The soil contamination noted in special survey R2501 is a result of a reactor water tank leak on March 30, 1984 (LER 84-004-00.) The water leak released +/- 8,000 gallons of water to surface soil before being allegedly recaptured and directed into the seal pit forebay area. The key question with respect to the 1984 leak is: why was there so much radiocesium in the reactor water storage tank that the leaking water left behind such excessive levels of soil contamination? The answer to this question, long a puzzle, was answered by documents released by the licensee pertaining to damaged fuel assemblies in the spent fuel pool. These damaged fuel assemblies discharged some of their spent fuel into reactor water systems; the reactor water storage tank became a repository for some of these fission products that were released as early as 1973.
Subsequent to the 1984 reactor water tank leak, the Maine Yankee Atomic Power Company suffered an additional episode of fuel cladding failure, which lead to its closing. As noted in many sections of RADNET, the important unanswered question is: what is the source term of the fuel cladding failures at MYAPC? That is, what quantity of spent fuel fission products leaked out of the damaged spent fuel assemblies, what were their pathways and what is the current location(s) of this contamination?
Readers of the section of the characterization summary printed in this file please note the following two pieces of information.
|EXAMPLE: SAMPLE LOCATION 00022 REPORTS 137Cs ACTIVITY OF 66.40 pCi/gm. THIS TRANSLATES TO 66,400 pCi/kg OF ACTIVITY IN A SAMPLE OF 1.716 kg OF SOIL. This is the highest level of 137Cs soil contamination ever documented in the public records of a Nuclear Regulatory licensed facility. Maximum average levels of 137Cs from weapons testing fallout in the Maine Yankee area soils and sediments are +/- 600 pCi/kg (.60 pCi/gm). In contrast, the Yankee Rowe facility, which had no known episodes of fuel cladding failure, had maximum levels of 137Cs contamination in the sediments of the effluent outfall basin, where the maximum contamination is to be expected, of not more than +/- 10,000 pCi/kg of 137Cs. The maximum soil contamination at MYAPC was well away from the effluent outfall basin. No data is available for samples taken within the confines of the effluent outfall basin at MYAPC.|
Please note pages 4 - 26 of the 36 page supplemental survey are duplicated below. Soil contamination levels in the remaining samples are generally at or near the minimum level of delectability, .05 to .08 pCi/gm (50 to 80 pCi/kg). Due to the decay of weapons testing 137Cs and its mobility in surface soil and marine sediments, there is no uniform level of cesium contamination in soils unaffected by source points such as MYAPC. The maximum average levels noted above for contamination not derived from MYAPC operations takes into consideration that erosion patterns and silting will often concentrate weapons testing-derived radiocesium in certain locations, especially areas where soils and silt collect after rainfall events.
Additional discussion of this report is contained in Patterns
of Noncompliance as well as in RADNET Section 12: Part 5-E:
Also available on the web from this report is: Characterization Summary for Survey Package Number: R0500.
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