Status Report - Cane Fiberboard Properties and Degradation Rates for Storage of the 9975 Shipping Package in KAMS
Thermal, mechanical and physical properties have been measured on cane fiberboard samples following accelerated aging for up to approximately 7 years. The aging environments have included elevated temperature < 250 ?F (the maximum allowed service temperature for fiberboard in 9975 packages) and elevated humidity. The results from this testing have been analyzed, and aging models fit to the data. Correlations relating several properties (thermal conductivity, energy absorption, weight loss and height decrease) to their rate of change in potential storage environments have been developed. Combined with an estimate of the actual conditions the fiberboard experiences in KAMS, these models allow development of service life predictions. Some of the predicted degradation rates presented in this report are relatively extreme. However, these relate to environments that do not exist within KAMS, or would be postulated only as upset conditions that would not likely persist for an extended period. For a typical package with ~10 watts internal heat load or less, and ambient temperatures below 90 ?F, the fiberboard experiences storage conditions less severe than any of the aging environments. Little or no degradation of the fiberboard is expected for typical storage conditions. It should be noted that the ultimate service life will be determined by the cumulative effect of degradation from all the conditions these packages might encounter. The assumptions and inputs behind the models in this report should be well understood before attempting to identify an actual service life in KAMS. Additional data continue to be collected to permit future refinements to the models and assumptions. For developing service life predictions, the ambient conditions within KAMS can be reasonably identified, and the temperature profiles within the various packages (with a range of heat loads and at varying locations within an array of packages) can be calculated. However, the humidity within the package is not as well characterized. While the outer drum does not provide an air-tight seal, it does greatly restrict the gain or loss of moisture in the fiberboard. Preliminary efforts have identified a relationship between the moisture content of fiberboard samples and the relative humidity of the surrounding air, but further work is needed in this area. Improvement in understanding this relationship might be realized with a change in the way humidity data are collected during field surveillances. It is recommended that the humidity be measured through a caplug hole before the package is removed from its storage location. The package would remain in thermal equilibrium, and anomalous humidity changes could be avoided. Further work should be performed to better define KAMS storage conditions and the environment within the 9975 shipping packages, and to identify appropriate limits for each property. This should be a joint effort by SRNL and NMM personnel. The results and model predictions presented in this report are applicable to 9975 packages with cane fiberboard overpack assemblies. A separate effort is underway to identify whether softwood fiberboard would behave similarly. In addition, the degradation models do not address the effects of non-conforming conditions such as the presence of excess moisture and mold, or beetle infestations.
- Research Organization:
- Savannah River Site (SRS), Aiken, SC (United States)
- Sponsoring Organization:
- USDOE (United States)
- DOE Contract Number:
- DE-AC09-08SR22470
- OSTI ID:
- 1062172
- Report Number(s):
- SRNL-STI-2013-00020; TRN: US1300252
- Country of Publication:
- United States
- Language:
- English
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