Even when shut down after a period of normal use, a large commercial nuclear reactor transfers
thermal energy at the rate of 150 MW by the radioactive decay of fission products. This heat
transfer causes a rapid increase in temperature if the cooling system fails. [Properties of steel
vessel: cp=470 J/kg.oC, melting point=1430 oC and Lf=270 kJ/kg]
a) Calculate the rate of temperature increase in degrees Celsius per
second (ºC/s) if the mass of the reactor core is 1.60×105 kg and it has
an average specific heat of 0.3349 kJ/kgº C. [2 marks]
b) How long would it take to obtain a temperature increase of 200ºC? [2
marks]
c) Considering the same rate of thermal energy transfer (150 MW) to the
steel containment vessel, how long it will take to melt 1.00% of the
steel vessel? (Assume, the initial temperature and mass of steel
containment vessel are 300oC and 5×105 kg respectively.) [4 marks]
d) Make a graph of temperature versus time for the process in question
(c). [2 marks]