Review of radiological surveillance reports

Maine Yankee Atomic Power Company
Confidential documents pertaining to fuel cladding failures

Also see the 1998 Union of Concerned Scientist's report on Fuel Cladding Failures at NRC supervised nuclear reactors.

The history of the Maine Yankee Atomic Power Company (MYAPC) is littered with clues that suggest significant loss of radiological controls occurred during "normal" reactor operations. As early as 1976, Charles Hess' post operational radiological survey noted the existence of an activation products hot particle discovered in one of only 50 samples in his survey. This was the first hint that "normal" reactor operations included discharges of significant amounts of radioisotopes and/or radiologically contaminated materials. During the early years of operation numerous other studies were made under the auspices of the Maine Sea Grant program to determine the viability of growing oysters and other marine shellfish in the heated effluents discharged from the MYAPC reactor into Montsweag Bay. All of these studies, without exception, documented alarming quantities of reactor-derived activation and fission products in marine pathways. (See A Review of Radiological Surveillance Reports.) Among the most controversial of these reports was Vaughn Bowen's 1981 study of Transuranium Nuclides Released from Water Cooled Nuclear Power Plants (See B-26.) When Bowen noted trace amounts of ²³⁹Pu in Maine Yankee batch discharges, his three year contract (Woods Hole Oceanographic Institute) was discontinued. In fact, all secondary as well as federally sponsored research reports on MYAPC operations and discharges and their environmental impact were discontinued; the last report in the literature other than the GTS Duratek Site Characterization Report cited elsewhere was S. Murray, 1982, Retention of Co-60 by the Sediments of Montsweag Bay, Maine. Oceanography.

The Maine Yankee proprietary inventory of its spent fuel pool issued on April 16, 1998, well after the reactor shutdown in December 1997, clearly documents at least two episodes of fuel cladding failure. While pinhole leaks in fuel assemblies are a relatively normal component of light water reactor operations, discharge of fuel pellets from the fuel assemblies into any environment on the grounds of a nuclear reactor indicates that a nuclear accident has occurred. Unfortunately, fuel cladding failures are the most common type of nuclear accident that afflict operating nuclear reactors. Appendix A, reprinted below, summarizes the radioactive material stored in the Maine Yankee spent fuel pool. Some items, such as control element assemblies, are highly radioactive components common to all nuclear power plant operations.

Table A.7, filtered waste stored in MYAPC SFP (spent fuel pool) constitutes a smoking gun with respect to prior fuel cladding failures at MYAPC. As the table notes, the filters date to a cleanup campaign in 1992; fuel cladding failures, probably involving axial cracking on the fuel assemblies, were severe enough so that loose fuel pellets were vacuumed up from the floor of the spent fuel pool. The vacuum filters are so radioactive that they must be sited as high-level waste, and will eventually end up in MYAPC dry casks in its new on site high-level waste storage facility, the ISFSI (Independent spent fuel storage installation).

Unfortunately, the spent fuel pool is not the only location in which fuel pellets from failed fuel assemblies were discharged. Prior to removal to the spent fuel pool the damaged fuel assemblies also discharged fuel pellets within the reactor vessel itself. MYAPC is a pressurized water reactor. In this type of reactor heat is transferred from the core to a heat exchanger via water kept under high pressure. Fuel pellets from axial cracks on the fuel assemblies were discharged into this reactor water system prior to removal of the damaged fuel to the spent fuel pool. These fuel pellets entered an environment in which the water is moving at a high velocity, under high pressure and at high temperatures. Under these conditions these fuel pellets, which at this point are essentially spent nuclear fuel wastes, would be broken up into minute particles and spread throughout the reactor water systems. The high levels of radioactivity contained in the reactor water storage tank leak of 1984 result from this contamination of the plant environment. The GTS Duratek Site Characterization is a landmark document in the history of nuclear power in the United States as it clearly shows the impact of fuel cladding failure in the form of a highly contaminated reactor water system and some of the highest levels of environmental contamination ever documented at a US nuclear facility.

David Lockbaum at the Union of Concerned Scientists has expressed the opinion that only a handful of US nuclear power plants would have experienced fuel cladding failure via axial cracking to a significant enough degree to necessitate vacing the spent fuel pool to retrieve spent fuel pellets. The October 31, 1974, fuel cladding failure at the Dresden, Illinois, reactor is the most severe known incident of loss of radiological controls at an NRC facility other than the Three Mile Island accident. Ironically, the Dresden fuel failures occurred within a few months of the first of Maine Yankee's fuel assembly failures. The fuel failure at MYAPC in the early years of its operation was not, however, the only incident of its kind at MYAPC. Table A.12 not only lists highly radioactive filters collected during a second 1995 cleanup, but also references filters (BT17) derived from a 6/11/97 vacuuming of the top of fuel assemblies as well as the reactor vessel cavity prior to removal of spent fuel from the reactor vessel after the 1997 final shutdown. As is well known in certain circles, the direct cause of the MYAPC reactor shutdown was a second round of fuel assembly failures that resulted in additional contamination of reactor water systems and environs. A complete inventory of the contents of the Maine Yankee spent fuel pool awaits further study by the licensee -- even they don't know what's in the spent fuel pool.

The following confidential documents represent only the tip of an iceberg of licensee generated data and reports that document the size and the extent of the fuel cladding failures at MYAPC. We do not have copies of Table A.12, inventory of the trash baskets stored in the spent fuel pool, Table A. 13 Non-fuel special nuclear material or Table A.14 fuel cycle (core history).

Other incidents of known fuel cladding failures have been recorded at Haddam Neck in Connecticut (apparently more severe than that at MYAPC), Oyster Creek, Seabrook in NH and most recently, at Vermont Yankee. More information on the accident at Vermont Yankee will be posted as soon as it is available.

Maine Yankee Atomic Power Company. (April 16, 1998). Appendix A: Spent fuel and other radioactive material stored in the Maine Yankee spent fuel pool. MYPS-101, Rev. 0. Maine Yankee Atomic Power Company, Wiscasset, ME.

Table A 7

Table A. 12

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