ~,-~,. Allis e~:ir . ~ ,~ ~ ~ i. ~~ ~~ East Amp . _oii~imbia ~f; OCR for page 31
Hanford Site Background West (A) 400 - Yalcima j Ridge 300- ;> v: :: ct c; ;> a: O- c' 100 - -100 - \ 200-E stArea HOa f0ardon[~: = ~ ~ — ~ ~~ a Ringold Formation ~ _ ~ ~ ~ it \_ Kilt Interbed ~ Basalt G99030045.93 Figure 2.9 Generalized east-west section through the Hanford Site showing the principal geologic formations. SOURCE: PNNL, 1999, Figure 6.1.3. 31 leaks of high-level waste from tanks and waste transfer lines. Leakage of high-level waste to the subsurface is suspected to have occurred in at least 67 of the 149 single-containment underground waste tanks in the 200 Area (Gephart and Lundgren,1998~. The word "suspected" is used to describe these leaks because the single-containment tanks were not designed with systems to detect leaks. Rather, leakage has been inferred by monitoring liquid levels in the tanks and by radiation monitoring in about 800 dry wells48 drilled in many of the tank farms (Figure 2.10~. The single-containment tanks were constructed beginning in 1945 and had a 20-year design life. The first tank leak, estimated to be around 10,000 gallons, is believed to have occurred in the U Tank Farm in 1956, about 10 years after it was constructed (Table 2.1~. The largest leak, estimated to be more than 100,000 gallons, is believed to have occurred in the T-Tank Farm in 1973 (DOE, 1 997a). The total amount of leakage from all 67 tanks is estimated to have been between 750,000 and 1.5 million gallons of high-level waste with an activity between about 450,000 swells completed in the vadose zone above the water table.

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32 Science and Technology for Environmental Cleanup and 1.8 million curies (Table 2.2~. Most of the liquids contained in these leaking tanks have been pumped into double-containment tanks (Gephart and Lundgren, 1998~. In some cases the remaining liquids were absorbed by adding diatomaceous earth. The subsurface in the 200 Area was also been contaminated with uranium from operation of the U-Plant from 1952 to 1958. An estimated N ~ Cs-137 Concentration {pCilg) i ) ~ i. i , . ~ I,,, ~ ,-!jj4A ,,, ~Jr, Figure 2.10 Calculated cesium-137 distributions in soil beneath the SX Tank Farm. Vertical lines represent dry wells in which gamma-ray measurements were made to determine cesium concentrations. Tanks labeled in red font are known leakers. SOURCE: DOE, 1 998a.

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Hanford Site Background 4,000 kilograms of uranium was disposed in two cribs during operation of this plant. Some of the uranium was later remobilized and transported to groundwater beneath the 200 Area when acid waste was inadvertently disposed to these cribs and additional disposal cribs were put into operation nearby. The acid remobilized the uranium in the crib and underlying sediment, and the liquids from a nearby crib transported this remobilized uranium to groundwater. This groundwater contamination is being contained through pump-ancl-treat operations (DOE, 2000e). Releases to the Columbia River 33 There were many releases of radioactive and chemical contaminants to the Columbia River during operation of the production facilities at the Hanford Site, and some releases from contaminated groundwater continue to the present. By far the largest releases occurred from the eight "single-pass" production reactors in the 100 Area, which released about 1 10 million curies to the river (Heeb and Bates, 1994~.'9 Up to 200,000 gallons per minute of treated river water was used to cool these eight reactors, and as the treated water passed through the reactor cores, naturally occurring elements in the water became activated by capturing neutrons. Additionally, a small percentage of the radionuclides released to the water were fission products from damaged fuel elements. The principal contaminants in the reactor effluents are shown in Table 2.3. Reactor operations also resulted in discharge of liquids into the subsurface around reactor sites, which later migrated through the grounclwater and into the river. As noted previously, cooling water contaminated with radionuclides from damaged fuel elements was sometimes diverted into trenches, as was contaminated water from the primary cooling loop on the N-Reactor. Process waste and water treatment chemicals (e.g., sodium dichromate) leaked or were disposed of at the reactor sites. Some of these contaminants continue to leak into the river. Pump-and-treat facilities and other treatment approaches20 are being implemented to reduce the inflow of these contaminants to the river. 49As noted elsewhere in this chapter, all of the production reactors except for the N-Reactor were cooled by pumping treated river water directly through the cores. On exiting the cores, the water was held in a retention basin for a few hours before being pumped back into the river. The N-Reactor had a closed primary loop to cool the core. Cooling water from the river was provided in a secondary loop that was isolated from the reactor core. 20For example, the oxidation state of chromium is being manipulated in groundwater near the D-Reactor to immobilize it in place and limit its migration into the river.

