Science- Illinois Issues, August, 1980

Science
By KEITH E. JACKSON

Buried problems at Sheffield

THE SHEFFIELD low-level radioactive waste disposal site in Bureau County is full. Studies have concluded that no immediate threat or hazard to the public health exists, but monitoring continues especially on the level and movement of tritium, a low-level radioactive waste, leaking into water below ground. It also has not been determined how to decommission the site. Another unresolved question is: Who will be responsible for maintaining the site and making certain the public health is never threatened?

The 20-acre Sheffield site was authorized by the Illinois Radioactive Wastes Act of 1963; and its last trench was filled in April 1978. Site responsibility is confusing. The State of Illinois owns the land, but the state leased it to the Nuclear Engineering Company, Inc. (NECO) of Louisville, Ky., which operated the site under a license granted by the U.S. Nuclear Regulatory Commission (NRC).

NECO operated the site from 1968 until March 1979, when it tried to withdraw from the site after giving up attempts to get NRC approval for site expansion. On March 8, 1979, NECO notified the NRC and Illinois Department of Public Health (IDPH) it was "unilaterally terminating" its license and lease to operate the site. But NECO was ordered to return to the site, repair deficiencies, and continue surveillance of the site under a March 22, 1979, preliminary injunction issued by the Bureau County Circuit Court, and the injunction has been continued.

Aside from the question before the court, another key issue is whether or not NECO can give up its operating license and lease without the permission of the NRC and IDPH, and if it can, under what conditions. NECO has entered into an agreement with NRC to maintain the site, maintain security, and to perform environmental monitoring until a finding is made by the Atomic Safety and Licensing Board, which was appointed by NRC to study the situation. There are neither laws regarding this situation nor regulations for decommissioning a disposal site.

The Sheffield site is currently monitored by the NRC and IDPH, and since 1976, the U.S. Geological Survey (USGS) has installed 58 test wells on and adjacent to the site in order to study the geohydrologic conditions and the movement of waste nuclides (a species of atom which constitutes the basic unit of a chemical element) in groundwater. A January 1980 report by the USGS concluded that tritium was the only radionuclide (a nuclide exhibiting radioactivity) found in soil moisture and groundwater at the site. The report also concluded that if other waste nuclides have leaked from the trenches at the site, they are apparently being absorbed by the clay particles in the unconsolidated material below the trenches. The report estimates that tritium in groundwater near the southeast corner of the site has moved about 25 feet per year since 1975. Tritium has not been found in water samples taken from test wells off the site.

IDPH personnel report that the concentration of tritium in water samples taken from some of the test wells on the site is within the state and federal safe drinking water standard of 0.00000002 curie (measurement of radioactivity based on disintegrations per second) per liter of water, but that samples taken from test wells near the trenches show about three times the standard. The tritium drinking water standard was designed to insure that no individiual receives more than 0.004 rem (a unit for measuring tissue damage caused by exposure to radiation) per year to the total body or any, organ, which is about the same as that of an average chest x-ray. The general background radiation in Illinois from both natural and man-made sources gives an individual an average of 0.1 to 0.15 rem per year. IDPH personnel say the amount of tritium in the samples has gradually increased since monitoring began in 1977, but tritium has not moved from the site and there is no

What's in those trenches?

The Sheffield site has 21 trenches filled with 2,936,384 cubic feet of solid low-level radioactive waste. The Illinois lease permitted burial of waste which emits less than 1 curie of radiation per cubic foot of waste (a curie is a measure of radioactivity and is that amount of a radioactive material which has 3.7 x 1010 disintegrations per second). No transuranics (metals with higher atomic numbers than uranium) were permitted; however, about 34 pounds of Plutonium, a transuranic, were buried at the site among the nearly three million cubic feet of waste under lease and license requirements. Much of the buried waste consists of gloves, aprons, boot covers, rags and tools contaminated in nuclear medicine or in the repair and maintenance of nuclear power plants. About 70 percent of the waste comes from Illinois facilities, and the rest from other states' facilities. The waste was put in metal drums and containers and then buried in the trenches. If wastes arrived in liquid form, they were mixed on site with concrete which was poured into 55-gallon drums and allowed to set before burial. The trenches range in size: 35 to 580 feet long, 8 to 70 feet wide, and 8 to 26 feet deep; spacing between trenches was usually 10 feet. The trenches were covered with three or more feet of clay, which was compacted to reduce seepage of precipitation into the trenches. About three feet of topsoil was placed on the clay and then contoured and seeded. French drains, which are loose stones covered with dirt, were constructed and graded at the bottom of each trench so that seepage out of the trenches could be monitored and collected in a pipe at the ends of the trenches.

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immediate hazard or threat to the public health.

According to an NRC spokesman, the movement of tritium in water at Sheffield is not unique because the situation has occurred at two other sites. Tritium has moved at the West Valley, N.Y., facility and has been detected outside the boundaries of the Maxey Flats, Ky., site. Both sites are also full.

Two of the three other disposal sites currently operating in the country at Beatty, Nev., and Hanford, Wash., have not had any problems with the movement of tritium, according to NRC staff, because there is not enough rainfall in these western states to allow water to penetrate the soil to the waste, react with it and carry tritium away. However, when rainfall is sufficient, as it is at the sites in the eastern states, the movement of tritium is expected since tritium will react with any water and there is no way to stop it, according to the NRC staff.

Tritium, however, does not present the extremely long-term problem of high-level radioactive material (such as spent fuel from a nuclear reactor), which takes thousands of years to decay to a level that is safe. Tritium has a half-life (the time required for a radioactive substance to lose half of its potency) of 12 1/2 years, therefore the problem of tritium movement at disposal sites is a relatively short-term problem.

Based on current knowledge, the Sheffield site does not pose an immediate threat to public health and safety, nor can it eliminate the radioactivity. But work is proceeding to devise the best method to assure that the radioactivity stays on site and does not endanger the public. Meanwhile monitoring and study will continue as the administration and courts deliberate and determine who is responsible for maintaining the site.

Support for this column, which reports policy developments concerning science and technology, is provided in part by a National Science Foundation grant to the Illinois Legislative Council Science Unit, where Keith E. Jackson is staff scientist.

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