A series of experiments to monitor the aging performance of Viton GLT O-rings used in the Model 9975 package has been ongoing for five years at the Savannah River National Laboratory. Sixty-two mock-ups of 9975 Primary Containment Vessels (PCVs) were assembled and heated to 200 or 300 oF. They were leak-tested initially and have been tested at nominal six month intervals to determine if they meet the criterion of leaktightness defined in ANSI standard N14.5- 97. To date, all of the original O-ring fixtures have maintained a leaktight seal at room temperature following up to three years exposure at temperature. It is expected that the actual 9975 O-rings in KAMS storage will maintain a leaktight seal for a significantly longer period of time than demonstrated by these fixtures, based on the less severe service conditions in KAMS.temperatures (350 450 :F) in an attempt to produce failures within the timeframe of this effort and to improve the predictive capability of the leak tests. Three of the five higher temperature fixtures have failed to remain leaktight. Predictive models being developed by SRNL compression stress relaxation tests will attempt to quantify the expected equivalent storage lifetime at actual storage conditions. The failure intervals from these fixtures will be considered in developing the overall confidence of these predictive models.
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