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34 Science and Technology for Environmental Cleanup TABLE 2.3 Selected Radionuclide Releases to the Columbia River from Single-Pass Hanford Reactors, 1944-1971 Radionuclidea Half-Life Total Curies (millions] Sodium-24 15 hours 12.6 Phosphorus-32 14.3 days 0.23 Zinc-65 245 days 0.49 Arsenic-76 26.3 hours 2.5 Neptunium-239 2.4 days 6.3 aAccording to the Hanford Dose Reconstruction Project (Ferris et al., 1994), these five radionuclides contributed more than 94 percent of the total dose to representative individuals who used Columbia River resources. SOURCE: Heeb and Bates, 1994. Production activities in the 200 East Area have created large groundwater contaminant plumes that are discharging nitrate and tritium into the Columbia River downstream of the 100 Area (Figure 2.8~. About 3,000 curies, on average, of tritium is discharged into the river each year from the site, based on sampling data (e.g., PNNL, 1999, 2000a) from the river near the upstream and downstream boundaries of the site. The Hanford Site contribution increases the radionuclide load in the Columbia River by about one-third. The remaining radioactivity in the river is from natural or man-made24 sources upstream of the Hanford Site. CLEANUP OF THE HANFORD SITE Hanford Site's defense mission waned in the late 1 980s, prompted by the shutdown of the N-Reactor in response to the Chernobyl accident and a thaw in the Cold War, and the focus of site activities shifted from plutonium production to environmental restoration. In 1989, DOE, the State of Washington Department of Ecology, and the U.S. Environmental Protection Agency entered into the Hanford Federal Facility Agreement and Consent Order, also known as the "Tri-Party Agreement," for achieving compliance with CERCLA (the Comprehensive Environmental Response, Compensation, and Liability Act) and RCRA (the Resource Conservation and Recovery Act) provisions of federal 24 Primarily from fallout left over from atmospheric tests of nuclear weapons.

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Hanford Site Background statutes, as well as state environmental protection laws.22 The Tri-Party Agreement defines and ranks cleanup and waste management commitments, establishes cleanup responsibilities, and provides enforceable milestones for achieving these commitments. Cleanup work at the Hanford Site has proceeded under this agreement since it was signed, although DOE has had to renegotiate many of the agreed-to milestones. In 1999, DOE released the Final Hanford Comprehensive Land- Use Plan Environmental Impact Statement (DOE, 1 999a),23 which lays out its preferred future land use at the Hanford Site after the cleanup program is completed. DOE's preferred alternative (Figure 2.11 ) includes the following provisions: 35 · The land surrounding the core of the Hanford Site (the Wahluke Slope north of the Columbia River and Arid Lands Ecology Reserve southwest of the Central Plateau) and Rattlesnake Mountain and Gable Butte will be preserved from impacts from intensive land-disturbing activities (e.g., mining or extraction of nonrenewable resources). . The Columbia River corridor will have a variety of land uses. The river islands and a quarter-mile buffer zone on each side of the river channel will be preserved to protect cultural and ecological resources. However, the "cocooned" reactors will not be moved for at least 50 years, and remediation will continue as necessary along the river. Additionally, B-Reactor will become a museum. Several sites along the river will be designated for recreational use. · Most of the Hanford Site will be designated as conservation zones to protect cultural, ecological, and natural resources. However, excavation will be permitted to obtain materials needed for DOE missions—for example, to construct barriers and caps to retard future contaminant movement at waste disposal sites. · The Central Plateau will be designated as industrial-exclusive use, which would allow current waste management activities to continue and new compatible facilities to be developed. · The portion of the site north of Richland will be designated as industrial, which would support future DOE missions or commercial industrial development. . An area in the southeastern portion of the site will be designated for research and development to support DOE's continuing 22CERCLA provisions govern the cleanup of contaminated sites, whereas RCRA provisions govern the treatment, storage, and disposal of waste generated at the site. 23Available on the Hanford Website at http://www.hanford.gov/eis/hraeis/ hraeis.htm.

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36 Science and Technology for Environmental Cleanup energy research mission. This area now contains the Laser Interferometer Gravitational Observatory. DOE recognizes that cleanup is likely to be incomplete, even in the areas designated for recreation and preservation, and that deed restrictions and continuing (in some cases, perpetual) institutional management will be required over much of the site to protect public and environmental health. Within the Central Plateau, the 200 Area will serve the site's continuing waste management mission. The major waste management Recreation (High Intensit! , . . . me, ~ (Mining) /~ Research and ~~ Development Recreation ~ (High Ir~ten~ty) Figure 2.11 Future land use at the Hanford Site. SOURCE: DOE, 1 999a, Figure 3.3.

