The Fukushima Daiichi nuclear accident The Fukushima Daiichi nuclear accident The Tohoku earthquake and tsunami that hit Japan on Ma rch 11, 2011 caused devastating damage. In this assignment, you will write an essay that deals only with the difficulties associated with the cooling of the Unit 1 reactor at the Fukushima Daiichi power plant. Before writing you r essay, you should perform the following calculations: 1. The Unit 1 reactor was a “ boiling water ” type reactor. These reactors generally work under high pressure and produce steam at temperatures around 380C . The power plant is a “ heat engine ” , so some of this thermal energy is released to the atmosphere and some is converted to electrical power. Use the efficiency equation from chapter 2 (page 60) to estimate the maximum possible effi ciency for this reactor. 2. The Unit 1 reactor was capable of producing 460MW of electrical power. Assuming that the plant ’ s efficiency was about 10% less than the optimal efficiency you found in the previous question, what was the thermal power output (in units of MW) of the reactor? 3. The reactor was shut down quickly after the earthquake struck, and hence the nuclear chain reaction was halted. However, the highly radioactive fission fragments within the reactor continued to decay and thus produce heat (t he so - called “ decay heat ” ). Combine your estimate of the thermal output during normal operation with the information in your textbook (see te xt above Fig. 5.13) to estimate the thermal output of the reactor just after the shutdown and one year after the sh utdown. 4. Heat can be removed from the reactor complex by allowing it to boil water. The process of boiling off a gallon ( = about 4 liters) of water that is initially at 20C takes approximately 9 . 8 × 10 6 Joules ( 9 . 8MJ ) . Combine this information with your previous work to com pute the rate that wat er must be supplied (in gallons per second) to carry away the heat so the reactor does not heat up and melt. Remember that a Watt is a Joule per second, or 1 W = 1 J / s . Once you have completed these calculations, you should write your essa y concentrating on t he difficulties with keeping the reactor cool after the earthquake, even though it had been shut down. Work at least some of the numbers you have calculated into your essay.