Preliminary Report: Effects of Irradiation and Thermal Exposure on Elastomeric Seals for Cask Transportation and Storage

Technical Report · Fri May 30 04:00:00 EDT 2014

DOI:https://doi.org/10.2172/1133388· OSTI ID:1133388

Verst, C. G. ^[1]; Skidmore, T. E. ^[1]; Daugherty, W. L. ^[1]

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1. Savannah River National Laboratory (SRNL), Aiken, SC (United States)

A testing and analysis approach to predict the sealing behavior of elastomeric seal materials in dry storage casks and evaluate their ability to maintain a seal under thermal and radiation exposure conditions of extended storage and beyond was developed, and initial tests have been conducted. The initial tests evaluate the aging response of EPDM elastomer O-ring seals. The thermal and radiation exposure conditions of the CASTOR® V/21 casks were selected for testing as this cask design is of interest due to its widespread use, and close proximity of the seals to the fuel compared to other cask designs leading to a relatively high temperature and dose under storage conditions. A novel test fixture was developed to enable compression stress relaxation measurements for the seal material at the thermal and radiation exposure conditions. A loss of compression stress of 90% is suggested as the threshold at which sealing ability of an elastomeric seal would be lost. Previous studies have shown this value to be conservative to actual leakage failure for most aging conditions. These initial results indicate that the seal would be expected to retain sealing ability throughout extended storage at the cask design conditions, though longer exposure times are needed to validate this assumption. The high constant dose rate used in the testing is not prototypic of the decreasingly low dose rate that would occur under extended storage. The primary degradation mechanism of oxidation of polymeric compounds is highly dependent on temperature and time of exposure, and with radiation expected to exacerbate the oxidation.

• Research Organization: Savannah River Site (SRS), Aiken, SC (United States); Savannah River National Laboratory (SRNL), Aiken, SC (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE), Nuclear Fuel Cycle and Supply Chain. Fuel Cycle Research and Development Program
• DOE Contract Number: AC09-08SR22470
• OSTI ID: 1133388
• Report Number(s): SRNL--STI-2014-00231; FCRD-UFD-2014-000317
• Country of Publication: United States
• Language: English

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