Thermal safety design considerations

Processing food to ensure safety requires the reduction of viable endospores to a negligible level. Because it is impossible to ensure that all spores are completely eliminated, a standard reduction rate of 10" has been accepted. That means that one surviving endospore for each 10 cans processed is acceptable. Through a combination of temperature and time, thermal processes for food sterilization can be designed (Teixeira, 1992 Johnson, 1999). Similar considerations are important for the sterilization of medical devices and bioreactor growth media. 

The assembly of these cells into a battery must take account of electrical engineering considerations, thermal control problems, questions of accessibility and maintenance and safety factors. With as many as 500-1000 cells involved it is evident that a series/parallel network will be required the design of this network poses particular problems for Na/S cells because of two characteristics they possess ... 

The selected diameter of micro fuel element, which is 1.8 mm, secures an exceptionally high heat exchange surface in the core, which results in a considerably lower heat flows and temperatures as compared to conventional BWRs or PWRs. The low thermal energy stored in the core secures high level of intrinsic safety in design basis and beyond design accidents. 

In designing a storage vessel for a cryogenic liquid, there are several considerations that should be made Is the system intended for long- or shortterm usage What type of liquid will be stored, and what rate of liquid loss can be tolerated Will the system be mobile or stationary What acceleration effects are anticipated for the system How much time and cost will be allowed for cooldown What will be the stratification and pressure effects on the system What type and thickness of material will be required for the inner and outer vessels and what will be the thermal conductivity of this material Other important aspects include the optimum type of insulation and the design of inner vessel supports, fill and drain lines, vapor vents, vapor diffusers, antislosh baffles, and safety devices. 

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