PROPERTIES OF FIBERBOARD OVERPACK MATERIAL IN THE 9975 SHIPPING PACKAGE FOLLOWING THERMAL AGING Page: 2 of 12
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Properties of Fiberboard Overpack Material in the 9975 Shipping Package Following Thermal Aging
W. L. Daugherty
Savannah River National Laboratory
Materials Science & Technology
Submitted for presentation at ASME PVP 2007
Many radioactive material shipping packages incorporate cane fiberboard overpacks for thermal
insulation and impact resistance. Mechanical, thermal and physical properties have been measured on
cane fiberboard following thermal aging in several temperature/humidity environments. Several of the
measured properties change significantly over time in the more severe environments, while other
properties are relatively constant. These properties continue to be tracked, with the goal of developing a
model for predicting a service life under long-term storage conditions.
The Savannah River Site (SRS) uses 9975 shipping packages to store plutonium and uranium materials
in the K-Area Materials Storage (KAMS) facility . Although the 9975 is a certified shipping
package, it continues to perform several safety functions in KAMS, including criticality prevention,
impact resistance, content containment, and fire resistance. The 9975 is used as a component of KAMS
to ensure the stored materials remain in a safe configuration during facility normal and accident
conditions. Celotex9 brand cane fiberboard, manufactured by Knight-Celotex, is contained between the
outer stainless steel drum and the inner lead shielding in the 9975 package. The fiberboard used in 9975
packages meets ASTM C208-95, Grade IV wall sheathing. Layers of fiberboard are laminated together
with water-based polyvinyl acetate (PVAC) adhesive.
The 9975 package is expected to perform its safety functions for at least 12 years from initial packaging
(2 years in transport + 10 years in storage). Uncertainty exists concerning the stability of the cane
fiberboard over time in the KAMS storage environment. Testing is being performed to predict a service
life for this material, and to validate satisfactory physical, mechanical and thermal performance over that
service life. This paper describes findings from testing of cane fiberboard after conditioning at specific
temperature and humidity levels.
The maximum normal operating temperature in the KAMS storage area is 120 F. Steady state thermal
analysis of the 9975 package predicts this would produce a maximum internal fiberboard temperature of
184 F. Off-normal or accident conditions can produce higher fiberboard temperatures, up to 250 F.
The 9975 shipping package safety analysis allows fiberboard operating temperatures of up to 250 F.
Since air / moisture can infiltrate the 9975 drum, the insulation can be exposed to moisture levels in
equilibrium with the ambient atmosphere. This would produce relative humidity levels up to 70% (at
133 F) or 20% (at 184 F), based on published psychrometric charts.
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Daugherty, W. PROPERTIES OF FIBERBOARD OVERPACK MATERIAL IN THE 9975 SHIPPING PACKAGE FOLLOWING THERMAL AGING, article, January 10, 2007; [Aiken, South Carolina]. (digital.library.unt.edu/ark:/67531/metadc890405/m1/2/: accessed October 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.