Heat sink/radiation loss

The fluid film system completely eliminates the heat sink/ radiation loss since the platens remain stationary. The heat in the platen is radiated into the product. The reservoir behind the platen is easy to insulate and this insulation remains in place with no hinderance to inspection or maintenance. Further, since the heat is controlled in zones corresponding to the need profile of the formulation, there is no wasteful input of energy into the product. 

A loss of energy from the reaction prior to completion of the reaction (i.e., radiation transfer to cold walls, a heat sink, etc.) can prevent the completion of the reaction, if conditions are borderline. In those cases, the energy input must be increased to compensate for the loss. 

Decay heat in fuel elements is assumed to be dissipated by means of heat conduction and radiation to the outside of the reactor pressure vessel, and then taken away to the ultimate heat sink by water cooling panels on the surface of the primary concrete cell. Therefore, no coolant flow through the reactor core would be necessary for the decay heat removal in loss of coolant flow or loss of pressure accidents. The maximum temperature of fuel in accidents shall be limited to 1 bOO C. 

The second loss is by radiation from the belt. The belt, which is of heavy construction for rigidity and flatness is a very significant heat sink. Some of this heat transfers to the panel where it is needed and some where it is not needed. The remainder is lost to the atmosphere by radiation during its idle return to the input end. This loss can be reduced by insulation but the problem of removing and restoring this insulation for inspection and maintenance access makes it impractical. A measurement on a double belt revealed a 20°F (11°C) loss in belt temperature during the return run. 

For a simple estimate of the sensitivity and its dependence on the detector parameters, such as the heat capacitance and thermal losses, we shall consider the following model [4.99]. Assume that the fraction p of the incident radiation power P is absorbed by a thermal detector with heat capacity H, which is connected to a heat sink at constant temperature (Fig. 4.73a). When G is the thermal conductivity of the link between the detector and the heat sink, the temperature T of the detector under illumination can be obtained from... 

In the case of a total loss of heat sink to the secondary circuit, heat removal directly from the vessel will play the major role in achieving a balance between the decay heat generated in the core and passive heat removal to the environment. In a hypothetical failure of this passive path, the vessel will be cooled by thermal conduction and radiation from its surface. 

Several inherent and passive safety features are incorporated in compact high temperature reactor. Due to negative temperature coefficient of reactivity, the power of the reactor comes down without necessitating any external control in case of increase in core temperature. The reactor also adopts passive systems like removal of core heat by natural circulation of liquid metal coolant in the main heat transport circuit, passive regulation and shut down systems. The reactor is also able to remove heat passively by way of conduction in the reactor block and by radiation and natural convection from the outer surface of the reactor during loss of heat sink. The paper deals with the details of passive systems incorporated in the AHWR and CHTR and the analysis performed for these systems. 

Transient simulations of SEALER have been carried out using the SAS4A/ SASSYS-1 codes as well as BELLA, a code written specifically for the purpose of safety-informed design of LFRs. Analysis shows SEALER to withstand unprotected withdrawal of a single control rod, loss of forced flow and loss of heat sink, thanks to its low power density, the capability of natmal convection for decay heat removal, and reliance on thermal radiation from the vessel as the ultimate heat sink. 

While the initial loss of the ultimate heat sink produced a small rise in fuel temperature in the reactor vessels of 5 and 6, and an increase in spent fuel temperatures, the fact that AC power was available, allowed plant personnel to prevent fuel melting and radiation release. For the first 8 days after the earthquake station personnel were able to keep the reactor vessels of Units 5 and 6 and the spent fuel pool fuel assemblies cool by injecting additional cool water and removing heated water, A reconnection to the Pacific Ocean as the ultimate heat sink was accomplished on the eighth day. The work was exceptionally difficult, but it was greatly simplified by the lower heat loads found in these units (Anon, 2012),... 

The containment is designed to condense steam and to contain fission products released at a loss of coolant accident (LOCA) so that offsite radiation doses do not exceed the specified criteria and to provide a heat sink and water source for certain safety related equipment. 

An infinite plate of thickness 2L is suddenly exposed to a constant-temperature radiation heat source or sink of temperature T,. The plate has a uniform initial temperature of T,. The radiation heat loss from each side of the plate is given by q - surface area. Assuming that the plate behaves as a lumped capacity, that is, k — =0, derive an expression for the temperature of the plate as a function of time. 

The various terms take into account the various sinks q < 0) or sources q > 0) of the heat balance. These include, specifically, the reaction itself, transport, agitation, radiation, and heat loss through evaporation and gas stream. In most cases the last four terms can be neglected (Bronn, 1971 Cooney, Wang, and Mateles, 1968 Mou and Cooney, 1976). The term for the reaction, the heat produced, is represented in Equ. 2.4c. The kinetics are, as always, introduced in the balance equation. All heats of reaction can be calculated from a series of T/t measurements using Equ. 3.70 when the specific heat capacity of the reactor system is known... 

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