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Hanford Site Background and cleanup activities planned in this area are approximately the following:24 37 · Spent nuclear fuel, special nuclear materials, and cesium and strontium capsules will be shipped off-site to a geologic repository for disposition. · All retrievable transuranic solid waste will be shipped to the Waste Isolation Pilot Plant in New Mexico. · High-level waste in the 200 Area tanks will be retrieved, immobilized in glass, and eventually shipped to a geologic repository. The low-activity radioactive waste streams created by processing this high- level waste will be immobilized and disposed of on site. · Soil and groundwater contamination from past tank leaks and leaks during the waste retrieval process, as well as any waste remaining in the tanks after retrieval, the tanks themselves, and ancillary equipment (e.g., piping and diversion boxes) will remain in place. It is likely that surface caps and barriers will be placed over tank farms. · Solid waste burial sites (including the ERDF) containing transuranic and low-level radioactive waste will remain in place and will be covered with surface caps and barriers. Vadose zone contamination from liquid discharges will mostly remain in place and be covered with surface caps and barriers. · Facilities, with the exception of chemical processing facilities ("canyons"), will be torn down, and some may be covered with surface caps or barriers. · Canyons with significant amounts of fixed contamination will be left in place and covered with a surface cap or barrier. Currently, "there is no single collection of DOE documents that constitute (or identify fully) the approved post closure end state" for the Hanford Site (DOE, 1 999g, p. 2.3~.25 To date, some end states for individual areas within the site have been established and are detailed in various environmental impact statements, environmental assessments, 24This information was provided in writing to the committee by the Integration Project after the committee's second meeting. 25The term end state is used to denote the condition of the site after DOE cleanup is completed. The end state can be characterized in terms of acceptable levels of residual contaminants or permissible site uses. The term is used in both its singular and its plural forms—for example, to refer to the overall end state for the Hanford Site or to the end states for specific regions or facilities within the site. See also An End State Methodology for Identifying Technology Needs for Environmental Management, with an Example from the Hanford Site Tanks (NRC, 1 999a).

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38 Science and Technology for Environmental Cleanup strategic plans, and recorcis of decision (e.g., DOE, 1998b, 1998e, 1999a, 2000f; see also the Hanford Strategic Plan at http://www.hanford.gov/ hsp/~. However, several end states are not fully agreed upon, particularly in the 200 Area. For example, end states for groundwater remediation, high-level waste tank closure, and other facility closures (e.g., closure of the chemical processing facilities) have not yet been established. Also, final cleanup levels have not been determined for much of the waste to be permanently disposed of in the 200 Area. The Columbia River comprehensive impact assessment (Kincaid et al., 2000, p. 3-3) coined the phrase "Hanford Site Disposition Baseline" (HSDB) to describe the suite of disposal and remedial actions that will occur as the Hanford Site moves towards closure. Accelerating Cleanup: Paths to Closure (DOE, 1 998b, p. ES-3) states that "where decisions have not yet been made, sites make assumptions (e.g., site planning end states) about how those cleanup actions might be carried out so that sites can define work and develop schedule and cost estimates." An initial statement of the Hanford Site Disposition Baseline (HSDB-2000) is available, and it consists of three tables covering the 100 Area; the 300, 400, and 600 Areas; and the 200 Area (Kincaid et al., 2000~. The tables list the material type requiring remediation, the corresponding HSDB assumptions, and data needs. A similar set of tables is available for the same three areas, which are titled "Identification of Differences and Issues for Material Type and Areas at Hanford."26 This has the advantage of referring to the Hanford Strategic Plan and to the environmental impact statements, environmental assessments, and records of decision to distinguish between disposition agreements, requirements, and assumptions. It also includes a summary of key differences among available documents and key issues. DISCUSSION The committee recognized early on in its information-gathering meetings that the absence of a clearly articulated end-state vision for the Hanford Site made it difficult to obtain a clear understanding of the exact nature and timing of future cleanup decisions. The lack of clearly defined decision points and options also makes it difficult for the Integration Project to develop an S&T program that is focused on filling well-defined knowledge gaps required to support well-defined site decisions, as detailed later in this report. 26These tables were provided to the committee by the Integration Project after its second meeting.

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Hanford Site Background Nevertheless, the Hanford Site Disposition Baseline and associated documents are, in the committee's view, very important to the S&T program because they indicate the general direction of work at the site and the kinds of knowledge gaps that may be important. In turn, this suggests the generic types of S&T that may be useful. 39 · These documents raise key issues for the S&T program for example, How clean is clean enough? especially as applied to the need to retrieve 99 percent of the waste from the high-level waste tanks as currently stipulated in the Tri-Party Agreement. S&T could help formulate logical scientific and technical approaches for resolving these sorts of issues. They allow gaps in site remediation programs to be identified so that S&T efforts can be focused. For example, there is no mention of long-term stewardship (see Chapter 1 ) in the baseline, and in other documents, stewardship is restricted to 50 to 75 years. Stewardship in the context of these documents does not deal with long-term degradation of facilities and barriers, particularly in the 200 Area, which could require S&T to develop a robust monitoring and maintenance capability to ensure the long-term stability of the site. · They indicate that the number of material dispositions not currently agreed upon is rather large. Agreements are being reached one at a time. A system that generically addresses the concerns of site stakeholders using logical, scientifically based information could help accelerate these decisions. If properly focused and timed, S&T could play a key role in resolving these issues by providing a technical basis for decision making by participating regulators and stakeholders. These documents are also valuable because they provide useful guidance to the Hanford S&T programs in progress. They highlight key issues that require resolution (e.g., decisions concerning material dispositions and end states not yet agreed upon) and potential knowledge gaps to be addressed by S&T. Planning end points and planning end states will no doubt continue to evolve with time as S&T results become available and remediation progresses, which in turn will influence the future course of S&T. This interplay between the cleanup program and S&T is discussed in more detail in Chapter 10.

Representative terms from entire chapter:

columbia river