Transient temperatures during the period of time beginning at the end of the fire transient and ending 4 hours later are plotted in Figures 9 and 10. Figure 9 shows the maximum temperatures in the lead shield, SCV, PCV and for any component within and including the lead shield. In Figure 9, the maximum temperature for all components shifts from the lead shield to the Pu oxide after 10 minutes of the post-fire cooling. After an hour, the SCV O-ring temperature begins to decrease. Because a solar heat flux is now applied for a long period of time , none was applied before the fire, the constant source of power from radionuclide decay in the contents causes the internal temperatures to gradually rise.
Temperatures increase until a new thermal equilibrium is established for the solar heat flux.
The maximum package temperatures with their limits are listed in the following table. The thermal analysis supported the expectation that small separations in the fiberboard insulation will not degrade the thermal performance of the 9975 package in an HAC fire. Temperature profile for the package prior to the fire phase. Temperature profile for the package after exposure to the 0.5 hr fire. 30 min. into the post-fire transient.