The high level radioactive waste from submarine reactors is just one of several types of radioactive waste generated by nuclear ships. Other types are liquid waste, solid waste, and so-called “mixed waste.”
Liquid Waste
Until 1973, the Navy routinely discharged its liquid radioactive waste within 12 miles of shore. A report issued by the Navy in 1992 describes the source of this liquid waste as follows:
“In the shipboard reactors, pressurized water circulating through the reactor core picks up the heat of nuclear reaction. The reactor cooling water circulates through a closed piping system to heat exchangers, which transfer the heat to water in a secondary steam system isolated from the primary cooling water… Releases from the shipboard reactors occur primarily when reactor coolant water expands as a result of being heated to operating temperature; this coolant passes through a purification system ion exchange resin bed prior to being transferred from the ship.”1 (Transfer from the ship involves discharge to ocean water.)
The most predominant radionuclide in the liquid waste is cobalt 60, whose half life is 5.3 years.
In 1983, an “inadvertent release” of radioactive water occurred at Pearl Harbor, apparently while the submarine USS Sargo was being serviced at the shipyard. The release was detected only after elevated levels of radioactivity were found on the wet suit of a diver involved in work on the submarine.
Extensive surveys of radioactivity have been made at Pearl Harbor in 1966, 1968, and 1985. The earlier surveys were made when liquid radioactive waste was routinely discharged into the harbor. Levels of cobalt 60 in those surveys were as high as 105 picocuries per gram (dry weight). In a survey conducted by the Environmental Protection Agency in 1985, the concentrations of cobalt 60 in the area of the shipyard “range from below detectable to 0.66 pCi per gram dry weight of sediment.” The EPA report explains the dramatic reductions in cobalt 60 concentrations as resulting in part from the decay process, which, in 1985, would have reduced the cobalt 60 concentrations to about one-tenth of their 1968 values. “Redistribution of bottom sediment over the years” might account for the rest of the diminished radioactivity.
Before 1973, the Navy reports, it released “millions of gallons per year” of radioactive liquids into harbors. Since then, the annual discharge has been “less than 25 thousand gallons per year.” That does not mean that the waste is not generated. Rather, it means simply that the waste is discharged into the open ocean. Still, the Navy states, overall levels of radioactivity from these discharges are extremely low – just 0.4 curie of radioactivity released from more than 100 ships during all of 1991, the Navy says. This, it adds, “is less than the naturally occurring radioactivity in a cube of seawater approximately 100 yards on a side.”
Solid Radioactive Waste
In 1991, nuclear-powered ships in the U.S Navy produced more than 88,500 cubic feet of unclassified radioactive solid waste, not counting reactor waste, according to a Navy report contained in a General Accounting Office study.2 Pearl Harbor’s share of this came to 2,792 cubic feet.
The waste consists of such materials as contaminated rags, plastic bags, papers, filters, ion exchange resin and scrap that is collected from ships and support facilities. Before 1970, these wastes, too, were dumped at sea.
Altogether, the volume of unclassified solid radioactive waste produced since 1961 exceeds 1.6 million cubic feet, or roughly 60,000 cubic yards. This is shipped to facilities licensed by the Nuclear Regulatory Commission to accept low level radioactive waste.
In addition, some of the “low level” radioactive solid waste is classified because, the Navy says, “the technical information inherent in the [reactor plant] component design is classified and must be federally protected.” In 1991, the amount of classified waste came to 11,437 cubic feet. This waste is shipped to Department of Energy disposal sites.
Finally there are the reactor compartments, which, even after defueling, require special handling as radioactive waste. According to the DeMars report, “The average reactor compartment disposal cost is approximately $7.5 million per reactor compartment. This includes costs incurred at the DOE Hanford Site, where defueled reactor compartments are shipped for burial. The eight reactor compartment disposals funded in Fiscal Year 1991 cost about $60 million total.”
Mixed Waste
When radioactive waste is also chemically hazardous, it is categorized as mixed waste and regulated under both the Atomic Energy Act and the Resource Conservation and Recovery Act. As yet, there is no repository for mixed waste.
The Navy states that its nuclear propulsion program activities “typically generate only a few hundred cubic feet of mixed waste each year. This small amount of mixed waste, along with limited amounts of mixed waste from program work conducted prior to 1987, will be stored pending the licensing of commercial treatment and disposal facilities.”
1 “Environmental Monitoring and Disposal of Radioactive Waste from U.S. Naval Nuclear-Powered Ships,” Report NT 92-1, February 1992, page 3.
2 See Admiral Bruce DeMars, director, Naval Nuclear Propulsion Office, “Disposal of Nuclear Materials and Radioactively Contaminated Materials of Nuclear-Powered Ships: Accounting for Shipyard Costs and Nuclear Waste Disposal Plans” (GAO/NSIAD-92-256, July 1992.)
Volume 4, Number 3 September 1993
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