Fig. 7 shows the transient response of the
reactor vessel (or water) temperature, Trf, with heat pipe heat
removal system, as calculated from Eq. (16). It is observed from the
graph that, after reactor shutdown, the water temperature continues
to rise for first 60 min reaching maximum of 305 C from
initial 282 C, followed by gradual drop in temperature with time.
The initial rise in reactor temperature is due to larger quantity of
decay heat from reactor core after shutdown process which exceeds
the heat pipe heat dissipation capacity. As the decay heat reduces
exponentially with time and drops below heat pipe capacity, gentle
drop in reactor vessel temperature is noted. If the overall thermal
resistance of heat pipe unit is doubled (~2.88 105 C/W) by
reducing heat pipe system size, then the extent of temperature rise
and time taken to reduce reactor temperature below certain value
will increase accordingly. In this case, the reactor will achieve
highest temperature of 404 C in 7 h before commencement of
cooling down operation. It should be noted that, in this case, the
temperature of the heat pipe evaporator will spike to ~400 C,
before cooling down commences, which can be considered as the
Fig. 7 shows the transient response of thereactor vessel (or water) temperature, Trf, with heat pipe heatremoval system, as calculated from Eq. (16). It is observed from thegraph that, after reactor shutdown, the water temperature continuesto rise for first 60 min reaching maximum of 305 C frominitial 282 C, followed by gradual drop in temperature with time.The initial rise in reactor temperature is due to larger quantity ofdecay heat from reactor core after shutdown process which exceedsthe heat pipe heat dissipation capacity. As the decay heat reducesexponentially with time and drops below heat pipe capacity, gentledrop in reactor vessel temperature is noted. If the overall thermalresistance of heat pipe unit is doubled (~2.88 105 C/W) byreducing heat pipe system size, then the extent of temperature riseand time taken to reduce reactor temperature below certain valuewill increase accordingly. In this case, the reactor will achievehighest temperature of 404 C in 7 h before commencement ofcooling down operation. It should be noted that, in this case, thetemperature of the heat pipe evaporator will spike to ~400 C,before cooling down commences, which can be considered as the
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